Hypoglossal Nerve XII Flashcards
What does the Hypoglossal Nerve innervate?
Both intrinsic and Extrinsic muscles of the tongue
Where are the cell bodies of lower motor neurons located?
Hypoglossal Nucleus (which is near the midline of the medulla)
Where do the axons of the lower motor neurons pass?
Inferolateral next to the medial lemniscus and pyramid
Where do the axons exit the medulla?
In the ventrolateral (preolivary) sulcus
where do the upper motor neurons arise from?
The tongue region of the precentral gyrus (primary motor cortex) and descend with the cortico spinal tract to the medulla
Once the upper motor neurons decend to the medulla with the corticospinal tract where do MOST of the fibers cross and synapse?
MOST fibers cross the midline and synapse in the contralateral hypoglossal nucleus
Where does the hypoglossal receive indirect sensory info from?
Solitary nucleus (taste) & Sensory trigeminal nuclei
How does the hypoglossal nucleus receive indirect sensory nuclei from Solitary nucleus (taste) & Sensory trigeminal nuclei?
By way of multisynaptic connections in the reticular formation
What do LMN lesions of the hypoglossal nerve/nucleus result in?
Paralysis and muscle wasting of both intrinsic and extrinsic muscles, of IPSILATERAL SIDE
Which way does the tongue deviate during protrusion of the tongue if there is a LMN lesion?
Toward the side of the lesion
—due to the unopposed action of the intact contralateral genioglossus muscle
What will patients have difficult with if there is a LMN lesion?
Eating and speaking (dysarthria)
UMN Lesions that occur prior to the crossing result in what?
Weakness of only extrinsic muscles on the side CONTRALATERAL to the lesion
Which way does the tongue deviate during protrusion if there is a UMN lesion?
OPPOSITE the side of the lesion
A stroke of a Paramedic branch of the anterior spinal artery may result in combinations of damage to what? (4)
- ) Hypoglossal nerve fibers
- ) Adjacent pyramid
- ) Medial lemniscus
- ) Ventral trigemino-thalamic tract
