Moyamoya Syndrome

Progressive disease that affects the cerebrovascular circulation. Characterized by narrowing and/or complete obstruction of the carotids. Clinically, may cause paralysis. Headaches, various vision problems, mental retardation, and psychiatric problems may occur. Cerebral hemorrhage (subarachnoid), cerebral infarction, severe headaches, speech disorders, and sudden onset of recurrent paralysis are part of the presentation but most often occur in juvenile moyamoya patients. Children may have convulsions or involuntary movements. Hemianopia, diplopia, bilateral decreased visual acuity, and inability to recognize objects are clinical symptoms.

(Figure)

Nishimoto-Takeuchi-Kudo-Suzuki Disease; Puff-of-Smoke Disease.

The estimated prevalence is undetermined and considered rare. Approximately 7% of all moyamoya cases are familial in Greece. The sex distribution is reported to be a female-to-male ratio of 1.8:1.

Sporadic; however, for the 7 to 10% that are familial cases, 24% of which are mother-sibling inherited, autosomal recessive. Gene map locus is 3-p24.2-p26. Although it may occur at any age, the age of onset tends to determine the various symptoms.

Moyamoya disease is a result of progressive stenosis of cerebral arteries located at the base of the brain. It affects the intracerebral part of the internal carotids and causes a secondary collateral network that produces a radiologic image of a “puff of smoke” during cerebral angiography (“moyamoya” in Japanese). This aspect may be idiopathic or secondary to a known cause (drepanocytic anemia, radiotherapy, tuberculous meningitis, or in some patients affected by neurofibromatosis type I or William syndrome). It is caused by fibrocellular thickening of the intima and disorganization of the lamina elastica of the affected arteries. The collateral network consists of smallor medium-size penetrating arteries, mainly at the base of the skull, and results in hemodynamic implications different from atherosclerotic cerebrovascular disease of the elderly patient.

Diagnosis is suggested by brain scans and magnetic resonance images showing multiple ischemic accidents of different ages, possibly hemorrhage and abnormal vessels at the base of the brain. Conventional angiography ascertains the diagnosis and assesses the stage of the disease.

In 50% of cases, the disease starts before age 10 years. It usually presents with transient motor disturbances resulting from transient brain ischemia. Progression may be insidious with headaches, epileptic seizures, language disorders, and upper cerebral dysfunctioning. More often signs are acute and focal, the most common being hemiplegia, sometimes hemichorea. The usual picture is alternating hemiplegia because of repeated deficiencies. Episodes are precipitated by hyperventilation (crying, blowing balloons) and emotions. Adults usually present with intracranial hemorrhage. Surgical treatment by creation of extracranial anastomosis (e.g., EDAS [encephaloduroarteriosynangiosis]).

Document full neurologic history and examination. Check if exercise tolerance can be tolerated without neurologic symptoms. Usual preoperative investigations. Ensure that seizure medication is maintained and check recent control of convulsions.

Patients have a precarious cerebral circulation where the collateral vessels in the ischemic hemisphere are maximally dilated. Their management requires maintenance of adequate cerebral blood flow, normalization of intracranial pressure, and avoidance of both cerebral vasoconstriction and vasodilation. Cerebral blood flow is decreased with hypocapnia, and hypercapnia may reduce collateral flow by intracerebral steal effect; normocapnia is preferred. Placement of invasive arterial monitoring allowing frequent control of arterial CO2 is mandatory. Regional cortical blood flow is decreased by inhaled anesthesia in patients with Moyamoya, and such an anesthetic may provoke intracerebral steal. Total intravenous anesthesia lacks these effects and therefore may be safer. Depth of anesthesia must be appropriate to prevent sudden changes in hemodynamics and intracerebral hemorrhage. Regional anesthesia is useful, especially in obstetric practice. Adequate postoperative pain relief is essential to prevent postoperative intracerebral hemorrhage secondary to pain. Avoid hypothermia. The priority is to maintain cerebral perfusion pressure.

Beware of both hypoventilation and hyperventilation, and titrate adequate pain relief. Chronic administration of phenytoin increases nondepolarizing neuromuscular blocker requirements, produces gingival hyperplasia and bleeding, and may cause hepatic dysfunction. Ketamine, enflurane, and methohexital are relatively contraindicated.

May be secondary to Sickle Cell Anemia, Neurofibromatosis Generalisata Type I, or Williams Syndrome. It is also present in some children with Alagille Syndrome.