Physiological MR modalities are highly useful for pathophysiological research in the human epilepsies and in experimental epilepsies. Physiological MR is most effectively interpreted in parallel analysis with structural MR imaging (MRI) and with other functional imaging modalities, in defining human epileptic pathophysiology. For example, new hippocampal lesions incurred during complex partial status epilepticus are most sensitively detected with diffusionweighted imaging (DWI), both in humans and in the rodent kainate model, and delayed imaging with structural MRI confirms the lesion as hippocampal sclerosis (HS). Physiological MR does not currently have a diagnostic role on general epilepsy care. Physiological MR and other functional imaging modalities serve as adjuncts to electrophysiological studies and structural MRI in planning epilepsy surgery.
Seizures and epilepsies
Epilepsy is the most common of disabling neurological conditions, and seizures are among the most common of neurological symptoms (Engel, 1989). Seizures are paroxysmal, transitory events that alter consciousness or other cortical function, due to episodic neurological, psychiatric, or extracerebral (particularly cardiovascular) dysfunction. Epileptic seizures are distinguished from other such events by their abnormally synchronized electrical discharges in localized or widely distributed groups of cerebral neurons; such hypersynchronous discharges do not occur during organic or psychogenic non-epileptic seizures, certain of which may produce behavior closely resembling that of epileptic seizures. Many individuals experience a single generalized tonic-clonic seizure some time in life, which can be caused by electrolyte disturbances, hypoglycaemia or other extracerebral conditions. Epilepsy is diagnosed only when persisting cerebral dysfunction causes recurring epileptic seizures.