:Acta N&rochirurgica
Acta Neurochir (Wien) (1990) 102:133-136
9 by Springer-Verlag1990
The Lateral Position-Dependant Occipital Approach- to Pineal and Medial Occipitoparietal Lesions Technical Note J. L. Stone a, G. R. Cybulski 1, R. M. Crowell 1, and R. A. Moody 2 1Division of Neurological Surgery,Cook County and Universityof Illinois Hospitals and Hektoen Institute for Medical Research, Chicago, Illinois, and the 2 Division of Neurosurgery, Guthrie Clinic, Sayre, Pennsylvania, U.S.A.
Summary A recent modification of the occipital transtentorial approach to the pineal region and medial-posteriorhemisphere is described. The patient is operated upon in a lateral reclining (park bench) position with the side to undergo occipitoparietal craniotomy, slightly dependant. Following dural opening to the margins of the superior sagittal and lateral sinuses, gentle traction with a brain spatula facilitates the occipital transtentorial and transfalcine approach to the incisural region. Ventricular or spinal fluid drainage is often helpful. The occipitallobe falls away from the midline and falcotentorial regions by gravity. Absence of occipital parasagittal bridgingveinsis a helpfulfeatureand carefulconvexitydural opening allows the occipitallobe to move laterally. Microsurgicaltreatment of pineal, splenial, falcotentorial and medial posterior hemisphere lesions may be greatly facilitated. Our experiencewith six cases is presented. To date, publishedresults of this operativeapproach have been excellent with the risk of hemianopsia, parenchymal venous infarction, and air embolus much lessened or eliminated. Keywords: Pineal lesion; medial AVM; dependant position; occipital transtentorial approach. A lateral decubitus operative position with an axillary roll (i.e. right side down) to which is added flexion of the hips and knees (left knee over right), and various degrees of face turn and flexion towards the floor is often referred to by neurosurgeons as the lateral, reclining, park-bench, semi- or three-quarter prone position. Such positioning has become a more frequently utilized approach to posterior fossa lesions and offers advantages over the sitting or semisitting operating positions. In the lateral reclining positions with the right side down, turning the patient's face towards the floor brings the left occipital area uppermost. However sufficient room is available to turn a generous, slightly dependant, right occipitoparietal craniotomy with mar-
gins at the sagittal and lateral venous sinuses. Dural opening combined with a lack of significant medial bridging veins allows the dependant right occipitoparietal lobe to fall away from the midline by gravity affording excellent transtentorial and transfalcine visualization of pineal, splenial, incisural and posterior medial lesions of the hemisphere with minimal brain retraction. The technical details of operative experience with two pineal region tumors, a medial occipitoparietal arteriovenous malformation (AVM), angioma of the corpus collosum splenium, large falcotentorial meningioma, and vein of Galen aneurysm are summarized below. A brief discussion and reference to the pertinent literature follows.
Operative Details A right sided (non-dominant) craniotomy is generally preferred, unless a left sided parasagittal lesion is present. Following general endotracheal anesthesia, placement of central intravenous and peripheral arterial lines, Foley catheter, and wrapping of the legs with elastic bandages, the patient is turned and lifted onto his right side. A spinal catheter for cerebrospinal fluid drainage may be placed. A blanket roll the same size or slightly thicker than the patient's upper arm is placed under the right axilla. The left hip is flexed about 120 degrees and the right hip 90 ~ A pillow is placed between the patient's knees. In more obese patients the dependant right arm will slip off the end of the operating table and is supported by a pillow (s) or padded arm board supported within the pin headholder table fix-
134
J.L. Stone etal.: Lateral Position-Dependant OccipitaI Approach
Fig. 1. Lateral position, right side down. The torso was turned approximately 30~ clockwise from the true lateral position and head further turned, flexed slightly and placed in the pin head holder, approximately45~ form the verticle axis
