Reduction in the motor unit number estimate (MUNE) after cerebral infarction.
BACKGROUND
The mechanism of the decrease in motor unit number estimates (MUNEs) after cerebral infarction has not been studied systematically. We examined the relationship between the degree to which MUNEs decreased and the other clinical features of patients with the infarction.


METHODS
Using a multiple point stimulation technique, we obtained the MUNE of the hypothenar muscle group in 13 age-matched control subjects and 30 patients with cerebral infarction. In all patients, we obtained the Japan Stroke Scale (JSS) and head MR images. In eight patients with acute cerebral infarction, admitted within 24 h after onset, we also obtained head MR angiograms and single-photon emission CT.


RESULTS
There was a decrease in the MUNE of the hypothenar muscle group on the affected side of 24 patients with cerebral infarction and hand weakness. The decrease in the MUNE started from 4 to 30 h after the infarction, when T1-weighted MR images of the brain involved were normal. The degree to which the MUNE decreased correlated with the part of the JSS showing the upper extremity weakness.


CONCLUSIONS
A decrease in the MUNE of the hypothenar muscle group within 30 h after cerebral infarction may be due to trans-synaptic inhibition of the spinal alpha motor neurons innervating this muscle.
Arasaki
Keisuke
K
Stroke Care Unit, Department of Neurology, NTT East Kanto Medical Center, Tokyo, Japan. arasaki@aikawanaika.or.jp
Igarashi
Osamu
O
Ichikawa
Yasumitsu
Y
Machida
Toru
T
Shirozu
Ichiro
I
Hyodo
Akira
A
Ushijima
Ryosuke
R
D000200:Action Potentials / Q000502:physiology; D000368:Aged; D000369:Aged, 80 and over; D002544:Cerebral Infarction / Q000473:pathology / Q000503:physiopathology*; D004558:Electric Stimulation; D004576:Electromyography; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology*; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D009410:Nerve Degeneration / Q000209:etiology / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D010291:Paresis / Q000209:etiology / Q000503:physiopathology; D010525:Peripheral Nerves / Q000503:physiopathology; D011237:Predictive Value of Tests; D011712:Pyramidal Tracts / Q000473:pathology / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000502:physiology; D013997:Time Factors; D014057:Tomography, X-Ray Computed