Doctors in France have warned colleagues not to assume that elderly persons who exhibit signs of Alzheimer’s disease actually have the disease and to investigate alternative causes. The advice follows a case in which a patient thought to have Alzheimer’s disease actually had treatable limbic encephalitis.
The case arose when a 70-year-old woman presented to hospital in July 2007 with a four-month history of confusion and episodic memory loss, but no past medical history. Physical and neurological examinations were normal, but neuropsychiatric tests showed memory and learning problems. Blood analysis was normal, but an MRI revealed a hippocampus abnormality usually associated with limbic encephalitis.
The patient was treated with cyclophosphamide infusions and steroids, and her symptoms improved. A relapse 18 months later was also treated successfully.
Limbic encephalitis can present as cognitive disorders with short-term memory impairment, temporal seizures and psychiatric disorders progressing over a few weeks.
“In our case, the diagnosis could have been mistaken for Alzheimer’s, especially since the brain CT scan was normal,” the doctors said. “However, the short period of evolution and associated MRI features were atypical for Alzheimer’s disease, and led us to look for limbic encephalitis.
“Discovery of new antibodies and autoimmune mechanisms has brought immunosuppressive treatments that have improved prognosis [for limbic encephalitis cases], particularly in cases associated with antibodies to cell-membrane antigens,” the doctors wrote. “It should now be regarded as a non-exceptional and treatable aetiology of rapidly progressive dementia.”
The Lancet 2010;376:656
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