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Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
V. Vanaclocha; N. Sáiz-Sapena y P. Monedero. Servicio de Neurocirugía, Servicio de Anestesiología y Reanimación. Clínica Universitaria, Universidad de Navarra. Pamplona, Navarra.
Resumen Los gliomas supratentoriales de bajo grado deben ser sometidos a exéresis completa. Cuando estas lesiones asientan en áreas elocuentes su extirpación puede resultar problemática debido a la posibilidad de inducir secuelas neurológicas. Si el procedimiento se practica bajo anestesia general la resección es frecuentemente subtotal. Intentando aumentar la radicalidad de la exéresis nuestro grupo la ha practicado bajo anestesia local, controlando intraoperatoriamente las funciones neurológicas en peligro. Diecisiete casos de gliomas de bajo grado fueron extirpados bajo anestesia local y sedación ligera. La exéresis quirúrgica fue completa en 15/17 y subtotal en 2/17. Postoperatoriamente sólo un pacienete presentó una hemiparesia ligera y dos más una disfasia motora transitoria. Concluimos diciendo que la craniotomÍa bajo anestesia local permite la extirpación, la mayor parte de las veces completa, de lesiones en áreas elocuentes del cerebro. PALABRAS CLAVE: CraniotomÍa. Anestesia local. Sedación.
Summary Low grade supratentorial gliomas should be removed radically. When they lay in eloquent areas its removal can be problematic due to the possibility of inducing neurological sequelae. If the procedure is performed under general anaesthesia the resection is often subtotal. Attempting to increase the radicality these cases were performed under local anaesthesia, controlling intraoperatively the endangered neurological functions. Seventeen cases of low grade gliomas were removed under local anaesthesia and light sedation. Surgical removal was complete in 15/17 cases and subtotal in 2/17. Postoperatively one patient had a slight hemiparesis and two more a transient motor duysphasia.
We conclude saying that craniotomy under local anaesthesia allows the removal, most of the times complete, of lesions in eloquent brain areas. KEY WüRDS: Craniotomy. Local anaesthesia. Sedation.
Introduction Before the Second World War all the craniotomies were performed under local anaesthesia. Cushing l3 and Dandt 4 went on using local anaesthesia for so long as the risks of ether and chloroform were frightening. Its use declined with the advent of the modern neuroanaesthesia and in the last thirty years it has been used for the surgical treatment of epilepsy resistant to anticonvulsant medication 3.'8.'9.31.43.47, and in some cases of removal of cerebral arterio-venous malformations laying close to eloquent brain areas 'O • Meanwhile, its application to the surgical removal of intrinsic brain tumours has been recommended more recentlt· '8 .23 • About one third of all the newly diagnosed brain tumours are so-called low grade gliomas (WHü Grades 1 and Ir)". It has been shown that any well delineated low grade glioma should be removed radically to offer the best chance of cure, to prevent tumour progression and to increase the recurrence-free-interval, as subtotal removal does not increase the progression free interval 12.'4.38.4'.48.51.55. Recurrences, even after radical removal, usually progress to malignant glioma, but the frequency of progressions is much lower after radical resection than after partial removaIS'. The possibility of inducing iatrogenic neurologic sequelae is a serious concern l8 , specially when these tumours are localised adjacent to or in eloquent brain areas 5.8.'4.38.39.54. Many of this latter tumours are considered inoperable by most surgeons and handled with stereotactic biopsy, followed by radiotherapy or no further treatment at all'".39. Unfortunately addition of radiotherapy to partial removal has been associated with an unfavourable outcome due to a much higher incidence of recurrences and early malignizations comparing with radical removal and no radiotherapyI.36.38.51.57', 95
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
The exact location of the tumour and its relationships to the nearby eloquent cortex are often depicted accurately on preoperative CT'·15.1ó.'7.J4.37Al and magnetic resonance imaging (MRI) studiesÓ.19.33, and can be of great help in surgical planning ,ó .5o . Unfortunately that is not enough as the normal structures are usually displaced and intraoperatively it can be difficult to distinguish them properly. In such cases, intraoperatively the central sulcus (sensorimotor cortex) can be localised by somatosensory evoked potentials'óA0.5,5ó, but that is of no help when the tumour is close to other areas not related with the motor strip (i.e. speech-related areas of Wernicke, Broca and gyrus angularis, as well as in sorne of the more significant connecting pathways like the arcuate fascicle, the visual pathways, etc.). In all this cases intraoperative mapping of the endangered nearby brain can be successfully achieved by cortical electrical stimulation7-9.1s .,o.2'.JOJ'.J5Aó.54. Intraoperative ultrasound sonography has been used in Neurosurgery for years and proved helpful to better localise and delineate the lesions to be removed'·lI.5J, but is of little help to define the exact anatomy of the nearby brain. As general anaesthesia allows a better control of any intraoperative event, both the surgeon and the anaesthesiologist prefer it as the patient' s airway and ventilation is better controlled. Unfortunately this modality of anaesthesia does not allow intraoperative control of any iatrogenic neurologic sequelae and both the surgeon and the patient know too late what has already happened. This usually leads to more conservative resections for fear of inducing neurological sequelae. This could be avoided by the intraoperative mapping of the endangered brain areas by means of electrical stimulation but the patient must be fully awake and cooperative'9. In order to achieve that the same procedure can be performed under local anaesthesia, allowing wider resections with good functional results 5.9A9.54. Operations in awake patients also offer the advantage of being able to «monitor» the functions by continuous clinical examinations of the contralaterallimbs and facial muscles and speech during the whole procedure, minimizing the risk of postoperative neurological deficits D "A7.". Thus the procedure can be anested when needed.
