Insulinoma Masquerading as Epilepsy: Diagnosis by Endoscopic Ultrasound (EUS)

Abstract

Insulinoma is a rare functional neuroendocrine neoplasm that causes hypoglycemia secondary to inappropriate insulin secretion. Its clinical presentation may mimic neurological disorders, often leading to delayed diagnosis. Methods: We report a case of insulinoma diagnosed by endoscopic ultrasound (EUS), accompanied by a narrative review of the recent literature. Results: A 28-year-old male presented with a history of recurrent seizure episodes for approximately ten years and had been treated as having epilepsy without adequate therapeutic response. During one episode, severe hypoglycemia was documented, fulfilling Whipple’s triad. Conventional imaging studies, including computed tomography and magnetic resonance imaging, failed to identify the lesion. Subsequently, EUS revealed a 25 × 20 mm hypoechoic mass located in the pancreatic tail. Fine-needle biopsy confirmed a well-differentiated grade 1 neuroendocrine tumor. The patient underwent distal pancreatectomy with complete resolution of symptoms. Conclusion: Insulinoma should be considered in the differential diagnosis of patients with atypical or difficult-to-control seizures. EUS is a highly sensitive tool for tumor localization, particularly in cases with negative conventional imaging studies.