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Harry R. van Loveren, Jeffrey T. Keller, Magdy El-Kalliny, Daniel J. Scodary and John M. Tew Jr.

✓ This report describes a surgical approach to the cavernous sinus. Based on the work of Parkinson, Dolenc, and other pioneering investigators, a comprehensive surgical approach for the treatment of lesions of the cavernous sinus is distilled and presented in 12 simple steps. The approach to surgical exploration of this region is divided into an extradural and intradural phase, each with six steps. The bony, neural, and/or vascular structures of each step are discussed. These steps may be used in their entirety for total exploration of the cavernous sinus, but also in part for lesions that involve only limited regions of the cavernous sinus. Either by design or circumstance, every intracranial neurosurgeon will eventually be led to the cavernous sinus region, and a clear understanding of cavernous sinus anatomy should be part of their armamentarium.

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Anterior cervical discectomy and interbody fusion

An experimental study using a synthetic tricalcium phosphate

Toshio Shima, Jeffrey T. Keller, Mariano M. Alvira, Frank H. Mayfield and Stewart B. Dunsker

✓ This study evaluates the histological and histochemical changes and osteogenicity of Synthos (tricalcium phosphate ceramic) implanted in the cervical intervertebral space. The cervical vertebrae from C-3 to C-6 were exposed in 20 dogs, and discectomy was performed at the third and fifth spaces. A dowel of Synthos was inserted into the third space, and a piece of fresh autologous graft from the humerus was inserted into the fifth space. The animals were divided into five groups with four animals in each. Four animals were sacrificed at each of 3, 6, 12, 18, and 22 weeks after the procedure. The C-3 to C-6 vertebrae were removed en bloc. One-half of each specimen was processed for histological examination of bone development, while the other half was processed for the two-color fluorescent labeling technique of Suzuki and Matthews for determination of osteogenesis at the time of operation and sacrifice. Various degrees of compression of the Synthos dowel were noted, with anterior and/or posterior displacement of the implant in 70% of the cases. Results indicate that the Synthos implant was biochemically and biomechanically unacceptable for the purposes of this investigation.

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Norberto Andaluz, Thomas A. Tomsick, Jeffrey T. Keller and Mario Zuccarello

✓Given the relatively benign natural history of cavernous carotid artery aneurysms and based on anecdotal reports in the literature of subarachnoid hemorrhage (SAH) or subdural hemorrhage (SDH) from these aneurysms, observation is warranted and typically recommended. In this case report, the authors describe a woman who harbored a partially thrombosed, giant cavernous aneurysm that ruptured after she underwent a balloon occlusion test (BOT) and predominately led to an SDH. The authors believe that this occurrence is the first such report in the English literature. They discuss possible mechanisms for this event and the literature related to SAH or SDH from cavernous aneurysms, including why cavernous aneurysms cause such hemorrhages. The authors also recommend that attention be paid to such lesions regarding the possibility of aneurysmal rupture following a BOT.

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Jamal M. Taha, John M. Tew Jr., Harry R. van Loveren, Jeffrey T. Keller and Magdy El-Kalliny

✓ Trigeminal neurinomas have traditionally been excised through conventional approaches. Because symptomatic tumor recurrence exceeds 50% after conventional procedures, the authors evaluated the use of skull base approaches to achieve complete resection and a lower rate of symptomatic recurrence. Comparisons of skull base with conventional approaches to trigeminal neurinomas have been limited to small series with short-term follow-up periods. The authors reviewed their experiences with conventional (frontotemporal transsylvian, subtemporal—intradural, subtemporal—transtentorial, and suboccipital) and skull base (frontotemporal extradural—intradural, frontoorbitozygomatic, subtemporal anterior petrosal, and presigmoid posterior petrosal) surgical approaches for the excision of trigeminal neurinomas. In this paper they report the results of 15 patients with trigeminal neurinoma who underwent 27 surgical procedures between 1980 and 1990. Seventeen of the procedures used conventional and 10 used skull base approaches. All patients had tumors arising from Meckel's cave and the porus trigeminus either initially or on recurrence. Tumors located in the cavernous sinus recurred most frequently (83%); other tumors that recurred frequently were those located in Meckel's cave and the porus trigeminus (67%), and the posterior fossa (17%). The tumor extended into the anterolateral wall of the cavernous sinus in 38% of patients with cavernous sinus involvement.

Tumor exposure and ease of dissection were superior with skull base approaches. Residual or recurrent tumors were found in 65% of patients following conventional approaches compared with 10% of patients following skull base approaches. Using skull base approaches, the surgeon was more accurate (90%) in estimating tumor excision than when using conventional approaches (43%). Perioperative complications were similar with both.

The authors discuss the indications, advantages, and limitations of each approach. Based on anatomical considerations, they propose a strategy to best resect these tumors.

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Repair of spinal dural defects

An experimental study

Jeffrey T. Keller, Carlos M. Ongkiko Jr., Mary C. Saunders, Frank H. Mayfield and Stewart B. Dunsker

✓ The search for an ideal substance for duraplasty has stimulated clinical and experimental investigations. To date a large number of materials have been employed for dural repair, although there is as yet no unanimity regarding the ideal material. Most of these studies have been concerned with cranial dura, and spinal duraplasty has received less attention. This study was designed to examine the repair of spinal dural defects in the dog. The materials chosen for this experiment were autologous fat, a polyester fiber mesh (Mersilene) and siliconecoated Dacron (Dura Film). Nineteen dogs were used in this study. Following lumbar laminectomy and the excision of elliptical pieces of dura (1.0 × 0.5 cm) at three noncontiguous levels, each of the defects was repaired using one of the three materials. Groups of animals were sacrificed at each of 3, 6, 12, and 24 weeks after dural repair. The lumbar region was removed en bloc and prepared for histological examination. Repair of the dural opening was achieved in all cases. The polyester fiber mesh was quite effective for dural repair, serving as a scaffold through which a neomembrane grew and united the dural edges. The results with autologous fat were similarly favorable. On the other hand, results with silicone-coated Dacron showed encapsulation by connective tissue, with the ventral aspect of the graft frequently compressing the underlying cord.