Patients and methods Our series includes seventeen patients (six females and eleven males) with brain tumours, that were removed under local anaesthesia and sedation, in a period of four years (January 1991 to December 1994). Each patient harboured only one lesiono During the same period a total of 127 craniotomies for brain gliomas were performed under general anaesthesia. The average age was 55.7 years. The two youngest patients were 25 and 28 years old, and had respectively a
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grade 1 and a grade II astrocytoma removed. The oldest patient was 70 years old and harboured a grade III astrocytoma. Tumours location was in the right hemisphere in five cases and in the left in twelve: 8/17 (47 %) in motor and 9/17 (53%) in speech related areas (2/17 -11.7%- in the hand motor area, 5117 -29.4%- in the arm motor area, 5117 -29.4%- in the area of Broca, 1117 -5.8%- left parietal -gyrus angularis-, 3/17 -17.6%- in the area of Wernicke and 1117 -5.8%- in the motor area of the lower limb). Preoperatively those lesions in or near Broca' s area (5/17,29.4%) underwent a dichotic hearing test and an intracarotid amobarbital test, in order to ascertain whether or not the speech function had been transfened to the other hemisphere. Unfortunately, in none of our cases had speech been transferred to the right hemisphere. The patients were kept nil per mouth since 8 hours prior to the surgical procedure. No premedication was prescribed. The surgical table was specially cuffed and had a good foamed headrest as in the awake patient the tolerance to the technique depends to a great extent on his or her comfortability's.'9. That was very important as the patient had to remain quiet and relaxed in a fixed position and warn the surgeon every time a slight change in position was needed. The surgical drapes were placed so that the patient had the maximum angle of vision, to avoid a claustrophobic feeling and allowing an excellent communication with the surgical-anaesthetic team. This was achieved by means of the Ganet table (Codman), placed over the surgical table, so that the whole patient remained undraped except the head. Moreover a big sterile adhesive plastic drape covering all the surgical field was used, allowing the patient to see light through it. The anaesthesiologist not only had an adequate access to the patient's airway, but also could see him and talk with him during the whole surgical procedure. The conversations between the staff in the operating room were discrete and limited to professional matters, avoiding that the patient had any feelings of rejection or lack of interest. At the entrance of the operating room there was a writing saying: «Silence please, patient awake». During the procedure the surgeon and the anaesthesiologist talked continuously to the patient, explaining each step, and specially each new sound (scratching of the periosteum, use of the craniotome if needed, Gigli saw, cureting of bone, etc.). The instruments with striking sounds, as the craniotome, induced apprehension in sorne patients. In such event hand powered instruments were used. The local anaesthetic agent used was Bupivacaine 0.25%, in account of its long duration of action (8-12
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
hours), special1y when combined with a vasoconstrictor agent. In most cases the operative procedure lasted 2-4 hours. Lidocaine 1% was added to achieve immediate anaesthesia and to reduce the initial discomfort as the Bupivacaine needs sorne minutes to induce anaesthesia. As vawconstrictor agent Ornipressine (8-ornithine-vasopressin, POR 8® Sandoz, V VI/mI), which is less toxic and more effective than Adrenaline was used. It induces local vasoconstriction in 10 minutes, that lasts at least 1-2 hours. The recommended dose is 1 UI for each 10 mI of local anaesthetic solution, not surpassing the 5 UI (one ampoule of POR 8® for 50 mI of local anaesthetic solution). Sedation was induced by the administration of 2-3 mg of Midazolam every 30-60 minutes, supplemented when necessary with Fentanyl 0.05 mg every 30 minutes. The doses were individual1y adjusted by the anaesthesiologist through the continuous evaluation of the state of consciousness and comfort of the patient. For the surgical incision a mixture of equal parts of Lidocaine 1% and Bupivacaine 0.25% to a total amount of 50 mI was used. To this were added 5 VI Ornipressine (1 UI/1 Oml local anaesthetic solution) and 0.2 mI of sodium bicarbonate 8.4% (to reduce the burning sensation). The injection was performed in the subcutaneous and subgaleal spaces. In pterional craniotomies another 10015 mI of local anaesthetic mixture were injected in the depth of the temporalis muscle. The injection of local anaesthetic mixture in the scalp was the most painful part of the procedure. The patient was forewarned of each prick that was to be given as wel1 as of the impending burning feeling induced by each infiltration. For this injections 25-G 5/8 (0.5x16mm) single use needle non-pyrogenic and a 20 mI syringe were used. Elevating the bone t1ap usually induces some local discomfort due to traction on the underlying dura, rather than to sensitivity to bone. This was reduced by pouring some Lidocaine 1% on the epidural space through the burr-holes. A mixture of equal parts of Lidocaine 1% and Bupivacaine 0.25% was used to achieve a rapid anaesthesia and long duration of the dura mater. A swab soaked in 5 to 10 mI of anaesthetic mixture was applied to the exposed dura. In those cases when the dura showed lacerations no anaesthetic agent was used in order to avoid inducing epileptic seizures. In these cases the anaesthesia was supplemented by administering small doses of Fentanyl, as described earlier. Once the bone t1ap had been elevated and the dura anaesthetised, the rest of the surgical procedure was virtuaHy painless. The maximum amount of local anaesthetic used never exceeded the maximum recommended dose for infiltration, i.e. 175 mg Bupivacaine (70 mI Bupivacaine 0.25%) and 300 mg Lidocaine (30 mI Lidocaine 1%).
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Pain due to manipulation of the insula orstretching of the cranial base vessels was controlled with small doses of i.v. Fentanyl when required. After opening the dura, in those cases that involved the motor strip, somatosensory evoked potentials (SEP) (Med.e1x, Sensor, London, England) were recorded simultaneously from 4 cortical surface electrodes each placed 10 mm apart distributed perpendicular across the central sulcus following the technique published by others 26 • To map the areas to be removed and the adjacent cortex, stimulation with a contacting bipolar electrode of 2 mm in diameter (IBAAB, Stockholm, Sweden), with a frequency of 25-50 Hz at an intensity between 10 and 20 mA and a duration of 5 to 10 milliseconds was utilised. A stimulus of low intensity which was increased slowly until response was achieved was used as a routine. The sensorimotor cortex was identified, if motor or sensory phenomena were proven by observer or indicated by the patierit. The motor speech area was stimulated until a speech arrest could be elicited following the technique widely described in the literature 44 -46 • In the vast majority of cases (12/17, 70.5 %) the lesion was identified by its macroscopic appearance at the cortical surface. In aH the cases intraoperative ultrasound sonography (Acuson XP/lO, Mountain View, California, USA) was performed to better delineate the lesiono In lesions appearing at the cortical surface the excision was started at the visible tumour. Ultrasound sonography was specially helpful to localise the five cases with tumours not coming out to the cortical surface, helping to decide the trajectory to be used to minimise brain damage. The cortical incision was always kept as small as possible, as al1 the cortex has impotant functions. In order to avoid manipulation of the brain, the tumour was vaporised with the aid of a defocused beam 50Watts C02 laser (Sharplan Industries, Tel Aviv, Israel). The cavity was irrigated copiously to avoid charring and local heating. Tumour removal commenced with slowly coring out of the centre. Meanwhile the anaesthesiologist maintained a continuos conversation with the patient and gave simple commands to monitor the functions of the exposed area (i.e. «raise your arm», «close your hand», and so on). As soon as any sign of neurological deficit appeared, no matter how minimal, surgery was immediately stopped. The whole area was revised and ultrasound sonography performed to study the amount and exact localisation of the remaining tumour. Often the resection could continue safely at another comer of the tumour. Intraoperative histological examination of the borders of the resection was performed in order to know if the resection was complete or only partial and when the resection had to continue or could be stopped. The average duration of the surgicaI procedures was 170 mino (range 120-210 min).
