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Autotomography with metrizamide myelography: An aid to visualisation of the cranio-cervical junction and cerebellar tonsils
ClinicaIRadiologY (1983) 34, 401-403 © 1983 Royal College of Radiologists
0009-9260/83/01330401502.00
Autotomography With Metrizamide Myelography: An Aid to Visualisation of the Cranio-cervical Junction and Cerebellar Tonsils TERENCE DOYLE and BRIAN TRESS
Department of Radiology, The Royal Melbourne Hospital, Grattan Street, Melbourne 3050, Australia A simple method for improved visualisation of the structures at the foramen magnum and upper cervical spine during supine metrizamide myelography by using autotomography is described. Ten patients have been examined by this technique and the relevant structures have been clearly outlined in every case. It is concluded that the significance of side-effects with this technique is not great when compared with the important information obtained. Techniques for routine cervical metrizamide myelography have been well described elsewhere (Sackett, 1978). With the patient prone, the contrast medium tends to layer ventrally and the dorsal part of the cranio-vertebral junction is poorly visualised (Fig. 1). Supine cervical metrizamide myelography has not previously been recommended except as a prelude to a thoracic study (Gabrielsen et al., 1980). Several authors have used tomography to improve visualisation of the cervical and thoracic regions because of poor opacification during prone myelography (Skalpe and Amundsen, 1975). However, lateral tomographic facilities are, often, not available in the fluoroscopic room and movement of the patient will result in
Fig. 1 - Routine prone, horizontal-beam lateral film of the cranio-eervical junction during metrizamide myelography. There is inadequate visualisation of the dorsal subarachnoid space at the head of the foramen magnum.
further dilution of the contrast medium. Autotomography, a technique which improves visualisation of midline structures in the lateral projection, requires only a standard, horizontally mounted X-ray tube (Ziedes des Nantes, 1950). This study was performed to evaluate autotomography in supine metrizamide myelography. METHOD A routine lumbar puncture is performed with a 22 gauge needle. This is preferable to a lateral C1-C2 puncture if there is clinical suspicion of cerebellar tonsillar herniation or other foramen magnum mass. With the patient prone, the neck well extended and the head of the fluoroscopic table down 15 °, 10 ml of 290 mg/ml metrizamide are instilled. This will be seen to collect in the cervical lordosis. Routine frontal and lateral prone films are taken. The patient is then turned supine, with great care to minimise contrast medium dilution, in the following manner. With the operator supporting the patient's head prone, assistants turn the trunk on one side. The operator then turns the head smoothly to a supine position (i.e. through 180 °) as the assistants turn the trunk supine. The table remains 15 ° head down. With the head flexed, a cross-table lateral film is taken (Fig. 2). This alone may be adequate to visualise the posterior aspect of the subarachnoid space at the foramen magnum but, if the contrast medium is too dilute, autotomography will salvage the situation. Autotomography is achieved by having the patient gently rotate the head from side to side, 15 ° on either side of midline, while a 3 s lateral exposure is made. Suitable radiographic factors for use with a grid and rare earth screens are 55 kV, 25 mA, 3s.
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Fig. 2 - Supine, horizontal-beam lateral film of the upper cervical region, showing better visualisation of the dorsal subarachnoid space.
Fig. 3 - Supine, horizontal-beam lateralautotomogram of the cranio-cervical junction. There is now improved definition of the structures around the foramen magnum and of the cerebellar tonsils.
RESULTS
include post-procedure headache, but Pantopaque myelography is also associated with headache in over 30% of patients (Kieffer et al., 1978). An increased incidence of temporary cortical EEG abnormalities may be expected and epileptics or patients on drugs lowering the 'fitting' threshold should not be subjected to this procedure. The significance of these side-effects is not great when compared with the possible consequences o f Pantopaque spill into the cranial subarachnoid spaces.
Ten patients have been examined in this manner to date. The cervical cord, medulla, fourth ventricle, subarachnoid space at the level o f the cerebellar tonsils and posterior aspect o f the foramen magnum have all been clearly outlined b y autotornography in every case (Fig. 3). All 10 patients suffered mild ~o moderate headache and two patients suffered 24 h episodes of confusion.
DISCUSSION The clinical diagnosis of lesions in the foramen magnum, such as meningioma or cerebellar tonsillar herniation, is notoriously difficult. Equally, the posterior aspect of the subarachnoid space at the level of the foramen magnum is a blind area when using conventional metrizamide myelography. Complications of supine cervical metrizamide myelography
Acknowledgement. We wish to record our debt to Dr Ivan Moseley who first sowed the seed of an idea for this study and we gratefully express our thanks to him.
REFERENCES Gabrielsen, T. O., Seeger, J. F., Knake, J. E., Burke, D. P. & Stilwill, E. W. (1980). C1-2 puncture with the patient supine for thoracic metrizamide myelography. Radiology, 136, 229-230.
A U T O T O M O G R A P H Y WITH M E T R I Z A M I D E M Y E L O G R A P H Y Kieffer, S. A., Binet, E. F., Esquerra, J. V., Hantman, R. P. & Gross, C. E. (1978). Contrast agents for myelography: clinical and radiological evaluation of Amipaque and Pantopaque. Radiology, 129, 695-705. Sackett, J. F. (1978). Cervical and lumbar routes for metrizamide cervical examination. Neuroradiology, 16, 273-274.
403
Skalpe, I. O. & Amundsen, P. (1975). Thoracic and cervical myelography with metrizamide. Radiology, 116, 1 0 1 106. Ziedes des Plantes, B. G. (1950). Examen du troisi~me et du quatri~me ventricule au moyen de petites quantit6s d'air. Acta Radiologica, 34, 399-407.
