Moyamoya Disease

Moyamoya Disease (Japanese: “puff of smoke”) is a cerebrovascular disorder characterized by progressive unilateral or bilateral stenosis of the distal internal carotid arteries (often extending to the anterior and middle cerebral arteries). Up to a quarter of patients may present with heterogenous psychiatric symptoms that may be misdiagnosed as a behavioural (especially in children), mood, or psychotic disorder. The etiology of Moyamoya is unknown.

• The prevalence of moyamoya is highest in Asian countries, including Korea, Japan, and China.
• In Japan, the incidence is estimated at 0.54 per 100,000 individuals, with with a female-to-male ratio of 2. Up to 15% of patients have a family history of the disease.

• Moyamoya can also occur secondary to atherosclerosis, autoimmune disorders, neoplasms, Down’s syndrome, and other illnesses.
  • In these cases it is referred to as Moyamoya syndrome.

• The core clinical feature is ischemia secondary to hypoperfusion, which can cause repeated transient ischemic attacks (TIAs) or stroke in the cerebral cortex (e.g. - frontal, parietal, and temporal lobes).
• Hemorrhagic stroke can also occur from rupture of fragile collateral vessels or aneurysms with intraventricular, intraparenchymal, and subarachnoid distributions.
• The disruption of the anterior circulation can result in hemiparesis, speech disturbance, and hemisensory impairments.
• Headache is a common presenting and persisting symptom even with treatment.
• Cognitive impairment is also common, with impairments in processing speed, verbal memory, verbal fluency, and executive function.

• Depression or anxiety in assessment of new focal neurological symptoms is more common.
• Transient ischemic attacks may be mistaken for anxiety and panic disorder.
• Psychiatric symptoms in moyamoya disease is heterogeneous, and affects up to 25% of patients.
  • In adults, refractory depression and psychosis with new focal neurological deficits may be signs of moyamoya.^[1]

• The absence of a family psychiatric history, particularly of psychotic illness, in combination with atypical illness features (e.g. - age at onset, visual hallucinations) should prompt a detailed neurological investigation, with MRI or MR angiography ordered rather than a screening CT.^[2]

• MRI with contrast, T2-weighted fluid-attenuated inversion recovery (FLAIR) may have hyperintense signals and new ischemic changes.

• Diagnostic cerebral angiograms will reveal fragile compensatory collateral vessels forming along the base of the brain, these fragile vessels resemble the diagnostic “puff of smoke,” hence the term moyamoya (もやもや) in Japanese.

• Surgical revascularization, via direct artery-to-artery anastomosis or indirect arteriosynangiosis, is the primary treatment to prevent cerebral infarction and restore perfusion and reserve capacity.
• Conservative management includes long-term aspirin, antiplatelet, or statin use.