Biomedical subjects

G Hayat

Publications and source records attributed to G Hayat.

5 recordsLinked to original sources

PubMed1996

Type II fiber predominance with motor neuron dysfunction.

Several variations in the muscle fiber distribution and differentiation have been described. Different hypotheses, including maturational dysfunction of motor neurons have been postulated. We present a 28 year-old male with proximal weakness, and negative family history. Motor strength was 4-/5 proximally and 4+/5 distally in the extremities. He was areflexic with trace triceps jerks. Electrophysiological studies showed motor neuron dysfunction. Marked type II fiber predominance 97% was noted without group atrophy on a vastus-lateralis muscle biopsy. Type 2A were the largest with type 2B and 2C smaller than type 1. A deltoid muscle biopsy and electrophysiological studies performed nine years earlier depicted the same changes. With electrophysiological studies consistent with static motor neuron dysfunction and clinical and pathological presentation of myopathy, we propose a functional abnormality of motor neuron in-utero leading to abnormal muscle fiber differentiation and growth.

Adult↗

PubMed1995

Magnetic resonance evidence of perineural metastasis.

Contiguous spread along perineural and endoneural spaces, that is, perineural tumor extension, in cutaneous squamous cell carcinoma is fairly common. Infrequently, these tumors spread and involve intracranial structures. One consequence of this complication is meningeal carcinomatosis which is underrecognized. Herein described is a patient with recurrent cutaneous squamous cell carcinoma with perineural invasion along the maxillary nerve that was subsequently shown by magnetic resonance imaging to the trigeminal root. The patient initially presented with a cavernous sinus syndrome but despite aggressive treatment, extensive meningeal carcinomatosis and cauda equina dysfunction developed. Awareness of perineural invasion and proper evaluation are crucial. Perineural spread intracranially worsens the prognosis and limits treatment options to palliation.

Aged↗

PubMed1995

Visual evoked potentials during hyperthermia.

OBJECTIVES: We sought to evaluate the effect of hyperthermia (HT) on central conduction pathways by alterations in pattern visual evoked potentials (PVEPs) in normal and demyelinated optic nerves. MATERIALS AND METHODS: We studied PVEP peak latency and amplitudes in 10 normal subjects and six patients with demyelinating optic neuropathy before and during HT. RESULTS: In normal subjects, a mean rise in temperature of 2.5 degrees C resulted in a decrease in the second positive peak (P2) latency of 6.1 ms (p < 0.0001) and a slight decline in P2 amplitude of 1.16 muV (p < 0.009). These results were compared to those obtained from six patients with multiple sclerosis. These patients had a history of monocular optic neuritis; two patients had had bilateral optic neuritis, and one patient had not had involvement of the optic nerve. Average temperature elevations during PVEPs were 1.60 degrees C. PVEPs among these patients showed decrease in mean P2 latencies, except in patients with multiple sclerosis, who showed an increase in latency with 60 min check size in the left eyes. There was a consistent decline in P2 amplitudes. Loss of amplitude was greater among the six optic nerves of those patients having transient, mild losses in visual acuity during HT. Reductions in P2 amplitude were best explained by partial or complete conduction block. CONCLUSIONS: These changes in conduction time and amplitude during HT provide a neurophysiologic correlation to the well-known sensitivity of demyelinated optic nerves to elevated temperatures. They are also relevant to the monitoring of central pathways in the operative or intensive care setting. The demonstrated reversible loss of amplitudes also gives promise to therapeutic manipulation of impaired pathways by impeding the loss of current from denuded nerve fibers.

Adult↗

PubMed1995

Efficacy of thymectomy in myasthenia gravis.

We sought to determine the efficacy of thymectomy in patients with myasthenia gravis (MG). The roles of age, gender, age of onset of MG, acetylcholine receptor antibodies (AchR's) titers, and pathology of the thymus gland were evaluated. Twenty-one patients were analyzed retrospectively. Twenty patients belonged to Osserman Class IIA or higher; 71.42% belonged to IIB. All patients were on either anticholinesterase and/or immunosuppressive agents. The mean follow up was three years. Seventy-six percent of the patients showed improvement by Osserman and by "results of treatment" classification, 14.28% were in complete remission, on no medications. The age, gender, age of onset, thymic pathology and AchR titers had no correlation with post-operative improvement. With longer follow up the beneficial effect is more apparent.

Adolescent↗

PubMed1994

Hyperdense basilar artery. An early computed tomography sign of thrombosis.

Noncontrast computed tomographic scans (CT scans) may show a hyperdense basilar artery before a brainstem infarct is visualized. This early sign should assist clinicians in confirming the diagnosis of basilar artery thrombosis. In a review of admission records of 750 patients with acute cerebrovascular disease from July 1991 to June 1993, at Saint Louis University Hospital, 20 patients were identified with clinical signs of nonlacunar, vertebrobasilar distribution infarction. Eight of these had pontomesencephalic ischemia. Their neuroimaging studies and medical records were evaluated. Four patients with acute clinical signs of pontomesencephalic infarction were found to have a hyperdense basilar artery on CT scans. The scans of 2 patients were excluded because of dolichoectasia; in the other 2 patients, the basilar artery appeared normal on the CT scan. The hyperdense basilar artery was detected within the early hours of neurological symptoms and often was the only detectable abnormality on the scan. In 3 patients extensive brainstem infarcts subsequently developed and they died. Basilar artery thrombosis was confirmed by pathological study in all these patients. In the fourth patient basilar artery occlusion and a large pontine infarct were evident by magnetic resonance imaging and angiography. A hyperdense basilar artery is a common feature on CT scans of patients presenting with an early clinical diagnosis of thrombosis. Untreated, the hyperintense basilar artery often portends a poor prognosis. Its ready recognition should guide further interventional studies and treatment.

Adult↗