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Kenan I. Arnautovic, Ossama Al-Mefty, T. Glenn Pait, Ali F. Krisht and Muhammad M. Husain

The authors studied the microsurgical anatomy of the suboccipital region, concentrating on the third segment (V3) of the vertebral artery (VA), which extends from the transverse foramen of the axis to the dural penetration of the VA, paying particular attention to its loops, branches, supporting fibrous rings, adjacent nerves, and surrounding venous structures.

Ten cadaver heads (20 sides) were fixed in formalin, their blood vessels were perfused with colored silicone rubber, and they were dissected under magnification. The authors subdivided the V3 into two parts, the horizontal (V3h) and the vertical (V3v), and studied the anatomical structures topographically, from the superficial to the deep tissues. In two additional specimens, serial histological sections were acquired through the V3 and its encircling elements to elucidate their cross-sectional anatomy. Measurements of surgically and clinically important features were obtained with the aid of an operating microscope.

This study reveals an astonishing anatomical resemblance between the suboccipital complex and the cavernous sinus, as follows: venous cushioning; anatomical properties of the V3 and those of the petrous-cavernous internal carotid artery (ICA), namely their loops, branches, supporting fibrous rings, and periarterial autonomic neural plexus; adjacent nerves; and skull base locations. Likewise, a review of the literature showed a related embryological development and functional and pathological features, as well as similar transitional patterns in the arterial walls of the V3 and the petrous-cavernous ICA. Hence, due to its similarity to the cavernous sinus, this suboccipital complex is here named the "suboccipital cavernous sinus." Its role in physiological and pathological conditions as they pertain to various clinical and surgical implications is also discussed.

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Luis A. B. Borba, Ossama Al-Mefty, Robert E. Mrak and James Suen

✓ Chordomas are rare tumors that usually occur in adults. This report describes four cases of intracranial chordomas treated in patients 20 years of age or younger by the senior author (O.A.M.) during a 4-year period. The authors also reviewed the literature on pediatric patients, which revealed that the clinical presentations, histological patterns, and behaviors of these tumors differ considerably depending on whether the patient is younger or older than 5 years of age. The younger population had a wider range of presenting symptoms, a greater prevalence of atypical histological findings with aggressive behavior, a greater range of cellularity than the classic chordomas, and a higher instance of metastasis; it showed no chondroid component compared to a 17.1% instance in the older patients. The prognosis for patients with a chordoma is related directly to the histological pattern of the tumor; the atypical chordoma carries a poor prognosis. The prognoses for children older than 5 years of age with a classic or chondroid tumor were not significantly different (p = 0.788). At follow up, the difference in survival rates between patients undergoing surgery plus radiation therapy and those who had surgery alone was statistically significant (p = 0.00446). No correlation was found between radical resection or radiation therapy and an improved prognosis for patients younger than 5 years of age who had a tumor with an atypical histological pattern. This study identifies and delineates the distinction between these age groups and provides a review of the potential prognostic factors.

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Mark A. Cobb, Muhammad Husain, Bruce J. Andersen and Ossama Al-Mefty

✓ It is well known that the histological appearance of meningiomas often fails to predict accurately the clinical behavior of the tumor. Therefore, attention has turned from tumor histology to tumor biology. Proliferating cell nuclear antigen (PCNA), a cell cycle-regulated protein, has been recently characterized as the cofactor of DNA polymerase-δ, an enzyme required for DNA replication. The rate of synthesis of PCNA directly correlates with the proliferative state of cells. Immunohistochemical labeling of this antigen is now possible with monoclonal antibodies that allow for its demonstration in routinely fixed, paraffin-embedded specimens.

In this study, the PCNA labeling index (LI) was determined for 83 meningiomas, including tumors with both benign and malignant clinical courses and with benign, atypical, and malignant histologies, apparent after total or subtotal resections. No statistical difference was found between the LI on recurrence and that found at initial presentation. In addition, stepwise multivariate regression analysis failed to identify any combination of factors (age, gender, race, age of specimen, tumor histology, Simpson grade of resection) that contributes to the predictive strength of the PCNA LI for tumor recurrence.

