Biomedical subjects
Publications and source records attributed to E L Zager.
Temporal muscle asymmetry is a common sequela of pterional craniotomies. The authors describe a simple technique of restoring the temporal muscle to its origin by microscrew fixation. This technique provides reliable preservation of temporal muscle bulk and function with little additional operating time and no compromise of operative exposure.
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BACKGROUND AND PURPOSE: Brain temperature during ischemia is known to strongly influence the extent of cellular injury. The objectives of the present study were to determine the effect of severe focal ischemia on brain temperature and to assess the influence of those changes on focal infarction. METHODS: Severe focal ischemia was produced in rats using permanent occlusion of the distal middle cerebral artery combined with transient (60-minute) bilateral carotid artery occlusion. The temperature of the ischemic focus was measured with a small subdural probe. Three groups of rats were studied. In the first group, brain temperature was permitted to decline spontaneously to 32 degrees C after occlusion. In the second, brain temperature was maintained at 37.5 degrees C during occlusion. In the third group, the brain temperature was maintained at 37.5 degrees C for 40 minutes postocclusion before cooling. After recovery for 24 hours, the volume of infarction was measured in histological sections. RESULTS: In the absence of cranial heating, the brain temperature fell to 33 degrees C by 10 minutes postocclusion, and infarct volume was 19 +/- 9 mm3 (mean +/- SEM; n = 6). Maintaining brain temperature at 37.5 degrees C increased the volume of infarction to 82 +/- 16 mm3 (n = 7; p < 0.001). Delayed cooling did not prevent the increase in infarct volume (75 +/- 16 mm3; n = 6). CONCLUSIONS: These results demonstrate that in the present model of transient focal ischemia, spontaneous cooling of the brain during ischemia diminishes the extent of focal infarction, relative to that observed when cerebral hypothermia is prevented or delayed for 40 minutes.
A previously healthy 25-year-old woman suddenly developed right-sided facial numbness and a headache. The neurological examination was within normal limits with the exception of meningismus and right-sided facial sensory loss. A computed tomographic scan and a magnetic resonance imaging study demonstrated an acute hematoma in the right cerebellopontine angle. A 4-vessel cerebral angiogram revealed no abnormalities. Posterior fossa exploration disclosed a large, partially thrombosed, fusiform anterior inferior cerebellar artery aneurysm, which indented the pons at the trigeminal root entry zone. The aneurysm was excised, and the patient made an excellent recovery. She was left with a persistent trigeminal sensory deficit. Anterior inferior cerebellar artery aneurysms are rare lesions that generally present with a cerebellopontine angle syndrome; occasionally, facial sensory loss is also a feature. Isolated trigeminal sensory findings, as illustrated in this case, are extremely unusual in posterior fossa vascular lesions.
Three unusual cases are reported in which communicating syringomyelia presented acutely. The first patient presented with paraplegia, the second with acute respiratory distress secondary to bilateral vocal cord paralysis, and the third with symptoms of acute brain-stem ischemia. Each patient had a communicating spinal cord syrinx associated with a posterior fossa and foramen magnum region anomaly (a huge posterior fossa arachnoid cyst in one and Chiari malformations in two). The mechanisms of craniospinal pressure dissociation and hindbrain herniation are discussed, along with other reported emergency presentations of syringomyelia.
Neural transplantation has recently emerged as an exciting extension of neural regeneration and plasticity studies. In this review, the roots of current attempts at autologous and heterologous grafting of neural tissue are traced. Grafts of peripheral and central nervous tissue have been shown to be viable after implantation in a variety of locations in adult animals' brain and spinal cord, and survival data are impressive. Donor tissue is optimal when harvested from fetuses, and successful growth and differentiation of neural grafts have been demonstrated in host animals in a broad age range. A variety of morphologic, physiologic, and behavioral parameters suggest a certain degree of integration of graft tissue into the host central nervous system, although technical limitations do not yet allow definitive statements regarding the extent of functional reinnervation. Perhaps the most promising and innovative of current studies are those that utilize a combination of peripheral and central neural tissue as transplant material. There are a number of possible applications of neural transplantation to clinical neurology and neurosurgery, some of which are discussed.
Protection of the brain and spinal cord against ischemia is a goal of vast clinical importance. One approach to this objective is to reduce the tissue's functional activity in order to preserve energy for the metabolic processes that are essential to viability. Experiments to explore ways of reducing function-related energy demands were performed on isolated rabbit retina, a well-characterized model of organized adult mammalian central nervous system (CNS) tissue. The retina was maintained in a nearly physiological state in a miniature "heart-lung" apparatus. Energy metabolism (oxygen consumption and glycolysis) and electrophysiological function (determined by electroretinogram) of the in vitro retina were monitored, and their responses to a series of agents that may reduce energy requirements were determined. Large reversible reductions in O2 consumption, glycolysis, and electrophysiological function were seen in response to mild hypothermia (-3 degrees to -6 degrees C), phenytoin (Dilantin, 100 to 200 mg/kg), chlordiazepoxide (Librium, 200 microM), lithium (1 to 4 mM), Mg++ (6 to 20 mM), strophanthidin (0.15 to 0.25 microM), CO2 (25% to 30%), 2-amino-5-phosphonovaleric acid (APV, 500 microM), amiloride (1 mM), and dantrolene (1 mM). One retina was exposed simultaneously to a combination of six of these agents, which reduced its oxidative and glycolytic metabolism to less than 50% of the control level. The retina recovered metabolic and electrophysiological function after a 2 1/2-hour exposure period. Other agents tested (diphenhydramine, midazolam, nifedipine, nimodipine, and quercetin) had effects on energy metabolism and electrophysiological function that were poorly reversible. Surprisingly little effect was seen in response to general anesthetic agents (thiopental and Althesin) and other CNS depressants (chlorpromazine, ethanol, lidocaine, paraldehyde, valproic acid, and baclofen). The presumed mechanisms through which these agents reduce cellular energy requirements, as well as their potential roles in the treatment of CNS ischemia, are discussed.
