Simultaneous Horner’s syndrome with anhidrosis and facial nerve palsy in internal carotid artery dissection

<h3></h3> A 54-year-old man presented with acute right neck and ear pain, lower motor facial nerve (FN) palsy and Horner’s syndrome (HS.) This followed a fall with neck hyperextension. MRI and MRA revealed a dissection of the right internal carotid artery (ICA) at the skull base. Antiplatelet were given. FN palsy almost resolved after 2 months but partial ptosis and miosis remained. Starch iodine test confirmed the absence of right facial sweating. Few reported similar cases. Third-order sympathetic fibers start from the superior cervical ganglion (SCG). Of these, vasomotor fibers for facial sweating and vasodilation run along the external carotid artery (ECA) and its branches. The oculosympathetic pathway runs along ICA and contains a few sudomotor fibers supplying a skin strip on the medial forehead. ICA dissection causes third order HS, so ipsilateral anhidrosis is not typical. ICA dissection just proximal to the carotid canal led to a hematoma that directly pressured the superior sympathetic ganglion leading to ipsilateral facial anhidrosis. Other theories include SCG ischemia or sudomotor fibers traction. FN palsy occurred simultaneously with HS. This was reported prior. The hematoma directly pressured the exiting FN at the skull base. Other theories include FN ischemia. FN blood supply is through ECA via the middle meningeal and nutrient arteries from ICA. This challenges the hypothesized anatomy and highlights second-order Horner’s and atypical cranial nerve involvement in ICA dissection to guide therapy.