Unilateral upper limb asterixis related to primary motor cortex infarction.
BACKGROUND
Unilateral upper limb asterixis related to cortical infarct is an unusual clinical picture. We found this association in two patients. Magnetic resonance imaging (MRI), somatosensory evoked potentials (SEPs), and electromyographic recording were performed.


METHODS
Two patients developed an acute upper limb ataxia with asterixis. This consisted of frequent arrhythmic loss of extensor muscle tone on instruction to maintain the wrist and fingers extended. Voluntary electromyographic activity in the left extensor digitorum communis muscle showed abrupt periods of interruption ranging from 90 to 260 milliseconds in duration in the first case and from 60 to 220 milliseconds in the second case. SEPs were normal. MRI disclosed a right cortical infarct within the primary motor cortex in both cases.


CONCLUSIONS
These findings indicate that asterixis was not related to a failure in the processing of proprioceptive input controlling the regulation of postural tone of the distal upper limbs because SEPs were normal. The involvement of primary motor cortex might suggest that asterixis results from an impairment of a centrally generated motor-command signal controlling the postural tone of the distal upper limb.
Nighoghossian
N
N
Service de Neurologie, Hôpital Neurologique, Lyon, France.
Trouillas
P
P
Vial
C
C
Froment
J C
JC
D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology; D002544:Cerebral Infarction / Q000150:complications*; D005073:Evoked Potentials, Somatosensory; D006801:Humans; D009044:Motor Cortex / Q000503:physiopathology; D009069:Movement Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology