“The hypoglossal (CN XII) nerve controls tongue movement. Nuclear or infra-nuclear lesions produce paralysis, atrophy, and fasciculations of the tongue on the involved side. Supranuclear lesions produce mild to moderate contralateral weakness that may be transient. (Bilateral supranuclear lesions, seen in pseudobulbar palsy, produce moderate to severe inability of the tongue to function)”.¹
Bilateral UMN lesion – small, immobile tongue
- vascular
- tumour
- motor neurone disease
Unilateral LMN lesion – fasciculation, wasting, weak
- vascular
- motor neurone disease
- syringobulbia
- posterior fossa tumours
- aneurysms
- chronic meningitis
- trauma
- syringomyelia
- cervical lymphadenopathy
- Arnold-Chiari malformation
Bilateral LMN lesion ± dysarthria
- Motor Neurone Disease
- Guillain Barre Syndrome
- Poliomyelitis
- Arnold-Chiari Malformation
Anatomical course of the Hypoglossal nerve:
In the submandibular triangle emerges between the Internal carotid Artery (ICA) and Internal Jugular Vein (IJV) deep to the posterior belly of the digastric muscle.
It then hooks around the occipital artery to cross over the External carotid Artery (ECA) and loop of the lingual artery, giving off the superior root of the ansa cervicalis as it does.
Passing forwards on surface of the hyoglossus, it separates it from the lingual artery, giving off a branch to thyrohyoid (C1) and then running deep to mylohyoid to enter the mouth.
References
Kim SY, Naqvi IA. Neuroanatomy, Cranial Nerve 12 (Hypoglossal) [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532869/.
Walker HK. Cranial Nerve XII: The Hypoglossal Nerve. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 65. Available from: https://www.ncbi.nlm.nih.gov/books/NBK388/.
