DISPROPORTIONATE LOSS OF CA(4) PARVALBUMIN-IMMUNOREACTIVE INTERNEURONS IN PATIENTS WITH AMMONS HORN SCLEROSIS

We studied differences in the number and morphology of parvalbumin-imm unoreactive (PV-IR) interneurons in 43 hippocampal specimens from pati ents with classical Ammon's horn sclerosis (AHS) who underwent anterio r temporal lobectomy, as compared with 14 autopsy and non-AHS surgical control specimens. PV-IR neuronal loss in the AHS specimens varied si gnificantly from that expected based on overall AHS-associated pyramid al and granule neuron loss. Most striking was the loss of PV-IR intern eurons in CA(4) of the AHS specimens, which was 12 times greater than AHS-associated pyramidal neuron loss, and significantly exceeded the P V-IR interneuron loss observed in the other sectors of the hippocampus . In addition, the PV-IR interneurons in the AHS specimens had markedl y smaller and less defined cell bodies and shortened and simplified de ndritic arbors compared with the PV-IR interneurons in the control spe cimens. Other differences noted in the AHS specimens included prominen t dendritic varicosities; the loss or interruption of a band formed by PV-IR terminals in the dentate gyrus; and the virtual absence of a sm all, intensely staining PV-IR interneuron with a short, exuberant dend ritic arbor that was readily identified in the autopsy specimens. We d iscuss these findings in relationship to the development of classical AHS and complex partial seizures (CPS).