Hemiballism due to an ipsilateral subthalamic nucleus lesion

Abstract

An 87-year-old right-handed man with untreated hypertension and hypercholesterolaemia presented with acute flinging and throwing movements of the left upper and lower limb. Clinical examination confirmed involuntary, irregular, wide amplitude movements of the left limbs consistent with left hemiballism in the absence of other neurological deficit. Blood count, CRP, glucose level, calcium, renal and liver function tests, ANF, lupus anticoagulant, anticardiolipin antibodies, thyroid function, serology of HIV, and arterial blood gas analysis were all normal. Brain MRI showed an acute infarction in the left (i.e. ipsilateral to the hemiballistic movements) subthalamic nucleus (STN) zone (Fig. 1), together with signs of chronic ischaemic microangiopathy in the brainstem and the periventricular areas (Fig. 2). [F] FDG PET performed 1 week after symptom onset revealed hypometabolism in the left hemispheric cortex (preserving only the anteromedial part of the frontal lobe) and the left caudate nucleus and the putamen (Fig. 1), probably due to deafferentation via connections between the STN and the ipsilateral basal ganglia system and the cortex, respectively. Carotid duplex sonography showed bilateral nonstenotic carotid atheroma. Electrocardiography and transthoracic echocardiography were normal. Recent infarction was probably due to occlusion of a small artery related to untreated cardiovascular risk factors. Secondary prevention treatment for ischaemic stroke was started. Neuropsychological testing 1 week after symptom onset showed a mild to moderate amnestic syndrome with preserved executive functions. Hemiballism disappeared progressively over the following months. [F] FDG PET 5 months after hemiballism onset showed near complete recovery of hypometabolism (Fig. 1), and neuropsychological testing normalized. Historically, acute hemiballism was thought to be related almost exclusively to contralateral (ischaemic or haemorrhagic) STN lesions. However, recently the era of modern neuroimaging has allowed identification of lesions often outside the STN (e.g. thalamus, globus pallidum, putamen, caudate nucleus, white matter, and cortex) [1]. The vast majority of lesions are contralateral to the hemiballism. Only a few cases with ipsilateral STN lesions have been described [2, 3]. The pathophysiology of ipsilateral hemiballism is poorly understood. The possibility that the STN exerts a bilateral control of motor function may explain this. This is supported by the observation that unilateral stereotaxic neurosurgery in Parkinson’s disease frequently results in bilateral improvement of abnormal movements. Anatomic pathways related to this bilateral control are unknown. [F] FDG PET in our patient nicely showed the connections between the STN and the other ipsilateral brain structures. DimitriRenard (&) A. Le Floch G. Castelnovo P. Labauge Department of Neurology, CHU Nimes, Hopital Caremeau, Place du Pr Debre, 30029 Nimes Cedex 4, France e-mail: dimitrirenard@hotmail.com