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Burak Sade and Joung H. Lee

Object

In this study, the authors aimed to identify the factors that would predict the operative distance between the trigeminal nerve (fifth cranial nerve) and the acousticofacial nerve complex (seventh–eighth cranial nerves) preoperatively when approaching the cerebellopontine angle (CPA) through the suboccipital retrosigmoid approach.

Methods

In 40 consecutive patients who underwent microvascular decompression of the trigeminal nerve via a sub-occipital retrosigmoid approach for trigeminal neuralgia, the following three parameters were assessed on preoperative magnetic resonance images: 1) the angle between the tentorium and the line drawn from the hard palate (tentorial angle); 2) the angle between the lines drawn along the petrous bones ventral to the internal auditory canals (petrous angle); and 3) the angle between the tentorium and the line connecting the opisthion to the inion (occipital angle). The distance between the trigeminal nerve and the acousticofacial nerve complex (referred to as “distance”) was measured intraoperatively. Statistical analysis was performed using the Pearson correlation test.

Results

The mean values were 50.9 ± 11.5° for the tentorial angle, 102.5 ± 13.1° for the petrous angle, 83.4 ± 9.7° for the occipital angle, and 3.1 ± 1.5 mm for distance. There was a strong inverse correlation between the tentorial angle and distance (r = −0.228, p = 0.08). The mean distance was 3.5 ± 1.9 mm for a tentorial angle less than 51° and 2.7 ± 1.1 mm for a tentorial angle of at least 51°. No correlation existed between either the petrous or occipital angles and distance.

Conclusions

The distance between the trigeminal nerve and acousticofacial nerve complex decreases in the presence of a steep tentorial angle. This limits the operating field between these cranial nerves when reaching the petroclival or the superior CPA regions through the retrosigmoid approach. Awareness of such anatomical features at the time of pre-operative planning is of paramount importance in selecting the optimum surgical approach and minimizing operative complications.

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Burak Sade and Joung H. Lee

✓Facial nerve schwannomas can occur anywhere from the internal auditory canal to the parotid gland. Schwannomas arising from the greater superficial petrosal nerve are exceedingly rare.

The authors report the case of a 63-year-old woman who presented with a selective low-frequency hearing loss of 3 weeks' duration. Neurological examination demonstrated a House–Brackmann Grade II facial paresis and asymmetrical hearing loss on the left side. Audiometric evaluation showed a significant loss of low-frequency hearing with a speech reception threshold (SRT) of 30 dB and a speech discrimination score (SDS) of 88% on the left side. Magnetic resonance imaging revealed a 2.4-cm enhancing left middle fossa mass. Near-complete resection was performed via a left temporal craniotomy. The tumor was located in the Glasscock triangle and had invaded the petrous bone overlying the cochlea. A very small piece of the tumor over the cochlea was left in order to preserve hearing. A postoperative audiogram showed significant improvement in the patient's hearing, with an SRT of 20 dB and an SDS of 100%. The histological findings were consistent with schwannoma.

The patient experienced postoperative improvement of hearing function despite cochlear involvement, which has previously been reported as an unfavorable factor for postoperative hearing outcome in facial nerve schwannomas.

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Soichi Oya and Joung H. Lee

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Burak Sade, Soichi Oya and Joung H. Lee

Object

There are various schools of thought when it comes to dural reconstruction following meningioma surgery, which are largely based on the personal experience of the individual surgeons. The authors' aim in this study was to review different dural reconstruction techniques, with an emphasis on their experience with the synthetic onlay dural graft technique.

Methods

The medical records of 439 consecutive patients who were surgically treated for an intracranial meningioma over a period of 7 years, and for whom dural reconstruction was performed using the onlay dural graft DuraGen (Integra Neurosciences) were reviewed retrospectively. The most common tumor location was the convexity (27.6%), and 12% of the patients had undergone previous surgery. Complications related to the closure technique and/or closure material, such as CSF leakage from the incision, rhinorrhea, or infectious or chemical meningitis were reviewed.

