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Biomedical subjects

S R Beydoun

Publications and source records attributed to S R Beydoun.

15 recordsLinked to original sources
PubMed2001

Secondary amyloidosis as a life-ending event in multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a disorder of peripheral nerve often associated with a high monosialoganglioside (GM1) antibody and multifocal conduction block. It has a chronic, indolent course with involvement of predominantly peripheral motor nerves, usually in an asymmetric fashion. There have been few reported cases of progression to frank quadriplegia. Secondary amyloidosis refers to the deposition of amyloid in various tissues due to an underlying chronic inflammatory state. We report the first case, to our knowledge, of a patient with MMN associated with high titer of GM1 antibody who developed acute paraplegia with both cranial nerve and worsening sensory involvement associated with multiorgan compromise due to a secondary amyloidosis involving the myocardium.

Amyloidosis↗
PubMed1998

Multifocal motor neuropathy with conduction block misdiagnosed as multiple entrapment neuropathies.

We describe a 58-year-old male with a few years history of multifocal weakness in the upper limbs with minimal to absent sensory complaints. He was diagnosed as having multiple compressive neuropathies, which required repeated decompressive surgeries. Electrodiagnostic studies prior to diagnosis were limited to a few nerves, evaluating only distal segments. Because of delay in making the diagnosis, his condition progressed, and possibly because of the unnecessary surgeries, he developed atrophy in some muscles, which resulted in significant motor disability. He was later diagnosed as having multifocal motor neuropathy with conduction block and has partially responded to intravenous immunoglobulin therapy.

Atrophy↗
PubMed1990

Long-term plasmapheresis therapy is effective and safe in children with chronic relapsing dysimmune polyneuropathy.

Since childhood, two persons, a boy age 12 and a girl age 24 years, with chronic relapsing dysschwannian neuropathy causing severe limb weakness have been maintained on frequent plasmapheresis for more than 8-1/2 and 9 years respectively. They are totally dependent on it. Onset of disease was at ages 2-1/2 and 9 years. Both patients had had major relapses, some requiring ventilatory support, despite continued maximally-tolerated pharmacologic antidysimmune treatment. Plasmapheresis was started in August 1980 and December 1979, respectively. The current schedule is a set of 3 in one week at eight-week intervals for patient 1 and twice every 7-10 days for patient 2. They have had more than 330 and more than 1,100 phereses respectively. Since beginning phereses, neither has had a major relapse, and both are functional in their daily life as students, although with slight and moderate residual weakness respectively. The dependence of these 2 patients on regular pheresis for the last 8-1/2 and 9 years proves its efficacy and safety in children. Long-term maintenance pheresis may be beneficial in patients with other forms of chronic dysimmune neuropathy.

Adult↗
PubMed1989

Ifosfamide encephalopathy.

We describe a case of reversible encephalopathy caused by the recently released anticancer drug Ifosfamide. The clinical course, role of EEG in monitoring and predicting encephalopathy, and putative mechanism of neurotoxicity is discussed. Short infusion times and/or prior CNS disease may increase the risk of encephalopathy.

Brain Diseases↗
PubMed1986

Analogs of thyrotropin-releasing hormone: hypotheses relating receptor binding to net excitation of spinal lower motor neurons.

Experimentally and clinically, treatment with high-doses of TRH produces a net excitation of spinal lower motor neurons (LMNs) that is subsequently reduced or completely lost through continuous or repeated exposure to the peptide. This is operationally termed "autorefractoriness" (AR). We have performed biochemical and in vivo pharmacologic experiments to investigate the mechanism(s) of AR. Biochemically, we classified TRH and several analogs into three groups based on their binding by spinal-cord TRH-receptors (TRH-Rs): high-affinity, (low nanomolar range; MeTRH, TRH); intermediate-affinity (mid-nanomolar range; MK-771, RX77368) or low-affinity (micromolar range; DN-1417, PNP). When tested in vivo for LMN excitatory activity in cordotomized (T8) rats, TRH and MK-771 produced rapid-onset excitation followed AR. In contrast, sustained excitation with much less AR was produced by the low affinity analog DN-1417. Based on these results, we have formulated two receptor-based hypotheses to explain AR: a) rapid TRH-R desensitization (conversion to an inactive form) by high- but not low-affinity TRH-analogs; and b) a slower down-regulation (cellular internalization) of the agonist-receptor complex, most evident with high-affinity agonists. Thus, low-rather than high-affinity TRH-analogs may be superior to TRH for providing sustained LMN excitation (increase of strength) in motor neuron degenerative disorders.

Animals↗