Case: starch-iodine test: a colored tool used in Horner syndrome to objectively confirm anhidrosis

A 46-year-old man presents to the emergency department with nausea, dizziness, dysphagia, and hiccups
.
Vascular risk factors include hypertension, hypercholesterolemia, and smoking
.
Physical examination reveals ptosis and slight mydriasis of the left eyelid, torsional nystagmus, and left-sided ataxia
.
The patient sweats profusely, but not on the left side of the face
.
To assess this objectively, we conducted the Minor's starch-iodine test
.
Anhidrosis was confirmed by observing the midline chromatic difference produced by the reaction of starch and iodine in water (Figure 1).

MRI shows left lateral medulla oblongata infarction due to acute thrombotic occlusion of the vertebral artery (not shown) (figure 2).

Thus, the patient was diagnosed with Wallenberg syndrome
.

(Figure 1: A: Thinly coated with 1 g starch, the subsequent dried 2% iodine tincture turns a striking blue color in the presence of sweat; B: ptosis and slight miosis)

(Figure 2: Left lateral medulla oblongata infarction seen in DWI)

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