Results

A CSF leak was encountered in 2 patients (0.4%), and 10 patients (2.3%) experienced graft-related complications in the form of chemical meningitis, cerebritis, and accumulation of extraaxial fluid. Infectious complications were seen in 4 patients (0.9%; bacterial meningitis, osteomyelitis, epidural abscess). None of the patients had pseudomeningocele that required a second intervention.

Conclusions

In the authors' experience, the incidence of CSF leakage following non-watertight reconstruction of the dura mater in meningioma surgery performed using dural onlay graft was 0.4%. Graft-related complications occurred in 2.3%. These figures compare favorably to the majority of the series in which watertight dural closure is described and emphasized.

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Soichi Oya, Burak Sade and Joung H. Lee

Object

The aim of this study was to describe the surgical technique used for removal of sphenoorbital meningiomas in the authors' practice and to review the operative outcome.

Methods

Review of the senior author's practice between 1994 and 2009 revealed 39 patients (mean age 48 years) eligible for this study. Clinical presentation, surgical technique, postoperative outcome, and follow-up data are presented. Surgical technique is detailed, with an emphasis on aggressive removal consisting of drilling of the hypertrophied sphenoid bone, orbital wall, and anterior clinoid process, followed by tumor removal and a wide resection of the involved dura. A simple dural closure without reconstruction of the orbital roof or the lateral wall of the orbit is also described.

Results

Gross-total resection was achieved in 15 cases (38.5%), near-total resection with small residual in the cavernous sinus or periorbita in 20 cases (51.3%), and subtotal resection in 4 cases (10.3%). Postoperative complications included trigeminal hypesthesia in 9 patients, oculomotor palsy in 3 patients, and seizure in 2 patients. Seven patients had recurrence within the mean follow-up period of 40.7 months. Preoperative visual deficits were present in 21 patients (53.8%). Of these, 14 (66.7%) experienced visual recovery to normal levels postoperatively. Statistical analyses revealed preoperative severe visual deficit and sphenoid bone hypertrophy as an independent risk factor and an independent favorable factor, respectively, for a favorable visual outcome. Proptosis was resolved (≤ 2 mm) in 73.5% of the authors' patients. No patient had postoperative enophthalmos.

Conclusions

In the authors' practice, surgery for sphenoorbital meningiomas consists of resection of the orbital/sphenoid intraosseous, intraorbital, and intradural tumor components. The authors believe that aggressive removal of the orbital/sphenoid intraosseous tumor is critical for a favorable visual outcome and tumor control. Furthermore, satisfactory cosmetic results can be achieved with simple reconstruction techniques as described.

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Varun R. Kshettry, Joung H. Lee and Mario Ammirati

Interest in studying the anatomy of the abducent nerve arose from early clinical experience with abducent palsy seen in middle ear infection. Primo Dorello, an Italian anatomist working in Rome in the early 1900s, studied the anatomy of the petroclival region to formulate his own explanation of this pathological entity. His work led to his being credited with the discovery of the canal that bears his name, although this structure had been described 50 years previously by Wenzel Leopold Gruber. Renewed interest in the anatomy of this region arose due to advances in surgical approaches to tumors of the petroclival region and the need to explain the abducent palsies seen in trauma, intracranial hypotension, and aneurysms. The advent of the surgical microscope has allowed more detailed anatomical studies, and numerous articles have been published in the last 2 decades. The current article highlights the historical development of the study of the Dorello canal. A review of the anatomical studies of this structure is provided, followed by a brief overview of clinical considerations.

