Needle electromyography of bulbar muscles in patients with amyotrophic lateral sclerosis: evidence of subclinical involvement.
OBJECTIVE
To determine if quantitative motor unit action potential (MUAP) analysis and peak ratio interference pattern analysis of the fifth, seventh, and eleventh cranial nerve innervated muscles are helpful in the assessment of subclinical bulbar involvement in ALS.


METHODS
With both electromyographic (EMG) techniques, electrical activity was recorded via needle electrodes from the right frontalis, masseter, and sternocleidomastoideus muscles of nine ALS patients without clinical bulbar signs (Frenchay score >85%) aged 40 to 87 years; 21 healthy subjects aged 27 to 74 years; and five ALS patients with clinical bulbar signs (Frenchay score <85%) aged 53 to 69 years.


RESULTS
The normal mean (2 SD) MUAP duration of the frontalis muscle was 7.4 (2.2) milliseconds; masseter muscle, 9.3 (3.1) milliseconds; and sternocleidomastoideus muscle, 10.9 (4.1) milliseconds. The normal mean (2 SD) peak ratio of the frontalis was 2.3 (1.1) milliseconds; masseter, 1.2 (0.4) milliseconds; and sternocleidomastoideus, 1.5 (0.7) milliseconds. Quantitative MUAP analysis was interpreted as neuropathic if MUAP duration, MUAP amplitude, or both exceeded the mean (+2 SD). Peak ratio interference pattern analysis was interpreted as neuropathic if the peak ratio, the number of small time intervals, or both were below the mean (-2 SD). If a result of either EMG technique was neuropathic in at least one of the three investigated muscles, bulbar involvement was assumed. Subclinical bulbar involvement could be detected by quantitative MUAP analysis in six ALS patients without clinical bulbar signs, and by peak ratio interference pattern analysis in two.


CONCLUSIONS
Conventional needle EMG of the fifth, seventh, and eleventh cranial nerve innervated muscles shows subclinical bulbar involvement quite frequently. Peak ratio interference pattern analysis is largely not helpful in detecting this involvement.
Finsterer
J
J
Ludwig Boltzmann Institute for Epilepsy and Neuromuscular Disorders, Vienna, Austria.
Erdorf
M
M
Mamoli
B
B
Fuglsang-Frederiksen
A
A
D000055:Accessory Nerve / Q000503:physiopathology; D000200:Action Potentials; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D003391:Cranial Nerves / Q000503:physiopathology*; D004576:Electromyography / Q000295:instrumentation / Q000379:methods; D005152:Facial Muscles / Q000294:innervation*; D005154:Facial Nerve / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000294:innervation; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D012016:Reference Values; D014276:Trigeminal Nerve / Q000503:physiopathology