Chronic persistent Horner's syndrome in trigeminal autonomic cephalalgia subtypes and alleviation with treatment: two case reports.

A chronic fixed partial or full Horner's syndrome can occur in trigeminal autonomic cephalalgia subtypes, but it can also be reversed in patients with treatment even after months to years of duration. This would suggest that the sympathetic dysfunction leading to the eye-related symptoms is from irritation of the sympathetic chain rather than permanent injury as the result of vasodilatory trauma after trigeminal autonomic reflex activation.