Clinical presentation and pathophysiology
Manifestation of the disease typically occurs during the first year of life. Infants develop focal seizures that over time become completely resistant to pharmacotherapy. A characteristic visual sign is a vascular skin lesion of the face — the so-called «port-wine stain» (port-wine stain).
In addition to seizures, the clinical profile includes developmental delay, progressive cognitive decline, hemiparesis, and hemianopia.
The pathogenesis is rooted in a vascular anomaly. Leptomeningeal angiomas pose a serious impediment to normal venous outflow from the brain structures. Consequently, chronic ischemia occurs locally. Prolonged oxygen deprivation inevitably leads to neuronal death (cortical atrophy) and massive calcium salt deposition. It is calcification that serves as a pronounced and specific sign of this pathology.
Challenges of early diagnosis
Students and young physicians often assume that a severe congenital anomaly is always visible on modern scans. However, early neuroimaging in Sturge-Weber syndrome is notoriously deceptive.
- Early MRI and CT: In children under two years of age, scans may appear entirely normal. Even with intravenous contrast enhancement, the pial angioma may remain imperceptible.
- Skull radiography: Specific changes develop gradually. By approximately 2 years of age, typical cortical calcifications begin to appear on skull radiographs, which, due to their configuration, are termed «tramline calcifications» (tramline calcifications).
Detailed MRI semiotics and progression
As the disease progresses, the MRI appearance becomes highly specific. A key finding is atrophy of the affected hemisphere (e.g., involving the frontal, parietal, occipital, and temporal lobes).
Findings on contrast-enhanced T1-weighted images (T1WI):
- Pial angioma: Demonstrates leptomeningeal contrast enhancement of varying intensity overlying the atrophic hemisphere.
- Choroid plexus: Enlargement of the ipsilateral choroid plexus (choroid plexus) is noted. A enhancing choroidal angioma may be detected (bilateral variants also occur).
- Diploë: Widening of the diploic space of the cranium with signs of contrast accumulation.
The venous system deserves special attention. MRI (especially T2) reveals dilated transependymal and transmedullary veins that serve a compensatory function, connecting the superficial and deep venous systems, as well as enlarged superficial and ependymal veins.
Cortical malformations and white matter changes
The syndrome is frequently accompanied by polymicrogyria (excessive gyral folding, overconvolution). Due to the partial volume effect, the affected cortex may paradoxically appear thickened on scans. However, upon careful analysis, the inner cortical margin exhibits the characteristic «lumpy bumpy» (lumpy bumpy) appearance typical of polymicrogyria.
Calcifications are visualized as foci of hypointense signal within the gyri and white matter on T1 and T2 sequences.
An interesting phenomenon occurs with the white matter: on the affected side, it looks darker than in the contralateral healthy hemisphere. This is due to the process of accelerated myelination (accelerated myelination).
In late stages of the disease, so-called «burnt out» (burnt out) cases develop. The pial angioma completely ceases to enhance with contrast, and scans visualize only a shrunken, totally calcified hemisphere.
Briefly: answers to topical questions
Which lobes of the brain are most frequently affected by leptomeningeal angioma in Sturge-Weber syndrome?
Leptomeningeal (pial) angiomas in Sturge-Weber syndrome most frequently involve the parietal and occipital lobes of the brain. Vascular changes are predominantly localized in these areas and are best visualized on T2* gradient-echo MRI. Cortical calcifications underlying the cortex and white matter are also typically identified in the parieto-occipital region. In individual clinical cases, leptomeningeal contrast enhancement may extend to the frontal, parietal, occipital, and temporal lobes.
What other phacomatoses must be considered in the differential neuroradiological diagnosis of Sturge-Weber syndrome?
Neurocutaneous syndromes that should be considered in the differential neuroradiological diagnosis of Sturge-Weber syndrome include:
- Neurofibromatosis type 1 (NF-1) — optic pathway gliomas and plexiform neurofibromas.
- Neurofibromatosis type 2 (NF-2) — bilateral vestibular schwannomas, meningiomas, and other tumors.
- Tuberous sclerosis (TS) — cortical-subcortical tubers and subependymal tumors.
- von Hippel–Lindau disease (von Hippel–Lindau disease).
Other neurocutaneous syndromes listed in sources include Ito hypomelanosis, basal cell nevus syndrome, PHACES syndrome, and neurocutaneous melanosis.
Sturge-Weber triad: Port-wine stain (skin), Tramline calcifications (X-ray), Drug-resistant seizures (clinical presentation).
Class and exam questions
Why might the cerebral cortex appear thickened on MRI in Sturge-Weber syndrome when the pathology is characterized by atrophy?
This is an optical illusion caused by polymicrogyria. Excessive folding of small gyri creates a partial volume effect, making the cortex appear thick, while its inner contour retains a «lumpy bumpy» appearance.
Does the pial angioma always enhance with contrast?
No, not always. In the earliest stages (under 2 years), it may not be visible at all, and in late stages («burnt out» cases), it ceases to enhance with contrast.
Why does the white matter on the side of the atrophied hemisphere appear darker?
The decreased signal intensity of the white matter on the affected side is caused by the phenomenon of accelerated myelination of nerve fibers.
What else to study on this topic
- Neurofibromatosis type 2: bilateral vestibular schwannomas
- Neurocutaneous melanosis and melanocytic nevi
- Other neurocutaneous syndromes: Ito hypomelanosis, PHACES syndrome
- Normal spinal cord development: gastrulation and neurulation
- Open spinal dysraphism (myelomeningocele)
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