Evaluation of auditory brainstem potentials in children with acute Herpes simplex encephalitis.

OBJECTIVE: In this study, auditory brainstem potentials (ABPs) were studied in children with Herpes simplex encephalitis (HSE) to determine the ABP abnormalities in HSE during childhood. We also wished to determine whether or not to use ABP in early diagnosis of HSE. METHOD: The study includes 28 children; eight children with acute HSE, nine with nonspecific encephalitis, and 11 healthy age-matched control subjects. The diagnosis of HSE was confirmed by the demonstration of Herpes simplex virus type 1 in CSF by polymerase chain reaction. Recordings of ABPs were performed by using Nihon Kohden Neuropack 2 device. RESULTS: The study includes eight children (four females and four males) with acute HSE, nine children (five males and four females) with nonspecific encephalitis, and 11 healthy age-matched control subjects (six males and five females). Age ranges of the patients and controls were between six months and 12 years. There was not statistically significant difference between the groups for age and gender (p > .05). There were significant differences in the mean latencies of the wave IV on the right ear and in the mean interpeak latencies (IPLs) of the waves III-V on the right and left ears between the nonspecific encephalitis group and the control group (p < .05). However, there were no statistically significant differences between the HSV and control groups (p > .05). In addition, there was no significant difference between HSV and nonspecific groups (p > .05). CONCLUSIONS: Our findings revealed that there were mild ABP abnormalities in children with nonspecific encephalitis, but no ABP abnormality in patients with HSV encephalitis. However, we think that more extensive and detailed studies should be performed to determine whether or not there were ABP abnormalities in childhood HSV encephalitis.

Retrograde amnesia and the volume of critical brain structures.

There are many controversies concerning the structural basis of retrograde amnesia (RA). One view is that memories are held briefly within a medial temporal store ("hippocampal complex") before being "consolidated" or reorganised within temporal neocortex and/or networks more widely distributed within the cerebral cortex. An alternative view is that the medial temporal lobes are always involved in the storage and retrieval (reactivation) of autobiographical memories (multiple trace theory). The present study used quantitative magnetic resonance imaging (MRI) in 40 patients with focal pathology/volume loss in different sites, to examine the correlates of impairment on three different measures of RA. The findings supported the view that widespread neural networks are involved in the storage and retrieval of autobiographical and other remote memories. Brain volume measures in critical structures could account for 60% of variance on autobiographical memory measures (for incidents and facts) in diencephalic patients and for 60-68% of variance in patients with frontal lesions. Significant correlations with medial temporal lobe volume were found only in the diencephalic group, in whom they were thought to reflect thalamic changes, but not in patients with herpes encephalitis or hypoxia in whom the temporal lobes were particularly implicated. The latter finding fails to support one of the main predictions of multiple trace theory, as presently expounded.