Weber syndrome
Overview
Weber's syndrome (superior alternating hemiplegia) is a form of stroke characterized by the presence of an oculomotor nerve palsy and contralateral hemiparesis or hemiplegia. It is caused by midbrain infarction as a result of occlusion of the paramedian branches of the posterior cerebral artery or of basilar bifurcation perforating arteries. This lesion is usually unilateral and affects several structures in the midbrain including: substantia nigra, corticospinal and corticobulbar tracts, and the oculomotor nerve fibers. The lesioned substantia nigra causes contralateral parkinsonism because its dopaminergic projections to the basal ganglia innervate the contralateral hemisphere motor field. The corticospinal fibers affected produce contralateral hemiparesis and typical upper motor neuron findings. Damage to the corticobulbar tract will produce difficulty with contralateral lower facial muscles and hypoglossal nerve functions. The oculomotor nerve fibers that are affected lead to ipsilateral oculomotor nerve palsy with a drooping eyelid and fixed wide pupil pointed down and out. The oculomotor damage will likely lead to diplopia.
Symptoms
Weber syndrome is indicated at birth by seizures accompanied by a large port-wine stain birthmark on the forehead and upper eyelid of one side of the face. The birthmark can vary in color from light pink to deep purple, and is caused by an overabundance of capillaries around the ophthalmic branch of the trigeminal nerve, just beneath the surface of the face. There is also malformation of blood vessels in the pia mater overlying the brain, on the same side of the head as the birthmark. This causes calcification of tissue and loss of nerve cells in the cerebral cortex. Neurological symptoms include seizures that begin in infancy and may worsen with age. Convulsions usually happen on the side of the body opposite the birthmark, and vary in severity. There may be muscle weakness on the same side. Some children will have developmental delays and mental retardation; about 5% will have glaucoma (increased pressure within the eye), which can be present at birth or develop later. Increased pressure within the eye can cause the eyeball to enlarge and bulge out of its socket (buphthalmos). Sturge-Weber syndrome rarely affects other body organs.
Prognosis
Although it is possible for the birthmark and atrophy in the cerebral cortex to be present without symptoms, most infants will develop convulsive seizures during their first year of life. There is a greater likelihood of intellectual impairment when seizures start before the age of 2 and are resistant to treatment.
Treatment
Laser treatment may be used to lighten or remove the birthmark. Anticonvulsant medications may be used to control seizures. Doctors recommend yearly monitoring for glaucoma, and surgery may be performed on more serious cases. Physical therapy should be considered for infants and children with muscle weakness. Educational therapy is often prescribed for those with mental retardation or developmental delays, but there is no complete treatment for the delays. Brain surgery involving removing the portion of the brain that is affected by the disorder can be successful in controlling the seizures experienced so that the patient has only a few seizures that are much less intense than pre-surgery.