Sturge-Weber syndrome

Key points

• Phakomatosis (neurocutaneous syndrome) - non-hereditary, caused by somatic mosaic mutation in GNAQ gene
• Classic triad: facial port-wine stain (naevus flammeus) + leptomeningeal angiomatosis + glaucoma
• Port-wine stain follows V1 distribution (ophthalmic division of trigeminal nerve); bilateral in ~15%
• Characteristic imaging: tram-track calcification (gyral cortical calcification) on CT, leptomeningeal enhancement on MRI
• Progressive cerebral atrophy and gliosis ipsilateral to the angioma

Epidemiology & risk factors

• Incidence ~1 in 20,000-50,000 live births
• Sporadic - somatic mosaic GNAQ (R183Q) mutation; not inherited, no sex predilection
• Only ~5-8% of children with facial port-wine stains have SWS; risk increases with bilateral or V1 + V2 involvement
• No association with other phakomatoses

Pathophysiology

• Somatic GNAQ mutation occurs early in embryogenesis, affecting neural crest cell derivatives
• Persistent embryonic vascular plexus in the leptomeninges fails to regress
• Leptomeningeal venous angioma causes chronic venous congestion → cortical ischaemia → neuronal loss → dystrophic calcification and gliosis
• Ipsilateral choroidal haemangioma → raised intraocular pressure → glaucoma
• Cortical calcification is not in vessel walls - it is in the second and third cortical layers (dystrophic)

Clinical features

• Port-wine stain: present at birth, unilateral V1 (± V2/V3), does not cross midline (but can be bilateral)
• Seizures: ~75-90%, onset typically in first year of life; focal contralateral seizures, may become intractable
• Hemiparesis/hemiplegia: contralateral to lesion, progressive
• Intellectual disability: variable, correlates with seizure severity
• Glaucoma: ipsilateral, ~30-70%; may be congenital or develop later
• Choroidal haemangioma: ipsilateral, can cause retinal detachment
• Incomplete forms exist (leptomeningeal angioma without port-wine stain, or vice versa)

Imaging / investigations

CT

• Tram-track (railroad track) calcification: serpiginous, gyral, cortical calcification - classically parieto-occipital
• Calcification typically not visible before age 2; becomes increasingly prominent with age
• Ipsilateral cerebral atrophy with calvarial thickening and enlarged ipsilateral paranasal sinuses (Dyke-Davidoff-Masson pattern)
• Enlarged ipsilateral choroid plexus (compensatory collateral drainage)

MRI

• Best modality for early diagnosis (before calcification develops)
• Post-contrast T1W: pial (leptomeningeal) enhancement, most prominent parieto-occipitally
• Ipsilateral choroid plexus enlargement and enhancement - an early and reliable sign
• Accelerated myelination in affected hemisphere (T1 shortening on early scans)
• Progressive cortical atrophy and subcortical white matter volume loss
• SWI/GRE: blooming from cortical calcification
• MR perfusion: decreased perfusion in affected cortex
• Ipsilateral choroidal haemangioma (enhancing thickening of posterior globe)

Angiography

• Paucity of superficial cortical veins (thrombosed/absent)
• Prominent deep medullary veins (collateral drainage)
• No arterial abnormality (this is a venous/capillary malformation)

Plain radiograph (skull)

• Tram-track calcification (historically the classic finding, now superseded by CT/MRI)

Differentials

• Calcification DDx: TORCH infections (CMV), tuberous sclerosis (subependymal), celiac disease (bilateral occipital), Fahr disease (basal ganglia), post-radiation
• Leptomeningeal enhancement DDx: meningitis, meningeal carcinomatosis, sarcoidosis, post-surgical
• Other phakomatoses with intracranial calcification: tuberous sclerosis (subependymal nodules), NF (rarely)

Management

• Seizure control: anticonvulsants; surgical resection or hemispherectomy for refractory epilepsy
• Glaucoma: topical/surgical management
• Laser therapy (pulsed dye laser) for port-wine stain
• Low-dose aspirin: may reduce stroke-like episodes and seizure frequency
• Neurodevelopmental support and regular ophthalmological follow-up