Diagnostic Guideline for Spontaneous Occlusion of the Circle of Willis ("Moyamoya" Disease)
1. 1)
a) Age of onset varies, but the young and female are more frequently affected. Solitary occurrence is common, but familial occurrence is occasionally seen.
b) Symptoms and course vary, presenting no symptoms (incidental findings), transient disorder, or fixed neurologic deficits of slight or severe degree.
c) Cerebral ischemia is more common in children, while intracranial hemorrhage is more common in adults.
2)
In children, hemiparesis, monoparesis, sensory impairment, involuntary movement, headache, or convulsive seizure appears often repeatedly and occasionally on alternating sides. Mental retardation or fixed neurologic deficits may be observed. Unlike in adults, intracranial hemorrhage is rare.
3)
In adults, symptoms similar to those in children may appear, but intraventricular, subarachnoid, or intracerebral hemorrhage of sudden onset occurs more frequently. Recovery from such hemorrhage with or without neurologic sequels is seen in most of the cases except for those with severe course and lethal outcome.
2.
Cerebral angiography is indispensable for the diagnosis, and presents at least the following findings:
1) Stenosis or occlusion at the terminal portion of the internal carotid artery and at the proximal portion of the anterior and middle cerebral arteries.
2) Abnormal vascular network seen in the vicinity of the arterial occlusion in arterial phase.
3) These findings present bilaterally.
When magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) fulfill the above criteria, cerebral angiography is not mandatory.
3. Etiology is unknown. There are none of such basic diseases as arteriosclerosis, autoimmune diseases, meningitis, neoplasm, Down's syndrome, Recklinghausen's disease, trauma or irradiation.
4. Pathological findings helpful for the diagnosis:
1) Intimal thickening causing stenosis or occlusion of the lumen is observed in and around the terminal portion of the internal carotid artery usually on both sides. Deposit of lipid is occasionally seen in the proliferating intima.
2) Arteries constituting the circle of Willis such as anterior and middle cerebral and posterior communicating arteries often show stenosis of various degree or occlusion associated with fibrocellular thickening of the intima, waving of the internal elastic lamina and attenuation of the media.
3) Numerous small arteries (perforating and anastomotic branches) are observed around the circle of Willis.
4) Reticular conglomerates of small vessels are often seen in the pia mater.
Diagnostic Criteria:
Referring to 1. mentioned above, the diagnostic criteria are classified as follows. Autopsy cases without cerebral angiography should be investigated separately referring to 4.
Definite case: one which fulfills all of 2 . and 3.
In children, however, a case which fulfills 2. 1) and 2) on one side and clearly presents with narrowing at the terminal portion of the internal carotid artery on the opposite side is also included.
Probable case (unilateral): one which fulfills 2. and 3 . except for 2. 3).