[Primarily unilateral herpes encephalitis. Long-term neuropsychological study of 9 cases]

Nine cases of post-herpetic encephalitis with predominant involvement of one temporal lobe at CT scan or MRI (6 on the left and 3 on the right sides) were studied 1 to 6 years after onset with repeated language and memory testing. The neuropsychological findings were well correlated with the lateralization and size of the lesions, as previously observed in unilateral temporal lobectomy. Compared with the usual bilateral form, the sequelae were mild, and all the patients, especially those with right hemisphere involvement, resumed a subnormal family life or social activity. In patients with left predominant lesions the anterograde amnesia concerned verbal information, especially logical and abstract, without visual amnesia. In some cases, the episodic verbal amnesia was associated with a semantic deficit which included the knowledge of some words. In one patient the colour, use and mental imagery of some objects corresponding to forgotten words were involved only for some specific groups (natural objects, whereas man-made objects fared better). Testing of verbal memory is proposed to determine the role of the preserved minor hemisphere in learning the context of word presentation, and words with concrete and visual connections which are better recalled than those with abstract or logical link. Disorders of behaviour or mood are usual in the 2 groups of lesions. Thus, herpes encephalitis in these asymmetrical and benign forms in an attractive model to study the role played by the temporal lobe and lateralization in memory.