Moyamoya Disease - Etiology

Etiology

The condition is believed to be hereditary and linked to q25.3, on chromosome 17 . In Japan the overall incidence is higher (0.35 per 100,000). In North America, women in the third or fourth decade of life are most affected. These women frequently experience transient ischemic attacks (TIA), cerebral hemorrhage or no symptoms. They have a higher risk of recurrent stroke and may be experiencing a distinct underlying pathophysiology compared to patients from Japan. Data suggest a potential benefit with surgery if early diagnosis is made. The pathogenesis of moyamoya disease is unknown.

Once it begins, the process of blockage (vascular occlusion) tends to continue despite any known medical management. In some people this leads to repeated strokes and severe functional impairment or even death. In others, this blockage may not cause any symptoms.

Moyamoya can be either congenital or acquired. Patients with Down syndrome, neurofibromatosis, or sickle cell disease can develop moyamoya malformations. It is more common in women than in men, although about a third of those affected are male . Brain radiation therapy in children with neurofibromatosis increases the risk of its development.

Recent investigations have established that both moyamoya disease and dural arteriovenous fistulas (AVFs) are associated with dural angiogenesis. These factors may represent a mechanism for vaso-occlusive ischemia contributing to the formation of dural AVFs. At least one case of simultaneous unilateral moyamoya disease and ipsilateral dural arteriovenous fistula has been reported at the Barrow Neurological Institute. In this case a 44-year-old man presented with headache, tinnitus, and an intraventricular hemorrhage, as seen on computed tomographic scans. Cerebral angiography showed a right moyamoya pattern and an ipsilateral dural AVF fed by branches of the external carotid artery and draining into the transverse sinus.This extremely rare coincidental presentation may have deeper pathogenic implications.