Motivation: Look - the hands are flapping. One of the useful tests in a confused patients is to ask them to stop traffic with outstretched hands. If the hands start flapping in a non-rhythmic way ('asterixis'), that is interpreted as proof of generalized toxic-metabolic encephalopathy. But, then again, there is probably a neural pathway underlying this mechanism. We often dismiss asterixis in a blase way, but can there be focal brain lesions underlying asterixis?
Paper: Degos, J-D., Verroust, J., Bouchareine, A., et. al. "Asterixis in Focal Brain Lesions" Arch Neurol. (1979); 36: 705-707
Methods: At Henri Mondor Hospital (Creteil, France), one of the authors documented twenty cases of asterixis with focal brain lesions. EMG was available for nine patients.
Results:
Midbrain Lesions: Four patients ranging from 38 to 62 years presenting with unilateral asterixis after abrupt onset weakness in the affected side.
Parietal Lesions: Seven cases of asterixis with pathologic proof in four occurred from parietal lesions. These lesions could occurred on contralateral side from the asterixis and could be from mass lesions (glioblastoma, abscess, metastatic lesion) or from stroke (hemorrhagic or ischemic).
Suspected Midbrain and Parietal Lesions: Six cases with suspected lesions. One of these cases was a right temporal glioblastoma invading the lenticular nuclei with left sided asterixis and another had an expanding right thalamic tumor with left sided asterixis.
Unclear lesions: Three cases of unilateral asterixis with accompanying unilateral weakness or numbness of unclear etiology.
EMG Recordings: During episodes of asterixis, there were 50-100 ms periods of electrical silence in both agonist and antagonist.
Discussion: This old paper shows that true asterixis is not purely a toxic-metabolic phenomenon. Apparently, parietal, midbrain, and thalamic lesions can result in contralateral asterixis. While this paper certainly does not suggest a pathophysiological explanation of asterixis, some important points are that: (1) asterixis appeared contralateral to the lesion meaning that usually the side with asterixis is the one that is weak or numb, (2) both cortical and deep lesions can result in asterixis,. I think that this account provides a cautionary note of dismissing asterixis as purely toxic phenomenon.
Paper: Degos, J-D., Verroust, J., Bouchareine, A., et. al. "Asterixis in Focal Brain Lesions" Arch Neurol. (1979); 36: 705-707
Methods: At Henri Mondor Hospital (Creteil, France), one of the authors documented twenty cases of asterixis with focal brain lesions. EMG was available for nine patients.
Results:
Midbrain Lesions: Four patients ranging from 38 to 62 years presenting with unilateral asterixis after abrupt onset weakness in the affected side.
Parietal Lesions: Seven cases of asterixis with pathologic proof in four occurred from parietal lesions. These lesions could occurred on contralateral side from the asterixis and could be from mass lesions (glioblastoma, abscess, metastatic lesion) or from stroke (hemorrhagic or ischemic).
Suspected Midbrain and Parietal Lesions: Six cases with suspected lesions. One of these cases was a right temporal glioblastoma invading the lenticular nuclei with left sided asterixis and another had an expanding right thalamic tumor with left sided asterixis.
Unclear lesions: Three cases of unilateral asterixis with accompanying unilateral weakness or numbness of unclear etiology.
EMG Recordings: During episodes of asterixis, there were 50-100 ms periods of electrical silence in both agonist and antagonist.
Discussion: This old paper shows that true asterixis is not purely a toxic-metabolic phenomenon. Apparently, parietal, midbrain, and thalamic lesions can result in contralateral asterixis. While this paper certainly does not suggest a pathophysiological explanation of asterixis, some important points are that: (1) asterixis appeared contralateral to the lesion meaning that usually the side with asterixis is the one that is weak or numb, (2) both cortical and deep lesions can result in asterixis,. I think that this account provides a cautionary note of dismissing asterixis as purely toxic phenomenon.
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