Large motor units are selectively affected following a stroke.
OBJECTIVE
Previous studies have revealed a loss of functioning motor units in stroke patients. However, it remained unclear whether the motor units are affected randomly or in some specific pattern. We assessed whether there is a selective loss of the large (high recruitment threshold) or the small (low recruitment threshold) motor units following a stroke.


METHODS
Forty-five stroke patients and 40 healthy controls participated in the study. Macro-EMG was recorded from the abductor digiti minimi muscle at two levels of force output (low and high). The median macro motor unit potential (macro-MUP) amplitude on the paretic side was compared with those on the unaffected side and in the controls.


RESULTS
In the control group and on the unaffected side, the macro-MUPs were significantly larger at the high force output than at the low one. However, on the paretic side the macro-MUPs at the high force output had the same amplitude as those recorded at the low force output. These changes correlated with the severity of the paresis.


CONCLUSIONS
Following a stroke, there is a selective functional loss of the large, high-threshold motor units. These changes are related to the severity of the symptoms.


CONCLUSIONS
Our findings furnish further insight into the pathophysiology of the motor deficit following a stroke.
Lukács
M
M
Department of Neurology, Miskolc Health Center, Kórház u. 1, H-3520 Miskolc, Hungary. mikluk33@hotmail.com
Vécsei
L
L
Beniczky
S
S
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009431:Neural Conduction; D011999:Recruitment, Neurophysiological / Q000502:physiology; D012720:Severity of Illness Index; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology*