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August 1999

Significance of Dystonic Posturing With Unilateral Automatisms

Arch Neurol. 1999;56(8):912-913. doi:10.1001/archneur.56.8.912

UNILATERAL DYSTONIC posturing of an upper extremity is an interesting phenomenon that occurs typically in seizures of temporal lobe origin.1 It is a clinically useful lateralizing sign, particularly when complex partial seizures do not generalize (version and focal clonic movements are good lateralizing signs for complex partial seizures becoming generalized). It is always contralateral to the side of the predominant ictal discharge, which is generally the side where the seizure started. This phenomenon also provides a window into mechanisms of ictal spread from the mesial temporal lobe. Efferent pathways from the amygdala in the stria terminalis project to the caudate nucleus, putamen, septal areas, preoptic nucleus, anterior hypothalamus, medial thalamic nuclei, and the nucleus accumbens septi.2 The fornix carries the principal efferent fibers from the hippocampus to the lateral septum, medial frontal cortex, gyrus rectus, and the nucleus accumbens septi.3 Relatively few fibers from the hippocampus reach the cingulum.4 Strictly unilateral dystonic posturing is uncommon in extratemporal seizures; stimulation of the mesial frontal regions usually produces bilateral asymmetric tonic posturing involving proximal more than distal parts of the limbs as well as the trunk.5 Hyperperfusion of the basal ganglia region during contralateral dystonic posturing has been elegantly demonstrated using ictal single photon emission computed tomographic scans.6 Interictal abnormalities in the same areas have also been detected using positron emission tomography with fludeoxyglucose F 18.7 Dystonic posturing affects mainly the distal upper extremity or distal preceding proximal involvement of the limb. The typical hand posture shows flexion of the wrist and metacarpophalangeal joints, extension of the fingers, as well as an element of rotation in the forearm.8 I feel strongly that dystonic posturing should be distinguished from tonic posturing and lateralized ictal paresis. More recently, head deviation away from the dystonic limb has been identified.9

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