Hypoglossal Nerve || Cranial Nerve 12 Pathway, Nerve Lesion

Hypoglossal Nerve (Cranial Nerve XII) Pathway 🧠
The hypoglossal nerve (CN XII) is responsible for innervating all the intrinsic and extrinsic muscles of the tongue, except for the palatoglossus muscle, which is innervated by the vagus nerve (CN X) 👅[1][4]. The nerve originates from the hypoglossal nucleus in the medulla oblongata of the brainstem 🧠[1][4]. Its fibers exit the brainstem through the anterolateral sulcus and pass through the hypoglossal canal in the occipital bone to enter the neck 🦴[1][4].
In the neck, the hypoglossal nerve descends vertically in the retrostyloid space, initially medial to the internal carotid artery 🫀[2]. It then crosses the artery and travels anteriorly, passing through the carotid triangle and submandibular triangle 🧭[2]. The nerve enters the sublingual space by passing between the anterior edge of the hyoglossus muscle and the posterior edge of the mylohyoid muscle 🚶‍♂️[2]. It travels along the superficial surface of the hyoglossus muscle and divides into terminal lingual branches to supply the tongue muscles 🎯[2][4].
Hypoglossal Nerve Lesions ⚠️
Damage to the hypoglossal nerve or its pathways can result in paralysis, atrophy, and fasciculations of the tongue on the affected side 😔[3][5]. Common causes of hypoglossal nerve lesions include:
- Tumors or bone abnormalities at the base of the skull 🧠[3]
- Aneurysms of arteries at the base of the brain 🩸[3]
- Strokes ⚡[3][5]
- Infections of the brainstem (brainstem encephalitis) 🦠[3]
- Injuries to the neck, such as from endarterectomy surgery 🏥[3]
- Amyotrophic lateral sclerosis (Lou Gehrig's disease) 😷[3][5]
Symptoms of hypoglossal nerve lesions include difficulty speaking, chewing, and swallowing due to tongue weakness 🗣️[3]. Diagnosis is made through imaging techniques like MRI to identify the underlying cause 📋[3]. Treatment focuses on addressing the underlying condition responsible for the nerve damage 🎯[3].
Citations:
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[2] radiopaedia.or...
[3] www.msdmanuals...
[4] en.wikipedia.o...
[5] www.ncbi.nlm.n...
[6] www.sciencedir...
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[8] teachmeanatomy...
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[13] www.elsevier.e...
[14] my.clevelandcl...
[15] www.medicalnew...