C) C8-T1

This patient has Horner syndrome which manifests with ipsilateral facial flushing, ptosis (superior tarsal muscle), miosis (pupil constriction), and anhidrosis (absence of facial sweating). It may also cause shoulder weakness if it affects the brachial plexus. Horner syndrome can be produced by a lesion anywhere along the three-neuron sympathetic pathway that originates in the hypothalamus and that supplies the head, eye, and neck. The first-order neuron descends caudally from the hypothalamus to the first synapse, which is located in the cervical spinal cord at levels C8-T2. A Pancoast tumor, which this patient likely has, is a lung cancer occurring at the lung apex, which may affect the cervical sympathetic plexus.

Key Learning Point

Horner syndrome manifests with ipsilateral facial flushing, ptosis, miosis, and anhidrosis and can be produced by a lesion anywhere along the sympathetic pathway that supplies the head, eye, and neck. This pathway passes through cervical spinal cord levels C8-T2.