Abstracts

RATIONALE: We have encountered a unique group of intractable temporal lobe epilepsy cases that show a significant decrease in neuronal density limited to the hippocampal CA4 and dentate fascia, which is designated as hilar sclerosis (HS). In endfolium sclerosis, the term originally defined by Margerison and Corsellis (Brain 1966; 89:499.), the dentate fascia is not included for consideration. Our aim is to find the possible clinical and other parameters that are different between conventional hippocampal sclerosis (CHS) and HS.
METHODS: We studied the hippocampal neuronal density in surgically resected hippocampi from 250 patients (median age:30 yrs, M:F=131:119), who underwent partial anterior temporal lobectomy for intractable temporal lobe epilepsy. Criteria for CHS were met when the neuronal density of CA1 was less than 60% of that of the non-epileptic postmortem hippocampal CA1. For HS, the combined average density of CA4 and dentate fascia should be less than 60% of that of non-epileptic hippocampi, while the CA1 neuronal density should be 60 % or more compared with that of non-epileptic hippocampi. Non-parametric statistical analysis was utilized to evaluate the differences in clinical and historical parameters between CHS and HS.
RESULTS: 172 out of 250 cases showed a significant neuronal density decrease in either CA1 (CHS) (n=160) or CA4 and dentate fascia (HS) (n=12), as defined above, while the remainder (78 cases) failed to show a statistically significant decrease in the neuronal density of the fields designated above. No statistically significant differences between CHS and HS were noted in age at the time of surgery (median yrs, 30 vs. 27.4), gender (M;F, 82:78 vs. 4:8), age at the time of the first non-febrile seizures (median months, 23 vs. 78) or duration of non-febrile seizure history (median yrs, 26.1 vs. 20.0). Other parameters that failed to show statistically significant differences include the family history of seizures, head trauma, infection or various perinatal risk factors. However, a history of febrile seizures was shown in 2 out of 12 HS cases (16.6%) , while it was positive in104 out of 160 CHS cases (65%) (p=0.0009). Also noted were significant differences between the two conditions in the frequency of extrahippocampal pathology (8/160 in CHS vs. 5/12 in HS) (p [lt]0.0001). Extrahippocampal pathology includes 5 tumors, 1 abscess and two ischemic disorders in CHS and 5 tumors in HS.
CONCLUSIONS: In hilar sclerosis, as compared with CHS, cases with a history of febrile seizures are less frequent and extrahippocampal pathology is more commonly encountered, which may, in part, be responsible for the unique pattern of neuronal density decrease observed in HS.
[Supported by: NIH 5PO1 NS39092]