Paraneoplastic Limbic Encephalitis Resembling Acute Herpetic Encephalitis

Introduction. Paraneoplastic limbic encephalitis (PLE) is a rare disorder that typically follows a chronic or subacute course of personality changes, memory loss, seizures, and hallucinations. Early diagnosis is difficult and characteristic symptoms can be mimicked by a variety of conditions. We present a case of PLE, initially presenting as acute herpetic encephalitis. Case Presentation. A 56-year-old male was admitted for evaluation of acute onset headache, fever, and confusion. On neurological examination he was confused with MMSE score of 15/30. CSF analysis revealed marked lymphocytic pleocytosis. A possible diagnosis of acute herpetic encephalitis was rendered and patient was treated with acyclovir. CSF PCR was negative. Cranial MRI revealed bilateral hyperintense lesions in medial temporal lobes with contrast enhancement. Despite treatment with acyclovir patient was deteriorated; thus, a paraneoplastic syndrome was suspected. Chest CT showed a right paratracheal lymph node mass, while a biopsy revealed neuroendocrine lung cancer. Auto antibodies to Hu were also detected. The patient was treated with steroids and chemotherapy. Six months later, he had complete tumour remission and marked neurological improvement. Discussion. PLE can rarely invade acutely, being indistinguishable from herpetic encephalitis. Inclusion of PLE in the differential diagnosis of acute encephalitis is of great clinical significance. 1. Introduction Limbic encephalitis (LE) is a rather rare disorder that mainly affects limbic structures and is characterized by mood-personality changes, sleep disturbances, seizures, hallucinations, and short-term memory loss that can progress to dementia. In most patients with typical LE, the diagnosis is suggested by the clinical presentation, combined with EEG findings (epileptic activity in one or both temporal lobes and focal or generalized slow activity), MRI (hyperintense signals in the medial portion of one or both temporal lobes), and the indicated CSF inflammatory changes. Although nonparaneoplastic and paraneoplastic limbic encephalitis (PLE) have similar clinical features, identification of the paraneoplastic cause commonly depends on finding the tumour, the paraneoplastic antibodies, or both [1]. PLE results from production of a neuronal protein by a tumour, which precipitates an immune-mediated reaction (humoral and T-cell mediated) against both the tumour and the central nervous system itself. There are two types of PLE, one with antibodies to intracellular antigens such as Hu, Ma2, CRMP5, and amphiphysin, that is considered