New-onset seizures misdiagnosed as psychogenic non-epileptic seizures: a case of paraneoplastic limbic encephalitis with primary testicular cancer

Behavioral psychiatric symptoms can be the only warning signs of more serious conditions such as paraneoplastic limbic encephalitis. Differentiating between primary psychiatric disorders and paraneoplastic neurological syndromes is crucial as they require distinct treatment approaches. In this case report, we provide an overview of paraneoplastic encephalitis and introduce a unique case that showcases a misdiagnosis of psychogenic non-epileptic seizures (PNES) in a male as the primary symptom of paraneoplastic encephalitis due to pure seminoma. This case highlights the underlying pathophysiology of antibody-mediated paraneoplastic encephalitis and its significance.

A 31-year-old male with no known past medical history presented due to recurrent seizures. There was no prior history of epilepsy or exposure to seizure-triggering agents. Imaging and electroencephalogram findings during his initial hospitalizations pointed to a potential diagnosis of PNES. The patient continued to experience seizures following discharge, leading to repeat hospitalizations. During the fourth hospitalization, the patient received mood-stabilizing anti-seizure medications and benzodiazepines, but he deteriorated and required intubation. It was during this time that the patient was transferred to our facility. Magnetic resonance imaging of the brain revealed multifocal areas of hyperintensity and restricted diffusion with avid enhancement. Immunotherapy was initiated with improvement of non-epileptic spells and encephalopathy. Outpatient workup uncovered malignant pure seminoma with metastases to the retroperitoneum. The authors theorize that paraneoplastic neurological disorders stemming from testicular cancer led to the neurological symptoms seen in this case.

This report highlights a rare occurrence of paraneoplastic limbic encephalitis associated with pure testicular seminoma, clinically manifested as PNES. The diagnostic challenge posed by variability of presenting symptoms in paraneoplastic encephalitis emphasizes the importance of accurate differentiation from conditions such as autoimmune encephalitis. Current diagnostic approaches for paraneoplastic and autoimmune etiologies involve detection of known antibodies, as well as brain imaging. Notable antibodies associated with psychogenic non-epileptic seizures symptoms include anti-GAD-65, anti-Ma2, KLH11-antibodies, anti-Hu, and NMDA receptor antibodies. Recognizing paraneoplastic limbic encephalitis symptoms is challenging and often leads to misdiagnosis or overlooking of malignancies highlighting the need for awareness, comprehensive evaluation and timely treatment. Through this comprehensive case analysis, we enhance the understanding of underlying mechanisms, associated symptoms, and treatment options.