Fig. 3. Lateral position, right side down, occipital transtentorial/ transfalcine exposure. The tentorium cerebellihas been opened (*) exposingthe superiorvermis.Spleniumof the corpus callosum(CC); falxcerebri(FALX);tentoriumcerebelli(TENT); veinof Galen (VG). The occipitaltranstentorial (--,) and occipitoparietaltransfalcine(,L) approaches are indicated by arrows
Fig. 2. Lateral position right side down. The skin incision for a generous right occipitoparietalcraniotomy begins above and lateral to the mastoid, across the parietal eminence, extending to the left of midline below the external occipital protuberance (0)
ation apparatus. The head, which has been held by the surgeon, is placed in the Mayfield 3 pin head rest with face further rotated from the lateral position 30-45 ~ towards the floor and flexed slightly (Fig. 1). A large blanket roll or sand bags are place ventral to the patient's chest and anterior superior iliac spine so the semiprone (45 ~ torso should not later rotate in relation to the fixed head. Ventral support is especially important if clockwise rotation of the table towards the floor is contemplated for optimal intracranial exposure. The left shoulder and arm may remain at the side, or be foreward flexed 60-90 ~ on pillows, folded blankets or a well padded in-air table splint. The table is flexed so that the right occiput is just above the level of the right heart. Adhesive tape gently pulls down the left shoul-
der. The midline external occipital protuberance and the right posterior mastoid prominence are marked out. Skin incision extends from 3 cm above the right mastoid tip, superiorly across the parietal eminence and inferiorly several centimeters below the external occipital protuberance and to the left of midline (Fig. 2). A large oval right occipitoparietal free bone flap is turned, bordered on the superior sagittal sinus medially and the lateral sinus inferiorly. Lasix and mannitol are given for brain relaxation before dural opening. Several dural flaps are hinged on the sagittal and lateral sinus margins and sutured to drill holes in the surrounding bone edge. The major parietal bridging veins to the sagittal sinus are visualized and protected. These important veins may be microdissected slightly to allow hemisphere mobility laterally but kept moist and frequently observed for possible later stretching. If hydrocephalus is present, and the patient has not been shunted, the right occipital horn is tapped. The medial right occipital and occipitoparietal cortical surfaces are gently mobilized from the midline with a hand-held brain spatula over telfa as CSF is suctioned from the interhemispheric and later the pericallosal cistern. The occipital lobe is cautiously allowed to protrude slightly through a lateral slit in the wide dural exposure. The deeper intracranial approach is basically occipital transtentorial and transfalcine. A flexible self-retaining retractor system such as the Greenberg or Leyla is utilized, although usually only one moderate sized, well placed retractor blade is needed. The operative microscope is brought into place as soon as the char-
135
J. L. Stone et al.: Lateral Position- Dependant Occipital Approach Table 1
Case #
Sex Age (yrs) History
Pathology
Surgery
Course
1
F
15
Headaches and papilledema CT/MRI: 1.5cm lesion in continuity with quadrigeminal plate.
Benign hamartoma with neuronal and glial elements.
VP-shunt followed by subtotal resection of tumor.
Remains asymptomatic at 3 years follow-up.
2
M
25
Headache, diplopia, and vomiting. CT/MRI: 3 cm diameter pineal region mass.
Germinoma
VP shunt followed by subtotal retion of tumor.
One year later he is well after radiation therapy but maintains a postoperative partial hemianopsia.
3
M
2
Enlarging head, cranial bruit, CT/Angiogram: Hydrocephalus, vein of Galen Aneurysm (Arteriovenous fistula) fed by posterior cerebral artery branches bilaterally.
VeinofGalenAneurysm observed at surgery,
Ventriculostomy at the time of craniotomy, incision of corpus callosum, and bilateral ligation of feeders.
NeuroIogically intact 12 years later and shunting procedure not required.
4
F
24
Headaches and papilledema. CT/Angiogram: 6-7 cm diameter intensely vascular pineal region tumor.
Hemangiopericytoma originating at the falcotentorial junction,
Ventriculostomy at the time of craniotomy, wide incision of falx, gross total removal in three stages.
Status post radiation therapy and VP shunt for a trapped temporal horn. Remains neurologically intact without recurrence 8 years later.