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A 10-year experience in the treatment of trigeminal neuralgia

Comparison of percutaneous stereotaxic rhizotomy and posterior fossa exploration

Harry van Loveren, John M. Tew Jr., Jeffrey T. Keller and Mary A. Nurre

✓ Of 1000 patients with classic trigeminal neuralgia who were treated during the last 10 years, 90% had an initial favorable response to medical therapy, but 75% (750 patients) failed to achieve satisfactory long-term relief. Of these, 700 patients were treated by percutaneous stereotaxic rhizotomy (PSR) and 50 were selected for posterior fossa exploration (PFE).

Of the 50 patients undergoing PFE, 82% had neurovascular contact at the trigeminal root entry zone, but only 46% were judged to have had significant neurovascular compression. Exploration was negative in 16% of patients and revealed neural compression by bone in 2%. Patients with neurovascular compression were treated by microvascular decompression (MVD); all other patients with exploratory surgery underwent partial sensory rhizotomy. At 3 years after PFE, 84% of patients are pain-free. Results are excellent in 68%, good in 12%, fair in 4%; 12% had a recurrence of their neuralgia. The 700 patients treated by PSR have been followed for 6 years. Results are excellent in 61%, good in 13%, fair in 5%, and poor in 1%; 20% had a recurrence.

This study indicates that there is no significant difference in results between PSR and PFE in the treatment of trigeminal neuralgia. The concept that neurovascular compression is a mechanical factor in the etiology of trigeminal neuralgia was supported, but neurovascular compression was less common than previously reported. Percutaneous stereotaxic rhizotomy is a less formidable procedure than PFE, and is easily repeated. Recent technical advances have improved the results obtained with PSR. Therefore, PSR remains the procedure of choice for the majority of patients with trigeminal neuralgia.

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Carlos M. Ongkiko Jr., Jeffrey T. Keller, Frank H. Mayfield and Stewart B. Dunsker

✓ Two cases are presented in which the patients developed an unusual complication following the use of an artificial dural substitute, silicone-coated Dacron (Dura Film). Both patients had undergone removal of a tumor and involved dura. The first patient developed a very thick connective-tissue capsule of the graft material which simulated a recurrent tumor. The second patient developed an acute hemorrhage initially thought to be an acute subdural hematoma beneath the artificial dura 9 weeks after tumor removal and implantation of the graft. A review of the literature and proposed mechanisms of these complications are presented.

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Hwa-shain Yeh, Jeffrey T. Keller, Kim A. Brackett, Edmund Frank and John M. Tew Jr.

✓ As microvascular surgery has developed, the necessity for smaller arterial prostheses of less than 2 mm in internal diameter (ID) has increased markedly. Glutaraldehyde-stabilized human umbilical arteries with 1.5 to 2.0 mm ID are smaller than any other graft material currently available. This study was designed to determine whether this graft material has potential clinical application for microanastomosis.

Twenty male albino rats, each weighing 400 to 500 gm, were used in this study. The abdominal aorta was exposed and a 3- to 4-mm segment was resected. A 10-mm interposition graft of glutaraldehyde-stabilized human umbilical artery was implanted by end-to-end anastomosis. The patency of the grafts was determined by repeated operative exploration at intervals of 1 week, and 1, 3, 9, and 12 months. Two grafts were found to be occluded each time at the 1-, 3-, and 9-month explorations. At each exploration time, five rats were sacrificed and histopathological studies conducted. All five remaining grafts were patent at 12 months.

There was no evidence of endothelial proliferation on the luminal surface of the patent grafts as determined by scanning electron microscopy. The luminal surface and underlying region consisted of an amorphous proteinaceous-like material. Significant degeneration of the vessel wall was noted in all grafts surviving over 9 months. Central necrosis surrounded by a chronic inflammatory process that extended to and included the adventitia was observed in the occluded grafts. While the patency demonstrated was good, the tissue changes noted in the walls of the grafts indicate that further study is necessary before this material can be used as a graft in humans.

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Magdy El-Kalliny, Harry van Loveren, Jeffrey T. Keller and John M. Tew Jr.

✓ The lateral dural wall of the cavernous sinus is composed of two layers, the outer dural layer (dura propria) and the inner membranous layer. Tumors arising from the contents of the lateral dural wall are located between these two layers and are classified as interdural. They are in essence extradural/extracavernous. The inner membranous layer separates these tumors from the venous channels of the cavernous sinus.

Preoperative recognition of tumors in this location is critical for selecting an appropriate microsurgical approach. Characteristics displayed by magnetic resonance imaging show an oval-shaped, smooth-bordered mass with medial displacement but not encasement of the cavernous internal carotid artery. Tumors in this location can be resected safely without entering the cavernous sinus proper by using techniques that permit reflection of the dura propria of the lateral wall (methods of Hakuba or Dolenc).

During the last 5 years, the authors have identified and treated five patients with interdural cavernous sinus tumors, which included two trigeminal neurinomas arising from the first division of the fifth cranial nerve, two epidermoid tumors, and one malignant melanoma presumed to be primary. The pathoanatomical features that make this group of tumors unique are discussed, as well as the clinical and radiological findings, and selection of the microsurgical approach. A more favorable prognosis for tumor resection and cranial nerve preservation is predicted for interdural tumors when compared with other cavernous sinus tumors.