Final answer:
Unilateral headache with partial Horner's syndrome may indicate a cluster headache or a serious condition like a tumor affecting the sympathetic pathway. Diagnostic imaging is required as the next step to determine the underlying cause.
Step-by-step explanation:
A unilateral headache with partial Horner's syndrome could be suggestive of a diagnosis of cluster headache or possibly indicate a more serious underlying pathology, such as a tumor compressing the sympathetic nerve pathway. Horner's syndrome is characterized by ptosis (dropping of the upper eyelid), miosis (pupil constriction), anhidrosis (decreased sweating), and sometimes enophthalmos (the sinking of the eyeball into the facial bones). These symptoms suggest an impairment of the sympathetic nerves supplying the eye and face.
Such symptoms can be caused by a tumor in the thoracic cavity because the sympathetic trunk, which controls these functions, runs along the spine from the base of the skull to the abdomen. A tumor in the thoracic cavity, such as a pancoast tumor (a tumor at the top of the lung), can affect the nearby sympathetic chain and lead to Horner's syndrome. The next step in management would typically involve diagnostic imaging, such as an MRI or CT scan, to evaluate the cause of these symptoms, followed by appropriate medical or surgical treatment based on the findings.