Hypoglossal nerve palsy

To test the function of the hypoglossal nerve, a person is asked to poke out his/her tongue. If there is a loss of function on one side (unilateral paralysis), the tongue will point toward the affected side, due to unopposed action of the genioglossus muscle (which pulls the tongue forward) on the side of the tongue that is usually innervated. This is the result of a lower motor neuron lesion (the damaged neuron directly innervates the skeletal muscle), and can lead to fasciculations and atrophy of the tongue.

Weakness of the tongue is displayed as a slurring of speech. The tongue may feel “thick”, “heavy”, or “clumsy.” Lingual sounds (i.e., l’s, t’s, d’s, n’s, r’s, etc.) are slurred and this is obvious in conversation. (from wikipedia-link)

Denervation Atrophy of the Tongue after Hypoglossal-Nerve Injury.  Luis Junquera, M.D., D.D.S., and Lorena Gallego, M.D., D.D.S.  N Engl J Med 2012; 367:156 (link)

A 69-year-old man presented for evaluation of an unusual color and decreased mobility on the right side of his tongue. He first noticed these symptoms 2 years previously. The patient had undergone radical dissection of the right side of the neck 7 years earlier for a malignant tumor of the right tonsil. Intraoral examination of the patient revealed hemiatrophy of the tongue, on the right side, and the inability to completely deviate the tongue toward the left side of the mouth on protrusion. The hypoglossal nerve (cranial nerve XII) supplies motor innervation to the muscles of the tongue. Damage to the hypoglossal nucleus or hypoglossal nerve can cause denervation atrophy of the tongue, as seen in this patient.  (from NEJM)

Link to an additional case of hypoglossal n. palsy (here)

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