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Horner's syndrome is characterized by a specific set of symptoms that arise from the disruption of sympathetic nerve pathways to the eye. The key features of Horner's syndrome include ptosis (drooping of the upper eyelid), miosis (constricted pupil), anhidrosis (lack of sweating on the affected side of the face), and enophthalmos (sunken appearance of the eyeball).

In the case of an internal carotid artery dissection, the interruption of sympathetic fibers, which typically travel along the carotid artery, can lead to the clinical manifestation of Horner's syndrome. This syndrome is a result of damage to the sympathetic nervous system and is not associated with other syndromes like locked-in syndrome, which is unrelated to sympathetic nerves and involves complete paralysis due to brainstem lesions.

Additionally, the parasympathetic nervous system response does not relate to the symptoms seen in Horner's syndrome. The symptoms from the sympathetic nervous system disruption are specific and clearly outlined in the combination of signs observed with Horner's. Thus, the recognition of these signs following internal carotid artery dissection sharply indicates Horner's syndrome as the relevant condition.