Teaching NeuroImage: Starch-Iodine Test: A Colorful Tool for Objectifying Anhidrosis in Horner Syndrome.

Abstract

A 46-year-old man presented in the emergency department with nausea, vertigo, dysphagia, and hiccups. Vascular risk factors included hypertension, hypercholesterolemia, and smoking. Ptosis and subtle miosis of the left eye, torsional nystagmus, and left-sided hemiataxia were found. The patient was sweating heavily, however not on the left side of his face. To objectively evaluate this, Minor's starch-iodine test was performed.1 Anhidrosis was confirmed by observing color difference respecting the midline that resulted from the reaction of starch and iodine in water. (Figure 1). MRI showed left lateral medullary infarction (Figure 2) due to acute thrombotic occlusion of the vertebral artery (not shown). Consequently, the patient was diagnosed with Wallenberg syndrome.2