In attempting to introduce a catheter into the right internal jugular vein, a resident inadveently damages the cervical sympathetic trunk in a patient. Which of the following findings is MOST likely to be seen in this patient as a result of the injury?
**Core Concept**
The cervical sympathetic trunk is a part of the sympathetic nervous system that plays a crucial role in regulating various autonomic functions, including vasomotor tone, sweating, and pupil dilation. Damage to this structure can lead to Horner's syndrome, a classic clinical presentation characterized by a triad of ptosis, miosis, and anhidrosis.
**Why the Correct Answer is Right**
The sympathetic nerves that run through the cervical sympathetic trunk innervate the superior tarsal muscle, causing it to relax, resulting in ptosis (drooping eyelid). Additionally, the sympathetic nerves stimulate the dilator pupillae muscle, causing pupil dilation. Damage to the cervical sympathetic trunk disrupts these functions, leading to miosis (pupil constriction) and anhidrosis (absence of sweating) on the ipsilateral side of the face. The sympathetic nerves also have a vasomotor effect on the blood vessels of the face, leading to vasodilation and increased blood flow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the clinical findings associated with damage to the cervical sympathetic trunk. Hemiplegia is a neurological deficit characterized by weakness or paralysis of one side of the body, which is not directly related to the sympathetic nervous system.
**Option B:** This option is incorrect because Horner's syndrome is a specific clinical presentation characterized by ptosis, miosis, and anhidrosis, whereas facial nerve palsy would result in weakness or paralysis of the muscles of facial expression.
**Option C:** This option is incorrect because the clinical findings associated with damage to the cervical sympathetic trunk do not include weakness or paralysis of the muscles of the face.
**Option D:** This option is incorrect because Horner's syndrome is a specific clinical presentation characterized by ptosis, miosis, and anhidrosis, whereas the clinical findings associated with damage to the cervical sympathetic trunk do not include sensory deficits or numbness.
**Clinical Pearl / High-Yield Fact**
Remember that damage to the cervical sympathetic trunk can lead to Horner's syndrome, a classic clinical presentation characterized by a triad of ptosis, miosis, and anhidrosis. This is a high-yield fact for exams, as it is a common clinical scenario that can be easily confused with other neurological deficits.
**Correct Answer:** B.