5
F
30
Incomplete removal of right medial parietal AVM ten years previously. Presents with disablying headaches, seizures, and pre-existing homonomous hemianopsia. CT/Angiogram: Right medial parieto-occipital AVM fed by the right posterior cerebral artery.
AVM
Spinal catheter drainage initiated at craniotomy. Craniotomy and clipping of main posterior cerebral artery feeders at their medial bend above the tentorial edge. The AVM was microdissected and totally excised from the interhemispheric surface and white matter to a depth of about 1.5 cm.
Two years after surgery headaches have abated, seizures controlled, and hemianopsia was not worsened.
6
14
51
Severe occipital headache. Subarrachnoid hemorrhage. CT/MRI/Angiogram: Suggested an angiographically occult angioma about 1.5cm diameter in the splenium of the corpus callosum extending laterally 1.5 cm to the left of the midline.
Venous angioma.
Spinal catheter drainage initiated at craniotomy. Gross total excision of the angioma.
Neurologically intact 6 months post-operatively.
acteristically white corpus callosum is well visualized. The splenium of the corpus callosum is readily identified and followed backward to the thickened arachnoid surrounding the blueish venous structures. The straight sinus is usually visualized at the falcotentorial junction, and the vein of Galen, origin of the internal cerebral, basal and other venous structures become ap-
parent. The tentorium is split from the incisural edge posteriorly for 1-11/2 cm by coagulating on a carefully lifted nerve hook well lateral to the straight sinus and away from any brain surface. This tentorial flap is next sutured to the falx affording an orienting view of the superior cerebellar vermis and precentral cerebellar vein. The falx or splenium of the corpus callosum may
136
J.L. Stone etal.:Lateral Position-Dependant Occipital Approach
be incised as necessary for contralateral or further anterior exposure. Access to the quadrigeminal region is between the vein of Galen and precentral vein. The encountered pathology is removed from surrounding structures by microneurosurgical technique. Venous channels which had been compressed by pathology tend to distend and could be easily damaged. Towards the end of the operative procedure it may not be necessary to have a brain retractor in place (Fig. 3). The operative experience in six cases is summarized in Table 1.
is lessened in the lateral reclining as compared to a sitting or semisitting position, but remains a small possibility. As surgeons become more comfortable with this operative approach we believe they will find this an increasingly useful route to the pineal, splenial, medial occipitoparietal and falcotentorial regions.
Discussion The lateral reclining position, operated side down, occipital transtentorial approach to the medial occipitoparietal and pineal regions yields a broad exposure without routinely sacrificing venous structures or brain tissue. Slight dependancy of the occipital lobe on the operated side, combined with a lack of parasagittal bridging veins, allows the medial occipitoparietal region to be gently moved laterally by gravity. Within the past year several surgeons have independantly reported a similiar patient positioning and occipital transtentorial/transfalcine operative approach to the pinealtentorial region with excellent results and a paucity of surgical complications 1, 2, 8. An occipital or occipitoparietal craniotomy and posterior interhemispheric, falcotentorial approach to excise medial occipital (parasplenial) AVMs has also been described 7' 12, 13 Hemianopsia post-operatively m a y frequently be avoided as the optic radiations lie deep to the parasplenial and precuneal regions, predominately lateral to the occipital horn 13. These are basically modifications of the occipital transtentorial/transfalcine approach to the pineal region popularized by Poppen, Jamieson and others in the 1960's and 1970's 3-6' 9 11. In the lateral reclining, operated side down position, the patients "up-side" shoulder is less of a nuisance to the surgeon than in the traditional lateral reclining approach to a unilateral posterior fossa lesion. The "operated side d o w n " exposure also provides optimal mobility of the operative microscope and ample r o o m to utilize one's first assistant more efficiently. Lateralized occipitoparietal hemispheric lesions extending more than 1.5 cm from the midline are not readily excised with this approach. The chance of an air embolus
Acknowledgement We wish to thank Mrs. Ernestine Daniels for kindly typing the manuscript.
