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Stereotactic Management of Brain Tumors
Review Article
STEREOTACTIC MANAGEMENT OF BRAIN TUMORS Shyam Sunder* and Rajendra Prasad ** *Associate Consultant,**Senior Consultant, Department of Neurosurgery, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi 110 076, India. Correspondence to:Dr. Rajendra.Prasad, 268/Sec15A. Noida 201301, India. e-mail:[email protected] Stereotactic and image-guided surgery has become increasingly important in the management of brain tumors. Although there are several stereotactic modalities that have been reported to be of value, it is the combination of techniques in a multimodality approach that seems to show the most promise. Both framebased and frameless guidance may facilitate tumor resection, allowing the optimal amount of resection while permitting avoidance of surrounding eloquent areas. Deep tumors may be localized and approached through a small burrhole, and surgical exposure may be minimized to protect uninvolved areas of the brain. There is increasing evidence that patients operated with imaging guidance have a more benign course and more rapid discharge, perhaps with a lower incidence of adverse neurological sequelae. Stereotactic conformal radiotherapy allows a higher tumor dose while sparing uninvolved brain from radiation more efficiently than conventional techniques, and residual tumor may be treated with a boost of stereotactic radiotherapy. Stereotactic instillation of radioisotopes may be used to treat cystic tumors. Stereotactic insertion of cannulae or radioisotope seeds permit efficient brachytherapy. Key words:Brain tumor, Stereotactic surgery,Image-guided surgery, Stereotactic radiosurgery
HISTORY THE earliest forms of stereotactic surgery in humans developed out of an apparatus that was designed by Victor Horsley and Henry Clarke in 1906 to study brain functions in monkeys. It was not until 1946, however, that two American researchers designed a stereotactic frame to guide brain surgery in humans. There were two difficulties in transferring a stereotactic system from other mammals to humans, however; one problem was the much greater degree of variation among humans in the location of various bony landmarks on the skull that were used to identify the approximate location of various parts of the brain. The other problem was the lack of a reliable imaging method for visualizing internal brain structures. By the 1940s, a method known as positive contrast ventriculography, in which some of the cerebral fluid in the ventricles of brain was withdrawn and replaced with air or another contrast medium that would show up on an X-ray, allowed surgeons to identify structures within the brain in relation to one another. Ventriculography made it possible to use such internal structures as the posterior commissure or pineal gland rather than various points on the outside of the skull as landmarks for brain surgery. Researchers compiled stereotactic atlases, or collections of photographs of crosssections of brain tissue, with reference grids around the Apollo Medicine, Vol. 5, No. 3, September 2008
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borders of each photograph. A surgeon could consult one of these atlas in order to calculate the exact location of a targeted brain structure with reference to the posterior commissure. Present-day stereotactic surgery still makes use of atlases, although they are now compiled from computer images rather than photographs [1]. DEFINITION Stereotactic surgery is an approach to tumor diagnosis and treatment that makes use of a system of threedimensional coordinates to locate a site as precisely as possible for biopsy or surgery. The English word stereotactic is a combination of a Greek root, stereo, which means “solid” or “having three dimensions,” and the Latin word tactus, which means “touch.” Stereotactic neurosurgery may make use of a conventional incision and burrhole to enter the patient’s skull or precisely focused beams of radiation to destroy tumor tissue. This second method, which is called stereotactic radiosurgery is not surgery in the usual sense of the word because no incision is involved [2]. INDICATION Stereotactic surgery may be performed either to obtain a tissue sample for biopsy or to remove or destroy the tumor itself. Stereotactic biopsies are the preferred method of
Review Article
confirming a diagnosis of a brain tumor, because of their precision and because they may offer the only method of obtaining a tissue sample if the tumor is located deep within the brain or close to structures that control vital functions especially brainstem tumor, pineal region tumors,thalamic gliomas, hypothalamic gliomas and hamartomas and tumors located near eloquent areas of brain such as speech areas and motor cortex. Stereotactic radiosurgery can be used to treat benign tumors such as acoustic neuromas, pituitary adenomas and meningiomas as well as malignant tumors of the brain or as a follow-up booster treatment for patients with recurrent tumors who have already received the maximum safe dose of conventional radiation therapy. Stereotactic radiosurgery with a gamma knife or X-Knife is most effective in treating relatively small tumors (an inch or less in diameter) with well-defined borders that have not invaded the brain; in addition, it is usually reserved for patients with a life expectancy of six months or longer. Large brain tumors may require debulking if not resectable by conventional open surgery prior to treatment with radiosurgery [3]. DESCRIPTION
carcinoma). He was evaluated with CT chest and abdomen which revealed primary in lung. He received whole brain radiation followed by booster radiation to brain stem lesion. This was followed by chemotherapy for the lesion in the lung. CASE 2 Forty years female presented with drowsiness, headache, weakness of left half of body of 2 weeks duration of grade-4/5. MRI brain (Fig.6) revealed thalamic lesion . He underwent MRI based stereotactic biopsy of the lesion. Histopathology revealed low grade glioma. Frameless stereotactic brain surgery In this method, images of the patient’s head from CT or MRI scans are uploaded into a computer for display on a monitor. Markers on the patient’s skin are registered by a probe linked to the computer by a (Fig.7) camera, which joins the position of the patient’s head on the operating table to the images on the computer monitor. In addition, the surgeon’s instruments contain light-emitting diodes (LEDs) that are tracked by the computer during the operation (Fig.8) [5].
