OBSOLETE: Non-herpetic acute limbic encephalitis

Non-herpetic acute limbic encephalitis (NHALE) is a term that was historically used to describe a form of acute limbic encephalitis affecting the brain's limbic system — particularly the hippocampus, amygdala, and medial temporal lobes — that is not caused by herpes simplex virus infection. This Orphanet entry (163924) is now classified as OBSOLETE, as the condition has been reclassified and absorbed into broader and more specific diagnostic categories, most notably autoimmune encephalitis. Many cases previously labeled as non-herpetic acute limbic encephalitis are now recognized as autoimmune limbic encephalitis, often associated with specific neuronal antibodies such as anti-NMDA receptor, anti-LGI1, anti-CASPR2, anti-AMPA receptor, or anti-GABA-B receptor antibodies. Some cases are paraneoplastic, occurring in association with underlying malignancies. Patients typically presented with acute or subacute onset of confusion, memory impairment (particularly short-term memory loss), seizures, psychiatric symptoms including personality changes, hallucinations, and behavioral disturbances. MRI often showed signal abnormalities in the medial temporal lobes, and cerebrospinal fluid analysis frequently revealed inflammatory changes. The condition primarily affects the central nervous system. Because this entity has been reclassified, current clinical practice focuses on identifying the specific underlying autoimmune or paraneoplastic etiology. Treatment approaches for autoimmune limbic encephalitis include immunotherapy (corticosteroids, intravenous immunoglobulin, plasma exchange), and second-line agents such as rituximab or cyclophosphamide. When a paraneoplastic cause is identified, treatment of the underlying tumor is essential. Early diagnosis and prompt immunotherapy are associated with better neurological outcomes. Patients suspected of having this condition should be evaluated under current autoimmune encephalitis diagnostic criteria.

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