National Physical Therapy Examination (NPTE) Practice Exam

In Horner's syndrome, one of the hallmark clinical manifestations is ptosis, which is the drooping of the upper eyelid. This occurs due to the disruption of sympathetic nerve pathways that normally contribute to elevating the eyelid through the action of the Mueller's muscle (also known as the superior tarsal muscle). When there is an interruption in these sympathetic fibers, the muscle becomes weakened, resulting in a noticeable droop of the eyelid.

Understanding the mechanisms of Horner's syndrome helps to appreciate why ptosis is a key sign; the syndrome can arise from various underlying causes, including lesions along the sympathetic pathway, anterior rami of the spinal nerves, or even tumors in the apex of the lung (Pancoast tumors). The sympathetic fibers involved are responsible for not only eyelid elevation but also other functions such as pupil dilation and sweating on the face.

This is in contrast to other options: pupil dilation would occur with sympathetic activation, exophthalmos (protrusion of the eyeball) is often associated with thyroid eye disease, and facial flushing is generally linked to parasympathetic or vascular issues rather than the sympathetic pathway involved in Horner's syndrome. Therefore, recognizing ptosis as a classic manifestation reinforces the