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Tuberous sclerosis or tuberous sclerosis complex (TSC) is a rare, multi-system genetic disease that causes benign tumours to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioural problems, skin abnormalities, lung and kidney disease. TSC is caused by mutations on either of two genes, TSC1 and TSC2, which encode for the proteins hamartin and tuberin respectively. These proteins act as tumour growth suppressors, agents that regulate cell proliferation and differentiation.[1]
The name, composed of the Latin tuber (swelling) and the Greek skleros (hard), refers to the pathological finding of thick, firm and pale gyri, called “tubers”, in the brains of patients postmortem. These tubers were first described by Désiré-Magloire Bourneville in 1880; the cortical manifestations may sometimes still be known by the eponym Bourneville’s disease.
The physical manifestations of tuberous sclerosis are due to the formation of hamartia (malformed tissue such as the cortical tubers), hamartomas (benign growths such as facial angiofibroma and subependymal nodules) and, very rarely, cancerous hamartoblastomas. The effect of these on the brain leads to neurological symptoms such as seizures, developmental delay and behavioral problems.
About 50% of people with TSC have learning difficulties ranging from mild to profound,[2] and studies have reported that between 25% and 61% of affected individuals meet the diagnostic criteria for autism, with an even higher proportion showing features of a broader pervasive developmental disorder.[3] A 2008 study reported self-injurious behavior in 10% of people with TSC.[4] Other conditions, such as ADHD, aggression, behavioral outbursts and OCD can also occur. Lower IQ is associated with more brain involvement on MRI.
Three type of brain tumours may be associated with TSC: i. Giant cell astrocytoma: (grows and blocks the CSF flow leading to dilatation of ventricles causing headache and vomiting. ii. Cortical tubers: after which the disease is named. iii. Sub-ependymal nodules: form in the walls of ventricles.
Classic intracranial manifestations of tuberous sclerosis include subependymal nodules and cortical/subcortical tubers.[5]
The tubers are typically triangular in configuration, with the apex pointed towards the ventricles, and are thought to represent foci of abnormal neuronal migration. The T2 signal abnormalities may subside in adulthood, but will still be visible on histopathological analysis. On magnetic resonance imaging, TSC patients can exhibit other signs consistent with abnormal neuron migration (radial white matter tracts hyperintense on T2WI, heterotopic gray matter).
Subependymal nodules are composed of abnormal, swollen glial cells and bizarre multinucleated cells which are indeterminate for glial or neuronal origin. There is no interposed neural tissue. These nodules have a tendency to calcify as the patient ages. A nodule that markedly enhances and enlarges over time should be considered suspicious for transformation into a subependymal giant cell astrocytoma (SEGA). A SEGA typically develops in the region of the foramen of Monro, in which case it is at risk of developing an obstructive hydrocephalus.
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