Abstract Details

Title Far-Field Potentials Reduced the Diagnostic Sensitivity of Hypothenar Motor Unit Number Estimation in Spinal and Bulbar Muscular Atrophy Patients

Topic Anterior Horn

Presentation(s) P03 - (-)

Poster/Presentation
Number 051

Objective

Background BACKGROUND: MUNE is one of the methods that can quantitatively evaluate the motor unit number and it has been employed as an electrophysiological marker of the disease progression in motor neuron disease, such as amyotrophic lateral sclerosis and SBMA. However, the hypothenar MUNE demonstrated lower sensitivity (93%) than another quantitative surface EMG method (the Clustering Index method; 100%) in our preceding study. Past studies demonstrated that FFPs generated mainly by the interosseous muscles contaminate the compound muscle action potential following the ulnar nerve stimulation.

Design/Methods DESIGN/METHODS: The subjects consisted of 29 SBMA patients and 27 healthy male controls. The data collected using multiple point stimulation MUNE in our preceding study were re-analyzed. Surface motor unit potentials (SMUPs) were classified into SMUPs from the abductor digiti minimi muscle (ADM-SMUP) or non-ADM SMUPs based on the waveform patterns from the 3-channel recordings.

Results RESULTS: Two hundreds and sixty three SMUPs from the control subjects and 207 SMUPs from the SBMA patients were accepted for the MUNE calculation. The mean areas of the ADM-SMUPs and non-ADM SMUPs in control subjects were 219.0±131.3 and 63.7±48.5 [micro]Vms, respectively. In SBMA patients, they were 1988.9±999.4 and 222.7±125.7 [micro]Vms. The percentages of non-ADM SMUPs were 68±22% (range 17-100%) in the control subjects and 84±15% (50-100) in SBMA patients. For the two patients who had been judged normal using MUNE, all or all but one SMUPs were of non-ADM origin.

Conclusions CONCLUSIONS: Variable contamination by the smaller non-ADM SMUPs generated mainly by FFPs may cause inaccuracy in the hypothenar MUNE and undermine its diagnostic yield.

Authors/Disclosures
Mana Higashihara, MD PRESENTER	No disclosure on file
Masahiro Sonoo	No disclosure on file
Tomotaka Yamamoto	No disclosure on file
Yu Nagashima	No disclosure on file
Martha Morrell, MD, FAAN (NeuroPace/Stanford University)	Dr. Morrell has received personal compensation for serving as an employee of NeuroPace. Dr. Morrell has stock in NeuroPace. The institution of Dr. Morrell has received research support from National Institutes of Health.
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
Shoji Tsuji, MD, PhD (University of Tokyo)	The institution of Dr. Tsuji has received research support from Novelpharma Co. Ltd..

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