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Burak Sade, Richard A. Prayson and Joung H. Lee

✓ Gliosarcomas are bimorphic intraaxial tumors. Involvement of the skull base is highly unexpected. The authors present the case of a temporal lobe gliosarcoma with significant infratemporal fossa extension. This 55-year-old man presented with a 1-month history of severe progressive headache. Neurological examination was unremarkable except for bilateral papilledema. Magnetic resonance imaging revealed a 6-cm right temporal mass with extension into the infratemporal fossa. The patient underwent a right frontotemporal craniotomy together with drilling of the sphenoid ridge and middle fossa floor. The tumor consisted of intraaxial, intracranial as well as extradural, and extracranial components with extension to the posterolateral wall of the sphenoid sinus. It had a relatively well-circumscribed dissection plane. Gross-total resection was achieved, and the middle fossa floor was reconstructed using a rotated temporalis muscle flap. The postoperative course was uneventful except for hypesthesia in the distribution of the maxillary division of the right trigeminal nerve. The histopathological diagnosis was consistent with gliosarcoma. Radiotherapy and chemotherapy consisting of temozolomide were administered subsequently, and the patient was recurrence free 12 months after his initial diagnosis.

In the presence of a mass lesion with both intraaxial and extracranial involvement, gliosarcoma should be considered among the differential diagnoses. Aggressive resection should be attempted, including the use of skull base surgical techniques to ensure an optimal outcome. The effect of skull base involvement to the overall treatment and outcome of patients with gliosarcomas would be difficult to determine given the rare occurrence of these lesions in such locations.

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Sarel J. Vorster, Richard A. Prayson and Joung H. Lee

✓ Solitary fibrous tumor (SFT) is a neoplasm first described as a tumor of mesenchymal origin involving soft tissues. The authors provide a review of the literature with detailed pathological analysis and radiological description of SFTs involving the central nervous system.

The authors report a rare case of a SFT of the thoracic spine in an adult man presenting with myelopathy. Magnetic resonance imaging revealed a well-circumscribed, intradural, extramedullary mass at the T2–3 level. Histological examination demonstrated a proliferation of predominantly spindle-shaped cells with a collagen-matrix background. Immunohistochemical staining was positive for vimentin and CD34 and negative for S-100 and epithelial membrane antigen with an MIB-1 labeling index of 2.6%. Review of the literature revealed 10 cases in which this tumor, frequently found in the pleura, was involved in the central nervous system.

Although rare and their clinical significance as yet unknown, SFTs may be considered in the differential diagnosis of intradural spinal cord lesions. The natural history is also unknown, but these tumors appear to be biologically benign.

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Samuel Tobias, Chang-Hyun Kim, Gregory Kosmorsky and Joung H. Lee

Object

Clinoidal meningiomas remain a major neurosurgical challenge. Surgery-related outcome has been less than desirable in the past, and little attention has been directed toward improving visual deficits. The authors advocate a skull base technique for the removal of these difficult tumors and describe its advantages in terms of improving extent of resection and enhancing overall outcome, particularly visual function.

Methods

A retrospective analysis was performed on data obtained in 26 consecutive patients with clinoidal meningiomas (including one patient with hemangiopericytoma) who underwent resection between June 1995 and January 2003. In 24 cases the skull base procedure involved extradural anterior clinoidectomy, optic canal unroofing, and optic sheath opening; in two cases a standard pterional craniotomy was performed. Fourteen of the 26 patients suffered significant preoperative visual deficits. All patients underwent thorough pre- and postoperative ophthalmological evaluations. The follow-up period ranged from 3 to 91 months (mean 42.3 months). Total resection was achieved in 20 patients (77%), and the majority (76.9%) of patients with preoperative visual impairment experienced significant improvement.

Conclusions

With the use of the skull base technique, total resection and excellent visual outcome may be achieved with minimal morbidity in most patients with clinoidal meningiomas.

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John A. Jane, Charles S. Haworth, William C. Broaddus, Joung H. Lee and Jacek Malik

✓ A technique for exposing far-lateral intervertebral disc herniations without disrupting the facet is described. This technique is a simple modification of the standard neurosurgical approach.