A magnetic resonance angiogram (MRA) of the brain revealed high-grade narrowing of the supraclinoid carotid arteries bilaterally consistent with early moya moya disease (Fig. 4A, B). There were no abnormalities of the circle of Willis and no arterial collateral networks that, in fully developed moya moya disease, cause the “puff of smoke” appearance on the angiogram. Because neurologic examination was normal, no intervention was recommended.
A follow-up MRA six months later was entirely normal (Fig. 4C, D). The initial MRA findings were therefore attributed to vasospasm. The patient was started on 10 mg sustained-release nifedipine per day for his headaches with complete relief.
MGDA is typically unilateral and associated with poor vision, although there are rare reports of cases with good visual acuity (3,5,8). Some patients report symptoms of flashes of light, floaters, and photophobia in the affected eye (5). Our patient was visually asymptomatic with an acuity of 20/20 in the affected eye, normal color vision, no afferent pupillary defect, and an enlarged blind spot on perimetry.
Both OCT and SLP attempt to quantify nerve fiber layer thickness, but the methods used are quite different. OCT passes near infrared light through the ocular structures, and the “echo” time of the reflected light is used to differentiate among various tissues (9). The data are displayed much like those of a magnetic resonance imaging scan, showing the retinal layers in a series of sagittal sections. SLP passes an infrared laser beam through the nerve fiber layer twice (10). Because the nerve fiber layer is birefringent, part of the beam is phase-shifted. The amount of phase shifting corresponds directly to the thickness of the nerve fiber layer. In our case, the two tests produced comparable results, indicating that there was a normal amount of nerve fibers present in the eye with MGDA. These tests help explain the virtually normal visual function in this eye.
Although MGDA may be isolated, numerous other ocular abnormalities have been associated with it, including nonrhegmatogenous retinal detachment, strabismus, anterior chamber cleavage syndromes, and lenticulohyaloid dysgeneses (1,11). Non-ocular associations include hypertelorism, basal encephalocele, agenesis of the corpus callosum, facial hemangiomas, and renal anomalies (1-3,12). The conjunctival lesion in our case may be a choristoma, but this could not be confirmed because the family declined biopsy.
There are several recent reports of the association of moya moya disease with MGDA (3-7), and our patient's initial MRA findings were consistent with this diagnosis. However, a follow-up MRA six months later was entirely normal, suggesting that cerebral vasospasm accounted for the initial MRA findings. (The source images of the initial MRA were carefully scrutinized to exclude the possibility the carotid stenoses represented susceptibility or slab boundary artifacts.) The association of MGDA with reversible cerebral vasospasm has not previously been reported.
Moya moya disease is a rare cerebrovascular disorder of unknown etiology characterized by progressive bilateral stenosis of the distal internal carotid arteries. The first sign of the disease is narrowing of the terminal branches of the internal carotid arteries. Because of this progressive narrowing, collateral circulation develops at the base of the brain. As narrowing progresses, the collateral vessels are often unable to supply the brain sufficiently and ischemia results. The disorder is more common in Asians, and the name moya moya derives from the Japanese term for “puff of smoke,” which describes the angiographic appearance of the abnormal collateral vessels. Children with moya moya disease often present with strokes, seizures, or recurrent headaches (5). Conversely, adults often present with intracranial hemorrhage secondary to the increased size and fragility of vessels (5). There is no medical treatment of this disorder, but extracranial-to-intracranial bypass procedures have been used in an attempt to bypass the stenotic or occluded arteries to avoid the consequent hemispheric ischemia.
Do some patients with MGDA have true moya moya disease and others have congenital anomalies or vasospasm of the distal internal carotid arteries that result in a moya moya-like vascular pattern? Bakri et al (6) reported a 10-year-old girl with MGDA, sphenoencephalocele, and moya moya disease who experienced a stroke. In contrast, Komiyami et al (7) reported a 29-year-old patient with MGDA, moya moya disease, and basal meningoencephalocele who had no cerebrovascular events attributable to moya moya disease for at least 10 years after the initial diagnosis and had normal cerebral blood flow. Hence, it appears that some cases with MGDA and moya moya disease may go on to experience vascular complications, whereas others may have a benign course. Those cases with a benign course may have congenital anomalies of the distal internal carotid arteries with a moya moya-like pattern but without progressive cerebrovascular disease or reversible cerebral vasospasm, as in our patient's case. None of the previously reported cases of MGDA and moyamoya disease (3-7) has included follow-up MRA or arteriography.
We recommend that patients with MGDA be screened with an MRA of the brain and that they be followed with serial MRAs if the results are abnormal to differentiate between true moya moya disease and vasospasm. A trial of calcium channel blockers is reasonable in those patients with MGDA who have headache because it may be on a vasospastic basis.
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