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Bennett M. Stein

✓ In six patients with pineal tumors, a posterior fossa approach was used to explore the pineal region. This approach avoided the deep venous system and led to no mortality and minimal morbidity. Because a certain percentage of pineal lesions are benign and amenable to resection, it is recommended that all pineal tumors be explored prior to a decision regarding radiotherapy.

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Bennett M. Stein

✓ In a series of 164 resected arteriovenous malformations (AVM's), 25 were located on the medial aspect of the cerebral hemispheres. These AVM's require special attention because of the following characteristics: 1) their obscure location, making resection more difficult than the usual AVM; 2) a high incidence of intraventricular hemorrhage; 3) their frequent involvement of the choroid plexus of the ventricles and the arteries and veins related to the choroid plexus; and 4) the configuration of their venous drainage, which is often to superficial veins as well as to the deep venous systems. The results achieved with excision of these difficult AVM's were good. There was no mortality and the morbidity rate was under 4%. The surgical exposures, which were tailored to the location of these malformations, are described in detail.

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Philip Cogen and Bennett M. Stein

✓ Few neurosurgeons have stressed the occurrence, manifestations, and resectability of intramedullary spinal arteriovenous malformations (AVM's). In six of 17 patients in the authors' series of operable spinal AVM's, the lesions had major intramedullary components. Three of these six patients presented with subarachnoid hemorrhage, and all had catastrophic neurological deficits which gradually improved. The hemorrhages appeared to originate from large venous varices lying adjacent to the intramedullary portion of the AVM. The mechanism explaining the sudden neurological deficit in the other three patients was presumed to be thrombosis within the venous varices associated with their AVM's. The reliability of the various radiographic procedures in identifying the intramedullary components of these AVM's is discussed. These malformations may be removed totally with a high degree of safety using microsurgical techniques. The postoperative course in this series of patients was gratifying in terms of improvement of neurological deficits. Postoperative angiography was not performed on all of these patients. However, the follow-up period averaged 5 years.

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Robert A. Solomon and Bennett M. Stein

✓ In a series of 250 intracranial arteriovenous malformations (AVM's), 12 malformations involved the brain stem. Nine of these lesions were treated surgically, with complete obliteration in eight. There were no operative deaths, and only two patients were made worse by surgery. In the nonsurgically treated group, one patient had embolization therapy and two patients underwent radiation therapy. Results in these three patients have not been satisfactory. These data indicate that brain-stem AVM's can be surgically removed with acceptable morbidity.

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Rodney A. Rozario and Bennett M. Stein

✓ When halo-pelvic traction is applied at a rapid rate it may induce cranial nerve palsies. The sixth, ninth, and tenth cranial nerves appear to be the most vulnerable. A proposed etiology is the stretching of these nerves resulting in a compromised blood supply with a consequent temporary paralysis which usually improves within 8 to 10 weeks.

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Robert A. Solomon and Bennett M. Stein

✓ In a series of 60 intramedullary spinal cord tumors, there were eight cases of hemangioblastoma. Seven of these eight patients displayed evidence of diffuse spinal cord enlargement over multiple levels at a considerable range beyond the actual location of the tumor. One patient had a large intramedullary cyst that accounted for only part of the enlargement, and one had multiple tumor nodules. Six other patients had no obvious explanation for the diffuse cord enlargement.

This phenomenon of extensive spinal cord enlargement appears to be unique to this type of tumor and not related to multiple tumors or extensive cyst formation. The cord enlargement seems to be related to edema and congestion of the spinal cord, perhaps secondary to the vascular shunt present in the hemangioblastomas. The possible pathophysiology and clinical importance of this observation is discussed.

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Robert A. Solomon and Bennett M. Stein

✓ A series of 250 surgically treated cerebral arteriovenous malformations (AVM's) is presented, in which 22 lesions were located primarily in the thalamus and caudate nucleus. A standardized interhemispheric approach through the posterior corpus callosum and into the atrium of the lateral ventricle was utilized for the surgical removal of these AVM's. Total removal was confirmed by angiography in 18 patients; removal was subtotal in four cases. There were no deaths in this group of patients. Disturbances of recent memory pre- and postoperatively were seen in half of the patients, but most of these deficits were temporary. Other complications included: postoperative homonymous hemianopsia (six cases), transient hemiparesis (three cases), hemisensory loss (two cases), Parinaud's syndrome (one case), and recurrent hemorrhage 2 years after surgery (one case). All 22 patients returned to their previous occupations and are leading independent lives. The results of this experience indicate that thalamocaudate AVM's can be effectively treated by resection.

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Eddy Garrido and Bennett M. Stein

✓ A patient who developed an embolic occlusion of the right middle cerebral artery while undergoing a cerebral arteriogram was successfully operated on by removal of the embolus under the surgical microscope. Early postoperative cerebrovascular spasm was a factor in the transient deterioration of the patient's neurological condition. When the patient was last seen 2 ½ months after surgery she was almost intact neurologically with only a mild right parietal dysfunction but with total resolution of the left hemiplegia. The literature is reviewed.

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Michael B. Sisti, Robert A. Solomon, and Bennett M. Stein

✓ Surgical resection of 10 obscure arteriovenous malformations (AVM's) was accomplished with craniotomy guided by computerized tomography (CT) or angiography and the use of the Brown-Roberts-Wells stereotactic frame. Stereotactic craniotomy was invaluable for resection of the following types of AVM's: 1) AVM's with a nidus less than 2 cm in diameter, 2) AVM's located in an eloquent area of the brain, and 3) AVM's located deep in the brain. Stereotactic localization of these AVM's on preoperative radiological studies provides a precise route to the nidus, often avoiding important areas of the brain. This series included six male and four female patients with a mean age of 32 years. All patients presented with an intracerebral hemorrhage, from which eight made a complete neurological recovery prior to surgery. Two AVM's were located on the cortex, three were found subcortically, and five were situated near the ventricles or in the deep white matter.

As a guide, angiography was used in six cases and CT in four cases. In each instance, the study providing the best image of the AVM nidus was employed. Postoperatively, no neurological deficits were found in eight patients and, in the two patients with preoperative deficits, neurological improvement was observed after recovery from surgery. Postoperative studies revealed complete removal of the AVM in all patients, and all lesions were confirmed histologically. The authors conclude that stereotactic craniotomy provides the optimum operative approach for the localization and microsurgical resection of AVM's that are either obscure or located deep in the brain.

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Michael B. Sisti, Abraham Kader, and Bennett M. Stein

✓ The surgical outcome in a series of small arteriovenous malformations (AVM's) that might have been considered optimal for radiosurgery is reviewed. In a total microsurgical series of 360 patients, 67 (19%) underwent resection of AVM's less than 3 cm in largest diameter, regardless of location. Many of these lesions (45%) were in locations that might be considered surgically inaccessible such as the thalamus, brain stem, medial hemisphere, and paraventricular regions. Complete angiographic obliteration of the AVM by microsurgical technique was accomplished in 63 patients (94%) with a surgical morbidity of 1.5% and no operative mortality. Patients with hemispheric AVM's had a cure rate of 100% and no neurological morbidity. Stereotactically guided craniotomy was used in 14 patients (21%) to locate and resect deep or concealed malformations. The results from five major radiosurgery centers treating similar-sized AVM's are analyzed. The authors' surgical results compare favorably with those from radiosurgery centers which, in their opinion, supports the conclusion that microneurosurgery is superior to radiosurgery, except for a small percentage of lesions that are truly inoperable on the basis of inaccessibility.