References 1. Ausman JI, Malik GM, Dujovny M, Mann R (1988) Threequarter prone approach to the pineal-tentorialregion. Surg Neurol 29:298-306 2. Clark WK (1987) Occipital transtentorial approach. In: Apuzzo MLJ (ed) Surgery of the third ventricle. Williams & Wilkins, Baltimore, pp 591-610 3. Glasauer FE (1970) An operative approach to pineal tumors. Acta Neurochir (Wien) 22:177-180 4. Jamieson KG (1971) Excision of pineal tumors. J Neurosurg 35: 550-553 5. Kempe LG (1968) Tumors of the third ventricle. In: Kempe LG (ed) Operative neurosurgery,vol I. Springer, New York, pp 145155 6. Lazar ML, Clark K (1974)Direct surgicalmanagementofmasses in the region of the vein of Galen. Surg Neurol 2:17-21 7. Martin NA, Wilson CB (1982) Medial occipital arteriovenous malformations. Surgical treatment. J Neurosurg 56:798-802 8. McCombJG, Apuzzo MLJ (1988) The lateral decubitus position for the surgical approach to pineal location tumors. Concepts Ped Neurosurg 8:186 199 9, Poppen JL (1966) The right occipital approach to a pinealoma. J Neurosurg 25:706-710 10. Raimondi AJ, Tomita T (1982) Pineal tumors in childhood. Epidemiology, pathophysiology, and surgical approaches. Child's Brain 9:239-266 11. Reid WS, Clark WK (1978) Comparison of the infratentorial and transtentorial approaches to the pineal region. Neurosurg 3:1-8 12. Salcman M, Nudelman RW, Bellis EH (1985) Arteriovenous malformations of the superior cerebellar artery: Excision via an occipital transtentorial approach. Neurosurgery 17:749-756 13. Ya~argilMG (1988) Microneurosurgery, Vol IIIB AVM &the Brain, clinical considerations,generaland specialoperative techniques, surgical results, monoperated cases. Cavernous and venous angiomas, neuroanesthesia. Thieme Medical Publishers, New York, pp 152-167 Correspondence and Reprints: James L. Stone, M.D., Chairman of Neurological Surgery, Cook County Hospital, 1835 West Harrison Street, Chicago, IL 60612, U.S.A.
Acta Neurochir (Wien) (1990) 102:133-136
9 by Springer-Verlag1990
The Lateral Position-Dependant Occipital Approach- to Pineal and Medial Occipitoparietal Lesions Technical Note J. L. Stone a, G. R. Cybulski 1, R. M. Crowell 1, and R. A. Moody 2 1Division of Neurological Surgery,Cook County and Universityof Illinois Hospitals and Hektoen Institute for Medical Research, Chicago, Illinois, and the 2 Division of Neurosurgery, Guthrie Clinic, Sayre, Pennsylvania, U.S.A.
Summary A recent modification of the occipital transtentorial approach to the pineal region and medial-posteriorhemisphere is described. The patient is operated upon in a lateral reclining (park bench) position with the side to undergo occipitoparietal craniotomy, slightly dependant. Following dural opening to the margins of the superior sagittal and lateral sinuses, gentle traction with a brain spatula facilitates the occipital transtentorial and transfalcine approach to the incisural region. Ventricular or spinal fluid drainage is often helpful. The occipitallobe falls away from the midline and falcotentorial regions by gravity. Absence of occipital parasagittal bridgingveinsis a helpfulfeatureand carefulconvexitydural opening allows the occipitallobe to move laterally. Microsurgicaltreatment of pineal, splenial, falcotentorial and medial posterior hemisphere lesions may be greatly facilitated. Our experiencewith six cases is presented. To date, publishedresults of this operativeapproach have been excellent with the risk of hemianopsia, parenchymal venous infarction, and air embolus much lessened or eliminated. Keywords: Pineal lesion; medial AVM; dependant position; occipital transtentorial approach. A lateral decubitus operative position with an axillary roll (i.e. right side down) to which is added flexion of the hips and knees (left knee over right), and various degrees of face turn and flexion towards the floor is often referred to by neurosurgeons as the lateral, reclining, park-bench, semi- or three-quarter prone position. Such positioning has become a more frequently utilized approach to posterior fossa lesions and offers advantages over the sitting or semisitting operating positions. In the lateral reclining positions with the right side down, turning the patient's face towards the floor brings the left occipital area uppermost. However sufficient room is available to turn a generous, slightly dependant, right occipitoparietal craniotomy with mar-
gins at the sagittal and lateral venous sinuses. Dural opening combined with a lack of significant medial bridging veins allows the dependant right occipitoparietal lobe to fall away from the midline by gravity affording excellent transtentorial and transfalcine visualization of pineal, splenial, incisural and posterior medial lesions of the hemisphere with minimal brain retraction. The technical details of operative experience with two pineal region tumors, a medial occipitoparietal arteriovenous malformation (AVM), angioma of the corpus collosum splenium, large falcotentorial meningioma, and vein of Galen aneurysm are summarized below. A brief discussion and reference to the pertinent literature follows.
