With specialized equipment and software, it is possible to estimate brain GABA levels. It may one day be possible to determine if a drug with effect on GABA is producing the desired elevation of brain GABA with this technique. 18-Flurodeoxyglucose or FDG is the workhorse ligand used in epilepsy work and is distributed in proportion to regional cerebral metabolism of glucose. In MTLE, the ipsilateral mesial temporal region, lateral temporal cortex and thalamus show glucose hypometabolism. Such widespread interictal dysfunction indicates that much more than the mesial temporal structures is involved in the ultimate epileptic disturbance, although the relationship between hypometabolism and degree of epileptogenicity is not well documented.
Neuronal activation results in a regional increase in cerebral blood flow.
MR uses the fact that the magnetic susceptibility of oxyhemoglobin and deoxy-hemoglobin are different and that with neuronal activation there relative proportions of these change regionally. The difference in MR signal during the performance of a task and during a baseline period is used to map brain activated during a specific task. Generation of activation maps is a technically and methodologically complex task. To date mapping of visual, somatosensory and motor areas have been used to demonstrate functional areas. The topography of activations obtained from fMRI has been compared with the results of electrical brain stimulation for validation.