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Biomedical subjects

L B Tamas

Publications and source records attributed to L B Tamas.

11 recordsLinked to original sources
PubMed1999

Dynamics of tremor-related oscillations in the human globus pallidus: a single case study.

Physiological evidence indicates that the resting tremor of Parkinson's disease originates in oscillatory neural activity in the forebrain, but it is unknown whether that activity is globally synchronized or consists of parallel, independently oscillating circuits. In the present study, we used dual microelectrodes to record tremor-related neuronal activity from eight sites in the internal segment of the globus pallidus (GPi) from an awake Parkinson's disease patient undergoing stereotaxic pallidotomy. We utilized spectral analysis to evaluate the temporal correlations between multiunit activity at spatially separated sites and between neural and limb electromyographic activity. We observed that some GPi neural pairs oscillated synchronously at the tremor frequency, whereas other neural pairs oscillated independently. Additionally, we found that GPi tremor-related activity at a given site could fluctuate between states of synchronization and independence with respect to upper limb tremor. Consistent with this finding, some paired recording sites within GPi showed periods of transient synchronization. These observations support the hypothesis of independent tremor-generating circuits whose coupling can fluctuate over time.

Brain Mapping↗
PubMed1995

Ossification of the anterior longitudinal ligament and Forestier's disease: an analysis of seven cases.

A retrospective review was conducted on the records and radiographs of six symptomatic patients and one asymptomatic patient with Forestier's disease. No other series of patients with this disease is found in the neurosurgical literature. Forestier's disease, also known as diffuse idiopathic skeletal hyperostosis (DISH), is an idiopathic rheumatological abnormality in which exuberant ossification occurs along ligaments throughout the body, but most notably the anterior longitudinal ligament of the spine. It affects older men predominantly; all of our patients were men older than 60 years of age. The disease is usually asymptomatic; however, dyspnea, dysphagia, spinal cord compression, and peripheral nerve entrapment have all been documented in association with the disorder. Five of the six symptomatic patients presented with dysphagia due to esophageal compression by calcified anterior longitudinal ligaments, and one patient developed recurrent spinal stenosis when scar tissue from a previous decompressive laminectomy became calcified. All patients responded well to surgery. Two of the four patients who underwent removal of cervical osteophytes required several months following surgery for the dysphagia to resolve. This would support the hypothesis that not all cases of dysphagia in Forestier's disease are due to mechanical compression. Dysphagia may result from inflammatory changes that accompany fibrosis in the wall of the esophagus or from esophageal denervation. Evaluation of dysphagia even in the presence of Forestier's disease must rule out occult malignancy. The authors' experience suggests that dysphagia in the setting of Forestier's disease is an underrecognized entity amenable to surgical intervention.

Aged↗
PubMed1993

General activation of cerebral metabolism with speech: a PET study.

We report the pattern of metabolic activation of the brain associated with speech, using 15O positron emission tomography (PET) in normal volunteers, as well as patients with or without language deficit. 15 trials were performed on 13 subjects. Regional oxygen metabolism with the subjects at rest was compared to that during a speech-from-memory task. As expected, there was strong activation of Broca's area and the medial left temporal lobe, corresponding to the motor speech and memory aspects of the task. In addition, both cerebellar hemispheres and pre-motor areas, as well as the right frontal operculum, supplementary motor area and right parietal lobe were active. This technique provided insight into the mechanism of aphasia in two subjects, even in one whose traditional language areas were structurally and metabolically intact at rest. We conclude that this practical activation technique may be useful not only in studying the physiology of normal brain, but also in understanding functional responses to disease.

Adolescent↗
PubMed1991

31P NMR spectroscopy of 9L cell line in culture: differential effects of high temperature on anchored cells and spheroids.

The differential effects of high temperature on 9L rat gliosarcoma cells cultured in two distinctive forms, namely, anchored monolayer cells and multicellular spheroids, were investigated using 31P nuclear magnetic resonance spectroscopy. The critical temperatures resulting in irreversible changes in cellular energetics were found to be significantly different: 45 degrees C for anchored cells and 43 degrees C for multicellular spheroids, respectively. Phosphomonoester levels in multicellular spheroids were found to be consistently higher than those in anchored monolayer cells regardless of the temperature to which they were exposed. The study demonstrates that tissue derived from a single cell line may exhibit different metabolic properties depending on its growth pattern.

Animals↗
PubMed1987

Saccadic eye-movements of children with cerebral palsy.

Oculomotor disorders are frequently observed in cerebral-palsied children, and are thought to contribute to impairment of verbal as well as non-verbal skills. The authors present the first quantitative analysis of saccadic eye-movements of these children, choosing those with normal verbal IQ but evidence of a learning disability. A majority showed various abnormalities of saccadic eye-movements and these should be taken into account when evaluating and treating children with cerebral palsy.

Cerebral Palsy↗
PubMed1986

Somatosensory evoked potentials after removal of somatosensory cortex in man.

Somatosensory evoked potentials (SEPs) to median nerve, ulnar nerve, thumb, middle finger, and posterior tibial nerve stimulation were recorded in a patient with a discrete resection of part of the postcentral somatosensory cortex as a treatment for focal epilepsy. Comparison of the different stimulation sites confirmed electrophysiologically the restricted locus of the lesion. The results strongly suggest that the early negative component (N20) and subsequent components recorded postcentrally are of cortical origin and depend upon postcentral gyrus cytoarchitectonic areas 3, 2, and 1. Moreover, these postcentral SEPs are distinct from precentrally recorded activity.

Adult↗
PubMed1986

Epilepsy after operation for aneurysms.

The authors reviewed 100 consecutive survivors of aneurysm operations and identified 3 patients who developed postoperative epilepsy. The use of prophylactic phenytoin in the first 67 cases did not seem to influence the patient's risk of developing epilepsy. It is concluded that with present microneurosurgical techniques the risk of postoperative epilepsy is small and unselective use of phenytoin prophylaxis should be reconsidered.

Craniotomy↗
PubMed1985

Cortical potentials associated with movement: a review.

Cortical potentials both preceding and following movement have been studied now for 20 years, since the advent of efficient averaging techniques. They have shed light on the physiology of movement initiation, have provided some insight into certain disease states, and may help our understanding of movement disorders in the future. The pertinent literature is reviewed.

Brain Damage, Chronic↗
PubMed1985

Intracranial mucocele mimicking arachnoid cyst: case report.

We describe a patient presenting with adult onset seizures whose computed tomographic scan was highly suggestive of arachnoid cyst. The cyst was removed by craniotomy and was found to be a mucocele on histological examination. During operation, no connection to the frontal sinus had been found. The very unusual combination of findings and their clinical implications are discussed.

Adult↗
PubMed1984

Physiological evaluation of the effect of fascicular ligation on neuromas in the rat.

Microfascicular double ligation and interligature heat sealing has been clinically successful in relieving neuroma pain. In rats, we found that this technique had no effect on the abnormal activities (such as mechanosensitivity and spontaneous activity) of single myelinated axons from neuromas or on their conduction velocity distribution. Assuming that the clinical success of this method is not fortuitous, we challenge the prevailing theory of the relationship between these abnormal unit activities and pain.

Animals↗