Frame based Stereotactic Surgery CASE 3 The first frame that was used in stereotactic surgery in the 1940s consisted of a plaster cap fitted to the individual patient with a head ring and electrode carrier mounted to it. In the early 2000s, however, stereotactic surgery makes use of a base ring attached to the patient’s skull, and an arc (Fig.1) ring to guide the surgeon in drilling a hole through the skull. After the base ring is attached to the patient’s scalp, he or she is taken to CT room or MRI room where CRW frame is attached and then coordinates are (Fig.2) calculated. Patient is then shifted to the operating room, where the base ring is attached to the operating table in order to hold the patient’s head steady. The entry site for the surgeon’s drill is selected, and the entry site and area of the tumor are located on a phantom that relates these points to the patient’s head (Fig.3). An arc ring is then attached to the base ring to guide the surgeon’s movements.This stereotactic system allows the surgeon to (Fig.4) make only a very small incision in the scalp, and make a burrhole in order to insert a biopsy needle [4]. CASE 1 Forty-two years old male presented with progressive loss of memory, difficulty in swallowing , and weakness of both upper and lower limbs of two months duration. MRI brain with contrast done revealed (Fig.5) multiple intracerebral lesion. He underwent stereotactic biopsy of the lesion. Histopathology came as metastasis (adeno-
Sixty two years female presented to us with history of two episodes of generalized tonic clonic seizures. She had past history of carcinoma of left breast, operated two years back and received radiation and chemotherapy for the same. CT Scan brain done revealed a left frontal lesion with edema (Fig.9). She underwent stereotactic craniotomy and decompression of lesion. Histopathology report came as poorly differentiated adenocarcinoma, secondary from breast. She received radiation for the same. Stereotactic Radiosurgery and Radiotherapy Stereotactic radiosurgery can be performed with three different types of machines to provide the radiation used to kill the tumor cells. The gamma knife is a stationary unit that contains 201 sources of gamma rays derived from cobalt-60 that can be focused by a computer on a small area of the brain (Fig.10). The radiation can be directed very precisely to the tumor without destroying nearby healthy tissue. The patient lies on a couch with a large helmet attached to his or her head frame. The helmet contains holes that allow beams of radiation to enter. The couch is then slid into a gantry containing the cobalt-60. Treatment time varies from several minutes to over an hour, depending on the size, shape, and location of the tumor. Gamma knife radiosurgery is usually a single-dose treatment. X-Knife is a useful alternative tool.
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Fig.1. Base ring attached to patients head
Fig.2. CRW frame head ring
Fig.3. Target being confirmed on phantom ring
Fig.4. Burr hole through which biopsy will be taken
Fig.5.
MRI brain with contrast done revealed multiple intracerebral lesions.
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Fig.6.
206
MRI Brain-Thalamic lesion, underwent MRI based stereotaxy
Review Article
Fig.7. Registration of data with the markers
Fig.8.
Instruments contain light-emitting diodes (LEDs) that are tracked by the computer during the operation.
