Imaging Features of isolated hypoglossal nerve palsy

Isolated Unilateral Hypoglossal Nerve Palsy Caused by Internal Carotid Artery Loop

“…The most common causes of isolated HN palsy are malignancy, surgery or iatrogenic, and idiopathic [1][2][3][4]. On the other hand, various arterial or venous vascular causes are rare, as demonstrated in multiple case reports and reported by very few literature reviews [1,2].…”

“…It is crucial to define the underlying pathology to manage the condition wisely. In literature, assorted arterial or venous vascular causes including internal carotid artery (ICA) dissection, vertebral artery (VA) compression, posterior inferior cerebellar artery (PICA) aneurysm, enlarged emissary vein, dural arteriovenous (AV) fistula and persistent hypoglossal artery were reported [1][2][3]. However, ICA loop related isolated cranial nerve palsy was not reported previously.…”

Hypoglossal Canal Cyst Causing Unilateral XII Nerve Palsy

“…Unilateral cranial nerve palsy of the hypoglossal nerve is an uncommon pathology, which may involve central, canalicular, nerve, or soft-tissue structures. 1 Isolated lesions in the hypoglossal canal are rare, with etiologies including schwannomas, synovial cysts, meningiomas, and juxtaarticular cysts. 1,2 With infranuclear involvement, typical symptoms include ipsilateral deviation of the tongue (toward the side of the lesion) with associated unilateral atrophy and tongue fasciculations.…”

“…1 Isolated lesions in the hypoglossal canal are rare, with etiologies including schwannomas, synovial cysts, meningiomas, and juxtaarticular cysts. 1,2 With infranuclear involvement, typical symptoms include ipsilateral deviation of the tongue (toward the side of the lesion) with associated unilateral atrophy and tongue fasciculations. Imaging plays a critical role in the diagnosis of hypoglossal nerve and hypoglossal canal lesions, as biopsy of such lesions is challenging due to difficult access to the nerve and morbidity risk.…”

“…In the setting of schwannomas or severely symptomatic lesions, surgery and focal radiotherapy are viable treatment options with high cure rates; however, permanent neurologic sequelae are common. 1,2 A conservative approach, including clinical and imaging follow-up is a reasonable alternative, as lesions of the hypoglossal canal have often been shown to spontaneously regress. 5…”