Objective: To examine the case of a patient with parkinsonism and agenesis of the corpus callosum whose alien limb phenomenology ceased after withdrawal from ropinirole.

Background: Alien limb phenomenon (ALP) is one of the oddities in neuroscience. The hallmark of ALP is involuntary yet purposeful limb actions devoid of conscious control. These can manifest as levitation, inter-manual conflict, mirror movements, enabling synkinesis, groping apraxia, and compulsive manipulation of tools. Sufferers deny ownership of the movements. Though the phenomenon is seen with corticobasal syndrome and various cerebrovascular lesions affecting the corpus collosum, there has been no previously reported connection with dopamine agonists.

Methods: Case Report

Results: A patient with advanced parkinsonism initially presented to us with left hand resting tremor, mild anomia, paraphasia and constructional apraxia. He had mild leg wearing-off dyskinesias and gait freezing requiring a walker. The tremor responded to carbidopa/levodopa, but ropinirole was added once motor fluctuations developed. Soon afterwards, his left hand exhibited involuntary grasping and inter-manual conflict, consistent with ALP. MRI imaging revealed complete corpus callosum agenesis and colpocephaly. Ropinirole was eventually discontinued due to his experiencing hallucinations and confusion. His levodopa was not changed. The ropinirole discontinuation was followed by immediate resolution of the hallucinations and the ALP.

Conclusions: This case 1) provides evidence that dopaminergic pathways may be involved in the pathophysiology of ALP, and 2) that more than one lesion may be required to manifest ALP, a second lesion hypothesis. Use of a dopamine agonist in the setting of callosum agenesis was enough to induce ALP in our patient. Dopamine plays a very important role on modulating motor programs, thus dopamine agonists potentially influence motor behaviors in the right setting. There are known diffuse dopaminergic projections within the striatum, the limbic system and the cortex. The dopamine pathways in the mesocortical and mesolimbic systems have been implicated in behavior, perception, memory and cognition. Affectation of the mesocortical system could have caused ALP in our patient with callosum agenesis, but submit the role of dopamine in this phenomenology requires further research.

References: J. Graff-Radford, M.N. Rubin, D.T. Jones, A.J. Aksamit, J.E. Ahlskog, D.S. Knopman, R.C. Petersen, B.F. Boeve, K.A. Josephs, The alien limb phenomenon, J. Neurol. 260 (2013) 1880–1888. doi:10.1007/s00415-013-6898-y.

A. Hassan, K.A. Josephs, Alien Hand Syndrome, Curr. Neurol. Neurosci. Rep. (2016). doi:10.1007/s11910-016-0676-z.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/alien-limb-syndrome-induced-by-a-dopamine-agonist-in-a-patient-with-parkinsonism-and-agenesis-of-the-corpus-callosum/