Journal of neurosurgery
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Journal of neurosurgery · Sep 1983
Case ReportsMannitol-induced rebleeding from intracranial aneurysm. Case report.
A case is presented in which rebleeding from an intracranial saccular aneurysm occurred a few minutes after intravenous administration of mannitol during surgery. The relationship between the reducing effect of mannitol on elevated intracranial pressure and the increased pressure gradient across the aneurysm wall, causing risk of rebleeding, is discussed. Procedures that can reduce this risk are summarized.
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Journal of neurosurgery · Aug 1983
Electrophrenic respiration following anastomosis of phrenic with branchial nerve in the cat.
Patients with high spinal cord injuries may be totally dependent on artificial ventilation. Prolonged use of mechanical devices requires intensive care, which restricts the mobility of these patients. Electrophrenic respiration has been used with success to overcome this difficulty. ⋯ Lack of rhythmic bursts of electrical activity in the anastomosed phrenic nerve and electromyographic activity in the ipsilateral hemidiaphragm confirmed that the anastomosed phrenic nerve remained disconnected from the respiratory motoneurons. Abundance of collagen matrix in the electron micrographs of the anastomosed phrenic nerve indicated that degeneration of the axons of phrenic motoneurons had occurred and the brachial nerve had grown into the phrenic nerve stump. These results indicate that electrophrenic respiration may be possible in patients with spinal cord injuries at the C-3 to C-5 vertebral levels if the phrenic nerve is kept viable by anastomosing it to a branch of the brachial nerve.
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Allen's weight-drop method for producing experimental spinal cord injuries was improved by placing a curved stainless steel plate anterior to the spinal cord to provide a smooth, hard surface for the receipt of posterior cord impact. In addition, an electronic circuit was used to ensure that cord injury was produced by a single impact, thereby enhancing the reproducibility of the injury mechanism. Using a spinal cord injury model with these modifications, the author found that the recovery of hindlimb function and the histopathological appearance of the injured cord 6 weeks after upper lumbar injury were closely related to injury magnitude. The curve of functional recovery versus injury magnitude has a sharp transition centered at 10 gm X 15 cm, and indicates that an injury of 10 gm X 20 cm produces a "threshold" lesion suitable for the future evaluation of spinal cord treatment methods.
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The microsurgical anatomy of the veins of the posterior fossa was defined in 25 cadavers. These veins are divided into four groups: superficial, deep, brain-stem, and bridging veins. The superficial veins are divided on the basis of which of the three cortical surfaces they drain: the tentorial surface, which faces the tentorium and is exposed in a supracerebellar approach, is drained by the superior hemispheric and vermian veins; the suboccipital surface, which is below and between the lateral and sigmoid sinuses and is exposed in a wide suboccipital craniectomy, is drained by the inferior hemispheric and inferior vermian veins; and the petrosal surface, which faces forward toward the posterior surface of the petrous bone and is retracted to expose the cerebellopontine angle, is drained by the anterior hemispheric veins. ⋯ The major deep veins in the fissures between the cerebellum and brain stem are the veins of the cerebellomesencephalic, cerebellomedullary, and cerebellopontine fissures, and those on the cerebellar peduncles are the veins of the superior, middle, and inferior cerebellar peduncles. The veins of the brain stem are named on the basis of whether they drain the midbrain, pons, or medulla. The veins of the posterior fossa terminate as bridging veins, which collect into three groups: a galenic group which drains into the vein of Galen; a petrosal group which drains into the petrosal sinuses; and a tentorial group which drains into the tentorial sinuses near the torcula.
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Journal of neurosurgery · Jun 1983
Intermittent versus continuous brain retraction. An experimental study.
Brain damage due to retraction was studied morphologically and physiologically in the dog brain. Two methods of retraction were compared using a retractor with a strain gauge: 1) continuous retraction; and 2) intermittent retraction. Total retraction time was 60 minutes for each method. ⋯ The power spectrum of the electrocorticogram showed full recovery after the release of retraction when the retraction force was less than 40 gm. With intermittent retraction, the damage was morphologically minimal with a retraction force of less than 50 gm, and recovery of the power spectrum of the electrocorticogram was prompt in comparison with continuous retraction. The results indicate the superiority of intermittent over continuous retraction.