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Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
Figure 1.- Preoperative MR image of a low grade glioma (G) in the insula under Broca 's area. The arrows point to the sylvianfissure. The arrow head points to the middle cerebral artery. Postoperatively the degree of tumour resection was evaluated by serial MRI studies, performed at 1 month and 3 months after surgery and then at every 6 months. Results Surgical resection under local anaesthesia with sedation, aHowed complete removal of the lesion in 15/17 (88.2%) of the cases, with per-operative preservation of the neurological functions of the areas involved in the surgical procedure (Figures 1 and 2). In the remaining 2/17 (11.8%) cases the resection was subtotal, as the procedure had to be terminated when signs of neurological deficits were detected, in both cases when most of the lesion had already been removed (Figures 3a, 3b and 4a, 4b). None of the deficits remained in any of these patients for longer than a few hours after the surgical procedure was terminated. The removed tumours were aH glial in nature: 8 astrocytomas grade 1; 6 grade II and 3 grade IlI. The grade III astrocytomas showed preoperative magnetic resonance imaging features characteristic of low grade gliomas, but pathological studies showed sorne areas of malignant change which necessitated classification as grade IlI. In 14/17 (82.3%) cases no iatrogenic neurological deficits were added (including the two in which the surgical procedure had to be stopped as the first neurological deficits appeared, but immediately recovered). In the remai98
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Figure 2.- Postoperative MR image of the patient fr0111 the figure 1 showing the extent of the tumour removal with no neurological deficits. Note the inverted image due to different MR scanner. The small black arrows point to the internal capsule and the big white arrow to the remains of the globus pallidus. ning 3/17 (17.7%) no deficits existed initiaHy, but 24-48 hours after the surgical procedure a deterioration of the neurological functions of the operated area was detected (mild hemiparesis in a case and motor dysphasia in two). AH of them recovered completely under treatment with corticosteroids, and regained their preoperative functional level in a week. None of our patients had intraoperative epileptic seizures, haemorrhages or needed urgent intubation. Discussion With the advent of CT and MR imaging techniques non-invasive preoperative identification of brain anatomy became possible2.6.ls.21.27.3J.J4A1.5o. In spite of aH, accurate preoperative localisation of eloquent brain areas is not always possible, speciaHy when the normal anatomy is distorted by a space occupying lesion,s.lw.J7. A decision that tumours located in or close to these areas are inoperable based alone on preoperative neuroimaging may be misleading 58 .59 . In fact many of the cases of our series (11/17, 64.7%) were referred from other hospitals elsewhere diagnosed as inoperable. Operability of lesions in the dominant frontal operculum is also dependant on whether or not speech function has been transferred to the other hemisphere. That can be
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
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Figures 3a and 3b.- Preoperative MR images of a low grade gUoma (G) lying close to the gyrus angularis. The patient was a 24 year old singer who wanted the tUl110ur removed but wished to keep singing. The arrows point to the sylvian fissure. ascertained preoperatively with the intracaratid amobarbital testlO and/or with the dichotic hearing test. In any case the fact the speech function is not transferred to the contralateral hemisphere should not prevent us fram attempting to remove the lesion as it was done in our 5/17 (29.4%) cases. Intraoperative electrical stimulation allows identification of the exact anatomical relationships between the lesion and its surrounding brain areas5.7.9.18.30.46, but it is the continuous intraoperative clinical monitoring which helps to avoid iatragenically induced neuralogical deficits by stopping the resection just on time24.29.54. The pracedure is very helpful but has to be carried out in awake, co-operative patients 56 . Local anaesthesia offers the advantage of allowing intraoperative electraphysiological testing to perform a more reliable identification of eloquent brain areas as well as monitoring of the endangered functions, and thus many surgeons prefer it if radical resection is considered3.2429.54. The additional ultrasound guidance to the lesion allows the surgeon to determine the least hazardous transcortical approach 26 . Glial neoplasms usually have an irregular geometric configuration being difficult to stay oriented within these irregula extension even if sophisticated computer systems are available. One has to consider that what is being operated is not a piece of wood or a frozen brain. That means that just the craniotomy induces distortions on the real anatomy and with progressive tumour removal the brain sinks in the cavity making that the stored image obtained preoperatively, available fram the computer, is a false
illusion that can lead to mistakes when every millimetre matters. We have found that we can not rely only on this frozen images obtained preoperatively and perform the pracedure under general anaesthesia. Sorne authors suggest the intraoperative use of ultrasound for the delineation of the tumour margins 4.11.25.26, although others repot that the results concerning differentiation between tumour margins and oedema, specially in low grade gliomas, are disappointing 53 . We have found useful the ultrasound to delineate the lesion at the beginning of the surgical pracedure but once the resection has progressed it is increasingly more difficult to differentiate between tumour margin and abnormal brain induced by the surgical manipulation. That was partially reduced by vaporising the tumour with a defocused C02 laser beam, avoiding mechanical handling and haemorrhage. A clear cut margin between tumour and normal brain is not always easy to define due to the infiltrating nature of sorne of these low grade gliomas. One has to rely in changes in colour and consistency, but that often fails. Intraoperative histological examination of the borders of the resection can be performed, allowing stepwise adaptation of the resection according to the histological results 24 . The pracedure is of help at least to know if sorne disease is left behind. In any case the surgical removal has to be stopped once any neurological deficit appears with disregard of how much tumour is left behind. We have found that more tumour can be removed fram other areas of the surgical field but not fram the one that has already indüced a neurological deficit, no matter how slight. 99
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
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Figures 4a and 4b.- Postoperative MR image ofthe patientfromfigure 3a and 3b. The lesion has been removed subtotally as the patient developed slurred speech during the procedure. She keeps singing with no further problems and is follow-up regularly. The arrows point to the sylvianfissure. Cavity left after subtotal removal of the lesion (C). Craniotomy under local anaesthesia with sedation has been recommended whenever there is a need for intraoperative control of the functions of the brain areas to be operated on 3.24 ,47. These tumours usually displace cortical functional areas without destroying themI6.IS.2S.27.34.3S.37 and performing the surgical procedure under local anaesthesia, allows a wider resection. Only superficial lesions should be removed under local anaesthesia54 . The surgical approach to deep areas, although possible, can be cumbersome and problematic3.28·29. The surgical procedure should not last too long, since maintaining the same posture for long periods of time can be quite difficult and very unpleasant for the patient. The intraoperative risks of haemorrhage, intracranial hypertension, epileptic seizures and respiratory arrest have to be thoroughly evaluated3.28.29.54. Local anaesthesia is not recommended for procedures that could be performed under general anaesthesia with no special risk of inducing neurological deficits1.7.S.2S.2954. Mild intraoperative deficits have been seen to improve postoperativey not only in our series but also in those of others 49 . The ideal is to stop the resection just once the deficit is starting, but that requires a thorough intraoperative clinical monitoring 3.S4 . In order to achieve that the patient has to be relaxed and co-operative, with full confidence on the surgical-anaesthetic team3.2S.29.54. The patient had to be thoroughly informed of the whole procedure, and most important is the psychological preparation for the procedure. What the patient will hear and see must be carefully controlled. The patient physical comfort is also a most important point. Maintaining one position during the whole 100
procedure must be made as easy as possible. Pain is what scares the patient most, so that good local anaesthesia is essential. The skin and the dura have nociceptors, but not the bone and the brain also lacks any sensitivity. Manipulation of the main vessels at the base and in the insula can induce pain or soreness. As the dura is only anaesthetised in the area of the surgicalfield, the intracranial remains sensitive as can be irritated by touching it with cotonoids, which may induce pain. Copious irrigation of the surgical field can induce a diffuse poorly localised pain, sometimes associated with a vegetative component (nausea and even vomiting). All this effects can be controlled by the anaesthesiologist using Midazolam and Fentanyl, according to demando Potential risks to be considered for the craniotomies under local anaesthesia with or without sedation, are epileptic seizures, intracranial hypertension (tumoral in origin but facilitated by the hypoventilation and the recumbent position, haemorrhages 2S.29 , a significant reduction in the level of consciousness, marked hypoventilation and secondary or toxic effects of the local anaesthetic or vasoconstrictor agents used 3 • We have always been very concerned about the possibility of epileptic seizures, and that is why a good venous access and an anaesthesiologist are essential. In the case of such an event Diazepam 5mgrs IV under slow perfusion is usually enough to control the crisis, as we have seen in sorne cases of stereotactic biopsy under local anaesthesia (not included in this series). In the craniotomies under local anaesthesia we did not need to use Diazepam as no epileptic seizures happened, but had
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
such event happened we were prepared to stop the procedure until the epileptic seizure had been controlled and the patient was fully awake again. In conclusion, craniotomy under local anaesthesia is a technique to be considered in the surgical removal of tumours located in eloquent areas of the brain, as it often allows the total removal of lesions in these areas, which otherwise could not be removed so radically under general anaesthesia without having to accept a high risk of important neurological sequelae5.9.3o'32. We like the patient to be fully awake during the whole surgical procedure. Others seem to prefer to keep the patient fully anaesthetised becoming awake and co-operative only to perform electrical corticalstimulation of the sensori-motor cortex, speech areas and tumour surface'·9.18.22.24.35.39.43.46.4'. We do not like it as patients do not seem to recover consciousness so fully when awaken from a general anaesthesia nor when they have had too much medication in order to keep them under deep sedation or under intravenous anaesthesia. The patient needs to be fully awake in order to co-operate fully during the tumour resection to allow clinical testing of the endangered brain functions. To perform this technique excellent co-operation and understanding between the surgical and the anaesthetic teams is needed, in order to reduce the discomfort of the patient to a minimum. The patient's cooperation can thus be facilitated so that the functions of the brain areas being threatened can be monitored accurately.
