✓ The histology of the intradural arteries was studied in 12 consecutive autopsy cases of patients dying 1 day to 15 months after their initial spontaneous subarachnoid hemorrhage. In all patients surviving 4 weeks or more and in one surviving 4 days, the lumina of the intracranial arteries were narrowed by subendothelial granulation tissue which thickened the intima. In all seven cases with structural changes in the intracranial arteries, vessels near the site of hemorrhage were involved; in four cases vessels remote from the site of hemorrhage were also involved. Changes were usually restricted to large arteries with a prominent muscular layer and confined to the subarachnoid space. The presence and degree of intimal thickening correlated with the distribution and amount of subarachnoid blood or its breakdown products. This process apparently does not represent an obliterative endarteritis involving vessels exclusively supplying infarcted brain, but is probably a reaction to mechanical or anoxic damage to the intima following vasoconstriction. It is suggested that this arterial structural change might be confused with delayed or prolonged “vasopasm.”

THOUGH intramedullary cavitation of the spinal cord was recognized earlier, the term "syringomyelia" was first used by Oliver d'Angers in 1837 for cavities within the cord, regardless of etiology. Using the term in this manner, Schlesinger in 190s 43 noted the occurrence of intramedullary cavities in relation to trauma, inflammation, vascular disorders, tumors, malformations of the nervous system, pachymeningitis, and leptomeningitis, while in other cases he could identify no associated pathology.Holmes, 24 Collier, 8 and Schneider 44 have studied the role of trauma in causing central cord cavitation. Tauber and Langworthy 45 reported cavities associated with arterial insufficiency. McLaurin, et al.,~5 have experimentally produced cavitation secondary to adhesive arachnoiditis. Netsky 36 has suggested arterial pathology as a basic cause of idiopathic syringomyelia, although, in general, the thickening and hyalinization of the blood vessels in the walls of syringes have been regarded as a secondary reaction, possibly due to hydrostatic pressure within the cyst.There is a high incidence of syringomyelia in association with intraspinal neoplasms. Kernohan, et al., ~s and Poser 3s reported an incidence of 53.5vffo and 31~ respectively. This association has been ascribed to necrosis within the tumor, 26 obstruction of vital arterial and venous channels by the tumor, u or transudation of fluid from such neoplasms as hemangioblastomas. 54 Poser ~8 in his recent exhaustive review concluded that both the syrinx and tumor result from abnormal glial and mesodernml elements included in the cord as a result of faulty closure of the dorsal raphe of the neuraxis during embryonic (tevelopment.Syringomyelia is often present in cases of dysraphic and dysplastic phenomena within

✓ With use of the Todd-Wells stereotaxic unit and appropriate biopsy needles, confirmation was obtained of the preoperative diagnosis in 25 of 31 deep-seated intracranial tumors. Selective criteria, preoperative evaluation, and the method of biopsy are described, and the advantages of stereotaxic biopsy discussed. The successful addition of stereotaxic cryosurgical treatment of two pinealomas following biopsy is briefly reported.

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