Figure 5.1. (a) Sagittal T1-weighted magnetic resonance image with contrast and (b) axial T2-weighted magnetic resonance image demonstrate a pineal region mass causing tectal compression; imaging characteristics are consistent with a 1.6-cm pineal cyst.

Figure 5.1. (d) Further dissection exposes the pineal region and the complex of deep veins.

Figure 5.1. (e) Mobilization of the veins exposes the pineal cyst, containing hemosiderin-stained cystic fluid. With the endoscope held by an assistant, four-handed endoscopy is performed, and the lesion is dissected circumferentially. The suction cannula provides countertraction while the pituitary forceps are used to roll the lesion away from adjacent points of connection.

Figure 5.1. (g) After being freed circumferentially, the lesion is removed.

Figure 5.1. (h) Final view of the resection cavity shows complete removal of the tumor.

Figure 5.2. (a) Axial and (b) sagittal T1-weighted magnetic resonance images with contrast demonstrate a pineal region cyst with compression of the tectum (b, arrow).

Figure 5.2. (g) The cyst is debulked and resected piecemeal to avoid damaging the deep venous circulation.

Figure 5.2. (h) Resecting the cyst often requires sharp dissection of the cyst capsule from the deep veins. After removal of the cyst contents, the remnant can be sharply resected from the veins.

Figure 5.2. (j) Watertight closure of the dura is essential to prevent leakage of cerebrospinal fluid after operations in the posterior fossa. When the dura is damaged, graft material should be used to complete the dural closure.

Figure 5.2. (k) Intraoperative photograph and illustration show how a single large bur hole cover can be used to repair a skull defect.

Figure 5.3. (d) Dissection of the arachnoid membrane develops the supracerebellar infratentorial path to the pineal region. The pineal tumor is visible beneath the arachnoid membrane. In this four-handed endoscopic resection, the surgeon uses microscissors and suction to perform dissection of the arachnoid bands, while the assistant maneuvers the endoscope.

Figure 5.3. (f) Suction is used to keep the operative field clear and to provide countertraction on the tumor.

Figure 5.3. (g) Pituitary forceps are used to remove the tumor piecemeal, gradually exposing the brainstem beyond the tumor.

Figure 5.3. (i,j) Postoperative (i) axial T1-weighted magnetic resonance image and (j) sagittal T1-weighted magnetic resonance image with contrast confirm gross-total resection of the tumor.

Figure 5.4. (a) Axial, (b) sagittal, and (c) coronal T1-weighted and (d) axial T2-weighted magnetic resonance images demonstrate a pineal region mass with layers of liquid contents of different densities in a cyst capsule and evidence of hemorrhage. The differential diagnosis was a pineal region cyst or a pineal tumor.

Figure 5.4. (f) Sharp dissection is used to release the arachnoid bands overlying the pineal region.

Figure 5.4. (h) The lesion is mobilized with a microdissector and removed piecemeal. Suction is used to mobilize the lesion while the microdissector is used to peel the lesion from the brainstem.

Figure 5.4. (j) The cavernous malformation adherent to the deep venous circulation is sharply mobilized using microdissectors and is ultimately removed using pituitary forceps.

Figure 5.4. (l) The removal of the lesion and the use of an angled endoscope make possible better views of the ventricular system as it narrows to the aqueduct of Sylvius.

Figure 5.5. (a) Axial and (b) sagittal T1-weighted magnetic resonance images and (c) coronal gradient-echo magnetic resonance image show a right posterior thalamic cavernous malformation with evidence of hemorrhage.

Figure 5.5. (g) The cavernous malformation is entered, releasing blood of various ages. The lesion is then dissected circumferentially using microdissectors, toothed forceps, and pituitary forceps.

Figure 5.5. (h) The resection cavity is inspected, and hemostasis is obtained.

Figure 5.5. Postoperative (j) axial and (k) coronal T1-weighted magnetic resonance images confirm complete removal of the lesion. The supracerebellar transtentorial approach enables resection of the lesion with minimal violation of overlying brain tissue.

Figure 5.6. Axial T1-weighted magnetic resonance images at two levels (a,b) demonstrate a complex cavernous malformation involving the left thalamus and mesencephalon.

Figure 5.6. (e) Intraoperative neuronavigation images show the trajectory used during the procedure to address this large, complex cavernous malformation involving the midbrain and thalamus. The lesion is accessed using a left lateral supracerebellar infratentorial approach with the patient in a modified park bench position. This approach facilitates entry into the brainstem with minimal transgression of normal tissue and places the surgeon down the long axis of the cavernous malformation. The dorsolateral surface of the midbrain can be accessed using the lateral mesencephalic sulcus safe entry zone or, for lesions that abut a pial plane, it can be accessed directly through the lesion. Disconnection of the tentorium affords the additional view and access necessary to remove the thalamic component of this lesion.