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7. Berger, M.S., Ojemann, G.A., Lettich, E.: Neurophysiologica1 monitoring during astrocytoma surgery. Neurosurg. C1inkj. North. Am. 1990; 1: 65-80. 8. Berger, M.S., Ghatan, B.S., Haglund, M.M., Dobbins, 1., Ojemann, G.A.: Low grade gliomas associated with intractable epilepsy: seizure outcome utilizing e1ectrocorticography during tumor resection. J. Neurosurg. 1993; 79: 62-69. 9. Black, P., Ronner, S.F.: Cortical mapping for defining the 1imits of tumor resection. Neurosurgery 1986; 20: 914919. 10. Burchiel, K.J., C1arke, H.K, Ojemann, G.A., Dacey, R.G., Winn, H.R.: Use of stimulation mapping and corticography in the excision of arteriovenous malformations in sensorimotor and language-related neocortex. Neurosurgery 1989; 24: 322-327. 11. Chand1er, W.F., Knake, J.E., McGillicudy, J.E., Lilleheii, K.O., Silver, T.M.: Intraoperative use of real-time ultrasonography in neurosurgery. 1. Neurosurg. 1982; 57: 157-163. 12. Ciric, 1., Ammirati, M., Vick, N., Mikhae1, M.: Supratentorial gliomas: surgica1 considerations and immediate postoperative resu1ts. Neurosurgery 1987; 22: 21-26. 13. Cushing, H., Eisenhardt, L.: Diagnosis, operative technique and end results. En Cushing H., Eisenhardt L., eds. Meningiomas: their classification, regionl behaviour, life history, and surgica1 end results. Springfield; Charles C Thomas 1938; 720-742. 14. Dandy, W.E.: The brain. En Lewis D., ed. Practice of surgery. Hagertown; Prior Co 1932; 5-12. 15. Ebelingj, U., Huber, P., Reu1en, H.J.: Loca1ization of the precentral gyrus in the CT and its clinical application. J. Neuro!. 1986; 233: 73-76. 16. Ebeling, v., Reulen, H.J., Huber, P.: Surgery of processes a10ng the pyramidal tract and the interna1 capsule. En Samii M., ed. Surgery around the brain stem and the third ventricle. Berlin; Springer 1986; 405-409. 17. Ebe1ing, U., Rikli, D., Huber, P., Reu1en, H.J.: The coronal suture, a useful landmark in neurosurgery? Craniocerebral topography between bony landmarks on the skull and the brain. Acta Neurochir. (Wien) 1987; 98: 130-134. 18. Ebeling, v., Schmid, U.D., Reulen, H.J.: Tumour surgery within the central motor strip: surgical results with the aid of electrical motor cortex stimulation. Acta Neurochir. (Wien) 1989; 101: 100-107. 19. Ebe1ingj, U., Steinmetz, H., Huang, Y., Kahn, T.: Topography and identification of the inferior precentra1 sulcus in MR imaging. AJNR 1989; 10: 937-942. 20. Ebeling, U., Schmid, U.D., Ying, Z.: Mapping bei Tumor-operationen in der Zentra1region. Schweiz Rundshau Med. Praxis 1991; 47: 1.318-1.323. 21. Ebeling, U., Huber, P.: Localization of centra11esions by corre1ation of CT findings and neuro1ogica1 deficits. Acta Neurochir. (Wien) 1992; 119: 17-22. 22. Ebeling, U., Schmid, U.D., Ying, Z., Reu1en, H.J.: Safe surgery of lesions near the motor cortex using intraoperative mapping techniques. A report of 50 patients. Acta Neurochir. (Wien) 1992; 119: 23-28. 101
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
23. Ebeling, U., Seilerk, R.W., Hasdemir, M.G.: Les astrocytomes differenciés (grade OMS II) de la région centrale: porteé et limites de la chirugie. Méd. Hyg. 1992; 50: 2.4882.493. 24. Ebe1ing, u., Kothbauer, K.: Circumscribed 10w grade astrocytomas in the dominant opercu1ar and insular region: a pi10t study. Acta Neurochir. (Wien) 1995; 13266-74. 25. Enzmann, D.R., Wheat, R., Marsha11, W.H., Bird, K, Murphy-Irwin, K., Karbon, K., Hambery, J., Si1verberg, O.D., Britt, R.H., Shuer, L.: Tumours of the central nervous system studied by computed tomography and ultrasound. Radiology 1985; 154: 393-399. 26. Firsching, R., Klug, N., Boner, U., Sanker, P.: Lesions of the sensorimotor region: somatosensory evoked potentials and ultrasound guided surgery. Acta Neurochir. (Wien) 1992; 118: 87-90. 27. Oado, M., Hanaway, J., Frank, R.: Functiona1 anatomy of the cerebral cortex by computed tomography. l Comput. Assist. Tomogr. 1979; 3: 1-19. 28. Oirvin, J.P.: Neurosurgica1 considerations and general methods for craniotomy under local anaesthesia. Int. Anaesthesiol. Clinj. 1986; 24: 89-114. 29. Girvin, J.P.: Resection of intracranial lesions under local anaesthesia. Int. Anaesthesiol. Clinj. 1986; 24: 133-135. 30. Oregorie, E.M., Goldring, S.: Localization of function in the excision of lesions from the sesorimotor region. J. Neurosurg. 1984; 61: 1.047-1.054. 31. Goldring, S.: A method for surgical management of focal epilepsy, specia11y as it relates to children. J. Neurosurg. 1978; 49: 344-356. 32. Goldring, S., Oregorie, E.: Surgical management of epilepsy using recordings to localize the seizure focus. Review of 100 cases. J. Neurosurg. 1984; 60: 457-466. 33. Jackson, G.D., Connelly, A., Oadian, D.O., Kumar, V.J., Harkness, W.F.J.: Epilepsy and tumors near the motor cortex: Preoperative identification of the motor strip using functional MRI. Epilepsia (SupplO 1993; 34: 120. 34. Kido, D.K., LeMay, M., Levason, A.W., Benson, W.E.: Computed tomographic localization of the precentral sulcus. Radiology 1980; 135: 373-377. 35. King, R.B., Schell, O.R.: Cortical localization and cortical monitoring during cerebral operations. J. Neurosurg. 1987; 67: 210-219. 36. Kitahara, M.: Clinical analysis of glioma: low grade astrocytoma. En Suzuki, J.L, ed. Treatment of glima. Berlin; Springer-Verlag 1988; 173-186. 37. Knopmann, D.S., Rubens, A.B.: The validity of computed tomography scan findings for the localization of cerebral functions. The re1ationship between computed tomography and hemiparesis. Arch. Neurol. 1986; 43: 328-332. 38. Laws, E., Wi11iam, F.T., Mm'vin, B.C., Okazaki, H.: Neurosurgica1 management of low-grade astrocytomas of the cerebral hemisphere. J. Neurosurg. 1984; 61: 665-673. 39. Le Roux, P.D., Berger, M.S., Hag1und, M.M ., Pich1er, W.H., Ojemann, O.A.: Resection of intrinsic tumors from 102
