How is Horners syndrome diagnosed?
What are the pharmacologic tests to diagnose Horner’s syndrome?
Instill 2% cocaine solution in both eyes, which dilates the pupils by preventing the reuptake of the sympathetic neurotransmitter norepinephrine.
If one eye fails to dilate, a diagnosis of Horner’s syndrome can be made because failure to dilate indicates an interruption of the sympathetic supply (norepinephrine) to that eye.
To further localize the lesion, one can use amphetamine in the affected eye, which displaces norepinephrine from the nerve terminal and dilates the pupil.
If the pupil dilates in response to this test, the lesion affects the third-order neuron, causing denervation hypersensitivity. Otherwise, the lesion is in the first- or second-order neurons.
