Parkinsonism and Related Disorders 19 (2013) 271–272 Contents lists available at SciVerse ScienceDirect Parkinsonism and Related Disorders journal homepage: www.elsevier.com/locate/parkreldis Letter to the Editor Hemichorea secondary to contralateral pontine haemorrhage Keywords: Hemichorea Pontine haemorrhage Frontoparietal diaschisis The estimated prevalence of movement disorders among patients with cerebrovascular disease is 1% with an incidence of 0.08% at 1 year. Hemichorea, with or without associated hemiballism, is the most common abnormal movement in the acute phase and the most prevalent among hyperkinetic disorders. Although an ischaemic insult of the basal ganglia has been recognised as the typical site responsible for hemichorea, different anatomical correlations have recently been described as being responsible for this condition [1]. We report the first description of hemichorea secondary to a pontine haemorrhage and discuss its potential pathophysiology. A 67-year-old woman with a history of dyslipidemia treated with atorvastatin came to the Emergency room due to involuntary movements of her left limbs that had began 3 days earlier. Physical examination only revealed a grade II/VI aortic murmur and involuntary movements in her left limbs, which were brief, non-stereotyped and typical of hemichorea. No other neurological symptoms or signs were present. Biochemical testing, blood count, coagulation study (including lupus anticoagulant and anticardiolipin antibodies) and an angio-magnetic resonance imaging (angio-MRI) study of intra- and extra-cranial vessels were normal. Computed tomography (CT) brain scan at admission and cranial MRI (after 1 week) showed a small-sized, right upper pons haemorrhagic lesion with acute appearance on the CT study (Fig. 1(a)) and sub-acute appearance on the MRI study (Fig. 1(c)–(d)). A 99mTc HMPAO single-photon-emission computed tomography (SPECT) study disclosed a decreased perfusion in the right frontoparietal region (Fig. 1(e)–(g)). The patient improved with oral haloperidol and could be discharged with a low dose of this neuroleptic. The first descriptions of vascular hemichorea showed lesions in the basal-ganglia region. It was later related to lesions in frontal, temporal and posterior parietal cortical areas, and even as a result of intra- and extra-cranial arterial disorders without an ischaemic MRI-established lesion. The pathophysiology of vascular chorea therefore remains obscure and several hypotheses have been proposed. One potential pathogenic mechanism of hemichorea when contralateral basal-ganglia infarction occurs might be the interruption of gamma-aminobutyric acid transmission from the striatum to the globus pallidus pars externa (GPe), which may increase the GPe neuronal activity and inhibit the subthalamic nucleus. The inhibition of this nucleus would result in loss of its control 1353-8020/$ – see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.parkreldis.2012.06.016 upon the globus pallidus interna (GPi) neurons, which ultimately would lead to a disinhibition of the motor thalamus. When cortical lesions are detected, some authors have stated that the interruption of glutamatergic excitatory connections from the cerebral cortex to the basal ganglia may result in functional derangement of the striatum [2]. These models do not fully explain the appearance of a hyperkinetic disorder following brainstem lesions. Neuroanatomical studies have clarified that contralateral hemisphere afferents reach the cerebellum via the brain-pontocerebellar circuit, from the dorsomedial and dorsolateral prefrontal cortex, posterior parietal region, upper temporal cortex, upper parahippocampal region and cingulate gyrus. Cerebellar hypoperfusion secondary to contralateral hemisphere damage is known as contralateral cerebellar diaschisis and, according to prior brain perfusion SPECT studies may affect up to 50% of patients with extensive fronto-temporal lesions. The cerebellar neocortex gives efferents to the contralateral cerebral hemisphere through the cerebellum-ponto-thalumus-cortical pathway. Although less common, cerebral hypoperfusion related to contralateral cerebellar lesions is called crossed cerebellocerebral diaschisis. Similarly, brain SPECT studies have shown diaschisis secondary to ischaemic pontine lesions, described in the ipsi- and contralateral cerebellar hemisphere and even in the ipsilateral frontoparietal region [3]. This case supports the existence of diaschisis