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nondominant face motor cortex using stimulation mapping: report of two cases. Surg. Neurol. 1991 ;36: 44-48. 40. Lueders, H., Lesser, R.P., Hahn, J., Dinner, D.S., K1em, O.: Cortical somatosensory evoked potentia1s in response to hand stimulation. J. Neurosurg. 1983; 58: 885-894. 41. Matsui, T., Hirano, A: An atlas of the human brain for computerized tomography. Tokyo; Igaku-Shoin 1978; 4252. 42. McCormack, B.M., Miller, D.C, Budzilovich, O.N., Voorhees, 0.1., Ransohoff, J.: Treatment and surviva1 of 10w-grade astrocytoma in adults 1977-1988. Neurosurgery 1992; 31: 636-642. 43. Obana, W.O., Laxer, K.D., Cogen, P.H., Wa1ker, J.A., Davis, R.L., Barbaro, N.M.: Resection of dominant opercu1ar gliosis in refractory partial epilepsy. J. Neurosurg. 1992; 77: 632-639. 44. Ojemann, O.A.: Individual variability in cortica11oca1ization oflanguage. l Neurosurg. 1979; 50: 164-169. 45. Ojemann, O.A, Dodri11, e.B.: Verbal memory deficits after temporal lobectomy for epilepsy. Mechanism and intraoperative prediction. J. Neurosurg. 1985; 62: 101-117. 46. Ojemann, O.A, Ojemann, J., Lettich, E., Berger, M.: Cortica110calization in 1eft, dominant hemisphere. An e1ectrical stimu1ation mapping investigation in 117 patients. J. Neurosurg. 1989; 71: 316-326. 47. Penfie1d, W., Pasquet, A.: Combined regional and general anaesthesia for craniotomy and cortical exploration. Anaesth. Ana1g. 1954; 33: 145-164. 48. Philippon, J.H., Clemenceau, S.H., Fauchon, FH., Foncin, J.F: Supratentoria110w-grade astrocytomas in adults. Neurosurgery 1993; 32: 554-559. 49. Rostomily, R.e., Berger, M.S., Ojemann, O.A., Lettich, E.: Postoperative deficits and functional recovery fo11owing remova1 of tumors involving the dominant hemisphere supp1ementary motor area. l Neurosurg. 1991; 75: 62-68. 50. Rowland, L.P., Mett1er, FA.: Relation between the coronal suture and the cerebrum. l Comp. Neurol. 1948; 89: 21-40. 51. Steiger, H.J., Markwalder, KV., Seiler, R.W., Ebeling, u., Reulen, H.J.: Early prognosis of supratentoria1 grade 2 astrocytomas in adult patients after resection or stereotactic biopsy. Acta Neurochir. (Wien) 1990; 106: 99-105. 52. Suzuki, A., Yasui, N.: Intraoperative 10calization of the central sulcus by cortical somatosensory evoked potentials in brain tumor. J. Neurosurg. 1992; 76: 867-870. 53. van Velthoven, V., Auer, L.M.: Practica1 application of intraoperative ultrasound imaging. Acta Neurochir. (Wien) 1990; 105: 5-13. 54. Walsh, A.R., Schmidt, R.H., Marsh, H.T.: Cortical mapping and local anaesthetic resection as an aid to surgery of Jwo and intermediate grade gliomas. Br. l Neurosurg. 1992; 6: 119-124. 55. Weingart, l, Olivi, A., Brem, H.: Supratentoriallowgrade astrocytomas in adults. Neurosurgery Quarterly 1991; 1: 141-151.
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within ar adjacent to eloquent areas
56. Wood, C.C., Spencer, D.D., Allison, T., McCarthy, G., Williamson, P.D., Goff, W.R.: Localization of human sensorimotor cortex during surgery by cortical surface recording of somatosensory evoked potentials. J. Neurosurg. 1988; 68: 99-111. 57. Wüllenweber, R., Kuhlendahl, H., Miltz, H.: Astrocytomas of the cerebral hemispheres. En Kuhlendahl H.K., Hensell V., eds. Modern aspects of neurosurgery, vol. 3. Amsterdam; Excerpta Medica 1973; 100-107. 58. Yasargil, M.G., Cravens, G.P., Roth, P.: Surgical approaches to «inaccessible» brain tumors. Clin. Neurosurg. 1988; 34: 42-111.
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59. Yasargi1, M.G., von Ammon, K., Cavazos, E., Doczi, T., Reeves, J.D., Roth, P.: Tumours of the limbic and paralimbic systems. Acta Neurochir. (Wien) 1992; 118: 40-52.
Vanaclocha, V.; Sáiz-Sapena, N.; Monedero, P.: Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas. Neurocirugía 1997; 8: 95-103.
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V. Vanaclocha; N. Sáiz-Sapena y P. Monedero. Servicio de Neurocirugía, Servicio de Anestesiología y Reanimación. Clínica Universitaria, Universidad de Navarra. Pamplona, Navarra.
Resumen Los gliomas supratentoriales de bajo grado deben ser sometidos a exéresis completa. Cuando estas lesiones asientan en áreas elocuentes su extirpación puede resultar problemática debido a la posibilidad de inducir secuelas neurológicas. Si el procedimiento se practica bajo anestesia general la resección es frecuentemente subtotal. Intentando aumentar la radicalidad de la exéresis nuestro grupo la ha practicado bajo anestesia local, controlando intraoperatoriamente las funciones neurológicas en peligro. Diecisiete casos de gliomas de bajo grado fueron extirpados bajo anestesia local y sedación ligera. La exéresis quirúrgica fue completa en 15/17 y subtotal en 2/17. Postoperatoriamente sólo un pacienete presentó una hemiparesia ligera y dos más una disfasia motora transitoria. Concluimos diciendo que la craniotomÍa bajo anestesia local permite la extirpación, la mayor parte de las veces completa, de lesiones en áreas elocuentes del cerebro. PALABRAS CLAVE: CraniotomÍa. Anestesia local. Sedación.
