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 frame- based 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method known as positive contrast ventriculography, in which some of the cerebral fluid in the ventricles of brain was withdrawn and replaced with air or another contrast medium that would show up on an X-ray, allowed surgeons to identify structures within the brain in relation to one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 cross- sections of brain tissue, with reference grids around the 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 three- dimensional 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 neuro- surgery 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 Apollo Medicine, Vol. 5, No. 3, September 2008 204
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Review Article
STEREOTACTIC MANAGEMENT OF BRAIN TUMORS
Shyam Sunder* and Rajendra Prasad ***Associate Consultant,**Senior Consultant, Department of Neurosurgery, Indraprastha Apollo Hospitals,
Stereotactic and image-guided surgery has become increasingly important in the management of braintumors. Although there are several stereotactic modalities that have been reported to be of value, it is thecombination of techniques in a multimodality approach that seems to show the most promise. Both frame-based and frameless guidance may facilitate tumor resection, allowing the optimal amount of resection whilepermitting avoidance of surrounding eloquent areas. Deep tumors may be localized and approached througha small burrhole, and surgical exposure may be minimized to protect uninvolved areas of the brain. There isincreasing evidence that patients operated with imaging guidance have a more benign course and more rapiddischarge, perhaps with a lower incidence of adverse neurological sequelae. Stereotactic conformalradiotherapy allows a higher tumor dose while sparing uninvolved brain from radiation more efficiently thanconventional 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 cannulaeor radioisotope seeds permit efficient brachytherapy.
THE earliest forms of stereotactic surgery in humansdeveloped out of an apparatus that was designed by VictorHorsley and Henry Clarke in 1906 to study brain functions inmonkeys. It was not until 1946, however, that two Americanresearchers designed a stereotactic frame to guide brainsurgery in humans. There were two difficulties intransferring a stereotactic system from other mammals tohumans, however; one problem was the much greater degreeof variation among humans in the location of various bonylandmarks on the skull that were used to identify theapproximate location of various parts of the brain. The otherproblem was the lack of a reliable imaging method forvisualizing internal brain structures.
By the 1940s, a method known as positive contrastventriculography, in which some of the cerebral fluid in theventricles of brain was withdrawn and replaced with air oranother contrast medium that would show up on an X-ray,allowed surgeons to identify structures within the brain inrelation to one another. Ventriculography made it possible touse such internal structures as the posterior commissure orpineal gland rather than various points on the outside of theskull as landmarks for brain surgery. Researchers compiledstereotactic atlases, or collections of photographs of cross-sections of brain tissue, with reference grids around the
borders of each photograph. A surgeon could consult one ofthese atlas in order to calculate the exact location of atargeted brain structure with reference to the posteriorcommissure. Present-day stereotactic surgery still makesuse of atlases, although they are now compiled fromcomputer images rather than photographs [1].
DEFINITION
Stereotactic surgery is an approach to tumor diagnosisand treatment that makes use of a system of three-dimensional coordinates to locate a site as precisely aspossible for biopsy or surgery. The English wordstereotactic is a combination of a Greek root, stereo, whichmeans “solid” or “having three dimensions,” and the Latinword tactus, which means “touch.” Stereotactic neuro-surgery may make use of a conventional incision andburrhole to enter the patient’s skull or precisely focusedbeams of radiation to destroy tumor tissue. This secondmethod, which is called stereotactic radiosurgery is notsurgery in the usual sense of the word because no incision isinvolved [2].
INDICATION
Stereotactic surgery may be performed either to obtain atissue sample for biopsy or to remove or destroy the tumoritself. Stereotactic biopsies are the preferred method of
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confirming a diagnosis of a brain tumor, because of theirprecision and because they may offer the only method ofobtaining a tissue sample if the tumor is located deep withinthe brain or close to structures that control vital functionsespecially brainstem tumor, pineal region tumors,thalamicgliomas, hypothalamic gliomas and hamartomas andtumors located near eloquent areas of brain such as speechareas and motor cortex.
