Acknowledging the Blind Spot of Bitemporal Hemianopsia: Keeping a High Index of Suspicion for Pituitary Macroadenomas in Uncommon Presentations

Background: Hyperglycemia in patients with type 2 diabetes mellitus commonly manifests as symptoms of polyuria, polydipsia, fatigue, and weight loss as a result of insulin resistance. In cases of severe hyperglycemia, patients may also experience visual disturbances and dizziness as a result of swelling of the lens and dehydration respectively. These symptoms are not generally accompanied by gait disturbance or fixed, focal deficits on neurological examination. As such, symptoms such as double vision, peripheral field vision loss, cranial nerve deficits, or significant unsteadiness may warrant a more extensive neurologic workup rather than simply attributing all symptoms to hyperglycemia. Clinical Case: A 57-year-old woman presented to the emergency department with five days of fatigue, polyuria, polydipsia and pre-syncope associated with dizziness. She also described double vision in her peripheral visual fields and episodes of gait disturbances causing her to have to lower herself to the ground on multiple occasions, without loss of consciousness. Her neurologic examination demonstrated mildly ataxic finger-to-nose testing and concern for peripheral field vision loss. Intake lab work revealed a blood glucose of 725 mg/dL and a hemoglobin A1C of 13.4%. Initial neuroimaging with computed tomography was unremarkable. Though her symptoms were thought to be due to severe hyperglycemia, an MRI brain was obtained due to abnormal neurologic examination. MRI demonstrated a 1.9 cm pituitary macroadenoma abutting the optic chiasm with concern for hemorrhage. Subsequent lab evaluation determined the pituitary macroadenoma non-functional with TSH, free T4, free T3, AM cortisol, AM ACTH, and prolactin all within normal limits. Her hyperglycemia was treated with insulin with clinical improvement in all regards except visual symptoms. She was deemed safe for discharge with neurosurgical follow-up regarding surgical removal of her macroadenoma. Conclusion: Although hyperglycemia may present with broad symptoms including vague neurologic symptoms, it is critical to keep a broad differential diagnosis when atypical symptoms such as persistent vision changes and gait disturbances are present, especially after improvement in glycemic control has been obtained. A low threshold should be held for obtaining neuroimaging, as it is prudent to rule-out life-threatening causes of neurologic dysfunction.