The role of lumbar puncture in the evaluation of dementia: the University of Pittsburgh Study.

In a retrospective study of 80 patients over 55 years old, the efficacy of lumbar puncture in evaluating elderly demented patients was examined. Despite a cost of $381 per procedure, in addition to cerebrospinal fluid (CSF) evaluation, no diagnosis was made on the basis of the information obtained in any of the patients (53 per cent) who underwent lumbar puncture. The only abnormalities found were 11 cases of nonspecific elevations in CSF protein and one case of abnormal cellularity not related to bacterial infection. An additional 422 cases of dementia from other series were reviewed, and only four patients were found whose diagnosis could have been made by lumbar puncture--one patient had neurosyphilis, and the other three were postencephalitic. In addition, the literature on complications of lumbar puncture was reviewed. There were no serious complications of lumbar puncture in the present study. The authors concluded that although it is low-risk, lumbar puncture cannot currently be recommended for routine use in the evaluation of elderly demented patients, but should be used in evaluating demented patients under 55 years of age, patients with rapid onset or progression of dementia, patients with syphilis serology in suspected cases of viral encephalitis, and patients with signs and symptoms of fungal meningitis.