Summary Low grade supratentorial gliomas should be removed radically. When they lay in eloquent areas its removal can be problematic due to the possibility of inducing neurological sequelae. If the procedure is performed under general anaesthesia the resection is often subtotal. Attempting to increase the radicality these cases were performed under local anaesthesia, controlling intraoperatively the endangered neurological functions. Seventeen cases of low grade gliomas were removed under local anaesthesia and light sedation. Surgical removal was complete in 15/17 cases and subtotal in 2/17. Postoperatively one patient had a slight hemiparesis and two more a transient motor duysphasia.
We conclude saying that craniotomy under local anaesthesia allows the removal, most of the times complete, of lesions in eloquent brain areas. KEY WüRDS: Craniotomy. Local anaesthesia. Sedation.
Introduction Before the Second World War all the craniotomies were performed under local anaesthesia. Cushing l3 and Dandt 4 went on using local anaesthesia for so long as the risks of ether and chloroform were frightening. Its use declined with the advent of the modern neuroanaesthesia and in the last thirty years it has been used for the surgical treatment of epilepsy resistant to anticonvulsant medication 3.'8.'9.31.43.47, and in some cases of removal of cerebral arterio-venous malformations laying close to eloquent brain areas 'O • Meanwhile, its application to the surgical removal of intrinsic brain tumours has been recommended more recentlt· '8 .23 • About one third of all the newly diagnosed brain tumours are so-called low grade gliomas (WHü Grades 1 and Ir)". It has been shown that any well delineated low grade glioma should be removed radically to offer the best chance of cure, to prevent tumour progression and to increase the recurrence-free-interval, as subtotal removal does not increase the progression free interval 12.'4.38.4'.48.51.55. Recurrences, even after radical removal, usually progress to malignant glioma, but the frequency of progressions is much lower after radical resection than after partial removaIS'. The possibility of inducing iatrogenic neurologic sequelae is a serious concern l8 , specially when these tumours are localised adjacent to or in eloquent brain areas 5.8.'4.38.39.54. Many of this latter tumours are considered inoperable by most surgeons and handled with stereotactic biopsy, followed by radiotherapy or no further treatment at all'".39. Unfortunately addition of radiotherapy to partial removal has been associated with an unfavourable outcome due to a much higher incidence of recurrences and early malignizations comparing with radical removal and no radiotherapyI.36.38.51.57', 95
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
The exact location of the tumour and its relationships to the nearby eloquent cortex are often depicted accurately on preoperative CT'·15.1ó.'7.J4.37Al and magnetic resonance imaging (MRI) studiesÓ.19.33, and can be of great help in surgical planning ,ó .5o . Unfortunately that is not enough as the normal structures are usually displaced and intraoperatively it can be difficult to distinguish them properly. In such cases, intraoperatively the central sulcus (sensorimotor cortex) can be localised by somatosensory evoked potentials'óA0.5,5ó, but that is of no help when the tumour is close to other areas not related with the motor strip (i.e. speech-related areas of Wernicke, Broca and gyrus angularis, as well as in sorne of the more significant connecting pathways like the arcuate fascicle, the visual pathways, etc.). In all this cases intraoperative mapping of the endangered nearby brain can be successfully achieved by cortical electrical stimulation7-9.1s .,o.2'.JOJ'.J5Aó.54. Intraoperative ultrasound sonography has been used in Neurosurgery for years and proved helpful to better localise and delineate the lesions to be removed'·lI.5J, but is of little help to define the exact anatomy of the nearby brain. As general anaesthesia allows a better control of any intraoperative event, both the surgeon and the anaesthesiologist prefer it as the patient' s airway and ventilation is better controlled. Unfortunately this modality of anaesthesia does not allow intraoperative control of any iatrogenic neurologic sequelae and both the surgeon and the patient know too late what has already happened. This usually leads to more conservative resections for fear of inducing neurological sequelae. This could be avoided by the intraoperative mapping of the endangered brain areas by means of electrical stimulation but the patient must be fully awake and cooperative'9. In order to achieve that the same procedure can be performed under local anaesthesia, allowing wider resections with good functional results 5.9A9.54. Operations in awake patients also offer the advantage of being able to «monitor» the functions by continuous clinical examinations of the contralaterallimbs and facial muscles and speech during the whole procedure, minimizing the risk of postoperative neurological deficits D "A7.". Thus the procedure can be anested when needed.
Patients and methods Our series includes seventeen patients (six females and eleven males) with brain tumours, that were removed under local anaesthesia and sedation, in a period of four years (January 1991 to December 1994). Each patient harboured only one lesiono During the same period a total of 127 craniotomies for brain gliomas were performed under general anaesthesia. The average age was 55.7 years. The two youngest patients were 25 and 28 years old, and had respectively a
26
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grade 1 and a grade II astrocytoma removed. The oldest patient was 70 years old and harboured a grade III astrocytoma. Tumours location was in the right hemisphere in five cases and in the left in twelve: 8/17 (47 %) in motor and 9/17 (53%) in speech related areas (2/17 -11.7%- in the hand motor area, 5117 -29.4%- in the arm motor area, 5117 -29.4%- in the area of Broca, 1117 -5.8%- left parietal -gyrus angularis-, 3/17 -17.6%- in the area of Wernicke and 1117 -5.8%- in the motor area of the lower limb). Preoperatively those lesions in or near Broca' s area (5/17,29.4%) underwent a dichotic hearing test and an intracarotid amobarbital test, in order to ascertain whether or not the speech function had been transfened to the other hemisphere. Unfortunately, in none of our cases had speech been transferred to the right hemisphere. The patients were kept nil per mouth since 8 hours prior to the surgical procedure. No premedication was prescribed. The surgical table was specially cuffed and had a good foamed headrest as in the awake patient the tolerance to the technique depends to a great extent on his or her comfortability's.'9. That was very important as the patient had to remain quiet and relaxed in a fixed position and warn the surgeon every time a slight change in position was needed. The surgical drapes were placed so that the patient had the maximum angle of vision, to avoid a claustrophobic feeling and allowing an excellent communication with the surgical-anaesthetic team. This was achieved by means of the Ganet table (Codman), placed over the surgical table, so that the whole patient remained undraped except the head. Moreover a big sterile adhesive plastic drape covering all the surgical field was used, allowing the patient to see light through it. The anaesthesiologist not only had an adequate access to the patient's airway, but also could see him and talk with him during the whole surgical procedure. The conversations between the staff in the operating room were discrete and limited to professional matters, avoiding that the patient had any feelings of rejection or lack of interest. At the entrance of the operating room there was a writing saying: «Silence please, patient awake». During the procedure the surgeon and the anaesthesiologist talked continuously to the patient, explaining each step, and specially each new sound (scratching of the periosteum, use of the craniotome if needed, Gigli saw, cureting of bone, etc.). The instruments with striking sounds, as the craniotome, induced apprehension in sorne patients. In such event hand powered instruments were used. The local anaesthetic agent used was Bupivacaine 0.25%, in account of its long duration of action (8-12
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
