Hyperglycemia-induced Occipital Lobe Seizures.

Hyperosmolar hyperglycemic state (HHS) and nonketotic hyperglycemia (NKH) are recognized complications of type 2 diabetes mellitus that can cause seizures. Occipital lobe seizures with isolated visual symptoms are rare and underrecognized. We present the case of a 70-year-old male with uncontrolled type 2 diabetes who experienced sudden onset of positive visual phenomena and a right inferior visual field defect. The patient had a hemoglobin A1c > 14% (∼130 mmol/mol) (reference range: < 6.5%; < 48 mmol/mol), no ketones, a normal anion gap, and a normal serum osmolality. Brain magnetic resonance imaging without contrast revealed subtle subcortical T2 hypointensity in the left occipital pole and an electroencephalogram showed a left occipital seizure focus. The patient did not meet HHS criteria, showing NKH alone may trigger occipital seizures. Following levetiracetam and insulin therapy, the patient's symptoms improved within an hour. At 7-month follow-up, he reported no recurrence. This case highlights the importance of early recognition of hyperglycemia-induced occipital seizures and suggests that subcortical T2 hypointensity may serve as a valuable diagnostic clue.