Final answer:
All of the symptoms listed—ptosis, miosis, and anhidrosis—are associated with Horner syndrome, which can be caused by the expansion of a syrinx in syringomyelia affecting the sympathetic nerves. A tumor in the thoracic cavity can disrupt this pathway and cause these symptoms.
Step-by-step explanation:
The possible symptoms of Horner syndrome are indeed all of the ones listed by the student: 1) Ptosis (drooping of the upper eyelid), 2) Miosis (constriction of the pupil), and 3) Anhidrosis (decreased sweating on the affected side of the face). This condition occurs due to disruption of the sympathetic nerves that supply the eye and surrounding facial tissues, which can be caused by a variety of conditions, including the expansion of a syrinx in syringomyelia in its late stages, which affects the lateral horn of the spinal cord.
A tumor in the thoracic cavity can affect these autonomic functions because the sympathetic nerve pathway that controls these functions passes through the thorax. Disruption of this pathway by a tumor can result in the symptoms characteristic of Horner syndrome. More generally, any lesion that impacts the sympathetic pathways, such as a stroke, neck trauma, or a tumor, may provoke Horner syndrome.