Stereotactic radiosurgery can be used to treat benigntumors such as acoustic neuromas, pituitary adenomas andmeningiomas as well as malignant tumors of the brain or asa follow-up booster treatment for patients with recurrenttumors who have already received the maximum safe doseof conventional radiation therapy. Stereotactic radiosurgerywith a gamma knife or X-Knife is most effective in treatingrelatively small tumors (an inch or less in diameter) withwell-defined borders that have not invaded the brain; inaddition, it is usually reserved for patients with a lifeexpectancy of six months or longer. Large brain tumors mayrequire debulking if not resectable by conventional opensurgery prior to treatment with radiosurgery [3].
DESCRIPTION
Frame based Stereotactic Surgery
The first frame that was used in stereotactic surgery inthe 1940s consisted of a plaster cap fitted to the individualpatient with a head ring and electrode carrier mounted to it.In the early 2000s, however, stereotactic surgery makes useof a base ring attached to the patient’s skull, and an arc(Fig.1) ring to guide the surgeon in drilling a hole throughthe skull. After the base ring is attached to the patient’s scalp,he or she is taken to CT room or MRI room where CRWframe 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 orderto hold the patient’s head steady. The entry site for thesurgeon’s drill is selected, and the entry site and area of thetumor are located on a phantom that relates these points tothe patient’s head (Fig.3). An arc ring is then attached to thebase ring to guide the surgeon’s movements.Thisstereotactic system allows the surgeon to (Fig.4) make onlya very small incision in the scalp, and make a burrhole inorder to insert a biopsy needle [4].
CASE 1
Forty-two years old male presented with progressiveloss of memory, difficulty in swallowing , and weakness ofboth upper and lower limbs of two months duration. MRIbrain with contrast done revealed (Fig.5) multiple intra-cerebral lesion. He underwent stereotactic biopsy of thelesion. Histopathology came as metastasis (adeno-
carcinoma). He was evaluated with CT chest and abdomenwhich revealed primary in lung. He received whole brainradiation followed by booster radiation to brain stem lesion.This was followed by chemotherapy for the lesion in thelung.
CASE 2
Forty years female presented with drowsiness,headache, weakness of left half of body of 2 weeks durationof 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 orMRI scans are uploaded into a computer for display on amonitor. Markers on the patient’s skin are registered by aprobe linked to the computer by a (Fig.7) camera, whichjoins the position of the patient’s head on the operating tableto the images on the computer monitor. In addition, thesurgeon’s instruments contain light-emitting diodes (LEDs)that are tracked by the computer during the operation(Fig.8) [5].
CASE 3
Sixty two years female presented to us with history oftwo episodes of generalized tonic clonic seizures. She hadpast history of carcinoma of left breast, operated two yearsback 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 anddecompression of lesion. Histopathology report came aspoorly differentiated adenocarcinoma, secondary frombreast. She received radiation for the same.
Stereotactic Radiosurgery and Radiotherapy
Stereotactic radiosurgery can be performed with threedifferent types of machines to provide the radiation used tokill the tumor cells. The gamma knife is a stationary unit thatcontains 201 sources of gamma rays derived from cobalt-60that can be focused by a computer on a small area of thebrain (Fig.10). The radiation can be directed very preciselyto the tumor without destroying nearby healthy tissue. Thepatient lies on a couch with a large helmet attached to his orher head frame. The helmet contains holes that allow beamsof radiation to enter. The couch is then slid into a gantrycontaining the cobalt-60. Treatment time varies fromseveral minutes to over an hour, depending on the size,shape, and location of the tumor. Gamma knife radiosurgeryis usually a single-dose treatment. X-Knife is a usefulalternative 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 multipleintracerebral lesions.
