T HE value of a chemical or pharmacological agent that temporarily would lower cerebrospinal-fluid pressure and decrease the mass of the brain is apparent to neurosurgeons. Since Weed and 1VfcKibben 4e,47 demonstrated that various hypertonic solutions could accomplish these effects, many agents have been tested. 6,14,17,22,29,45,49,55 Each of these substances has been found to have certain disadvantages or toxic effects. The use of hypertonic urea for these purposes originally was proposed by Fremont-Smith and Forbes, 15 and Wolff and Forbes, 64 and was restudied by Fremont-Smith eta/., ~3 Smythe et a/., 39 and Javid and Settlage. ~5 This material was difficult to prepare for sterile intravenous injection, but when lyophilized urea and invert sugar became available it found wide acceptance. ~4,42,44 While hypertonic urea frequently is effective in lowering cerebrospinal-fluid pressure and decreasing the mass of the brain, there are certain theoretical and practical objections to its use. Urea is distributed throughout total body water, n.4~ although it does equilibrate relatively slowly with brain water and cerebrospinal fluid, s.33 Thus, unless the urea administered were excreted fairly rapidly, one would expect dissipation of its osmotic gradient as equilibration of urea with brain water and cerebrospinal fluid

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An increase in catecholamine secretion after insulin injection has been repeatedly demonstrated in animals ( 1-4) and humans (5,6,7). This response is caused by hypoglycemia rather than insulin per se, since it is abolished when hypoglycemia is prevented by simultaneous administration of glucose (4J).The locus at which the hypoglycemia acts to increase catecholamine secretion is unsettled. The increase is blocked by adrenal denervation( 1 ,%lo) indicating that a neural mechanism is involved. Brooks ( 1 1) suggested that this mechanism was spinal since he found that cats with cervical cord transections survived following the injection of doses of insulin that were regularly fatal in cats with denervated adrenals. However Duner (3) suggested that the hypothalamus was involved because he found that when he produced local hyperglycemia by injecting glucose solution directly into the hypothalamus, catecholamine secretion fell.In the present studies it was found that the transection of the midbrain and cervical spinal cord in dogs did not eliminate the marked increase in catecholamine secretion following injection of insulin, but removal of the midthoracic portion of the spinal cord abolished it.Materials and methods. Thirty-three male mongrel dogs weighing 8.5-18.6 kg were fasted for 24 hours, then anesthetized with pentobarbital and subjected to cannulation of the right lumboadrenal vein by the method of Hume and Nelson(l2). Cannulas were also placed in the femoral artery and vein.No further surgery was performed in 5 dogs, which served as controls. In 4 animals, the brainstem was transected at the midcollicular level through a parieto-occipital craniotomy. In three animals, the spinal cord was transected at the level of the second cervical seg-* Supported by USPHS grants. ment, and in one at the level of the seventh cervical segment. In 6 dogs the thoracic and lumbar portions of the spinal cord were removed. This was accomplished by performing laminectomies in the lower cervical and upper lumbar regions, dividing the cord, threading a heavy wire through the spinal canal between the laminectomies, attaching a gauze plug to the wire and extracting the cord segment by pulling the plug through the spinal canal. Bleeding was controlled by packing the canal with gauze. In 14 dogs, smaller segments of the spinal cord were removed.In all dogs, 1-2 units of crystalline zinc insulin per kg of body weight were injected one to two hours after all surgical manipulations were completed. Samples of adrenal venous and peripheral arterial blood were collected 15 and 5 minutes before, and 15, 30, 60, 90 and 120 minutes after the injection. The blood collected was generally replaced by transfusion of blood from normal dogs. Blood pressure was monitored continuously using a femoral arterial cannula, a Statham StrainGauge and a Grass model 5 polygraph. Body temperature was monitored by means of a thermistor probe in the rectum, and body temperature was maintained above 35°C by the use of external heat when necessary. At the end of the e...

T HE intracranial epidermoid and dermoid tumors (cholesteatomas, or pearly tumors) are uncommon, benign and grow slowly. The location of the tumor in some instances may preclude complete removal, but even partial excision will often result in prolonged or permanent relief of signs and symptoms. The neurological disabilities caused by these tumors are often relatively slight.We reviewed the cases of patients at the University of California Medical Center and the Veterans' Administration Hospital, San Francisco, who had intracranial epidermoid and dermoid tumors and who were treated during the past ~0 years. (One patient was first treated ~5 years ago.) Lesions that involved the skull exclusively were not included in this review.