This is the motor nerve of the tongue. The nucleus lies in the floor of the 4th ventricle and the fibres emerge as rootlets and pass through the anterior condylar foramen. It passes behind the internal carotid artery, then in front of the vagus nerve and enters the tongue on top of the hyoglossus muscle. Due to its course, it is particularly vulnerable to pathology and more particularly surgery in this region. Paralysis leads to failure to protrude the tongue on that side and the tongue deviates to that side as a result of unopposed action of the contralateral muscles.
The term bulbar palsy is used to describe malfunction of the lower cranial nerves from the IX to XII and is of lower neuron type; it may be bilateral or unilateral. Pseudobulbar palsy used to describe malfunction of these nerves when the lesion is higher and is of the upper motor neuron type.
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