Operative Details A right sided (non-dominant) craniotomy is generally preferred, unless a left sided parasagittal lesion is present. Following general endotracheal anesthesia, placement of central intravenous and peripheral arterial lines, Foley catheter, and wrapping of the legs with elastic bandages, the patient is turned and lifted onto his right side. A spinal catheter for cerebrospinal fluid drainage may be placed. A blanket roll the same size or slightly thicker than the patient's upper arm is placed under the right axilla. The left hip is flexed about 120 degrees and the right hip 90 ~ A pillow is placed between the patient's knees. In more obese patients the dependant right arm will slip off the end of the operating table and is supported by a pillow (s) or padded arm board supported within the pin headholder table fix-
134
J.L. Stone etal.: Lateral Position-Dependant OccipitaI Approach
Fig. 1. Lateral position, right side down. The torso was turned approximately 30~ clockwise from the true lateral position and head further turned, flexed slightly and placed in the pin head holder, approximately45~ form the verticle axis
Fig. 3. Lateral position, right side down, occipital transtentorial/ transfalcine exposure. The tentorium cerebellihas been opened (*) exposingthe superiorvermis.Spleniumof the corpus callosum(CC); falxcerebri(FALX);tentoriumcerebelli(TENT); veinof Galen (VG). The occipitaltranstentorial (--,) and occipitoparietaltransfalcine(,L) approaches are indicated by arrows
Fig. 2. Lateral position right side down. The skin incision for a generous right occipitoparietalcraniotomy begins above and lateral to the mastoid, across the parietal eminence, extending to the left of midline below the external occipital protuberance (0)
ation apparatus. The head, which has been held by the surgeon, is placed in the Mayfield 3 pin head rest with face further rotated from the lateral position 30-45 ~ towards the floor and flexed slightly (Fig. 1). A large blanket roll or sand bags are place ventral to the patient's chest and anterior superior iliac spine so the semiprone (45 ~ torso should not later rotate in relation to the fixed head. Ventral support is especially important if clockwise rotation of the table towards the floor is contemplated for optimal intracranial exposure. The left shoulder and arm may remain at the side, or be foreward flexed 60-90 ~ on pillows, folded blankets or a well padded in-air table splint. The table is flexed so that the right occiput is just above the level of the right heart. Adhesive tape gently pulls down the left shoul-
der. The midline external occipital protuberance and the right posterior mastoid prominence are marked out. Skin incision extends from 3 cm above the right mastoid tip, superiorly across the parietal eminence and inferiorly several centimeters below the external occipital protuberance and to the left of midline (Fig. 2). A large oval right occipitoparietal free bone flap is turned, bordered on the superior sagittal sinus medially and the lateral sinus inferiorly. Lasix and mannitol are given for brain relaxation before dural opening. Several dural flaps are hinged on the sagittal and lateral sinus margins and sutured to drill holes in the surrounding bone edge. The major parietal bridging veins to the sagittal sinus are visualized and protected. These important veins may be microdissected slightly to allow hemisphere mobility laterally but kept moist and frequently observed for possible later stretching. If hydrocephalus is present, and the patient has not been shunted, the right occipital horn is tapped. The medial right occipital and occipitoparietal cortical surfaces are gently mobilized from the midline with a hand-held brain spatula over telfa as CSF is suctioned from the interhemispheric and later the pericallosal cistern. The occipital lobe is cautiously allowed to protrude slightly through a lateral slit in the wide dural exposure. The deeper intracranial approach is basically occipital transtentorial and transfalcine. A flexible self-retaining retractor system such as the Greenberg or Leyla is utilized, although usually only one moderate sized, well placed retractor blade is needed. The operative microscope is brought into place as soon as the char-
135
J. L. Stone et al.: Lateral Position- Dependant Occipital Approach Table 1
Case #
Sex Age (yrs) History
Pathology
Surgery
Course
1
F
15
Headaches and papilledema CT/MRI: 1.5cm lesion in continuity with quadrigeminal plate.
