Intermittent Horner's syndrome on alternate sides: a hint for locating spinal lesions.

A patient with a cervical intramedullary ependymoma is described who exhibited a Horner's syndrome on alternate sides. Pharmacological study demonstrated damage to the pre-ganglionic sympathetic neurons. Disregarding cases with the Shy-Drager syndrome, three comparable case reports have been found in the literature where the fluctuating expression of Horner's syndrome, alternating from one side to the other, was attributable to a lesion of the cervical spinal cord. In contrast to the present patient, the pharmacological responses of these patients indicated a lesion of the central sympathetic pathway.