**5. Clinical manifestations in adults**

Hemorrhagic manifestations are more common in adults than in children. These haemorrhages are seen in 42% of the adults. The location of the bleeding can be intraventricular, intraparenchymal or subarachnoid.

Underlying mechanism:

Rupture of fragile collateral vessels as a result of chronic oligemia [23].

Development of cerebral aneurysms at the apex of the basilar artery and posterior communicating artery, areas of increased shear stress due to shifting circulatory pattern at the base of the brain is another source of haemorrhage [24].

Quasi MMD is common in adults, and the manifestations may range from asymptomatic to catastrophic haemorrhage and rebleeding with a moribund prognosis [13].

Ischemic symptoms are more common in the paediatric population, as described above. Amongst the ischemic symptoms transient ischemic attacks(TIA) are more common in the paediatric population with an incidence of 81% and infarctions are experienced by adults in approximately 51% [25].

Reason for the above observation could be due to better development of leptomeningeal collaterals (LMCs) in children than adults [25]. Various factors have been implicated in this observation: [25].

Ageing: Significant decrease in LMCs and increased tortuosity and vascular resistance in leptomeningeal vessels.

Concomitant diseases in adult MMD patients like hypertension may have an effect on the development of collaterals.

Focal cerebral ischemia may stimulate cytokines' secretion, such as angiogenic peptides and vascular endothelial growth factor (VEGF). These cytokines levels are lower in adults.

Associated underlying conditions are commonly observed in adults with MMD. Clinical clues for associated disorders: [10].



Special Precautions to be exercised:

EEG: Hyperventilation may precipitate an acute oligemic episode, thus caution has been exercised in patients with suspected moyamoya disease. Specific alterations in MMD/MMS have characteristic changes in EEG, consisting of the gradual decrease in frequency and amplitude activation after hyperventilation. These EEG changes are referred to as re-build-up phenomenon [2].

Anaesthesia and postop care. Travelling to high altitudes.

Exercise.