hours), special1y when combined with a vasoconstrictor agent. In most cases the operative procedure lasted 2-4 hours. Lidocaine 1% was added to achieve immediate anaesthesia and to reduce the initial discomfort as the Bupivacaine needs sorne minutes to induce anaesthesia. As vawconstrictor agent Ornipressine (8-ornithine-vasopressin, POR 8® Sandoz, V VI/mI), which is less toxic and more effective than Adrenaline was used. It induces local vasoconstriction in 10 minutes, that lasts at least 1-2 hours. The recommended dose is 1 UI for each 10 mI of local anaesthetic solution, not surpassing the 5 UI (one ampoule of POR 8® for 50 mI of local anaesthetic solution). Sedation was induced by the administration of 2-3 mg of Midazolam every 30-60 minutes, supplemented when necessary with Fentanyl 0.05 mg every 30 minutes. The doses were individual1y adjusted by the anaesthesiologist through the continuous evaluation of the state of consciousness and comfort of the patient. For the surgical incision a mixture of equal parts of Lidocaine 1% and Bupivacaine 0.25% to a total amount of 50 mI was used. To this were added 5 VI Ornipressine (1 UI/1 Oml local anaesthetic solution) and 0.2 mI of sodium bicarbonate 8.4% (to reduce the burning sensation). The injection was performed in the subcutaneous and subgaleal spaces. In pterional craniotomies another 10015 mI of local anaesthetic mixture were injected in the depth of the temporalis muscle. The injection of local anaesthetic mixture in the scalp was the most painful part of the procedure. The patient was forewarned of each prick that was to be given as wel1 as of the impending burning feeling induced by each infiltration. For this injections 25-G 5/8 (0.5x16mm) single use needle non-pyrogenic and a 20 mI syringe were used. Elevating the bone t1ap usually induces some local discomfort due to traction on the underlying dura, rather than to sensitivity to bone. This was reduced by pouring some Lidocaine 1% on the epidural space through the burr-holes. A mixture of equal parts of Lidocaine 1% and Bupivacaine 0.25% was used to achieve a rapid anaesthesia and long duration of the dura mater. A swab soaked in 5 to 10 mI of anaesthetic mixture was applied to the exposed dura. In those cases when the dura showed lacerations no anaesthetic agent was used in order to avoid inducing epileptic seizures. In these cases the anaesthesia was supplemented by administering small doses of Fentanyl, as described earlier. Once the bone t1ap had been elevated and the dura anaesthetised, the rest of the surgical procedure was virtuaHy painless. The maximum amount of local anaesthetic used never exceeded the maximum recommended dose for infiltration, i.e. 175 mg Bupivacaine (70 mI Bupivacaine 0.25%) and 300 mg Lidocaine (30 mI Lidocaine 1%).
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Pain due to manipulation of the insula orstretching of the cranial base vessels was controlled with small doses of i.v. Fentanyl when required. After opening the dura, in those cases that involved the motor strip, somatosensory evoked potentials (SEP) (Med.e1x, Sensor, London, England) were recorded simultaneously from 4 cortical surface electrodes each placed 10 mm apart distributed perpendicular across the central sulcus following the technique published by others 26 • To map the areas to be removed and the adjacent cortex, stimulation with a contacting bipolar electrode of 2 mm in diameter (IBAAB, Stockholm, Sweden), with a frequency of 25-50 Hz at an intensity between 10 and 20 mA and a duration of 5 to 10 milliseconds was utilised. A stimulus of low intensity which was increased slowly until response was achieved was used as a routine. The sensorimotor cortex was identified, if motor or sensory phenomena were proven by observer or indicated by the patierit. The motor speech area was stimulated until a speech arrest could be elicited following the technique widely described in the literature 44 -46 • In the vast majority of cases (12/17, 70.5 %) the lesion was identified by its macroscopic appearance at the cortical surface. In aH the cases intraoperative ultrasound sonography (Acuson XP/lO, Mountain View, California, USA) was performed to better delineate the lesiono In lesions appearing at the cortical surface the excision was started at the visible tumour. Ultrasound sonography was specially helpful to localise the five cases with tumours not coming out to the cortical surface, helping to decide the trajectory to be used to minimise brain damage. The cortical incision was always kept as small as possible, as al1 the cortex has impotant functions. In order to avoid manipulation of the brain, the tumour was vaporised with the aid of a defocused beam 50Watts C02 laser (Sharplan Industries, Tel Aviv, Israel). The cavity was irrigated copiously to avoid charring and local heating. Tumour removal commenced with slowly coring out of the centre. Meanwhile the anaesthesiologist maintained a continuos conversation with the patient and gave simple commands to monitor the functions of the exposed area (i.e. «raise your arm», «close your hand», and so on). As soon as any sign of neurological deficit appeared, no matter how minimal, surgery was immediately stopped. The whole area was revised and ultrasound sonography performed to study the amount and exact localisation of the remaining tumour. Often the resection could continue safely at another comer of the tumour. Intraoperative histological examination of the borders of the resection was performed in order to know if the resection was complete or only partial and when the resection had to continue or could be stopped. The average duration of the surgicaI procedures was 170 mino (range 120-210 min).
97
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
Figure 1.- Preoperative MR image of a low grade glioma (G) in the insula under Broca 's area. The arrows point to the sylvianfissure. The arrow head points to the middle cerebral artery. Postoperatively the degree of tumour resection was evaluated by serial MRI studies, performed at 1 month and 3 months after surgery and then at every 6 months. Results Surgical resection under local anaesthesia with sedation, aHowed complete removal of the lesion in 15/17 (88.2%) of the cases, with per-operative preservation of the neurological functions of the areas involved in the surgical procedure (Figures 1 and 2). In the remaining 2/17 (11.8%) cases the resection was subtotal, as the procedure had to be terminated when signs of neurological deficits were detected, in both cases when most of the lesion had already been removed (Figures 3a, 3b and 4a, 4b). None of the deficits remained in any of these patients for longer than a few hours after the surgical procedure was terminated. The removed tumours were aH glial in nature: 8 astrocytomas grade 1; 6 grade II and 3 grade IlI. The grade III astrocytomas showed preoperative magnetic resonance imaging features characteristic of low grade gliomas, but pathological studies showed sorne areas of malignant change which necessitated classification as grade IlI. In 14/17 (82.3%) cases no iatrogenic neurological deficits were added (including the two in which the surgical procedure had to be stopped as the first neurological deficits appeared, but immediately recovered). In the remai98
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Figure 2.- Postoperative MR image of the patient fr0111 the figure 1 showing the extent of the tumour removal with no neurological deficits. Note the inverted image due to different MR scanner. The small black arrows point to the internal capsule and the big white arrow to the remains of the globus pallidus. ning 3/17 (17.7%) no deficits existed initiaHy, but 24-48 hours after the surgical procedure a deterioration of the neurological functions of the operated area was detected (mild hemiparesis in a case and motor dysphasia in two). AH of them recovered completely under treatment with corticosteroids, and regained their preoperative functional level in a week. None of our patients had intraoperative epileptic seizures, haemorrhages or needed urgent intubation. Discussion With the advent of CT and MR imaging techniques non-invasive preoperative identification of brain anatomy became possible2.6.ls.21.27.3J.J4A1.5o. In spite of aH, accurate preoperative localisation of eloquent brain areas is not always possible, speciaHy when the normal anatomy is distorted by a space occupying lesion,s.lw.J7. A decision that tumours located in or close to these areas are inoperable based alone on preoperative neuroimaging may be misleading 58 .59 . In fact many of the cases of our series (11/17, 64.7%) were referred from other hospitals elsewhere diagnosed as inoperable. Operability of lesions in the dominant frontal operculum is also dependant on whether or not speech function has been transferred to the other hemisphere. That can be
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
