Recanalized Internal Carotid Artery Dissection in Cryptogenic Horner Syndrome

Isolated Horner Syndrome (HS) evaluation does not reveal an underlying etiology in 80% of patients. Thus, isolated HS is most often cryptogenic, and this leads to uncertainty regarding a potential missed diagnosis for both the physician and patient. Internal carotid artery dissection (ICAD) is found in in 8% of HS patients and is the most common identifiable HS etiology. ICADs repair spontaneously, resulting in ICA lumen recanalization within 6 months. HS, however, can persist beyond ICA recanalization, and HS patients may not seek care at symptom onset resulting in presentation delay. Thus, cryptogenic HS may be the result of ICAD that has recanalized by the time of presentation. Following ICAD recanalization, subtle irregularities in ICA caliber that are detectable with ICA imaging can persist, and specialized analysis of ICA imaging from cryptogenic HS patients may support this hypothesis.