between the pons and the ipsilateral frontoparietal region. Previous functional imaging studies of vascular chorea have fundamentally shown contralateral striatal hypoperfusion and contralateral thalamus hyperperfusion in line with the theory of thalamus disinhibition. In other aetiologies, such us hyperglycaemia-induced hemichorea, even contralateral cortical frontal hypermetabolism has been reported. However, in contrast with the current basal ganglia–cortical networks models, in our case there is a reduced cortical perfusion of the contralateral frontal cortex showing an interesting parallel with the fact that stimulation of subthalamic nucleus for Parkinson’s disease is associated with a reduction in frontal cortex activity. Previous studies have reported ‘rubral’ tremor and dystonia following pontomesencephalic lesions, but they were not present in our case [4]. Another interesting finding is the fact that the haemorrhage lies in the vicinity of the reticulospinal tract. In primates, the reticulospinal tract has been found to be anatomically related to the internal pallidum and substantia nigra through the pedunculopontine and cuneiform nucleus 272 Letter to the Editor / Parkinsonism and Related Disorders 19 (2013) 271–272 Fig. 1. A – Arrival axial CT showing a hyperdense pontine lesion corresponding with an acute haemorrhage B – Follow up cranial CT showing the resolution of the pontine haemorrhage. C – Axial T2*-weighted gradient echo sequence image with sub-acute right pontine haemorrhage. D – Axial FLAIR image showing a hypointense lesion related to a subacute pontine haemorrhage. E,F,G – Sagittal, coronal and axial 99mTc HMPAO SPECT images with hypoperfusion over the right frontoparietal region. [5]. Our clinico-radiological findings could indicate that this basal ganglia–brain stem network could also exist in humans and have a role in the development of different movement disorders. Current basal-ganglia functional organisation establishes two entry points from the cortex to the motor circuit of the basal ganglia, the striatum and the subthalamic nucleus. Striatal efferent neurons connect to the GPi and GPe by two different projection systems, the ‘indirect’ and ‘direct’ pathways. We propose that when cortical lesions or cortical hypoperfusion occurs, the cortico-subthalamic pathway may play a substantial role in the control of basal-ganglia output, as the actions mediated by the so-called hyperdirect pathway are similar in polarity to those in the indirect pathway but are considered to be much faster. In the absence of precise knowledge of the pathophysiology of pontine hemichorea, an ipsilateral pontofrontoparietal diaschisis, with interruption of the excitatory connections of the cortico-striatum and cortico-subthalamic pathway seems the most plausible explanation. The appearance of similar symptoms after lesions at different levels, the variety of manifestations secondary to the same process and the involvement of brain regions by remote lesions illustrate the complexity of brain networks. Acknowledgements None. References [1] Chung SJ, Im JH, Lee MC, Kim JS. Hemichorea after stroke: clinical-radiological correlation. J Neurol 2004;251:725–9. [2] Young AB, Penney JB. Biochemical and functional organization of the basal ganglia. In: Jankovic J, Tolosa E, editors. Parkinson’s disease and movement disorders. Philadelphia: Lippincott Williams & Wilkins; 2002. p. 1–10. [3] Fazekas F, Payer F, Valetitsch H, Schmidt R, Flooh E. Brain stem infarction and diaschisis. A SPECT cerebral perfusion study. Stroke 1993;24:1162–6. [4] Loher TJ, Krauss JK. Dystonia associated with pontomesencephalic lesions. Mov Disord 2009;24:157–67. [5] Rolland AS, Karachi C, Muriel MP, Hirsch EC, François C. Internal pallidum and substantia nigra control differents parts of the mesopontine reticular formation in primate. Mov Disord 2011;26:1648–56. Davinia Larrosa*, César Ramón Service of Neurology, University Hospital ‘Central de Asturias’, C/Celestino Villamil S/N., 33006 Oviedo, Spain Elena Santamarta Service of Radiology, University Hospital ‘Central de Asturias’, Oviedo, Spain Nahla Zeidan Service of Nuclear Medicine, University Hospital ‘Central de Asturias’, Oviedo, Spain Julio Pascual Service of Neurology, University Hospital ‘Central de Asturias’, C/Celestino Villamil S/N., 33006 Oviedo, Spain * Corresponding author. Tel.: þ34 985 108 000x36206. E-mail addresses: davinialc@gmail.com, davinialc@hotmail.com (D. Larrosa) 4 August 2011