“If It Looks Like a Duck, then It Probably is a Duck!” No, Rarely It is not

Abstract

Hyponatremia is one of the major conditions that mimic stroke. Hyponatremia is known to cause focal neurological deficits; however, reported herein is a rare neurologic manifestation of hyponatremia, which mimics a proximal posterior cerebral artery occlusion. A 70-year-old man was admitted to our emergency unit with an acute history of vomiting, confusion, and impaired vision. Neurologic examination showed impaired orientation, left homonymous hemianopia, and left-sided hemispatial neglect. Hyponatremia was detected, and magnetic resonance imaging showed no abnormalities. The patient recovered completely after the correction of the serum sodium levels. This case illustrates that the clinical presentation of acute hemispatial neglect and homonymous hemianopia, which commonly implies a stroke, may result from hyponatremia. Hyponatremia should be considered in patients presenting with focal neurologic deficits, for which imaging evidence of a stroke cannot be shown.