Moyamoya disease is a relatively uncommon, chronic cerebral vasculopathy of unknown aetiology that is characterised by unilateral or bilateral stenosis or occlusion of the proximal portion of the carotid arteries, together with an abnormal vascular network at the base of the brain. Most childhood cases manifest with the signs and symptoms of cerebral ischaemia or infarction, whereas intracerebral haemorrhage prevails in adults.1 2 We describe here a case of moyamoya disease in a 29 year old multiparous woman, who presented with involuntary limb movements induced by singing.

A 29 year old woman, gravida two, para two, presented to the neurological outpatient clinic at Chungbuk National University Hospital with recurrent episodes of brief involuntary movements affecting her left hand and arm. The movements were characterised as unilateral, brief, coarse, irregular, and wavering. There was no history of neuroleptic drug therapy, or family history of involuntary movement.

General physical, neurological, and neuropsychological examinations were unremarkable. Baseline blood tests, ECG, and chest radiography all yielded normal results. The episodes of the patient's involuntary movements were unique, in that they usually appeared while she was opera type singing in a choir at church. They were also occasionally provoked by some conditions of hyperventilation such as blowing to cool hot soup, or blowing the dust off a table. This suggested an underlying ischaemic pathophysiology and prompted us to investigate changes in brain vasculature and parenchyma. The short lived choreiform movements were usually preceded by a tingling sensation in her left hand, which occasionally extended to the left leg.

An EEG between ischaemic episodes disclosed diffuse slow waves bilaterally over the hemispheres; these slow waves increased as “build up” with the appearance of delta waves during hyperventilation. Magnetic resonance imaging showed areas of high signal intensity in both frontal subcortical regions, suggestive of focal ischaemic lesions (fig A and B). We determined the patient's cerebral vascular reserve using technetium-99m-HMPAO brain SPECT with acetazolamide challenge. This demonstrated a decreased vascular reserve in both frontal and temporal lobes, as well as in the basal ganglia. Magnetic resonance angiography and subsequent four vessel angiography showed nearly complete obstruction of the terminal portion of each internal carotid artery and the outline of a moyamoya network (fig C and D). Staged encephaloduroarteriosynangiosis was performed on the left and right sides, 1 week apart, resulting in an eventual amelioration of the patient's involuntary movements.

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(A and B) FLAIR axial images, showing bilateral focal ischaemic lesions in the frontal white matter. Low signal intensities surrounded by hyperintense rims are chronic lacunae (arrows) (C) Time of flight MR angiography, indicating that both middle cerebral arteries were unidentifiable. Note multiple tortuous flow signals, suggestive of moyamoya vessels (arrowheads). (D) Right internal carotid angiogram, demonstrating middle cerebral artery occlusion, moyamoya vessels (curved arrows), and the leptomeningeal collateral blood flow from the posterior circulation (straight arrows).

Chorea is one of the rarer, although acknowledged, presenting features of moyamoya disease; chorea is usually observed in children.3 4 It is suggested that about 6% of patients with moyamoya disease have chorea.5 Other types of involuntary movements have been described in patients with moyamoya disease: Valsalva related seizures,6 recurrent episodes of carpopedal spasm,7 recurrent torticollis,8and limb shaking transient ischaemic attack.9 Hemichorea is characterised by unilateral, brief, coarse, irregular, wavering, involuntary movements, and is usually caused by some asymmetric, focal brain lesion. The clinical presentation of our patient was associated with opera type singing.

Singing requires both hyperventilation and the breath holding Valsalva's manoeuvre. Hyperventilation causes an increase in arterial oxygen tension, which subsequently causes vasoconstriction, which, in turn, reduces blood flow. In addition, Valsalva's manoeuvre increases cerebral venous pressure, which then increases intracranial blood volume and intracranial pressure, thereby reducing the arterial perfusion pressure. Thus, in those regions of the basal ganglia and cortex that are already critically perfused, hyperventilation and Valsalva's manoeuvre can easily lead to transient ischaemic insult, which may be clinically manifested by involuntary movements. It seems likely that hyperventilation and breath holding act synergistically to reduce brain perfusion. In this patient, the hemichoreic episodes were attributed to hypoperfusion of the contralateral cerebral hemisphere, and not to epileptogenic activity. Staged left and right encephaloduroarteriosynangiosis, using a frontal branch of the superficial temporal artery, was carried out, 1 week apart. This procedure eventually ameliorated the patient's choreic movements.

Chorea is not unusual in moyamoya disease. However, the causes of chorea are manifold and careful neuroradiological and clinical evaluation is required to distinguish them.10 Our findings emphasise that moyamoya disease should be included in the differential diagnosis of adult onset chorea. Recognition of this uncommon form of occlusive carotid disease is important in the early diagnosis and proper management of neurological deficits.