0009-9260/83/01330401502.00
Autotomography With Metrizamide Myelography: An Aid to Visualisation of the Cranio-cervical Junction and Cerebellar Tonsils TERENCE DOYLE and BRIAN TRESS
Department of Radiology, The Royal Melbourne Hospital, Grattan Street, Melbourne 3050, Australia A simple method for improved visualisation of the structures at the foramen magnum and upper cervical spine during supine metrizamide myelography by using autotomography is described. Ten patients have been examined by this technique and the relevant structures have been clearly outlined in every case. It is concluded that the significance of side-effects with this technique is not great when compared with the important information obtained. Techniques for routine cervical metrizamide myelography have been well described elsewhere (Sackett, 1978). With the patient prone, the contrast medium tends to layer ventrally and the dorsal part of the cranio-vertebral junction is poorly visualised (Fig. 1). Supine cervical metrizamide myelography has not previously been recommended except as a prelude to a thoracic study (Gabrielsen et al., 1980). Several authors have used tomography to improve visualisation of the cervical and thoracic regions because of poor opacification during prone myelography (Skalpe and Amundsen, 1975). However, lateral tomographic facilities are, often, not available in the fluoroscopic room and movement of the patient will result in
Fig. 1 - Routine prone, horizontal-beam lateral film of the cranio-eervical junction during metrizamide myelography. There is inadequate visualisation of the dorsal subarachnoid space at the head of the foramen magnum.
further dilution of the contrast medium. Autotomography, a technique which improves visualisation of midline structures in the lateral projection, requires only a standard, horizontally mounted X-ray tube (Ziedes des Nantes, 1950). This study was performed to evaluate autotomography in supine metrizamide myelography. METHOD A routine lumbar puncture is performed with a 22 gauge needle. This is preferable to a lateral C1-C2 puncture if there is clinical suspicion of cerebellar tonsillar herniation or other foramen magnum mass. With the patient prone, the neck well extended and the head of the fluoroscopic table down 15 °, 10 ml of 290 mg/ml metrizamide are instilled. This will be seen to collect in the cervical lordosis. Routine frontal and lateral prone films are taken. The patient is then turned supine, with great care to minimise contrast medium dilution, in the following manner. With the operator supporting the patient's head prone, assistants turn the trunk on one side. The operator then turns the head smoothly to a supine position (i.e. through 180 °) as the assistants turn the trunk supine. The table remains 15 ° head down. With the head flexed, a cross-table lateral film is taken (Fig. 2). This alone may be adequate to visualise the posterior aspect of the subarachnoid space at the foramen magnum but, if the contrast medium is too dilute, autotomography will salvage the situation. Autotomography is achieved by having the patient gently rotate the head from side to side, 15 ° on either side of midline, while a 3 s lateral exposure is made. Suitable radiographic factors for use with a grid and rare earth screens are 55 kV, 25 mA, 3s.
402
CLINICAL RADIOLOGY v v
v
~
t
2
• v
v
~v
,
v
,"
:
Fig. 2 - Supine, horizontal-beam lateral film of the upper cervical region, showing better visualisation of the dorsal subarachnoid space.
Fig. 3 - Supine, horizontal-beam lateralautotomogram of the cranio-cervical junction. There is now improved definition of the structures around the foramen magnum and of the cerebellar tonsils.
RESULTS
include post-procedure headache, but Pantopaque myelography is also associated with headache in over 30% of patients (Kieffer et al., 1978). An increased incidence of temporary cortical EEG abnormalities may be expected and epileptics or patients on drugs lowering the 'fitting' threshold should not be subjected to this procedure. The significance of these side-effects is not great when compared with the possible consequences o f Pantopaque spill into the cranial subarachnoid spaces.
Ten patients have been examined in this manner to date. The cervical cord, medulla, fourth ventricle, subarachnoid space at the level o f the cerebellar tonsils and posterior aspect o f the foramen magnum have all been clearly outlined b y autotornography in every case (Fig. 3). All 10 patients suffered mild ~o moderate headache and two patients suffered 24 h episodes of confusion.
DISCUSSION The clinical diagnosis of lesions in the foramen magnum, such as meningioma or cerebellar tonsillar herniation, is notoriously difficult. Equally, the posterior aspect of the subarachnoid space at the level of the foramen magnum is a blind area when using conventional metrizamide myelography. Complications of supine cervical metrizamide myelography
Acknowledgement. We wish to record our debt to Dr Ivan Moseley who first sowed the seed of an idea for this study and we gratefully express our thanks to him.
REFERENCES Gabrielsen, T. O., Seeger, J. F., Knake, J. E., Burke, D. P. & Stilwill, E. W. (1980). C1-2 puncture with the patient supine for thoracic metrizamide myelography. Radiology, 136, 229-230.
A U T O T O M O G R A P H Y WITH M E T R I Z A M I D E M Y E L O G R A P H Y Kieffer, S. A., Binet, E. F., Esquerra, J. V., Hantman, R. P. & Gross, C. E. (1978). Contrast agents for myelography: clinical and radiological evaluation of Amipaque and Pantopaque. Radiology, 129, 695-705. Sackett, J. F. (1978). Cervical and lumbar routes for metrizamide cervical examination. Neuroradiology, 16, 273-274.
403
Skalpe, I. O. & Amundsen, P. (1975). Thoracic and cervical myelography with metrizamide. Radiology, 116, 1 0 1 106. Ziedes des Plantes, B. G. (1950). Examen du troisi~me et du quatri~me ventricule au moyen de petites quantit6s d'air. Acta Radiologica, 34, 399-407.