Seventeen patients with petrous meningiomas managed at St. Michael's Hospital, during the years 1973-1987, were retrospectively reviewed. There were 15 females and 2 males; their ages ranged from 42 to 68 years (mean age: 53 years). The clinical presentation most commonly included headache and eighth cranial nerve dysfunction; the average duration of symptoms was 6 years (3 month - 27 years). Computed tomography was performed in 15 cases. The mean tumour size was 2.5 centimeters (0.5 - 4 cm). The most common site of tumour origin was at or medial to the poms acousticus. Meningioma was suspected preoperatively in 10 of the 15 patients who had preoperative CT scans. Complete excision was obtained in 12 cases. There were no operative deaths after initial resections. Postoperative morbidity included worsening of pre-existing hearing loss in six patients, transient facial nerve palsies in six, permanent facial nerve palsies in four and new facial or corneal hypesthesia in three. Two patients developed cerebrospinal fluid fistulae. Tumour recurrence occurred into two patients in whom a complete resection was anticipated. Also, in two patients with incompletely resected tumours second operations were required. Fourteen patients are alive, 13 of whom care for themselves independently. The average follow-up was 5 years (6 months - 9 years). It seems appropriate to recommend initial radical surgical excision of these benign tumours, where possible, in order to prevent tumour recurrence.

Immunohistochemical stains for cytokeratins, vimentin, epithelial membrane antigen, carcinoembryonic antigen and S-100 were performed on nine ecchordoses and 10 chordomas. 100% of the ecchordoses were positive for cytokeratin, vimentin and epithelial membrane antigen. 78% were S-100 positive. 100% of the chordomas stained positively for cytokeratin, vimentin and S-100 and 90% were positive for epithelial membrane antigen. No ecchordosis or chordoma was carcinoembryonic-antigen positive. These findings are interesting for two reasons. First, the similar staining properties of chordoma and ecchordosis physaliphora support the embryologic hypothesis of their common origin from the fetal notochord. Second, they indicate that when an ecchordosis causes symptoms prompting surgical resection, differentiation of the lesion from chordoma with routine immunohistochemistry would not be helpful.

The course of a patient with an olfactory neuroblastoma treated with conventional doses of chemotherapeutic agents and radiotherapy is presented. The patient survived 34 months after tumour necrosis with resultant pneumocephalus requiring surgical intervention.

This paper reviews our recent studies on the mechanism of cerebral vasospasm following subarachnoid hemorrhage (SAH) in monkeys. Middle cerebral artery (MCA) vasospasm was maximal at 7 days, resolving by 14 days, and absent at 28 days after SAH. Arterial fibrosis was not detected during vasospasm, although there was intimal hyperplasia with fibrosis 28 days after SAH. On scanning electron microscopy, smooth muscle cells from vasospastic arteries had corrugated cell membranes and appeared similar to cells contracted pharmacologically, suggesting that vasospastic smooth muscle is contracted. Morphometric analysis of arteries obtained 7 days after SAH showed no significant increases in arterial wall area of vasospastic arteries compared with normal MCAs. The results suggest vasospasm in monkeys is not due to hypertrophy, hyperplasia, or fibrosis in the arterial wall. Vasospasm may be mainly vascular smooth muscle contraction, which damages the arterial wall, leading to secondary structural changes in the arterial wall which occur after angiographic vasospasm.

DX centers are semiconductor dopants which form deep states due to a large lattice relaxation. At low temperature, the DX centers exhibit persistent photoconductivity. When exposed to light in a spatial pattern, the photocarriers are confined to the illuminated regions by Coulomb interaction with the localised DX centers. The resulting spatial modulation of the free carrier density gives rise to a modulation of both the electrical conductivity and the dielectric constant. We demonstrate both effects by measurements of the conductance anisotropy and optical diffraction of samples exposed to excitation in a striped pattern. Erasure is achieved by thermal annealing. The constrast ratio of the conductivity modulation is greater than 108; in our experiment it is limited to ∼100 by light scattering. We estimate that 100nm resolution is feasible. Optical diffraction efficiencies up to 40% have been demonstrated in a stripe-illuminated thick sample. The persistence of the written patterns at low temperature is potentially useful in high-density data storage applications and the fabrication of erasable submicron devices.