Gastric adenocarcinoma: A one-of-a-kind etiology of autoimmune paraneoplastic encephalitis.

INTRODUCTION AND IMPORTANCE: Paraneoplastic neurologic syndromes are a group of neurologic disorders that can affect any part of the nervous system and are mediated by immune pathogens produced by cancer. These disorders occur distant to a malignant tumor and are not caused by metastasis, nutritional disorders or side effects of therapy related to the tumor.

CLINICAL FINDINGS: We present the case of a 47-year-old male patient who was admitted to the emergency department due to 1 month of neurological impairment including generalized tonic-clonic movements. He was admitted to the institution and was taken to multiple neurologic tests, all of which were normal, including a negative panel for onconeural antibodies. He persisted with seizures and was taken to a 24-hour video electroencephalogram which showed features consistent with moderate encephalopathy and focal epileptiform activity, which evolved into status epilepticus. Suspecting immune - mediated encephalitis, a therapeutic trial was started with methylprednisolone and plasma exchange, and a positron emission tomography was indicated. The positron emission tomography showed in the brain regions of marked hypometabolism and hypermetabolic thickening of gastric infiltrative aspect fundocorporal topography. Upper gastrointestinal endoscopy revealed in the subcardial region a mass-like lesion with an ulcer-infiltrative appearance, pathology showed an adenocarcinoma.

CONCLUSION: Autoimmune encephalitis as a paraneoplastic neurological syndrome of a gastric adenocarcinoma have been documented in few patients in the literature. It is important to describe and recognize clinical findings in this cases to be able to suspect malignancy and thus have early diagnosis, start treatment promptly and avoid irreversible neurological sequelae.