Relationship among glottal area, static supraglottic compression, and laryngeal function studies in unilateral vocal fold paresis and paralysis.

Summary In this study, we evaluated the relationship between laryngeal function measures and glottal gap ratio and normalized measures of supraglottic behaviors in patients with unilateral vocal fold paresis (UVFP). Thirty-one patients were found to have unilateral vocal fold paresis by videoendoscopy and laryngeal electromyography, and 13 controls participated in this study. Patients with UVFP demonstrated significantly larger glottal gap ratios (p=0.016) than control subjects. The nonparalyzed or contralateral vocal fold was associated with significantly more static false vocal fold compression (p=0.03) compared with the paralyzed vocal fold or with the controls. Patients with unilateral vocal fold paresis were divided into subgroups: those with normal or abnormal maximum phonation time, flow, or pressure measures. Smaller glottal gap ratios were identified in patients with normal maximum phonation times and flow measures. Greater false vocal fold activity was identified in unilateral vocal fold paresis patients with normal laryngeal function measures than in unilateral vocal fold paresis patients with abnormal measures. These findings suggest that some patients with documented unilateral paresis and glottal incompetence can compensate for vocal fold weakness such that their acoustic and aerodynamic measures are normal

Molecular genetic analysis of nucleotide polymorphisms associated with ethambutol resistance in human isolates of Mycobacterium tuberculosis

PubMed ID: 10639358Ethambutol (EMB) is a central component of drug regimens used worldwide for the treatment of tuberculosis. To gain insight into the molecular genetic basis of EMB resistance, approximately 2 Mb of five chromosomal regions with 12 genes in 75 epidemiologically unassociated EMB-resistant and 33 EMB- susceptible Mycobacterium tuberculosis strains isolated from human patients were sequenced. Seventy-six percent of EMB-resistant organisms had an amino acid replacement or other molecular change not found in EMB-susceptible strains. Thirty-eight (51%) EMB-resistant isolates had a resistance- associated mutation in only 1 of the 12 genes sequenced. Nineteen EMB- resistant isolates had resistance-associated nucleotide changes that conferred amino acid replacements or upstream potential regulatory region mutations in two or more genes. Most isolates (68%) with resistance- associated mutations in a single gene had nucleotide changes in embB, a gene encoding an arabinosyltransferase involved in cell wall biosynthesis. The majority of these mutations resulted in amino acid replacements at position 306 or 406 of EmbB. Resistance-associated mutations were also identified in several genes recently shown to be upregulated in response to exposure of M. tuberculosis to EMB in vitro, including genes in the iniA operon. Approximately one-fourth of the organisms studied lacked mutations inferred to participate in EMB resistance, a result indicating that one or more genes that mediate resistance to this drug remain to be discovered. Taken together, the results indicate that there are multiple molecular pathways to the EMB resistance phenotype

Investigating the neural basis of stuttering using transcranial magnetic stimulation: Preliminary case discussion

Neuroimaging studies have found particular areas of the brain to be over- or under-active in persons who stutter (PWS) suggestive of atypical lateralization of speech and language processing. This study used single pulse transcranial magnetic stimulation (TMS) to investigate differences in left and right tongue motor cortex excitability in three adult male PWS compared with five adult control speakers (four males). TMS pulses were applied to the left and right side of the head over the tongue motor cortices. Measures of excitability included: active motor threshold (AMT, i.e. the amount of stimulation required to elicit a consistent motor evoked potential (MEP) in the tongue), and the y-intercept and slope of linear regressions derived from plots of electromyography contraction levels versus MEP amplitudes (input-output facilitation curves). The results are presented as a series of case discussions. The control group exhibited increased excitability for the left tongue motor cortex compared with the right based on y-intercept measures, although no inter-hemispheric excitability differences were found based on AMT or slope measures. A reversed pattern of excitability was found for the PWS who exhibited decreased and increased left and right tongue motor cortex excitability, respectively, based on the y-intercept and AMT measures compared with the control group. The results provide support for the suggestion of interhemispheric excitability disturbances in PWS and warrants further investigation using TMS techniques