A 56-year-old woman with metastatic breast carcinoma presented on her terminal hospital admission with diplopia secondary to bilateral abducens nerve palsies. Postmortem examination revealed a sellar mass composed of an unsuspected pituitary adenoma infiltrated by metastatic carcinoma. Review of the literature revealed only seven patients with this rare neoplasm-to-neoplasm metastasis, none of whom were reported to have had abducens palsies.
In this review, the authors present a critical overview of the historical development, indications, complications, operative techniques, and results of procedures for the alleviation of the major dyskinesias. Emphasis is placed upon recent refinement of technique, particularly stereotaxis, as well as neurophysiologic stimulation and recording, computerized tomographic scanning (CT) and magnetic resonance imaging (MRI). Specific disorders that may be amenable to surgical therapy include spasticity secondary to spinal cord pathology, cerebral palsy, and multiple sclerosis; the tremor and rigidity of Parkinson's disease; essential tremor; dystonia; spasmodic torticollis; post-traumatic and postinfarction intention tremor; cerebral palsy with tremor; hemiballismus; myoclonus; and dyskinesias induced by L-DOPA.
The neuropeptides vasopressin, adrenocorticotropin (ACTH), and beta-endorphin seem to have important effects on memory and learning. Animal studies attempting to demonstrate these effects are difficult to interpret because of the complexity of behavior that is described as "learning" and the impossibility of assessing verbal learning in animals. This article therefore reviews some of the animal literature on neuropeptides and learning, but focuses primarily upon studies in humans, both in normal volunteers and in patients with neurological disorders. Vasopressin enhances learning under some conditions. Intranasal administration has been associated with improvement on psychometric tests in patients with mild Alzheimer's disease and Korsakoff's psychosis, although these findings are not uniform. It improves performance on memory tests in normal volunteers, but does not seem to improve the memory deficit after head trauma. Cerebrospinal fluid levels are low in patients with Alzheimer's disease. ACTH and melanocyte-stimulating hormone (MSH) are two peptides the primary behavioral effect of which seems to be on attention or goal-motivated behavior rather than on memory processes themselves. Visual discrimination and the ability to continue repetitive tasks are enhanced; in mentally retarded subjects, the administration of ACTH or MSH improves performance on a variety of neuropsychological tests. It does not, however, improve cognitive function in the elderly. Endogenous opioids including beta-endorphin and met-enkephalin seem to have primarily an amnesic effect in animal studies. Their role in human learning is still uncertain, although naloxone, which antagonizes their effects, has been associated with improved cognitive performance in patients with Alzheimer's disease. These data underscore the complexity of the processes associated with human memory and the rudimentary state of our present knowledge. Whatever the mechanisms, however, vasopressin, ACTH, and endogenous opioids seem to have important effects upon memory.
The effects of hypophysectomy and dexamethasone administration on S-adenosylmethionine (SAM) levels in the adrenal, liver, pineal, and various brain regions were examined to determine the central and peripheral relationships between SAM and glucocorticoids in vivo. A simple and sensitive radioenzymatic assay was developed to measure tissue SAM concentrations following removal of its demethylated metabolite, S-adenosylhomocysteine (SAH), whose presence precludes accurate SAM determinations. Three patterns of SAM control emerged. In the adrenal, pineal, striatum, and midbrain, SAM levels fell after hypophysectomy and were restored by dexamethasone administration. In the thalamus, hypothalamus, hippocampus, and cerebellum, SAM levels increased after hypophysectomy and were not altered further by dexamethasone administration. In the liver, cortex, septum, and pons-medulla, SAM levels were not affected by either hypophysectomy or dexamethasone administration. These results suggest that multiple controls regulate SAM levels in vivo. The control factors are both highly tissue and region specific. While glucocorticoids are an important regulatory factor of SAM in some peripheral and CNS tissues, they are not the sole regulatory factor. In CNS regions where hypophysectomy increases SAM levels but glucocorticoid administration does not reverse the effects, other hypothalamic hormones, pituitary hormones, or neural factors may be involved in SAM regulation. Likewise, in regions where neither hypophysectomy nor glucocorticoid administration affects SAM levels, hypothalamic or neural factors may be involved even though pituitary factors do not appear to be important.
We describe a case of atlantoaxial joint subluxation and cervical myelopathy in a patient with rheumatoid arthritis. Magnetic resonance imaging (MRI) demonstrated a large periodontoid pannus compressing the upper cervical cord. Neurological function improved rapidly after treatment with intravenous pulse corticosteroids given before surgical fusion of the cervical spine. Post operative MRI showed a significant reduction in size of the pannus.