Recurrent spatial disorientation and amnestic episodes associated with lung adenocarcinoma: a serum- and CSF-negative paraneoplastic case.

Recurrent seizure-like episodes with preserved motor function and negative conventional investigations pose a significant diagnostic challenge, particularly in elderly patients. We report an elderly patient presenting with recurrent, stereotyped episodes of spatial disorientation and amnesia. Extensive evaluation, including brain MRI, cerebrospinal fluid analysis, electroencephalography, serum tumor markers, and neuronal antibody testing, was unrevealing. The patient did not meet the 2016 criteria for possible autoimmune encephalitis. A previously monitored pulmonary nodule was surgically resected and confirmed as lung adenocarcinoma. Remarkably, neurological episodes completely resolved following tumor resection and did not recur after discontinuation of antiseizure medication during 10 months of follow-up. This case highlights a potential tumor-related seizure-associated network dysfunction in the absence of detectable antibodies or overt limbic inflammation. Careful tumor evaluation should be considered in similar diagnostic dilemmas, even when conventional autoimmune markers are negative.