Fig.9. Left frontal lesion with edema
Fig.10. Stereotactic radiosurgery using gamma knife 207
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Fig.11. LINAC
Fig.14. Post operative image
Fig.12. Cyclotron
Fig.13. MRI brain-Sellar suprasellar lesion with solid and cystic component measuring 5.6x 4cm compressing the chiasm Apollo Medicine, Vol. 5, No. 3, September 2008
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Fig.15. Recurrence of tumor
Review Article
Fig.16. Stereotactic catheter placement
Fig.17. 5 years post radiation with no recurrence of tumor
Radiosurgery can also be performed with a linear accelerator (Fig.11) (also called LINAC), which is a device that produces high-energy photons that can be used to treat larger tumors, metastatic tumors, or arteriovenous malformations. Linear accelerators are preferred for multisession treatments using smaller doses of radiation. Radiosurgery performed with divided doses is known as fractionated radiosurgery; The advantage of fractionated treatment is that it allows a higher total dose of radiation to be delivered to the tumor without harming nearby normal tissues. The beams of radiation from a LINAC are shaped to a very high degree of accuracy by metal tubes known as collimators. Unlike the gamma knife unit, the LINAC moves around the patient during treatment, delivering arcs of radiation matched by computer to the shape of the tumor.
measuring 5.6x 4cm compressing the chiasm (Fig.13). There was no hydrocephalus.Corticosteroid and thyroid replacement was done preoperatively. He underwent Left pterional craniotomy and decompression of cystic portion. Post operatively CT scan done revealed decompression of cystic portion (Fig.14). He developed recurrence of symptoms after 4 months (Fig.15]. He again underwent stereotactic placement of catheter with aspiration of cyst (Fig.16). He also received radiation. He was followed up for 5 years with no clinical or radiological reccurence (Fig.17).
The third type of machine that can be used for radiosurgery is a cyclotron, which is a nuclear reactor used to accelerate charged particles (usually protons or ions) to high levels of energy that can be used for radiosurgery (Fig.12) [6].
COMPLICATION The complications of stereotactic surgery are hematoma formation, infection, brain edema, worsening of neurological symptoms. The complication rate varies from 0-4%. The risks of stereotactic radiosurgery are nausea and omiting,headaches,dizziness,fatigue,hairloss,radiation necrosis,leukoencephalopathy ,worsening of brain edema [7,8]. CONCLUSION Stereotactic biopsy is a safe and accurate procedure with
CASE 4 Thirty-six year old male who presented with headache, decreased vison and excessive tiredness of one month duration. On examination he had bitemporal hemianopia with, vison of- R(6/6), L(6/9). He had left sided primary optic atrophy. There was no motor deficit. Complete endocrinological evaluation was done. He was hypothyroid with decreased testosterone level. MRI brain done revealed sellar suprasellar lesion with solid and cystic component 209
Table1 Senior Authors experience with stereotactic framebased and frameless surgery Total No of patients 122
Stereotactic biopsy 90
Stereotactic craniotomy Frameless - 22 Frame based-10
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Review Article
a diagnosis rate of more than 90%. (Senior authors series of 122 cases). Stereotactic craniotomy can be done either frame based or frameless and helps in accurate marking of scalp flap with small craniotomy, small cortical incison and preservation of neural tissue. Stereotactic radiation is a useful adjunct both for benign and malignant lesions of brain either postsurgery or as a primary treatment alone. REFERENCES 1. Patric J Kelly, Introduction and Historical Aspects, Tumor Stereotaxis, Philadelphia: WB Saunders Company (1991). 2. Malcolm F Pell, Eric R Cosman, David Thomas. Handbook of stereotaxy using CRW apparatus. 3. Lawrence Chin, MD, William Regine, MD, Principles and Practice of Stereotactic Radiosurgery (2008).
Apollo Medicine, Vol. 5, No. 3, September 2008
210
4. L Dade Lunsford, Ajay Niranjan, Aftab A. Khan, Douglas Kondziolka. Establishing a Benchmark for Complications Using Frame-Based Stereotactic Surgery.Stereotact Funct Neurosurg 2008; 86: 278-287. 5. Zinreich S J, et al. Frameless Stereotaxic Integration of CT Imaging Data: Accuracy and Initial Applications, Radiology, 1993; 188(3): 735-742. 6. Hidefumi Aoyama; Hiroki Shirato; Masao Tago; Keiichi Nakagawa, Stereotactic Radiosurgery Plus Whole-Brain Radiation Therapy vs Stereotactic Radiosurgery Alone for Treatment of Brain Metastases.JAMA. 2006; 295:24832491. 7. Kondziolka, A. Firlik, L. Lunsford. Complications of stereotactic brain surgery. Neurologic Clinics, 16(1)35-54 . 8. William DM, Baerts, JAAPJDE LANGE, Complications of the Mayfield skull Anaesthesiology, 1984, 61, 460.
