Pure hippocampal sclerosis - A rare cause of dementia mimicking Alzheimer's disease

Objectives: To identify patients with pure hippocampal sclerosis (HS) as a cause of dementia, to determine whether they have had histories of hypotens ion or hypoxia, and to compare the clinical features of patients with pure HS with a control group of AD patients without HS. Methods: In a retrospect ive study, the authors reviewed all 1771 cases received in their dementia b rain bank from 1978 through 1996 to identify those patients with pure HS, d efined as severe degeneration and gliosis of the CA1 sector and subiculum o f the hippocampal formation in the absence of other significant dementing d isease such as Alzheimer's changes. The control group included all patients received during the same period with severe AD without HS, infarcts, or ot her dementing disease. Results: Seven pure HS cases (0.4%) were identified. None had any episodes of syncope, hypotension, or hypoxia reported in asso ciation with dementia onset. Six had memory loss as the primary presenting symptom, and all became progressively demented. Forty-five AD patients with out HS were identified for the control group. There were no clear clinical differences between the two groups with regard to sex, age at onset, risk f actors for vascular disease, symptoms of cerebrovascular disease; treatment with tranquilizing medications, treatment for depression, or nursing home placement. There was a tendency for heart disease to be more prevalent and the duration of illness to be shorter in the patients with pure HS. Conclus ions: Pure hippocampal sclerosis (HS) occurred in only 0.4% of our dementia patients. Clinically, the seven patients with pure HS were similar to our AD control group. Further research is needed to determine the causes of HS and why HS appears to mimic AD.