A rare cause of isolated hypoglossal nerve palsy secondary to internal carotid artery dissection

A 51-year-old male was admitted to the acute medical ward with a severe spontaneous throbbing left-sided headache and left-sided tongue deviation. He also reported a “golf ball” sensation in his mouth for two weeks. Left tongue deviation and prominent lingual tonsils were noted on examination; however, the remaining neurological and cranial nerve examinations were unremarkable. MRI head showed a left internal carotid artery dissection (ICAD) with mural haematoma and no associated infarct.

A non-contrast CT head ruled out any haemorrhage and did not show any significant abnormal findings. MRI Head, MRA Head, and MRA Carotids were performed to find a cause for any intracranial or extracranial cause of hypoglossal nerve palsy and found a significant narrowing with smooth tapering and complete blockage of the left ICA. Furthermore, on T1 fat-saturated images, the left ICA is increased in diameter in the distal cervical part and shows a large crescentic hyperintensity, suggesting intramural haematoma/sluggish flow. The actual lumen is significantly narrowed and eccentric and does not show any flow. There is attenuation of the left middle cerebral artery, which is probably a filling by collaterals.

Overall, MR findings show left ICAD associated with a mural haematoma extending from the distal cervical part up to the cavernous segments of the ICA.

Background

ICAD results from a tear within the tunica intima, the innermost layer of the internal carotid artery. Despite its infrequent occurrence, this condition has significant clinical implications, potentially leading to reduced blood flow, clot formation, and an increased risk of stroke. Trauma, or less frequently, spontaneous factors can trigger ICAD, resulting in the accumulation of blood within the arterial layers [1,6]. ICAD is a notable cause of ischaemic stroke among young and middle-aged patients [2,3].

Cranial-nerve palsies can be detected in about 12% of patients with spontaneous carotid-artery dissection. The lower cranial nerves are most affected, particularly the hypoglossal nerve, and the involvement of various combinations of nerves has been described. Hypoglossal nerve palsy due to ICAD is a rare occurrence, accounting for only 5% of cases and only around 0.5% of ICA dissections cause an isolated hypoglossal palsy [4,5].

Diagnosing this condition promptly can be challenging as angiography may miss the dissection, particularly when there are no obvious changes in the arterial lumen geometry [6].

Clinical Perspective

Common clinical presentations of ICAD include severe headaches, focal neurological deficits, and cranial nerve palsies. The characteristic unilateral headache develops in two-thirds of patients [6]. In this case, the patient presented with a severe headache and left hypoglossal nerve palsy characterised by tongue deviation towards the affected side.

Imaging Perspective

MRI and MRA of the head and carotid arteries were performed. These showed a significant narrowing and complete blockage of the left internal carotid artery, along with a large crescentic hyperintensity on T1-weighted fat-saturated images, suggestive of an intramural haematoma. The absence of flow within the lumen of the affected artery confirmed the occlusion.

Outcome

The management of ICAD involves a multidisciplinary approach. Interventional neuroradiology reviewed this case for consideration of angioplasty; however, as this was the first episode of dissection, no stroke occurred, and there were no contraindications to anticoagulants. Immediate intervention was deemed unnecessary. The patient was followed up with CTA performed after 16 weeks and this showed arterial recanalisation.

Take Home Message / Teaching Points

1. ICAD can present with various neurological symptoms, including cranial nerve palsies such as hypoglossal nerve palsy.
2. MRI and MRA are valuable imaging modalities for the diagnosis and evaluation of ICAD providing information on the extent of the dissection and associated complications.

All patient data have been completely anonymised throughout the entire manuscript and related files. The patient has provided verbal consent for the use of images and publication of the case report in any medical journal.