et al. clamp,
STEREOTACTIC MANAGEMENT OF BRAIN TUMORS Shyam Sunder* and Rajendra Prasad ** *Associate Consultant,**Senior Consultant, Department of Neurosurgery, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi 110 076, India. Correspondence to:Dr. Rajendra.Prasad, 268/Sec15A. Noida 201301, India. e-mail:[email protected] Stereotactic and image-guided surgery has become increasingly important in the management of brain tumors. Although there are several stereotactic modalities that have been reported to be of value, it is the combination of techniques in a multimodality approach that seems to show the most promise. Both framebased and frameless guidance may facilitate tumor resection, allowing the optimal amount of resection while permitting avoidance of surrounding eloquent areas. Deep tumors may be localized and approached through a small burrhole, and surgical exposure may be minimized to protect uninvolved areas of the brain. There is increasing evidence that patients operated with imaging guidance have a more benign course and more rapid discharge, perhaps with a lower incidence of adverse neurological sequelae. Stereotactic conformal radiotherapy allows a higher tumor dose while sparing uninvolved brain from radiation more efficiently than conventional techniques, and residual tumor may be treated with a boost of stereotactic radiotherapy. Stereotactic instillation of radioisotopes may be used to treat cystic tumors. Stereotactic insertion of cannulae or radioisotope seeds permit efficient brachytherapy. Key words:Brain tumor, Stereotactic surgery,Image-guided surgery, Stereotactic radiosurgery
HISTORY THE earliest forms of stereotactic surgery in humans developed out of an apparatus that was designed by Victor Horsley and Henry Clarke in 1906 to study brain functions in monkeys. It was not until 1946, however, that two American researchers designed a stereotactic frame to guide brain surgery in humans. There were two difficulties in transferring a stereotactic system from other mammals to humans, however; one problem was the much greater degree of variation among humans in the location of various bony landmarks on the skull that were used to identify the approximate location of various parts of the brain. The other problem was the lack of a reliable imaging method for visualizing internal brain structures. By the 1940s, a method known as positive contrast ventriculography, in which some of the cerebral fluid in the ventricles of brain was withdrawn and replaced with air or another contrast medium that would show up on an X-ray, allowed surgeons to identify structures within the brain in relation to one another. Ventriculography made it possible to use such internal structures as the posterior commissure or pineal gland rather than various points on the outside of the skull as landmarks for brain surgery. Researchers compiled stereotactic atlases, or collections of photographs of crosssections of brain tissue, with reference grids around the Apollo Medicine, Vol. 5, No. 3, September 2008
204
borders of each photograph. A surgeon could consult one of these atlas in order to calculate the exact location of a targeted brain structure with reference to the posterior commissure. Present-day stereotactic surgery still makes use of atlases, although they are now compiled from computer images rather than photographs [1]. DEFINITION Stereotactic surgery is an approach to tumor diagnosis and treatment that makes use of a system of threedimensional coordinates to locate a site as precisely as possible for biopsy or surgery. The English word stereotactic is a combination of a Greek root, stereo, which means “solid” or “having three dimensions,” and the Latin word tactus, which means “touch.” Stereotactic neurosurgery may make use of a conventional incision and burrhole to enter the patient’s skull or precisely focused beams of radiation to destroy tumor tissue. This second method, which is called stereotactic radiosurgery is not surgery in the usual sense of the word because no incision is involved [2]. INDICATION Stereotactic surgery may be performed either to obtain a tissue sample for biopsy or to remove or destroy the tumor itself. Stereotactic biopsies are the preferred method of
Review Article
confirming a diagnosis of a brain tumor, because of their precision and because they may offer the only method of obtaining a tissue sample if the tumor is located deep within the brain or close to structures that control vital functions especially brainstem tumor, pineal region tumors,thalamic gliomas, hypothalamic gliomas and hamartomas and tumors located near eloquent areas of brain such as speech areas and motor cortex. Stereotactic radiosurgery can be used to treat benign tumors such as acoustic neuromas, pituitary adenomas and meningiomas as well as malignant tumors of the brain or as a follow-up booster treatment for patients with recurrent tumors who have already received the maximum safe dose of conventional radiation therapy. Stereotactic radiosurgery with a gamma knife or X-Knife is most effective in treating relatively small tumors (an inch or less in diameter) with well-defined borders that have not invaded the brain; in addition, it is usually reserved for patients with a life expectancy of six months or longer. Large brain tumors may require debulking if not resectable by conventional open surgery prior to treatment with radiosurgery [3]. DESCRIPTION
carcinoma). He was evaluated with CT chest and abdomen which revealed primary in lung. He received whole brain radiation followed by booster radiation to brain stem lesion. This was followed by chemotherapy for the lesion in the lung. CASE 2 Forty years female presented with drowsiness, headache, weakness of left half of body of 2 weeks duration of grade-4/5. MRI brain (Fig.6) revealed thalamic lesion . He underwent MRI based stereotactic biopsy of the lesion. Histopathology revealed low grade glioma. Frameless stereotactic brain surgery In this method, images of the patient’s head from CT or MRI scans are uploaded into a computer for display on a monitor. Markers on the patient’s skin are registered by a probe linked to the computer by a (Fig.7) camera, which joins the position of the patient’s head on the operating table to the images on the computer monitor. In addition, the surgeon’s instruments contain light-emitting diodes (LEDs) that are tracked by the computer during the operation (Fig.8) [5].
