Reversible Cortical Visual Symptoms of Hyperosmolar Hyperglycemic State May Occur in Patients with Borderline Serum Osmolality

Hyperosmolar hyperglycemic state (HHS) is a severe complication of uncontrolled diabetes, often presenting with nonlocalizing neurologic symptoms such as encephalopathy. Rarely, focal neurologic deficits like hemianopsia can occur, even with serum osmolality below the diagnostic threshold for HHS. We report two cases of hyperglycemic patients with borderline serum osmolality presenting with neuro-ophthalmologic symptoms. Case 1 involved a 43-year-old male with type 1 diabetes who developed right-sided visual disturbances and was found to have cortical T2/FLAIR hyperintensity and subcortical hypointensity in the left temporal lobe and posterior cingulate gyrus. Case 2 involved a 64-year-old female with untreated type 2 diabetes and hypertension who presented with bright flashes and left homonymous hemianopsia. MRI revealed subtle cortical T2/FLAIR hyperintensity and subcortical hypointensity in the right occipital lobe, findings initially missed on radiological review. In both cases, symptoms resolved with glycemic control and treatment. These cases underscore the importance of recognizing neuro-ophthalmic symptoms as potential manifestations of hyperglycemia, even when serum osmolality is below the diagnostic threshold for HHS. The structural brain changes demonstrated by subtle radiographic findings corresponded to the patients' focal neuro-ophthalmic deficits. The reversibility of these findings with glycemic control highlights the critical need for early recognition and intervention.