diagnose the cause include liver and renal function tests, complement levels, cryoglobulin levels, Rh factor, anti-nuclear antibody, c- and p-ANCA, serologies for hepatitis B and C, lupus anticoagulant, and anti-cardiolipin antibody. A brain meningeal biopsy is the gold standard in diagnosis and confirmation.

Imaging studies can also facilitate the diagnosis. MRI and angiography may detect CNS lesions but there are no pathognomonic MRI findings. CT and MRI changes will occur in areas of ischemia or hemorrhage. MRI is more sensitive for identifying small foci and for detecting multiple CNS lesions. MR angiography may show narrowing of the larger intracranial vessels but standard angiography is necessary to delineate many of the subtle changes characteristic of vasculitis (Fig. 16). These include multiple arterial occlusions, especially of the small vessels over the convexity, segmental stenosis of intracranial vessels sometimes separated by dilations causing a beaded appearance, and intracerebral an-eurysms. However, none of these findings are specific to vasculitis.

6. Treatment

Treatment varies with the specific condition. After the specific syndrome is identified, the inciting agents are avoided and the underlying condition is treated. Steroid administration is the mainstay of treatment and can be guided by the size of the involved vessels. Large-vessel involvement responds well to cortico-steroids alone, whereas small- and medium-sized vasculitides respond better to a combination of cyclophosphamide and steroids. Steroids should be gressive occlusion of the distal portions of the internal carotid arteries and proximal portions of the anterior and middle cerebral arteries (Fig. 17). A compensatory network of small collateral vessels form in the adjacent areas at the base of the brain producing the characteristic appearance of a puff of smoke (moyamoya is Japanese for ''wavering puff of smoke''). Symptoms are due to cerebral ischemia and/or hemorrhage and can occur on alternating sides because of the bilateral nature of the disease. Although some patients present with only headache or visual disturbance, symptoms can include serious neurological deficits such as hemiparesis, motor aphasia, seizure, and mental alteration.

2. Epidemiology

Moyamoya is particularly prevalent in Japan and Korea, where 10% of patients have a family history of the disease. This increased incidence in Asian populations and familial occurrence has also led to the hypothesis of HLA gene involvement. The disease is more prominent in females, with a ratio of 1:1.8. It is rare, with a reported incidence of 0.35 per 100,000 people, but it is probably underdiagnosed because it is

Figure 16 Cerebral angiogram of a patient with vasculitis revealing multiple focal areas of abnormal stenosis followed by dilatation throughout the brain.

decreased to the lowest effective dosage to minimize side effects. Low-dose methotrexate, V immunoglobulin, or plasmapheresis can be used in difficult or select cases. Hypertension should be treated along with any underlying conditions. Surrogate markers of inflammation, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), antinuclear antibody (ANA), and antinutrophil cytoplasmic antibody (ANCA), can be used to follow the course of the disease.

7. Summary

The vasculitides are a clinically and pathologically heterogeneous group of disorders characterized by inflammation of the blood vessels that may represent a primary or secondary disease process. Additional insight into the pathoetiology will enhance our ability to effectively diagnose and treat these disorders.

B. Moyamoya Disease 1. General Considerations

Moyamoya disease is a rare progressive occlusive cerebrovascular disorder. It is characterized by pro often asymptomatic. The age distribution is bimodal, with the first peak occurring between the ages of 10 and 14 and the second between ages 40 and 49.

3. Pathogenesis

Histopathological changes occur in the terminal ICA and proximal ACA and MCA. Vessel walls display multilayered intimal fibrous thickening and markedly wavy, often duplicated or triplicated, internal elastic lamina. The thickened intima contains an increased number of smooth muscle cells but no inflammatory infiltrate, atherosclerosis, or fibrinoid necrosis. The media is usually atrophic. Varying degrees of intimal thickening are evident.

Moyamoya is an entity of unknown etiology. Both a congenital component (due to polygenic inheritance) and an acquired component (due to trauma, infection, brain tumor, radiation, or autoimmune disease) have been proposed. Recently, aberrations of vascular growth factors and cytokines have been implicated. Basic fibroblast growth factor (b-FGF) has been reported to be significantly higher in the CSF of patients with moyamoya disease than in patients with arteriosclerotic cerebrovascular occlusive disease. Increased activity of b-FGF and b-FGF receptors has also been noted in the superficial temporal artery wall.

4. Clinical Features

The clinical characteristics vary depending on the age of diagnosis. Among pediatric patients the initial symptoms are mainly due to cerebral ischemia (TIAs) and are recurrent and progressive. Their symptoms can be induced by crying, coughing, straining, or hyperventilation. In most children, the vascular obstructions rapidly progress and well-developed moya-moya vessels are noted within 2 or 3 years of the first attack. Whereas only 10% of children suffer intracranial hemorrhage, the incidence exceeds 60% in adults. Hemorrhage most often occurs in the basal ganglia, thalamus, or ventricle. Vascular obstructions in adults progress slowly if at all.

5. Diagnosis

The diagnostic criteria of the disease are based mainly on angiographic findings and the following guidelines have been proposed by the Ministry Health Welfare Japan:

• Stenosis or occlusion of the intracranial internal carotid artery or the adjacent ACAs and MCA

• Abnormal vascular network adjacent to the stenosed artery identified during the arterial phase of angiography

Figure 17 Moyamoya: AP and lateral cerebral angiogram revealing right middle cerebral artery occlusion with prominent collateral lenticulostriate and leptomeningeal vessels giving a characteristic "puff of smoke'' appearance.

• Bilateral findings on angiography

• No other identifiable cause

The angiographic findings must be present bilaterally for definite diagnosis but many believe unilateral lesions progress to become bilateral. MRI and MRA have made the diagnosis of moyamoya possible without exposing patients to the invasiveness of conventional angiography. Common MR findings include multiple dilated abnormal vessels at the basal ganglia and/or thalamus, narrowing or occlusion of major arteries of the circle of Willis, parenchymal changes including ischemic infarctions predominantly in watershed areas, intracranial aneurysms (especially in the posterior circulation and moyamoya vessels), and intracerebral hemorrhages. Electroencephalograph (EEG) can also help in diagnosis of children with moyamoya disease. In more than half the cases a characteristic EEG finding termed "rebuildup" can be found. The rebuildup is considered to be related to decreased perfusion reserve of the ischemic brain.

6. Treatment

The hemodynamics of moyamoya disease are characterized by low CBF with extremely high vascular resistance in the collaterals at the base of the brain. Revascularization has been shown to be useful in preventing further ischemic attacks but does not prevent rebleeding in the hemorrhagic group of adults with moyamoya disease. Several surgical revascular-ization procedures are used in moyamoya disease to decrease hemodynamic stress and thereby reduce moyamoya vessel prominence and increase collateral circulation. These include direct, indirect, and combined revascularization techniques. Direct bypass can be accomplished with superficial temporal artery to MCA anastomoses. Indirect bypasses include omen-tum transplantation, encephalo-galeo-synangiosis, encephalo-myo-synangiosis, encephalo-duro-arterio-synangiosis, encephalo-myo-arterio-synangiosis, and encephalo-duro-arterio-myo-synangiosis. Surgical re-vascularization is controversial in adult moyamoya disease because it does not necessarily prevent rebleeding.

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