Frame based Stereotactic Surgery CASE 3 The first frame that was used in stereotactic surgery in the 1940s consisted of a plaster cap fitted to the individual patient with a head ring and electrode carrier mounted to it. In the early 2000s, however, stereotactic surgery makes use of a base ring attached to the patient’s skull, and an arc (Fig.1) ring to guide the surgeon in drilling a hole through the skull. After the base ring is attached to the patient’s scalp, he or she is taken to CT room or MRI room where CRW frame is attached and then coordinates are (Fig.2) calculated. Patient is then shifted to the operating room, where the base ring is attached to the operating table in order to hold the patient’s head steady. The entry site for the surgeon’s drill is selected, and the entry site and area of the tumor are located on a phantom that relates these points to the patient’s head (Fig.3). An arc ring is then attached to the base ring to guide the surgeon’s movements.This stereotactic system allows the surgeon to (Fig.4) make only a very small incision in the scalp, and make a burrhole in order to insert a biopsy needle [4]. CASE 1 Forty-two years old male presented with progressive loss of memory, difficulty in swallowing , and weakness of both upper and lower limbs of two months duration. MRI brain with contrast done revealed (Fig.5) multiple intracerebral lesion. He underwent stereotactic biopsy of the lesion. Histopathology came as metastasis (adeno-
Sixty two years female presented to us with history of two episodes of generalized tonic clonic seizures. She had past history of carcinoma of left breast, operated two years back and received radiation and chemotherapy for the same. CT Scan brain done revealed a left frontal lesion with edema (Fig.9). She underwent stereotactic craniotomy and decompression of lesion. Histopathology report came as poorly differentiated adenocarcinoma, secondary from breast. She received radiation for the same. Stereotactic Radiosurgery and Radiotherapy Stereotactic radiosurgery can be performed with three different types of machines to provide the radiation used to kill the tumor cells. The gamma knife is a stationary unit that contains 201 sources of gamma rays derived from cobalt-60 that can be focused by a computer on a small area of the brain (Fig.10). The radiation can be directed very precisely to the tumor without destroying nearby healthy tissue. The patient lies on a couch with a large helmet attached to his or her head frame. The helmet contains holes that allow beams of radiation to enter. The couch is then slid into a gantry containing the cobalt-60. Treatment time varies from several minutes to over an hour, depending on the size, shape, and location of the tumor. Gamma knife radiosurgery is usually a single-dose treatment. X-Knife is a useful alternative tool.
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Fig.1. Base ring attached to patients head
Fig.2. CRW frame head ring
Fig.3. Target being confirmed on phantom ring
Fig.4. Burr hole through which biopsy will be taken
Fig.5.
MRI brain with contrast done revealed multiple intracerebral lesions.
Apollo Medicine, Vol. 5, No. 3, September 2008
Fig.6.
206
MRI Brain-Thalamic lesion, underwent MRI based stereotaxy
Review Article
Fig.7. Registration of data with the markers
Fig.8.
Instruments contain light-emitting diodes (LEDs) that are tracked by the computer during the operation.
