Objective: To describe two patients who presented with hemichorea from isolated MCA stenosis without evidence of basal ganglia stroke.

Background: Hyperkinetic movement disorders can occur following an acute stroke in the basal ganglia.¹ There are rare reports of patients presenting with hemichorea from isolated MCA stenosis without evidence of basal ganglia stroke on MR imaging.^2,3

Method: We herein report two further similar cases of hemichorea from MCA M1 stenosis without basal ganglia ischemic stroke.

Results: Case 1: A 76-year old woman was referred to the movement disorder clinic to rule out Huntington’s disease. She developed involuntary movements on her right leg, which spread to her right arm over one year. On examination, she had right hemichorea. MRA of the brain showed severe stenosis of left proximal MCA M1 stenosis and bilateral anterior cerebral artery, consistent with Moyamoya pattern. MRI of the brain showed multiple old cortical infarcts in left parietal lobe and posterior frontal lobe/precentral gyrus. There was no obvious basal ganglia or white matter infarct. Carotid ultrasound showed no carotid stenosis. 
Case 2: A 65-year old woman developed sudden onset of difficulty coordinating her left arm. Next day, family member noted an involuntary jerking of her left arm. She was taken to Emergency Room, where MRI brain/EEG and further work up was negative. The etiology of chorea was unclear and she was referred to the movement disorder clinic. On examination, she had left hemichorea. On reviewing her CTA, moderate right MCA M1 stenosis was noted. CT angiography of neck showed no carotid stenosis.

Conclusion: Stenosis of MCA M1 segment can cause hemichorea, without apparent ischemic stroke on MRI brain imaging, and without carotid stenosis. Possible explanation include subclinical stroke not visible on conventional imaging, chronic hypoperfusion and stress to the basal ganglia without apparent stroke, compensatory hyperperfusion of thalamus and certain basal ganglia structures,⁴ functional imbalance in the striatum and cerebral cortex, and metabolic changes (similar to nonketotic hyperglycemic hemichorea/hemiballism).⁵  Vascular imaging to exclude middle cerebral stenosis is necessary for patients presenting with hemichorea, even when the MRI of the brain does not show acute or chronic ischemic stroke.

References: [1] Ghika-Schmid F, Ghika J, Regli F, Bogousslavsky J. Hyperkinetic movement disorders during and after acute stroke: the Lausanne Stroke Registry. J Neurol Sci. 1997 Mar 10;146(2):109-16. doi: 10.1016/s0022-510x(96)00290-0. Erratum in: J Neurol Sci 1997 Nov 25;152(2):234-5. PMID: 9077506.
[2] Ueta Y, Kato H, Naito M, Taguchi T, Terashi H, Aizawa H. Persistent Hemichorea as a Preceding Symptom of Cerebral Infarction Due to Middle Cerebral Artery Stenosis. Intern Med. 2021 Dec 1;60(23):3805-3808. doi: 10.2169/internalmedicine.7191-21. Epub 2021 Jun 12. PMID: 34121005.
[3] Chung SJ, Lee HS, Yoo HS, et al. A case of isolated middle cerebral artery stenosis with hemichorea and moyamoya pattern collateralization. J Mov Disord. 2013;6(1):13-16. doi:10.14802/jmd.13003
[4]Nabatame H, Nakamura K, Matsuda M, Fujimoto N, Shio H. Hemichorea in hyperglycemia associated with increased blood flow in the contralateral striatum and thalamus. Intern Med. 1994 Aug;33(8):472-5. doi: 10.2169/internalmedicine.33.472. PMID: 7803913.
[5] Battisti C, Forte F, Rubenni E, Dotti MT, Bartali A, Gennari P, Federico A, Cerase A. Two cases of hemichorea-hemiballism with nonketotic hyperglycemia: a new point of view. Neurol Sci. 2009 Jun;30(3):179-83. doi: 10.1007/s10072-009-0039-5. Epub 2009 Mar 21. PMID: 19305947.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/hemichorea-secondary-to-middle-cerebral-artery-mca-stenosis-without-evidence-of-ischemic-stroke-in-the-basal-ganglia/