Examining the effects of age, sex, and body mass index on normative median motor nerve excitability measurements.
ABSTRACT The purpose of this study was to build a large reference database of excitability measures in normal subjects and to examine the effects of age, sex, and BMI.
One hundred and five healthy subjects had median motor nerve excitability testing performed at the wrist using the automated threshold-tracking program, QTRAC. Statistical linear regression was used to explore relationships between nerve excitability and the independent variables.
The main effect of age is a reduced superexcitability. Lesser effects are flattening of the normalized stimulus response curve and reduction in threshold change following strong hyperpolarizing currents. Females have lower thresholds than males and small but significant differences in voltage-gated potassium channel (KCNQ) mediated properties (late subexcitability, accommodation half time, and threshold undershoot following depolarizing electrotonus), as well as a small increase in superexcitability. BMI has no influence on nerve excitability data and does not explain sex-related differences in threshold.
Age and sex have few and small effects on excitability parameters.
The expression of nodal KCNQ channels appears to be greater in females. Age-related increases in subexcitability may be attributable to changes in the muscle fibre and not the nerve.
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ABSTRACT: Mc HUGH J.C., TRYFONOPOULOS D., FENNELLY D., CROWN J. & CONNOLLY S. (2012) European Journal of Cancer Care Electroclinical biomarkers of early peripheral neurotoxicity from oxaliplatin Peripheral neuropathy is the principal dose-limiting side effect of chemotherapy with oxaliplatin. Early biomarkers of oxaliplatin-related neuropathy (ON) are important for guiding management and as outcomes for neuroprotective trials. We compared a number of clinical and neurophysiological techniques to identify early features of ON. Median nerve motor excitability testing, nerve conduction studies, vibration perception threshold (VPT) and clinical assessments were carried out on 17 patients and 105 controls. Neuropathy was graded using the total neuropathy score and National Cancer Institute Common Toxicity Criteria scales. Oxaliplatin causes a length-dependent sensory neuropathy. The most sensitive early marker of neuropathy was abnormal VPT in the foot followed by diminished sensory nerve action potential amplitudes. Median nerve excitability studies revealed no biologically significant effects of treatment on motor axons. VPT is an easily applicable and effective marker of neuropathy at low cumulative doses of oxaliplatin. Nerve excitability measures may be useful in predicting ON but motor studies do not reveal early cumulative changes following treatment with the drug.European Journal of Cancer Care 05/2012; 21(6):782-9. · 1.31 Impact Factor
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ABSTRACT: Introduction: Subtle involvement of peripheral nerves may occur in multiple sclerosis. Motor excitability studies have suggested upregulation of slow K(+) currents, probably secondary to altered motoneuron properties resulting from the central lesion. This study concentrates on sensory axons. Methods: Excitability of median nerve axons at the wrist was studied in 26 patients. Results: Sensory recordings were possible in 22 patients, and reduced superexcitability was the sole abnormality. There was no evidence for changes in membrane potential or demyelination. The decrease was significant in patients taking immunomodulatory therapy. These findings could be reproduced in a computer model by changing the gating of fast K(+) channels. Motor axon findings were consistent with previously reported increased slow K(+) current. Conclusions: The sensory findings differ from motor findings. They can be explained by a humoral factor, possibly cytokines, which can penetrate the paranode and have been documented to alter the gating of K(+) channels. Muscle Nerve, 2012.Muscle & Nerve 05/2012; · 2.31 Impact Factor