Hypoglossal-Nerve Palsy Caused by Carotid Dissection
A 56-year-old man presented with severe left-sided headache unresponsive to several aspirin tablets. Although the headache subsided within 3 days, he noted progressive difficulties in articulation and a deviation of his tongue to the left (Figure 1).
A magnetic resonance image of the head and neck showed a thickened wall of the left internal carotid artery resulting from an intramural hematoma in the subcranial segment (Figure 2). The vessel lumen was not compromised, suggesting a diagnosis of subadventitial carotid artery dissection.
The subcranial segment of the carotid artery is predisposed to injury from sudden neck movements. No trauma was apparent in our patient, so other causes of dissection such as hereditary connective-tissue disorders were considered but could be ruled out. In our case, the dissection may have been triggered by an emotional eruption during a quarrel. The left-sided headache was likely due to the arterial tear and an expansion of the outer vessel wall. This, in turn, compressed the adjacent hypoglossal nerve, resulting in nerve palsy. The hypoglossal nerve innervates the ipsilateral muscles of the tongue. A deviation of the protruded tongue to the left side indicates left-sided dysfunction of the hypoglossal nerve because the contralateral genioglossal muscle pushes the tongue forward and, in the case of contralateral palsy, toward the affected side. Cranial-nerve palsies are seen in 12% of patients with carotid artery dissection. Most dissections heal spontaneously. In our patient, tongue movement returned to normal within a few weeks.