AMYGDALA DAMAGE IN EXPERIMENTAL AND HUMAN TEMPORAL-LOBE EPILEPSY

The amygdala complex is one component of the temporal lobe that may be damaged unilaterally or bilaterally in children and adults with tempo ral lobe epilepsy (TLE) or following status epilepticus. Most MR (magn etic resonance) imaging studies of epileptic patients have shown that volume reduction of the amygdala ranges from 10-30%. In the human amyg dala, neuronal loss and gliosis have been reported in the lateral and basal nuclei. Studies in rats have more specifically identified the am ygdaloid regions that are sensitive to status epilepticus-induced neur onal damage. These areas include the medial division of the lateral nu cleus, the parvicellular division of the basal nucleus, the accessory basal nucleus, the posterior cortical nucleus, and portions of the ant erior cortical and medial nuclei. Otherwise, other amygdala nuclei, su ch as the magnocellular and intermediate divisions of the basal nucleu s and the central nucleus, remain relatively well preserved. Amygdala kindling studies in rats have shown that the density of a subpopulatio n of GABAergic inhibitory neurons that also contain somatostatin may b e reduced even after a low number of generalized seizures. While analy ses of histological sections and MR images indicate that in approximat ely 10% of TLE patients, seizure-induced damage is isolated to the amy gdala, more often amygdala damage is combined with damage to the hippo campus and/or other brain areas. Moreover, recent data from rodents an d nonhuman primates suggest that structural and functional alterations caused by seizure activity originating in the amygdala are not limite d to the amygdala itself, but may also affect other temporal lobe stru ctures. The information gathered so far on damage to the amygdala in e pilepsy or after status epilepticus suggests that local alterations in inhibitory circuitries may contribute to a lowered seizure threshold and greater excitability within the amygdala. Furthermore, damage to s elect nuclei in the amygdala may predict impairment of performance in behavioral tasks that depend on the integrity of the amygdaloid circui ts. (C) 1998 Elsevier Science B.V. All rights reserved.