The hypoglossal nerve (XII cranial nerve) is the twelfth of the twelve cranial nerves and is the motor nerve of the tongue: it innervates the intrinsic and extrinsic muscles of the tongue allowing its movements and its functioning is essential for speaking, chewing and swallowing in a normal way, therefore an alteration of its function can interfere in a more or less serious way in these functions, temporarily or irreversibly .
Causes and risk factors
An altered function of the hypoglossal nerve can be determined by inflammation or injury, in turn determined or favored by various conditions and pathologies, including:
- amyotrophic lateral sclerosis;
- bone abnormality at the base of the skull;
- brain stroke;
- brain stem infection;
- neck injury, such as in the surgical removal of a neck artery obstruction (endarterectomy).
More generally, any factor capable of causing compression or rupture can cause damage to the hypoglossal nerve.
Nerve damage at the level of the lower motor neuron can lead to atrophy of the muscles of the tongue or fasciculations of the tongue (“bag of worms”). Damage to the upper motor neuron will not lead to atrophy or fasciculations, but only weakness of the innervated muscles. When the hypoglossal nerve is inflamed or injured, weakness or paralysis of the movement of the tongue on one side will occur. If the damage is particularly extensive, the tongue will move to the weaker side ( deviation of the tongue from hypoglossal injury ). Hypoglossal nerve damage can ultimately result in difficulty speaking, chewing, and swallowing.
The diagnostic process generally starts from an ENT examination, in which the doctor, thanks to the medical history and physical examination, can ask the diagnostic doubt of lesion of the hypoglossal nerve. Generally the tests that may be necessary to reach a diagnosis are:
- indirect and / or direct laryngoscopy ;
- otoscopy ;
- examination of the sensitivity of the lateral wall of the pharynx;
- functional control of the last cranial nerves, particularly glossopharyngeal and accessory;
- neck ultrasound;
- radiographs, CT scan or magnetic resonance imaging;
- finger oximeter oximetry ;
- blood gas analysis ;
- spirometry ;
- tracheobroncoscopy ;
- electromyography: cricothyroid muscle (from the outside), vocal muscle (endolaringea);
- pharyngeal swab ;
- blood test;
- laboratory tests.
Not all exams are always necessary. Generally, the opinion of a neurologist and neurosurgeon is needed.
Therapy and rehabilitation
There is no single cure that resolves inflammation of the hypoglossal nerve : the specific treatment is set on the basis of the upstream cause that caused the inflammation. In some cases the inflammation gradually decreases spontaneously. A nerve injury is generally considered to be a very serious condition with poor prognosis and almost never spontaneous recovery. The treatment of the lesion is neurosurgical and consists of suturing the two stumps of the nerve by means of nerve grafts . Unfortunately, it often happens that one of the stumps of the nerve cannot be found with impossibility for nerve reconstruction. The rehabilitation following can be a long process and with fairly modest results, especially if the patient is elderly and poorly responsive to speech therapy