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Figures 3a and 3b.- Preoperative MR images of a low grade gUoma (G) lying close to the gyrus angularis. The patient was a 24 year old singer who wanted the tUl110ur removed but wished to keep singing. The arrows point to the sylvian fissure. ascertained preoperatively with the intracaratid amobarbital testlO and/or with the dichotic hearing test. In any case the fact the speech function is not transferred to the contralateral hemisphere should not prevent us fram attempting to remove the lesion as it was done in our 5/17 (29.4%) cases. Intraoperative electrical stimulation allows identification of the exact anatomical relationships between the lesion and its surrounding brain areas5.7.9.18.30.46, but it is the continuous intraoperative clinical monitoring which helps to avoid iatragenically induced neuralogical deficits by stopping the resection just on time24.29.54. The pracedure is very helpful but has to be carried out in awake, co-operative patients 56 . Local anaesthesia offers the advantage of allowing intraoperative electraphysiological testing to perform a more reliable identification of eloquent brain areas as well as monitoring of the endangered functions, and thus many surgeons prefer it if radical resection is considered3.2429.54. The additional ultrasound guidance to the lesion allows the surgeon to determine the least hazardous transcortical approach 26 . Glial neoplasms usually have an irregular geometric configuration being difficult to stay oriented within these irregula extension even if sophisticated computer systems are available. One has to consider that what is being operated is not a piece of wood or a frozen brain. That means that just the craniotomy induces distortions on the real anatomy and with progressive tumour removal the brain sinks in the cavity making that the stored image obtained preoperatively, available fram the computer, is a false
illusion that can lead to mistakes when every millimetre matters. We have found that we can not rely only on this frozen images obtained preoperatively and perform the pracedure under general anaesthesia. Sorne authors suggest the intraoperative use of ultrasound for the delineation of the tumour margins 4.11.25.26, although others repot that the results concerning differentiation between tumour margins and oedema, specially in low grade gliomas, are disappointing 53 . We have found useful the ultrasound to delineate the lesion at the beginning of the surgical pracedure but once the resection has progressed it is increasingly more difficult to differentiate between tumour margin and abnormal brain induced by the surgical manipulation. That was partially reduced by vaporising the tumour with a defocused C02 laser beam, avoiding mechanical handling and haemorrhage. A clear cut margin between tumour and normal brain is not always easy to define due to the infiltrating nature of sorne of these low grade gliomas. One has to rely in changes in colour and consistency, but that often fails. Intraoperative histological examination of the borders of the resection can be performed, allowing stepwise adaptation of the resection according to the histological results 24 . The pracedure is of help at least to know if sorne disease is left behind. In any case the surgical removal has to be stopped once any neurological deficit appears with disregard of how much tumour is left behind. We have found that more tumour can be removed fram other areas of the surgical field but not fram the one that has already indüced a neurological deficit, no matter how slight. 99
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
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Figures 4a and 4b.- Postoperative MR image ofthe patientfromfigure 3a and 3b. The lesion has been removed subtotally as the patient developed slurred speech during the procedure. She keeps singing with no further problems and is follow-up regularly. The arrows point to the sylvianfissure. Cavity left after subtotal removal of the lesion (C). Craniotomy under local anaesthesia with sedation has been recommended whenever there is a need for intraoperative control of the functions of the brain areas to be operated on 3.24 ,47. These tumours usually displace cortical functional areas without destroying themI6.IS.2S.27.34.3S.37 and performing the surgical procedure under local anaesthesia, allows a wider resection. Only superficial lesions should be removed under local anaesthesia54 . The surgical approach to deep areas, although possible, can be cumbersome and problematic3.28·29. The surgical procedure should not last too long, since maintaining the same posture for long periods of time can be quite difficult and very unpleasant for the patient. The intraoperative risks of haemorrhage, intracranial hypertension, epileptic seizures and respiratory arrest have to be thoroughly evaluated3.28.29.54. Local anaesthesia is not recommended for procedures that could be performed under general anaesthesia with no special risk of inducing neurological deficits1.7.S.2S.2954. Mild intraoperative deficits have been seen to improve postoperativey not only in our series but also in those of others 49 . The ideal is to stop the resection just once the deficit is starting, but that requires a thorough intraoperative clinical monitoring 3.S4 . In order to achieve that the patient has to be relaxed and co-operative, with full confidence on the surgical-anaesthetic team3.2S.29.54. The patient had to be thoroughly informed of the whole procedure, and most important is the psychological preparation for the procedure. What the patient will hear and see must be carefully controlled. The patient physical comfort is also a most important point. Maintaining one position during the whole 100
procedure must be made as easy as possible. Pain is what scares the patient most, so that good local anaesthesia is essential. The skin and the dura have nociceptors, but not the bone and the brain also lacks any sensitivity. Manipulation of the main vessels at the base and in the insula can induce pain or soreness. As the dura is only anaesthetised in the area of the surgicalfield, the intracranial remains sensitive as can be irritated by touching it with cotonoids, which may induce pain. Copious irrigation of the surgical field can induce a diffuse poorly localised pain, sometimes associated with a vegetative component (nausea and even vomiting). All this effects can be controlled by the anaesthesiologist using Midazolam and Fentanyl, according to demando Potential risks to be considered for the craniotomies under local anaesthesia with or without sedation, are epileptic seizures, intracranial hypertension (tumoral in origin but facilitated by the hypoventilation and the recumbent position, haemorrhages 2S.29 , a significant reduction in the level of consciousness, marked hypoventilation and secondary or toxic effects of the local anaesthetic or vasoconstrictor agents used 3 • We have always been very concerned about the possibility of epileptic seizures, and that is why a good venous access and an anaesthesiologist are essential. In the case of such an event Diazepam 5mgrs IV under slow perfusion is usually enough to control the crisis, as we have seen in sorne cases of stereotactic biopsy under local anaesthesia (not included in this series). In the craniotomies under local anaesthesia we did not need to use Diazepam as no epileptic seizures happened, but had
Craniotomy under local anaesthesia and sedation for the removal of brain tumours within or adjacent to eloquent areas
such event happened we were prepared to stop the procedure until the epileptic seizure had been controlled and the patient was fully awake again. In conclusion, craniotomy under local anaesthesia is a technique to be considered in the surgical removal of tumours located in eloquent areas of the brain, as it often allows the total removal of lesions in these areas, which otherwise could not be removed so radically under general anaesthesia without having to accept a high risk of important neurological sequelae5.9.3o'32. We like the patient to be fully awake during the whole surgical procedure. Others seem to prefer to keep the patient fully anaesthetised becoming awake and co-operative only to perform electrical corticalstimulation of the sensori-motor cortex, speech areas and tumour surface'·9.18.22.24.35.39.43.46.4'. We do not like it as patients do not seem to recover consciousness so fully when awaken from a general anaesthesia nor when they have had too much medication in order to keep them under deep sedation or under intravenous anaesthesia. The patient needs to be fully awake in order to co-operate fully during the tumour resection to allow clinical testing of the endangered brain functions. To perform this technique excellent co-operation and understanding between the surgical and the anaesthetic teams is needed, in order to reduce the discomfort of the patient to a minimum. The patient's cooperation can thus be facilitated so that the functions of the brain areas being threatened can be monitored accurately.
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