The epileptogenic focus/substrates which include infections, tumours, leucodystrophies, developmental malformations, gliosis, vascular malformations, encephalitis, infarct and thrombosis were identified based on the magnetic resonance imaging features for each of these lesions.
Computed tomography is widely available, very useful in the emergency setting and can detect major structural abnormalities and calcifications, but its sensitivity in the detection and characterisation of subtle cortical abnormalities, hippocampal lesions, leucodystrophies, vascular malformations, which is important in epilepsy imaging and also the detection of posterior fossa lesions is low.
Other rare causes of white matter hyperintensities include cerebral vasculitis, primary angiitis, leucodystrophies
, infective conditions such as Lyme disease and the neurosarcoidosis.
Hereditary leucoencephalopathies, often called leucodystrophies, can be separated into three categories: 1) metabolic leucoencephalopathies caused by defects in gene coding for enzymes or proteins involved in the cell metabolism, and for which the diagnosis is currently based on biochemical analysis of plasma and urines samples; 2) leucodystrophies caused by defects in gene coding for proteins not directly involved in metabolic pathways and for which the diagnosis is directly based on gene testing; and 3) leucoencephalopathies without any known biochemical abnormalities or mutated genes.
These conditions can be related to inborn errors of metabolism or genetic leucodystrophies. Main causes of leucodystrophies with identified enzyme deficiency are summarized in Tables 1 and 2.
It is difficult to discuss in detail the MR aspect of all inherited metabolic leucodystrophies. However, common radiological aspects often seen are:
Interestingly, some leucodystrophies with known mutated genes have specific patterns of MR.