Horner's Syndrome Without Anisocoria: How It
Can Happen

S. Randhawa, MD
R.H. Kardon, MD, PhD, sponsor

Introduction: Four patients with sympathetic palsy and no miosis of the pupil demonstrated unequivocal pharmacologic evidence of Horner's syndrome. 3 patients initially had miosis but recovered, and 1 patient had a larger pupil in the eye with Horner's.

Methods: Four patients were referred for a diagnosis of Horner's syndrome. In 3 patients (pituitary apoplexy, carotid dissection, and carotid cavernous occlusion), the miosis and anisocoria resolved over time. The fourth patient presented with a larger pupil in the eye with ptosis and pain following cluster headaches. All patients underwent computerized pupillography (to demonstrate "dilation lag") and pupil photography before and after pharmacologic testing (10% cocaine) to confirm a Horner's syndrome. After resolution of miosis in three patients, they underwent repeat cocaine testing and pupillography; in addition, adrenergic supersensitivity testing (at a separate visit) was performed in all patients.

Results: Three patients in whom miosis resolved had unequivocally positive cocaine testing at the first test and even after its resolution. The fourth patient with cluster headache, who presented with a larger pupil in the ptotic eye, also had positive cocaine testing. All four patients localized to the post-ganglionic neuron with hydroxyamphetamine. In all patients, the pupil on the side of the lesion demonstrated supersensitivity to adrenergic testing (in the absence of miosis) on a separate visit.

Conclusion: In Horner's syndrome, development of adrenergic supersensitivity may occasionally lessen/reverse the typical miosis expected in oculosympathetic paresis. This compensatory change may cause a patient with Horner's syndrome to not be diagnosed, even though there is subnormal sympathetic discharge at the dilator muscle.