Sturge–Weber Syndrome

Sturge-Weber syndrome (SWS), scientifically classified as encephalotrigeminal angiomatosis, is a rare neurocutaneous disorder that originates from errors during embryonic development. It is a type of phakomatosis, a category of congenital conditions affecting the central nervous system, skin, and eyes. Unlike many other phakomatoses, SWS is not typically inherited; rather, it arises sporadically due to a mosaic somatic activating mutation in the GNAQ gene.

This mutation occurs after fertilization, meaning that only a subset of the body's cells will carry the altered gene. This mosaicism explains the variable expressivity and the fact that affected individuals usually do not pass the condition to their offspring. The GNAQ gene plays a crucial role in cell signaling pathways, and its aberrant activation during early development leads to the abnormal proliferation of blood vessels, the hallmark of SWS.

The clinical presentation of Sturge-Weber syndrome is highly variable, ranging from mild to severe. The most consistent feature is the port-wine stain (nevus flammeus) on the face, typically unilateral and following the distribution of the trigeminal nerve. This vascular malformation is a key diagnostic indicator.

Neurologically, SWS is often associated with leptomeningeal angiomatosis, which involves abnormal blood vessels in the pia mater and arachnoid mater, the membranes covering the brain. This can lead to chronic cerebral blood flow disturbances, leading to progressive neurological deficits. Seizures are a common and often early symptom, occurring in up to 80% of affected individuals, and can be difficult to control. Intellectual disability, hemiparesis (weakness on one side of the body), and stroke-like episodes are also frequently observed.

Ocular involvement is also significant, with glaucoma being a major concern, affecting up to 70% of patients. Other ocular findings include choroidal lesions and strabismus, which can lead to vision loss if not managed promptly.

The diagnosis of Sturge-Weber syndrome is primarily clinical, supported by imaging studies. The presence of a facial port-wine stain, especially when unilateral and associated with neurological or ocular findings, strongly suggests SWS. Neuroimaging plays a critical role in confirming the diagnosis and assessing the extent of the disease.

CT scans are particularly useful for detecting intracranial calcifications, which often appear as bilateral, curvilinear densities in the cerebral cortex, resembling 'tram tracks.' MRI provides more detailed anatomical information, revealing leptomeningeal angiomatosis, cerebral atrophy (shrinkage of brain tissue), and vascular abnormalities. Angiography may be used in select cases to further delineate the vascular malformations. The absence of leptomeningeal angiomatosis in the presence of a port-wine stain generally excludes the diagnosis of SWS.

Currently, there is no cure for Sturge-Weber syndrome. Management focuses on alleviating symptoms and preventing complications. Antiepileptic medications are the mainstay for seizure control, with treatment tailored to the individual's seizure type and frequency.

Neurosurgical interventions, such as hemispherectomy (removal of a portion of the brain), may be considered for intractable epilepsy, although this is a significant procedure. Ocular management involves regular monitoring for glaucoma and prompt treatment with medications or surgery to preserve vision. Physical, occupational, and speech therapy are essential for addressing developmental delays and motor deficits.

Ongoing research is exploring targeted therapies that could address the underlying genetic defect or the abnormal vascular proliferation, offering hope for more definitive treatments in the future.