Benign hamartoma with neuronal and glial elements.
VP-shunt followed by subtotal resection of tumor.
Remains asymptomatic at 3 years follow-up.
2
M
25
Headache, diplopia, and vomiting. CT/MRI: 3 cm diameter pineal region mass.
Germinoma
VP shunt followed by subtotal retion of tumor.
One year later he is well after radiation therapy but maintains a postoperative partial hemianopsia.
3
M
2
Enlarging head, cranial bruit, CT/Angiogram: Hydrocephalus, vein of Galen Aneurysm (Arteriovenous fistula) fed by posterior cerebral artery branches bilaterally.
VeinofGalenAneurysm observed at surgery,
Ventriculostomy at the time of craniotomy, incision of corpus callosum, and bilateral ligation of feeders.
NeuroIogically intact 12 years later and shunting procedure not required.
4
F
24
Headaches and papilledema. CT/Angiogram: 6-7 cm diameter intensely vascular pineal region tumor.
Hemangiopericytoma originating at the falcotentorial junction,
Ventriculostomy at the time of craniotomy, wide incision of falx, gross total removal in three stages.
Status post radiation therapy and VP shunt for a trapped temporal horn. Remains neurologically intact without recurrence 8 years later.
5
F
30
Incomplete removal of right medial parietal AVM ten years previously. Presents with disablying headaches, seizures, and pre-existing homonomous hemianopsia. CT/Angiogram: Right medial parieto-occipital AVM fed by the right posterior cerebral artery.
AVM
Spinal catheter drainage initiated at craniotomy. Craniotomy and clipping of main posterior cerebral artery feeders at their medial bend above the tentorial edge. The AVM was microdissected and totally excised from the interhemispheric surface and white matter to a depth of about 1.5 cm.
Two years after surgery headaches have abated, seizures controlled, and hemianopsia was not worsened.
6
14
51
Severe occipital headache. Subarrachnoid hemorrhage. CT/MRI/Angiogram: Suggested an angiographically occult angioma about 1.5cm diameter in the splenium of the corpus callosum extending laterally 1.5 cm to the left of the midline.
Venous angioma.
Spinal catheter drainage initiated at craniotomy. Gross total excision of the angioma.
Neurologically intact 6 months post-operatively.
acteristically white corpus callosum is well visualized. The splenium of the corpus callosum is readily identified and followed backward to the thickened arachnoid surrounding the blueish venous structures. The straight sinus is usually visualized at the falcotentorial junction, and the vein of Galen, origin of the internal cerebral, basal and other venous structures become ap-
parent. The tentorium is split from the incisural edge posteriorly for 1-11/2 cm by coagulating on a carefully lifted nerve hook well lateral to the straight sinus and away from any brain surface. This tentorial flap is next sutured to the falx affording an orienting view of the superior cerebellar vermis and precentral cerebellar vein. The falx or splenium of the corpus callosum may
136
J.L. Stone etal.:Lateral Position-Dependant Occipital Approach
be incised as necessary for contralateral or further anterior exposure. Access to the quadrigeminal region is between the vein of Galen and precentral vein. The encountered pathology is removed from surrounding structures by microneurosurgical technique. Venous channels which had been compressed by pathology tend to distend and could be easily damaged. Towards the end of the operative procedure it may not be necessary to have a brain retractor in place (Fig. 3). The operative experience in six cases is summarized in Table 1.
is lessened in the lateral reclining as compared to a sitting or semisitting position, but remains a small possibility. As surgeons become more comfortable with this operative approach we believe they will find this an increasingly useful route to the pineal, splenial, medial occipitoparietal and falcotentorial regions.