Fig.9. Left frontal lesion with edema
Fig.10. Stereotactic radiosurgery using gamma knife 207
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Fig.11. LINAC
Fig.14. Post operative image
Fig.12. Cyclotron
Fig.13. MRI brain-Sellar suprasellar lesion with solid and cystic component measuring 5.6x 4cm compressing the chiasm Apollo Medicine, Vol. 5, No. 3, September 2008
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Fig.15. Recurrence of tumor
Review Article
Fig.16. Stereotactic catheter placement
Fig.17. 5 years post radiation with no recurrence of tumor
Radiosurgery can also be performed with a linear accelerator (Fig.11) (also called LINAC), which is a device that produces high-energy photons that can be used to treat larger tumors, metastatic tumors, or arteriovenous malformations. Linear accelerators are preferred for multisession treatments using smaller doses of radiation. Radiosurgery performed with divided doses is known as fractionated radiosurgery; The advantage of fractionated treatment is that it allows a higher total dose of radiation to be delivered to the tumor without harming nearby normal tissues. The beams of radiation from a LINAC are shaped to a very high degree of accuracy by metal tubes known as collimators. Unlike the gamma knife unit, the LINAC moves around the patient during treatment, delivering arcs of radiation matched by computer to the shape of the tumor.
measuring 5.6x 4cm compressing the chiasm (Fig.13). There was no hydrocephalus.Corticosteroid and thyroid replacement was done preoperatively. He underwent Left pterional craniotomy and decompression of cystic portion. Post operatively CT scan done revealed decompression of cystic portion (Fig.14). He developed recurrence of symptoms after 4 months (Fig.15]. He again underwent stereotactic placement of catheter with aspiration of cyst (Fig.16). He also received radiation. He was followed up for 5 years with no clinical or radiological reccurence (Fig.17).
The third type of machine that can be used for radiosurgery is a cyclotron, which is a nuclear reactor used to accelerate charged particles (usually protons or ions) to high levels of energy that can be used for radiosurgery (Fig.12) [6].
COMPLICATION The complications of stereotactic surgery are hematoma formation, infection, brain edema, worsening of neurological symptoms. The complication rate varies from 0-4%. The risks of stereotactic radiosurgery are nausea and omiting,headaches,dizziness,fatigue,hairloss,radiation necrosis,leukoencephalopathy ,worsening of brain edema [7,8]. CONCLUSION Stereotactic biopsy is a safe and accurate procedure with
CASE 4 Thirty-six year old male who presented with headache, decreased vison and excessive tiredness of one month duration. On examination he had bitemporal hemianopia with, vison of- R(6/6), L(6/9). He had left sided primary optic atrophy. There was no motor deficit. Complete endocrinological evaluation was done. He was hypothyroid with decreased testosterone level. MRI brain done revealed sellar suprasellar lesion with solid and cystic component 209
Table1 Senior Authors experience with stereotactic framebased and frameless surgery Total No of patients 122
Stereotactic biopsy 90
Stereotactic craniotomy Frameless - 22 Frame based-10
Apollo Medicine, Vol. 5, No. 3, September 2008
Review Article
a diagnosis rate of more than 90%. (Senior authors series of 122 cases). Stereotactic craniotomy can be done either frame based or frameless and helps in accurate marking of scalp flap with small craniotomy, small cortical incison and preservation of neural tissue. Stereotactic radiation is a useful adjunct both for benign and malignant lesions of brain either postsurgery or as a primary treatment alone. REFERENCES 1. Patric J Kelly, Introduction and Historical Aspects, Tumor Stereotaxis, Philadelphia: WB Saunders Company (1991). 2. Malcolm F Pell, Eric R Cosman, David Thomas. Handbook of stereotaxy using CRW apparatus. 3. Lawrence Chin, MD, William Regine, MD, Principles and Practice of Stereotactic Radiosurgery (2008).
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4. L Dade Lunsford, Ajay Niranjan, Aftab A. Khan, Douglas Kondziolka. Establishing a Benchmark for Complications Using Frame-Based Stereotactic Surgery.Stereotact Funct Neurosurg 2008; 86: 278-287. 5. Zinreich S J, et al. Frameless Stereotaxic Integration of CT Imaging Data: Accuracy and Initial Applications, Radiology, 1993; 188(3): 735-742. 6. Hidefumi Aoyama; Hiroki Shirato; Masao Tago; Keiichi Nakagawa, Stereotactic Radiosurgery Plus Whole-Brain Radiation Therapy vs Stereotactic Radiosurgery Alone for Treatment of Brain Metastases.JAMA. 2006; 295:24832491. 7. Kondziolka, A. Firlik, L. Lunsford. Complications of stereotactic brain surgery. Neurologic Clinics, 16(1)35-54 . 8. William DM, Baerts, JAAPJDE LANGE, Complications of the Mayfield skull Anaesthesiology, 1984, 61, 460.
et al. clamp,