Recent evidence indicates that Wall (1970) may have been premature in concluding that dorsal column lesions produce no discernable sensory defects. Much of the negative evidence Wall presented to support this view is inconclusive. In addition several studies have reported significant sensory deficits in animals with severed dorsal columns. On the other hand, the literature strongly supports Wall's view that dorsal column lesions cause motor disturbances. A review of the anatomical and electrophysiological literature reveals growing evidence for the dissociation of two major subsystems relaying in the dorsal column nuclei. The possible functions of these two systems are discussed.

Forty-eight surgically removed pituitary adenomas have been investigated hy electron microscopy. Distinct differences in fine structural appearances permitted their separation into 5 classes: 1) Growth hormone, (GH)-cell tumors; 2) Prolactin cell tumors; 3) Mixed adenomas composed of GH and prolactin cell's; 4) Adrenocorticotrophic-Melanocyte stimulating hormone (ACTH-MSH) cell tumors; 5) Undifferentiated cell adenomas. Densely and sparsely granulated tumors were distinguished within forms appeared to represent well defined entities, they may be variants of the same tumor differing only in pace of hormone production and/or release. Number and size of secretory granules varied considerably among tumors composed of the same cell type indicating that pituitary tumor classification cannot be based solely on granule morphology. This classification takes into account morphogenesis with emphasis on clinical features and structure-function relationship.

Ultrastructural changes in the zone of clamping of the middle cerebral artery of the squirrel monkey are described after application of a surgical clip. The experimental model utilized has been widely applied to the study of cerebral ischemia and possibly has relevance to clamps applied to the cerebral vessels during neurosurgical treatment of patients with cerebrovascular disorders.

The earliest changes within the arterial wall were found in the smooth muscle (media) and accompanying fasciculi of nerves. Changes within the nerve bundles were sufficiently advanced following 4 hours of vascular clipping to suggest temporary or permanent impairment of neurogenic innervation of the cerebral vessels distal to the trunk of the vessel clipped.

A patient with Von Hippel-Lindau's disease was followed from the time of diagnosis to the time of his death 13 years later. He was asymptomatic when the diagnosis was made, although a hemangioblastoma of the medulla was found on angiography. The patient's course and autopsy are described and the features of this disease are reviewed.

The object of this study was to determine if traumatic brain edema (BE) and increased intracranial pressure (ICP) reduce cerebral blood flow (CBF). Two groups of patients were studied, one with slight BE and ICP less than 20 mm Hg., the other with pronounced BE and ICP over 20 mm Hg. Although ICP was higher and cerebral perfusion pressure lower in pro-nounced edema there was only a small and non-significant reduction in CBF and no difference in cerebro-vascular resistance. Since traumatic BE does not increase resistance to blood flow through the brain, cerebral perfusion can be maintained if an adequate perfusion pressure is established. This in turn, demands the monitoring and control of ICP.

The first reported case of lissencephaly resulting from a consanguinous union strengthens the supposition that in some cases, it is transmitted as an autosomal recessive trait. Comparison of this case with a sporadically occuring case of lissencephaly, with different cortical morphology, suggests that lissencephaly may be an example of either varying gene expressivity or gene-tic heterogeneity. Lissencephaly and pachygyria may eventually be shown to be due to different causes, some inherited, some acquired. The classical examples of lissencephaly are different morphologically from a case in which antenatal cytomegalovirus infection had produced a small smooth brain. This suggests that antenatal viral infections are destructive rather than teratogenic.

The records of 107 patients with supratentorial astrocytomas, Grades 1 and 2, treated surgically between I960 and 1970 were analyzed. Abstracted clinical data was retrospectively analyzed with respect to the relative significance of different factors affecting survival. Twenty-eight patients were alive at the time of follow-up in 1974. Age, clinical grade at surgery and radiation therapy were the most important determinants of prolonged postoperative survival.

The more malignant astrocytomas occurring in the Province of Alberta had previously been reviewed. The present study was carried out to demonstrate the relative influence of histologic grade of astrocytomas and to analyze the factors affecting postoperative survival in the low grade, supratentorial astrocytomas.

The role of computerized transaxial tomography (CTT) of the brain in 100 post-operative tumor cases is assessed. CTT proves an accurate method of determining tumor recurrence and in evaluating such complications as intracerebral hemorrhage, subdural or extradural hemorrhage, cerebral infarction, hydrocephalus and shunt patency. Its accuracy decreases the need for interventional procedures. Its usefulness may be limited by the presence of metal clips or plates, by radio-opaque contrast media or intracranial air.

A case of benign intracranial hypertension due to prolonged administration of a low dose of Vitamin A is described in a young male investigated as a brain tumor suspect. Computerized axial tomography showed small and symmetrical lateral ventricles which was consistent with the diagnosis. The syndrome of benign intracranial hypertension and its relationship to chronic Vitamin A toxicity is discussed.

A 61 year old man had chronic renal failure because of oxaluria and renal calculi. Two years before death, while on hemodialysis, he developed severe progressive peripheral neuropathy. At autopsy calcium oxalate crystals were found in the peripheral nerves and other tissues. Nerve lesions included segmental demyelination, axonal degeneration and crystalline deposits within the myelin sheath. Ultrastructurally there were foci of osmiophilic granular material within myelin lamellae and endoneurium, and pleomorphic lamellar bodies in the perinuclear Schwann cell cytoplasm.

It is probable that chronic hemodialysis favors the deposition of oxalate in the Schwann cells and the development of neuropathy in patients with primary hyperoxaluria and renal failure.

This experiment investigates the holding property of polyglycolic acid suture in repair of divided dog sciatic nerves and the influence of absorption of this synthetic material on regeneration. The conclusion is that PGA maintains its tensile strength sufficiently long to allow both physical union and good regeneration of the divided nerve. The suture absorption does not influence regeneration.

The relationships between the center and the surround of the receptive field of the rabbit retinal ganglion cell were investigated. This was done by coupling localized light spots and electrical activation of the retina and by analyzing the time of the excitatory and inhibitory periods. The responsiveness to the electrical transretinal pulse revealed a) that ON stimulation in OFF-center cells and OFF stimulation in ON-center cells, elicited a primary period of inhibition with a short latency; b) the long latency response of surround stimulation was not preceded by an inhibitory period unless the center was simultaneously stimulated in the same direction; c) a transient response to a stationary spot of light is followed by a period of inhibition. These results are discussed in relation to the known cellular retinal networks.