[Cerebral toxocariasis: a rare cause of cognitive disorders. A contribution to differential dementia diagnosis].

We report on a 65-year-old woman with depressive symptoms and cognitive deficits confirmed by psychometric tests. Routine blood tests, serology, EEG, and cranial computed tomography (CCT) being normal, the CSF revealed an eosinophilic reaction and a positive antibody titre against Toxocara canis. After treatment with two oral courses of albendazole, the eosinophils had disappeared, whereas the antibody titre had increased. One year later, the patient's cognitive symptoms had improved, and new antibodies against toxocara were seen in the peripheral blood. This increase in antibodies represents an expected immunological reaction to the increased exposition to toxocara antigen under effective therapy. The infection might go back to the patient's youth, when she was a shepherd for several years and in close contact to dogs. A review of the literature did not yield other reports of toxocara infections leading to cognitive or other psychiatric symptoms. Taking the toxocara infection as the cause of this patient's cognitive defects, we propose that lumbar punction becomes part of the diagnostic standard in differential diagnosis of dementia.