Discussion The lateral reclining position, operated side down, occipital transtentorial approach to the medial occipitoparietal and pineal regions yields a broad exposure without routinely sacrificing venous structures or brain tissue. Slight dependancy of the occipital lobe on the operated side, combined with a lack of parasagittal bridging veins, allows the medial occipitoparietal region to be gently moved laterally by gravity. Within the past year several surgeons have independantly reported a similiar patient positioning and occipital transtentorial/transfalcine operative approach to the pinealtentorial region with excellent results and a paucity of surgical complications 1, 2, 8. An occipital or occipitoparietal craniotomy and posterior interhemispheric, falcotentorial approach to excise medial occipital (parasplenial) AVMs has also been described 7' 12, 13 Hemianopsia post-operatively m a y frequently be avoided as the optic radiations lie deep to the parasplenial and precuneal regions, predominately lateral to the occipital horn 13. These are basically modifications of the occipital transtentorial/transfalcine approach to the pineal region popularized by Poppen, Jamieson and others in the 1960's and 1970's 3-6' 9 11. In the lateral reclining, operated side down position, the patients "up-side" shoulder is less of a nuisance to the surgeon than in the traditional lateral reclining approach to a unilateral posterior fossa lesion. The "operated side d o w n " exposure also provides optimal mobility of the operative microscope and ample r o o m to utilize one's first assistant more efficiently. Lateralized occipitoparietal hemispheric lesions extending more than 1.5 cm from the midline are not readily excised with this approach. The chance of an air embolus
Acknowledgement We wish to thank Mrs. Ernestine Daniels for kindly typing the manuscript.
References 1. Ausman JI, Malik GM, Dujovny M, Mann R (1988) Threequarter prone approach to the pineal-tentorialregion. Surg Neurol 29:298-306 2. Clark WK (1987) Occipital transtentorial approach. In: Apuzzo MLJ (ed) Surgery of the third ventricle. Williams & Wilkins, Baltimore, pp 591-610 3. Glasauer FE (1970) An operative approach to pineal tumors. Acta Neurochir (Wien) 22:177-180 4. Jamieson KG (1971) Excision of pineal tumors. J Neurosurg 35: 550-553 5. Kempe LG (1968) Tumors of the third ventricle. In: Kempe LG (ed) Operative neurosurgery,vol I. Springer, New York, pp 145155 6. Lazar ML, Clark K (1974)Direct surgicalmanagementofmasses in the region of the vein of Galen. Surg Neurol 2:17-21 7. Martin NA, Wilson CB (1982) Medial occipital arteriovenous malformations. Surgical treatment. J Neurosurg 56:798-802 8. McCombJG, Apuzzo MLJ (1988) The lateral decubitus position for the surgical approach to pineal location tumors. Concepts Ped Neurosurg 8:186 199 9, Poppen JL (1966) The right occipital approach to a pinealoma. J Neurosurg 25:706-710 10. Raimondi AJ, Tomita T (1982) Pineal tumors in childhood. Epidemiology, pathophysiology, and surgical approaches. Child's Brain 9:239-266 11. Reid WS, Clark WK (1978) Comparison of the infratentorial and transtentorial approaches to the pineal region. Neurosurg 3:1-8 12. Salcman M, Nudelman RW, Bellis EH (1985) Arteriovenous malformations of the superior cerebellar artery: Excision via an occipital transtentorial approach. Neurosurgery 17:749-756 13. Ya~argilMG (1988) Microneurosurgery, Vol IIIB AVM &the Brain, clinical considerations,generaland specialoperative techniques, surgical results, monoperated cases. Cavernous and venous angiomas, neuroanesthesia. Thieme Medical Publishers, New York, pp 152-167 Correspondence and Reprints: James L. Stone, M.D., Chairman of Neurological Surgery, Cook County Hospital, 1835 West Harrison Street, Chicago, IL 60612, U.S.A.
