Dystonia an unusual presentation in pediatric moyamoya disease: Imaging findings of a case.

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by idiopathic occlusion of bilateral internal carotid arteries and the development of characteristic leptomeningeal collateral vessels along anterior or posterior circulation. We present an unusual case of MMD presenting with generalized dystonia as the predominant manifestation.

Introduction

Moyamoya disease (MMD) is a nonatherosclerotic progressive arteriopathy. It causes occlusion of the cerebral vasculature most frequently affecting the intracranial internal carotid arteries and proximal segments of the middle cerebral and anterior cerebral arteries. It may also involve the posterior circulation. The occlusion of the major intracranial arteries is associated with appearance of a tuft of fine collateral vessels at the base of the brain.[1] The clinical presentations include transient ischemic attacks, ischemic strokes in children and hemorrhage in adults. Atypical presentations in the form of headaches, seizures, cognitive impairment, and dementia are also seen. The clinical presentation as an isolated initial manifestation with predominant movement disorders is extremely rare, especially in the pediatric population.[2]

Case Report

An 11-year-old male child presented with a 6 month history of the progressive recurrent dystonic posturing of limbs and trunk. There was no history of visual loss, motor weakness, sensory deficit or any bladder and bowel disturbance. Higher mental functions were normal. There was no significant family, perinatal, and developmental history. The general physical, cardiovascular, respiratory, and per abdominal examination were unremarkable. His biochemical examination including a complete hemogram, blood sugar level, renal, and hepatic function tests was normal. He was subjected to magnetic resonance imaging (MRI) of brain examination which revealed multiple focal and confluent T2-weighted and fluid attenuated inversion recovery weighted hyperintense lesions in bilateral basal ganglia and periventricular regions [Figure 1a–d]. The precontrast magnetization prepared rapid acquisition gradient echo (MPRAGE) images showed these areas as hypointensities [Figure 2a and b], with filling of contrast on postcontrast MPRAGE images [Figure 2c and d]. Due to distribution of these lesions predominantly along basal ganglia vasculopathy was suspected and patient was subjected to magnetic resonance angiography next day using time-of-flight technique which showed abrupt occlusion of terminal parts of bilateral internal carotid arteries [Figure 3a and b], with attenuated anterior and posterior circulations arteries and multiple collaterals giving “puff of smoke appearance” [Figure 3c and d]. Hence, the diagnosis of MMD was confirmed.

Figure 1

Axial T2-weighted (a and b) and fluid attenuated inversion recovery images (c and d) showing multiple focal and confluent hyperintensities (white arrows)

Figure 2

Axial magnetization prepared rapid acquisition gradient echo precontrast (a and b) images showing hypointense foci which on postcontrast images (c and d) show enhancement (white arrows)

Figure 3

Magnetic resonance angiography (time-of-flight technique) images show abrupt occlusion of terminal parts of bilateral internal carotid arteries yellow arrows in (a and b), axial image show collaterals in posterior circulation white thick arrow in (c), coronal image shows attenuated arteries with multiple collaterals giving puff of smoke appearance white arrow in (d)

Discussion

MMD is a chronic hemodynamic ischemic disease of the central nervous system. It is a progressive bilateral occlusive state of the distal internal carotid artery and the proximal segments of the middle cerebral as well as anterior cerebral arteries. It is bilateral but asymmetric. The intracranial vascular changes are primary and truly idiopathic. In this rare form of vasculopathy, two peaks of incidence have been described – one in the first decade and other in the fourth decade.[3] The clinical presentation of the patients is variable according to age. The pediatric patients are prone to focal neurological deficits and seizures due to ischemia. Pandey et al. revealed multiple small ischemic watershed infarcts on MRI in three patients of MMD who presented with movement disorders in the bilateral frontal subcortical white matter.[4] The adults are more vulnerable to hemorrhagic complications. Involuntary movements such as chorea and dystonia are rare forms of clinical presentation. Lyoo et al.[5] suggested that movement disorders appear as a manifestation of MMD with an estimated frequency of 3–6%.

The dystonic movements are self-limited and are usually no symptoms or signs of disease are noted in the interval between episodes. Symptoms of movement disorders in these patients probably occur due to ischemia or changes in excitatory and inhibitory circuits interconnecting cerebral cortex and the basal ganglia.[6]

The basal ganglia receive cortical afferents from associative cortical areas such as prefrontal, temporal, posterior parietal, and preoccipital cortices.[7] Ischemic dysfunction of basal ganglia, the thalamus, cerebral cortex, and brainstem have also been implicated to stimulate simple or complex movement disorders.

Im et al. operated six patents of MMD presenting with involuntary movements and suggested that in all patients movement features improved completely within 3 months of bypass grafts secondary to improved cerebral perfusion.[8]

The early recognition of MMD as the etiology for movement disorders help in managing these patients with direct and indirect bypass surgery which offers an effective means of revascularization. We conclude that should be included in the differential diagnosis of pediatric patients presenting with recurrent involuntary movements, dystonia, chorea, and athetosis. We also suggest that pediatric patients of dystonia undergoing MRI brain examination, should be supplemented with MRA to rule out vasculopathy presenting as a rare cause of movement disorders.

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Conflicts of interest

There are no conflicts of interest.