Insulinoma masquerading as neurologic disease – Case report and review of the literature

Insulinomas are the most frequent etiology of hypoglycemia in a non-diabetic patient and the most common functional neuroendocrine tumors of the pancreas, with an annual incidence of about 4 cases per million1, 2. The majority of insulinomas are “well-differentiated endocrine tumors” or grade 1 tumors, as defined by World Health Organization3 . Most tumors are benign, solitary and occur sporadically. However, about 10% are associated with multiple endocrine neoplasia type 1 (MEN-1)1,2. Despite the majority being benign tumors, hypoglycemic symptoms caused by the hyperinsulinemia are frequently debilitating4 . Whipple triad (hypoglycemia, symptoms of hypoglycemia – either adrenergic or neuroglycopenic – and relief of these symptoms after administration of glucose) is usually present and should alert to the diagnosis2,5. After the diagnosis is made, locating the tumor can be challenging because most tumors are small4 . Nonetheless, locating the tumor is crucial, once the only definite treatment is surgical excision1,2. The majority of patients reach normalization of glucose levels after surgery. Incomplete resection leads to persistent symptoms and although uncommon in sporadic insulinomas, recurrence can be as high as 20% in patients with MEN-1 syndrome6,7.