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Fig.16. Stereotactic catheter placement Fig.17. 5 years post radiation with no recurrence of tumor
Radiosurgery can also be performed with a linearaccelerator (Fig.11) (also called LINAC), which is a devicethat produces high-energy photons that can be used to treatlarger tumors, metastatic tumors, or arteriovenousmalformations. Linear accelerators are preferred for multi-session treatments using smaller doses of radiation.Radiosurgery performed with divided doses is known asfractionated radiosurgery; The advantage of fractionatedtreatment is that it allows a higher total dose of radiation tobe delivered to the tumor without harming nearby normaltissues. The beams of radiation from a LINAC are shaped toa very high degree of accuracy by metal tubes known ascollimators. Unlike the gamma knife unit, the LINACmoves around the patient during treatment, delivering arcsof radiation matched by computer to the shape of the tumor.
The third type of machine that can be used for radio-surgery is a cyclotron, which is a nuclear reactor used toaccelerate charged particles (usually protons or ions) to highlevels of energy that can be used for radiosurgery (Fig.12)[6].
CASE 4
Thirty-six year old male who presented with headache,decreased vison and excessive tiredness of one monthduration. On examination he had bitemporal hemianopiawith, vison of- R(6/6), L(6/9). He had left sided primaryoptic atrophy. There was no motor deficit. Completeendocrinological evaluation was done. He was hypothyroidwith decreased testosterone level. MRI brain done revealedsellar suprasellar lesion with solid and cystic component
measuring 5.6x 4cm compressing the chiasm (Fig.13).There was no hydrocephalus.Corticosteroid and thyroidreplacement was done preoperatively. He underwent Leftpterional craniotomy and decompression of cystic portion.Post operatively CT scan done revealed decompression ofcystic portion (Fig.14). He developed recurrence ofsymptoms after 4 months (Fig.15]. He again underwentstereotactic placement of catheter with aspiration of cyst(Fig.16). He also received radiation. He was followed up for5 years with no clinical or radiological reccurence (Fig.17).
COMPLICATION
The complications of stereotactic surgery are hematomaformation, infection, brain edema, worsening ofneurological symptoms. The complication rate varies from0-4%. The risks of stereotactic radiosurgery are nausea andomiting,headaches,dizziness,fatigue,hairloss,radiationnecrosis,leukoencephalopathy ,worsening of brain edema[7,8].
CONCLUSION
Stereotactic biopsy is a safe and accurate procedure with
Table1 Senior Authors experience with stereotacticframebased and frameless surgery
Total No of Stereotactic Stereotacticpatients biopsy craniotomy
122 90 Frameless - 22Frame based-10
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a diagnosis rate of more than 90%. (Senior authors series of122 cases). Stereotactic craniotomy can be done eitherframe based or frameless and helps in accurate marking ofscalp flap with small craniotomy, small cortical incison andpreservation of neural tissue. Stereotactic radiation is auseful adjunct both for benign and malignant lesions ofbrain either postsurgery or as a primary treatment alone.
REFERENCES
1. Patric J Kelly, Introduction and Historical Aspects, TumorStereotaxis, Philadelphia: WB Saunders Company (1991).
2. Malcolm F Pell, Eric R Cosman, David Thomas. Handbookof stereotaxy using CRW apparatus.
3. Lawrence Chin, MD, William Regine, MD, Principles andPractice of Stereotactic Radiosurgery (2008).
4. L Dade Lunsford, Ajay Niranjan, Aftab A. Khan, DouglasKondziolka. Establishing a Benchmark for ComplicationsUsing Frame-Based Stereotactic Surgery.Stereotact FunctNeurosurg 2008; 86: 278-287.
5. Zinreich S J, et al. Frameless Stereotaxic Integration of CTImaging Data: Accuracy and Initial Applications,Radiology, 1993; 188(3): 735-742.
6. Hidefumi Aoyama; Hiroki Shirato; Masao Tago; KeiichiNakagawa, Stereotactic Radiosurgery Plus Whole-BrainRadiation Therapy vs Stereotactic Radiosurgery Alone forTreatment of Brain Metastases.JAMA. 2006; 295:2483-2491.
7. Kondziolka, A. Firlik, L. Lunsford. Complications ofstereotactic brain surgery. Neurologic Clinics, 16(1)35-54 .
8. William DM, Baerts, JAAPJDE LANGE, et al.Complications of the Mayfield skull clamp,Anaesthesiology, 1984, 61, 460.
