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Cranial nerve XII - the Hypoglossal nerve


Signs and Symptoms of Lesions

Supranuclear lesion:  with the individuals tongue at rest - normal size with no fibrillation (twitching); contralateral hemiplegia (paralysis); on protrusion - deviates contralateral to lesion. Conditions to consider: Medullary hemorrhage; brain tumors/abscess; arteriosclerosis; multiple sclerosis; poliomyelitis; amyotrophic lateral sclerosis; bulbar paralysis; pseudobulbar paralysis;  syringobulbia; syphilis. Somatoform disorders must be differentiated.

Peripheral lesion (dependent upon degree of degeneration) with the individuals tongue at rest - ipsilateral atrophy and/or lingual paralysis; with protrusion of the tongue - ipsilateral deviation to the side of the lesion with possible fibrillation (twitching). Conditions to consider: concussion or skull fracture; upper cervical misalignments, dislocation (SD); vertebral basilar accidents; aneurysms or thrombosis at the Circle of Willis; tuberculosis; syphilitics with CNS involvement; neurotoxins.

Nuclear (Medullary) lesion: in addition to the symptoms mentioned with peripheral lesion fasciculation precedes lingual atrophy as well as ipsilateral loss of sensation of touch, temperature and pain; when bilateral there is total paralysis of the tongue conditions to consider are the same as with supranuclear lesion.

Cortical Lesion: uncoordinated speech and language.

Striatum Lesion: periodic non-rhythmic movements of the tongue. 

Psychogenic: demonstrates speech impediment such as lisping, slurring, stuttering and lingual tics; with hysterical paralysis there is no degeneration of shape or size of the tongue but there will be a noticeable resistance to passive movement which is not exhibited with a true neurogenic involvement.


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Hypoglossal Nerve Test

Initially the individual is requested to press their tongue to the inside of each cheek, the practitioner utilizing one or two fingers can monitor the outside of the cheek for tongue strength.

Hypoglossal nerve test 1

The individual is then requested to open their mouth and with tongue at rest the practitioner observes for twitching as well as the size and shape of the tongue.

Hypoglossal nerve test 2

Finally the individual is requested to protrude the tongue, the practitioner observes for paralysis and/or deviation to one side or the other in addition to tremors. Utilizing gloves or a gauze strip between the practitioners thumb and index finger, the practitioner grasp the tip of the tongue and attempts to laterally deviate from side to side, noticing resistance and again observing for coordinated effort. With tremors/twitching consider Amyotrophic Lateral Sclerosis (ALS / Lou Gehrig’s Disease).

Hypoglossal nerve test 3

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