Chapter 34 - Magnetic resonance spectroscopy in seizure disorders

Summary

Introduction

The official International League Against Epilepsy classification divides epilepsy into generalized and partial (focal or localization related) seizures. In generalized epilepsy (accounting for approximately 40% of cases), the epileptic discharge begins simultaneously over both cerebral hemispheres, presumed to reflect an underlying diffuse abnormality. In focal epilepsies (accounting for the majority of other cases), the discharge begins in a localized region, reflecting a lesion or other focal abnormality.

Brain metabolism in genetic and acquired causes of seizures

Generalized seizures appear to be largely inherited, whereas partial seizures are principally acquired. While this is broadly true, focal epilepsies may also have a genetic background, and generalized epilepsies may also have coexisting developmental abnormalities. Recently, there has been progress in identifying specific inherited epilepsies and finding genetic linkages and genetic defects. The first gene found was a missense mutation affecting the γ₂-subunit of the neuronal nicotinic acetylcholine receptor. It was discovered in patients with autosomal dominant nocturnal frontal lobe epilepsy a focal epilepsy first described in 1994. Other known epilepsy, genes include mutations affecting ion channels, such as potassium channels (KCNQ2 and KCNQ3) and sodium channels (SCN1B), [6,7] or the γ-aminobutyric acid (GABA)-A receptor.[8] The mutation in the GABA_A receptor γ₂-subunit is particularly interesting, as it was found in a family with childhood absence epilepsy and febrile convulsions. For the common inherited epilepsies, such as childhood absence epilepsy, the inheritance is complex, and other factors influence the expression of disease.