The alien limb phenomenon

Abstract

Alien limb phenomenon refers to involuntary motor activity of a limb in conjunction with the feeling of estrangement from that limb. Alien limb serves as a diagnostic feature of corticobasal syndrome. Our objective was to determine the differential diagnoses of alien limb and to determine the features in a large group of patients with the alien limb with different underlying etiologies. We searched the Mayo Clinic Medical Records Linkage system to identify patients with the diagnosis of alien limb seen between January 1, 1996, and July 11, 2011. One hundred and fifty patients with alien limb were identified. Twenty-two were followed in the Alzheimer's Disease Research Center. Etiologies of alien limb included corticobasal syndrome (n = 108), stroke (n = 14), Creutzfeldt Jakob disease (n = 9), hereditary diffuse leukoencephalopathy with spheroids (n = 5), tumor (n = 4), progressive multifocal leukoencephalopathy(n = 2), demyelinating disease (n = 2), progressive dementia not otherwise specified (n = 2), posterior reversible encephalopathy syndrome (n = 1), corpus callosotomy (n = 1), intracerebral hemorrhage (n = 1) and thalamic dementia (n = 1). Ten of 14 cerebrovascular cases were right hemisphere in origin. All cases involved the parietal lobe. Of the 44 patients with corticobasal syndrome from the Alzheimer's Disease Research Center cohort, 22 had alien limb, and 73 % had the alien limb affecting the left extremities. Left sided corticobasal syndrome was significantly associated with the presence of alien limb (p = 0.004). These findings support the notion that the alien limb phenomenon is partially related to damage underlying the parietal cortex, especially right parietal, disconnecting it from other cortical areas.

Figure 1

Regional Infarct Distribution The location of the zones of infarction are displayed on a template brain and color coded by case (A). The regional frequency of involvement across the brain in each of these 9 cases is displayed by projecting the frequency of lesion overlap onto a surface rendering (B). Regions of the brain with only a single case involved are on the orange end of the spectrum and the region of the right parietal lobe with the maximum number of cases overlapping (5 of the 9) is on the blue/violet end of the spectrum. These cases correspond with cases 1-9 from Table 4.

Figure 2

Montage of select cases demonstrating radiographic changes associated with the alien limb among different pathological processes. The cases are described from top to bottom, from left to right: (a) coronal T-1 MRI demonstrating right parietal atrophy attributed to CBS; (b) axial T-2 weighted FLAIR sequence showing right hemispheric cortical ribboning associated with CJD; (c) T-2 weighted FLAIR sequence showing a large demyelinating lesion in the right posterior corona radiata in a demyelinating disorder not otherwise specified; (d) coronal T-1 waited sequence with prominent left parietal encephalomalacia associated with a now-resolved intracranial hemorrhage; (e) coronal T-2 weighted FLAIR sequence demonstrating bilateral subdural hematomata with subarachnoid hemorrhage and associated cortical irritation of the right parietal lobe; (f) coronal gadolinium-enhanced T-1 weighted sequence showing a right parietal tumor; (g) axial FLAIR image demonstrating characteristic changes of the posterior reversible encephalopathy syndrome; (h) axial FLAIR sequence demonstrating bilateral corona radiata abnormalities in hereditary diffuse leukodystrophy with axonal spheroids; (i) axial DWI demonstrating a right parietal infarct. In all cases, the alien limb was contralateral to the afflicted parietal lobe.