However, for LIs less than 2%, only one of 26 gross totally resected tumors recurred (mean follow up 53 months); for LIs more than 7%, five of 13 gross totally resected tumors recurred (mean follow up 55 months). The difference in recurrence rates between gross totally resected meningiomas with PCNA LIs less than 2% and those with PCNA LIs more than 7% achieved statistical significance with a Fisher's exact probability equaling 0.011. The authors conclude that quantitative PCNA labeling of meningiomas is a promising technique that can provide meaningful prognostic information.

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Ossama Al-Mefty, Luis A. B. Borba, Nobuo Aoki, Edgardo Angtuaco and T. Glenn Pait

✓ Ventral extradural lesions at the craniovertebral junction are commonly exposed through the transoral or transmaxillary approach. The disadvantages of these approaches include: 1) difficulty in reaching laterally located lesions; 2) ineligibility of patients with an intradental distance of less than 25 mm or severe macroglossia; 3) the need for a separate procedure for stabilization and fusion; and 4) the risk of infection from transgressing a contaminated field. In this report, the authors describe the use of the transcondylar approach to extradural nonneoplastic lesions of the anterior craniovertebral junction for decompression and stabilization. Advantages of this approach include: 1) a short distance to the lesion; 2) a wide surgical envelope; 3) direct visualization of the dural sac, eliminating manipulation of the brainstem or upper spinal cord; 4) easy identification and control of the ipsilateral vertebral artery; 5) direct visualization and preservation of the lower cranial nerves; and 6) a sterile field. In addition, occipitocervical fusion and instrumentation can be performed during the same procedure. The transcondylar approach, based on anatomical studies in cadavers, was used to treat eight patients with ventral nonneoplastic lesions at the craniocervical junction. The technique and results are described.

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H. Louis Harkey, Ossama Al-Mefty, Isam Marawi, Dudley F. Peeler, Duane E. Haines and Lon F. Alexander

✓ Twelve dogs developed a delayed onset of neurological abnormalities from chronic cervical cord compression that was characteristic of myelopathy. The animals were divided into two groups and matched according to degree of neurological deficit. Six animals underwent decompression through removal of the anteriorly placed compressive device. Throughout the experiment, serial neurological examinations and somatosensory evoked potential studies were performed on each animal. Spinal cord blood flow measurements were obtained during each surgical procedure and at sacrifice. Magnetic resonance images were obtained after compression and before sacrifice.

All animals in the decompressed group showed significant neurological improvement after decompression; no spontaneous improvement in neurological function was seen in the compressed group. On pathological examination, irreversible changes including large motor neuron loss, necrosis, and cavitation were seen in four of the animals in the decompressed group and five in the compressed group.

Cervical spondylotic myelopathy in humans is known to respond to decompression; this study provides further evidence that this animal model for chronic compressive cervical myelopathy accurately reflects the disease process seen in humans.

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Franco DeMonte, Harold K. Smith and Ossama Al-Mefty

✓ Despite recent advances in surgery of the cavernous sinus, meningiomas in that area offer a formidable challenge. The rationale for aggressive surgical removal of cavernous sinus meningiomas is based on the presumption that the extent of removal is inversely related to the rate of recurrence. Over the past 10 years, 41 patients with histologically benign meningiomas involving the cavernous sinus underwent aggressive surgery. Total removal, as confirmed by intraoperative inspection and postoperative radiological studies, was achieved in 31 patients (76%). Twelve patients have been followed for more than 5 years; 10 underwent total tumor removal and only one of these experienced recurrence (5 years after surgery). The other two patients underwent subtotal removal and had symptomatic and radiological evidence of regrowth 3 and 4 years after surgery. Pre-existing cranial nerve deficits improved in only 14% of the patients, remained unchanged in 80%, and worsened permanently in 6%. Seven patients experienced a total of 10 new cranial nerve deficits, four of which involved the nerves subserving ocular motor function. Extraocular muscle function did not worsen in the 25 patients with a seeing eye ipsilateral to the tumor, and no instance of visual worsening occurred.

Two patients died 4 months after surgery, one from severe delayed vasospasm and hypothalamic infarction and the other because of a myocardial infarction. Another patient died from a pulmonary embolus on the 9th postoperative day. There were three instances of cerebral ischemia; one was transient, lasting less than 24 hours, while two were related to injury of the middle cerebral artery and resulted in residual hemiplegia. Other complications included three cases of nonfatal pulmonary emboli, two cerebrospinal fluid leaks, and one instance each of exposure keratitis, acute hypothyroidism, and cerebral edema.