Acute Hemianopia Associated With Nonketotic Hyperglycemia: A Case Report With Advanced Neuroimaging Findings

Nonketotic hyperglycemia (NKH) can present with acute neurological symptoms such as tremor, ballismus, seizures, hemianopia, and coma, and may be associated with abnormal signal intensities on brain MRI. We report the case of a woman in her 50s with poorly controlled diabetes mellitus (HbA1c 15.9%) who was admitted with a chief complaint of right homonymous hemianopia. No other neurological deficits were observed. At presentation, the patient's blood glucose level was markedly elevated (608 mg/dL), with a blood pH of 7.36, negative ketone bodies, and an increased serum osmolality of 301 mOsm/L, consistent with a diagnosis of nonketotic hyperglycemia (NKH). Brain MRI performed on the day of admission revealed subcortical hypointensities in the left occipital and parietal lobes on T2-weighted images (T2WI). Arterial spin labeling (ASL) demonstrated increased perfusion in the corresponding areas. Proton magnetic resonance spectroscopy (¹H-MRS) showed a reduction in N-acetylaspartate (NAA) levels in the same region. Following glycemic control, her visual field deficits improved, and the subcortical MRI abnormalities resolved. Given the temporal correlation between symptom resolution and imaging normalization, the patient was diagnosed with NKH-induced hemianopia with transient MRI abnormalities. While subcortical T2 hypointensities are a known radiologic feature of NKH, associated findings on ASL and ¹H-MRS have been rarely documented. We present this case alongside a review of the relevant literature.