Figure 5.6. (g) The cavernous malformation is dissected from the adjacent brainstem. Coagulation is used sparingly to avoid thermal injury to critical tracts.

Figure 5.6. (h) The cavernous malformation is removed piecemeal.

Figure 5.6. (j) Remnants of the cavernous malformation are mobilized off the adjacent brainstem and removed.

Figure 5.6. (o) The lesion is dissected free and removed piecemeal. The addition of lighted bipolar forceps and lighted suction improves visualization at the depths of such deep approaches.

Figure 5.6. (p) Once mobilized, the cavernous malformation is removed using toothed forceps or pituitary forceps. Care must be taken to preserve the developmental venous anomaly associated with these lesions.

Figure 5.6. Postoperative (r,s) axial T2-weighted magnetic resonance images confirm complete removal of the cavernous malformation after the second procedure.

Figure 5.7. (a) Sagittal T1-weighted and (b) axial T2-weighted magnetic resonance images demonstrate a posterior thalamic cavernous malformation.

Figure 5.7. (e) The pulvinar is then used to gain access to the cavernous malformation. The pulvinar tolerates manipulation and can be safely used to gain access to the thalamus via a transcortical parieto-occipital approach. Although not essential, the use of a minimally invasive port or a retractor can improve visualization of the ventricle and beyond.

Figure 5.7. (f) After dissection from adjacent tissues, the cavernous malformation is removed piecemeal.

Figure 5.7. (h) Final inspection of the resection cavity is performed, and hemostasis is obtained.

Figure 5.8. (e) The use of a lighted suction cannula and/or lighted bipolar forceps greatly assists with illumination at this depth.

Figure 5.8. (f) The choroidal fissure is opened to gain access to the lesion, which was exophytic into the third ventricle in this patient. The choroidal fissure can be opened either on the forniceal side or on the thalamic side of the fissure. Although there are merits and drawbacks to each approach, opening the fissure on the thalamic side can avoid retraction injury to the fornices. The choroid plexus can also be used as a cushion during retraction of the fornix.

Figure 5.8. (h) The opening is expanded to facilitate suction and to accommodate a second microinstrument to mobilize and resect the lesion. In this case, pituitary forceps are used to debulk the cavernous malformation piecemeal.

Figure 5.8. (j) Once mobilized, the cavernous malformation is removed by peeling it from adjacent structures.

Figure 5.8. (k) Pituitary forceps are used to peel away bands of cavernous malformation adherent to adjacent brain tissue.

Figure 5.8. (m) After removal of the cavernous malformation, the depth of the surgical cavity can be appreciated.

Figure 5.8. (n) Final inspection of the resection cavity is performed, and hemostasis is obtained before closure.

Figure 5.9. (a) Sagittal and (b) coronal T1-weighted magnetic resonance images demonstrate a right thalamic cavernous malformation. (b) Coronal image shows a developmental venous anomaly (arrow) associated with the cavernous malformation. For the optimal trajectory to the lesion, the anterior interhemispheric craniotomy should be placed two-thirds in front of and one-third behind the coronal suture.

Figure 5.9. (d) The interhemispheric fissure is opened to release the frontal lobes and to provide a direct path to the corpus callosum. The anterior cerebral arteries, which course over the corpus callosum, can be dissected and mobilized to perform the callosotomy.

Figure 5.9. (f) The opening into the thalamus is expanded to arrive at the lesion.

Figure 5.9. (g) The cavernous malformation is identified and dissected from the adjacent brain tissue. The steps of the dissection process are as follows: (1) create the cortical opening using sharp dissection; (2) expand the cortical opening using forceps to stretch it; (3) decompress the cavernous malformation by removing the blood; (4) mobilize the cavernous malformation from adjacent structures using a combination of microdissectors, microforceps, and microscissors; (5) remove the cavernous malformation piecemeal while taking care to preserve the developmental venous anomaly associated with it; (6) peel and remove the remnants of the cavernous malformation from the resection cavity; (7) inspect the resection cavity and obtain hemostasis; and (8) perform a final check of the resection cavity.

Figure 5.9. (i) Lighted microinstruments illuminate the depth of deep surgical corridors. The lighted suction provides illumination, keeps the operative bed dry, and provides countertraction during dissection.

