Unknown Inheritance Patterns

STURGE-WEBER SYNDROME

Sturge is credited with the first report of this syndrome, which appeared in a 6-year-old girl who had a facial angioma, buphthalmos, and contralateral partial seizures.y Sturge surmised that she had an underlying cerebral angioma, but it was not until 18 years later that a cerebral angioma affecting the leptomeninges of these patients was first described. Weber reported the presence of intracranial calcifications in skull radiographs of these patients, Dimitri noted double serpentine calcifications, and Krabbe correctly pointed out that the calcifications were located primarily in the cerebral substance rather than in the vessel walls. Van der Hoeve believed that this syndrome was the "fourth phakomatosis."

Sturge-Weber syndrome (SWS) is characterized by a congenital facial angioma (nevus flammeus, port-wine stain) that is associated with signs and symptoms of an ipsilateral leptomeningeal angioma. The facial angioma is usually unilateral, although it can be bilateral, and involves at least the upper face, superior eyelid, or periorbital region. Angiomas can also occur in other areas of the head including the nasopharynx, palate, lips, gingiva, and tongue, as well as the neck, trunk, and extremities. The facial angioma conforms to the sensory divisions of the trigeminal nerve, but its configuration may be determined by the embryological facial development. Leptomeningeal angiomas can also occur in the absence of any facial angioma. In this case, although the signs are similar to those of SWS, the patients should be considered to have a different disorder referred to as leptomeningeal angiomatosis. SWS has no known recognized pattern of inheritance, but there is one report of a father and son who had facial angiomas and glaucoma.

Most patients with SWS have seizures, often beginning in infancy, that are primarily partial motor seizures, but some patients have secondary generalization. Other seizure types, such as myoclonic, tonic, and atonic seizures as well as infantile spasms, can occur less frequently. Earlier studies noted a seizure frequency of 70 to 90 percent. In a retrospective study of 102 patients, 88 patients had a leptomeningeal angioma affecting one cerebral hemisphere, and 14 patients had bilateral hemispheric involvement.y Seizures occurred in 75 percent of these patients. Among the patients with unilateral involvement, 63 had seizures, the mean age of seizure onset being 24 months. Thirteen of the 14 patients with bilateral involvement had seizures, the mean age of onset being 6 months.

At least half of patients with SWS are mentally subnormal, and behavioral problems are common. As seizures of early onset increase in frequency and severity, mental function and behavior often regress. In the retrospective study noted previously, 25 of 88 patients with unihemispheric leptomeningeal involvement who did not have seizures were of average intelligence; 1 of 14 patients with bilateral hemispheric involvement was unaffected by seizures, and that patient was of average intelligence. Others have documented that SWS patients with seizures have a notably higher incidence of developmental delay and emotional and behavioral problems, and these patients need special education. These observations are important considerations in patient management. Hemisensory deficits can occur but are sometimes difficult to document reliably in very young and mentally subnormal patients. Homonymous hemianopia has been noted in about one third of patients, and glaucoma secondary to choroidal angioma is found in one fourth. Other ocular abnormalities include iridic heterochromia in which the hyperpigmented iris is ipsilateral to the facial angioma, optic atrophy, and strabismus.

Electroencephalographic studies often show decreased amplitude and frequency of electrocerebral activity overlying the affected hemisphere. Other commonly noted abnormal electroencephalographic features include multiple and independent spike foci. Intracranial calcifications on skull radiographs are present in about 90 percent of patients, are usually found in the occipital or parieto-occipital region, and have a serpentine linear, parallel configuration ("tram sign"). They are rarely observed on plain skull radiographs during infancy but are present in most patients by the end of the second decade. CT of the head demonstrates intracerebral calcifications and cerebral atrophy more readily than do plain skull radiographs and has documented calcific deposits during the first few months of life. MRI, however, is the neuroimaging study of choice to show the extent of structural abnormalities of SWS.

Cerebral angiography demonstrates decreased cerebral venous drainage and dilation of the deep cerebral veins. y , y A variety of vascular abnormalities, including thrombotic lesions, dural venous sinus abnormalities, and arteriovenous malformations, has been observed in about a third of patients. Positron emission tomography (PET) can provide some measure of cerebral metabolic impairment, and serial PET scans can demonstrate the progression of the disease process. W Moreover, PET scans can provide important information that can be used to guide careful selection of patients for focal cortical resection or hemispherectomy. Single-photon emission computed tomography can also reveal useful information about cerebral perfusion.

Characteristic pathological features of SWS include thickened hypervascularized leptomeninges, which primarily affect the occipital, parietal, or temporo-occipital lobes. Meningeal vessels are small and tortuous, producing a dark, purplish blue color. These abnormal vessels rarely enter the underlying atrophic cerebral hemisphere. Calcific deposits are primarily located in the molecular and outer pyramidal cortical layers, but small calcific spicules can be found in some small cerebral vessels. The pathogenesis of calcium deposition in the brain substance is not well understood.

Management of patients with SWS requires careful attention not only to the patient's neurological deficits but also to the associated behavioral and emotional problems.y Convulsive disorders are treated by administration of standard

antiepileptic drugs, but seizures in some patients may be refractory to medical management. These patients should be considered for focal cerebral resection of the affected lobes or hemispherectomy.y Management of the associated problems of mentally subnormal patients or those with behavioral or emotional disturbances requires the skills not only of the physician but of competent psychologists and social workers as well.

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