Figure 5.9. (j) After the lesion is fully mobilized, it is resected piecemeal.

Figure 5.9. Postoperative (l) axial and (m) sagittal T2-weighted magnetic resonance images confirm complete removal of the cavernous malformation.

Figure 5.10. (a) Sagittal T1-weighted and (b) axial T2-weighted magnetic resonance images demonstrate an exophytic thalamic cavernous malformation. Because the lesion extends almost exclusively into the ventricular system, a left anterior interhemispheric craniotomy is performed to remove it. The head is turned horizontally to be parallel to the floor, with the lesion side down.

Figure 5.10. (d) Intraoperative photograph and illustration show the opening of the choroidal fissure. Opening the fissure on the thalamic side minimizes injury to the fornix. Placing the choroid plexus as a buttress between the surgeon and the fornix helps minimize retraction injury to the fornix.

Figure 5.10. (e) The cavernous malformation, which protrudes into the ventricle, is readily identified.

Figure 5.10. (g) The lesion is removed from the cavity.

Figure 5.10. (h) Final inspection of the cavity demonstrates cavernous malformation remnants adherent to the thalamus. These strands are carefully peeled from the thalamus using toothed forceps. It is often difficult to distinguish between cavernous malformation remnants and hemosiderin-stained brain indicative of a prior hemorrhage. Care must be exercised, especially when removing lesions from eloquent areas, to avoid removing normal hemosiderin-stained brain.

Figure 5.10. Postoperative (j) sagittal T1-weighted and (k) axial T2-weighted magnetic resonance images confirm the complete removal of the cavernous malformation.

Figure 5.11. Axial T2-weighted magnetic resonance images at multiple levels (a–c) demonstrate a complex right thalamic lesion consistent with a cavernous malformation.

Figure 5.11. (g) This approach readily exposes the thalamus and the entire mesial temporal lobe. Opening the tentorium demonstrates hemosiderin-stained brain tissue, which neuronavigation images show corresponds to the cavernous malformation.

Figure 5.11. (i) The brain tissue overlying the cavernous malformation is sharply incised using microscissors.

Figure 5.11. (j) The lesion is removed piecemeal using microdissectors and forceps.

Figure 5.11. (m) The resection cavity is inspected, and hemostasis is obtained.

Figure 5.12. (a) Axial T2-weighted magnetic resonance image demonstrates flow voids in the right thalamus of a 13-year-old patient consistent with a history of a thalamic arteriovenous malformation and a hemorrhage at the age of 8 years. (b) Axial computed tomogram demonstrates evidence of a new hemorrhage.

Figure 5.12. (e) Anteroposterior internal carotid artery and (f) lateral vertebral artery angiograms at the time of the second hemorrhage when the patient was 13 years old, 5 years after the initial hemorrhage, document significant interval growth of the arteriovenous malformation. Stage 1 embolization: In anticipation of surgical resection, the patient underwent staged embolization of this complex arteriovenous malformation.

Figure 5.12. Stage 2 embolization: (i) Anteroposterior and (j) lateral right internal carotid artery angiograms demonstrate significant reduction after embolization of a second middle cerebral artery branch to the malformation that resulted in further devascularization of the lesion.

Figure 5.12. Stage 4 embolization: (m) Towne and (n) lateral right vertebral artery angiograms after stage 4 embolization of right posterior cerebral artery feeders to the malformation.

Figure 5.12. (p) Arterial pedicles to the malformation are identified and coagulated. Two different non-stick bipolar forceps are used for large complex lesions. The bipolar forceps are kept in an ice-cold bath and their use is alternated. Cold irrigation is generously used throughout the dissection and devascularization of the arteriovenous malformation.

Figure 5.12. (q) The coagulated vessels are sharply cut close to the nidus of the arteriovenous malformation.

Figure 5.12. (s) Neuronavigation images confirm that the deep margin of the arteriovenous malformation has been reached.

Figure 5.12. (u) Small arterial feeders at the depth of the resection cavity are identified and coagulated before being cut. The use of arteriovenous malformation clips may be necessary to control bleeding from these deep feeders, which can retract into the brain parenchyma and be a nuisance cause of bleeding.

Figure 5.12. (v) Once fully devascularized, the deep draining vein is coagulated before being cut.

Figure 5.12. (x) Postoperative lateral internal carotid artery angiogram demonstrates complete removal of the arteriovenous malformation.

Figure 5.13. (a) Axial and (b) sagittal T1-weighted, (c) axial T2-weighted, and (d) coronal gradient-echo magnetic resonance images demonstrate a large mesencephalopontine hemorrhage caused by rupture of a cavernous malformation.

Figure 5.13. (f) The basilar artery is mobilized carefully to avoid injury to the basilar perforators. Basilar artery mobilization provides the surgeon with a small entry corridor in the midline, at a region called the interpeduncular fossa safe entry zone (dashed line), to remove lesions in the centromedian mesencephalon.

Figure 5.13. (g) The opening into the brainstem should run parallel to the ascending and descending fiber tracts, although they are sparse in the midline in this location, to minimize interrupting them.

Figure 5.13. (i) The use of lighted bipolar forceps and suction cannulas can greatly facilitate the resection of lesions in deep surgical corridors. In this case, the lighted suction cannula provides illumination and countertraction as the cavernous malformation is mobilized.

Figure 5.13. (j) The lesion is resected piecemeal and removed.

Figure 5.13. Postoperative (l) axial and (m) sagittal T1-weighted magnetic resonance images demonstrate complete removal of the lesion.

Figure 5.14. (a) Axial, (b) sagittal, and (c) coronal T1-weighted magnetic resonance images demonstrate a cavernous malformation in the midbrain of a patient with a history of three prior hemorrhages.

Figure 5.14. (e) Mobilization of the vein of the lateral mesencephalic sulcus enables the surgeon to use this safe entry zone to approach deep-seated lesions in the dorsolateral midbrain. In this case, the surface of the brainstem has hemosiderin discoloration from prior hemorrhages.

Figure 5.14. (f) A sharp opening is made into the brainstem at the lateral mesencephalic sulcus safe entry zone (dashed line) and is expanded using microscissors. The opening may also be expanded with microforceps, using a spreading maneuver to increase working room.

Figure 5.14. (h) Cavernous malformations are often associated with developmental venous anomalies. In this case, a developmental venous anomaly could be visualized deep within the resection cavity. These structures should be preserved to achieve the optimal outcome after resection of the cavernous malformation.

Figure 5.14. (i) The cavernous malformation is peeled from the brainstem using suction to provide countertraction as the pituitary forceps mobilize the lesion.

Figure 5.14. Postoperative (k) sagittal T1-weighted and (l) axial T2-weighted magnetic resonance images demonstrate complete removal of the lesion.

Figure 5.15. (a) Axial, (b) sagittal, and (c) coronal T1-weighted magnetic resonance images demonstrate a midbrain cavernous malformation with evidence of hemorrhage.

Figure 5.15. (e) In cases that require supratentorial visualization, the tentorium can be cut to obtain a superior view. This transtentorial approach can also be used to expose the posterior mesial temporal region and the thalamus.

Figure 5.15. (f) The tentorium is cut with microscissors after being coagulated using bipolar cautery. Because the tentorium may contain venous lakes, care should be taken when coagulating and cutting it.

Figure 5.15. (h) The opening is expanded parallel to the ascending and descending fibers.

Figure 5.15. (i) The lesion is visualized and debulked.

Figure 5.15. (l) The resection bed is inspected, and hemostasis is obtained.

Figure 5.16. (a) Sagittal and (b) coronal T1-weighted and (c) axial T2-weighted magnetic resonance images demonstrate a large pontine cavernous malformation with evidence of hemorrhage.

Figure 5.16. (e) Sharp dissection is used to make a small opening into the brainstem.

Figure 5.16. (g) The lesion is mobilized, dissected, and removed piecemeal.

Figure 5.16. (h) Remnants of the cavernous malformation are removed using toothed forceps.

Figure 5.16. Postoperative (j) coronal T1-weighted and (k) axial T2-weighted magnetic resonance images demonstrate complete resection of the lesion, with some fluid in the resection cavity. The T2-weighted magnetic resonance image also shows the pathway into the brainstem to remove the lesion.

Figure 5.17. (a) Axial and (b) sagittal T1-weighted magnetic resonance images demonstrate a midbrain cavernous malformation with evidence of hemorrhage.

Figure 5.17. (d) Neuronavigation imaging is used to select the optimal site for the callosotomy.

Figure 5.17. (e) Sharp dissection is used to expand the opening in the corpus callosum.

Figure 5.17. (g) A combination of microdissectors and toothed forceps is used to mobilize the lesion from the adjacent brainstem.

Figure 5.17. (h) Remnants of the cavernous malformation are peeled from the brainstem using pituitary forceps and suction.

Figure 5.17. Postoperative (j) axial and (k) sagittal T1-weighted magnetic resonance images demonstrate complete removal of the lesion and show the location of the craniotomy used for the posterior interhemispheric approach.