Cranial Nerves IX X XI XII Flashcards
0
Q
Course of CN XII
A
- fibers exit upper medulla
- rootlets attached b/t the pyramid & olive (preolivary sulcus).
- nerve exits the skull via the hypoglossal foramen.
- descends in the carotid sheath, posterior to the ICA and IJV.
- Courses in submandibular triangle before passing deep to the mylohyoid muscle to enter the oral cavity
- Within the oral cavity it distributes branches to the muscles of the tongue.
- C1 fibers join the hypoglossal nerve as it descends in the neck.
- Form superior root of ansa cervicalis, nerve to the thyrohyoid & nerve to the geniohyoid.
1
Q
hypoglossal nerve (CN XII): Function & Origin
A
- The hypoglossal nerve is the motor nerve of the tongue.
- Innervates all muscles of the tongue except palatoglossus
- which is innervated by CN X.
- LMNs of CN XII are located in the hypoglossal nucleus in the upper medulla.
2
Q
Lesions to CN XII
A
- Unilateral damage to the hypoglossal nerve causes paralysis and atrophy of ipsilateral tongue muscles.
- Tongue deviates to side of the lesion on attempted protrusion due to weakness of genioglossus muscle.
3
Q
Spinal accessory nerve (CN XI): Function & Origin
A
- The spinal accessory nerve is purely motor.
- Innervates SCM and the upper part of the trapezius.
- It is unique in that it arises from the spinal cord (C1-C5).
- Originates from the accessory nucleus
- column of cells in ventral horn of upper cervical spinal cord.
- nucleus extends into lower medulla as the supraspinal nucleus.
4
Q
Course of CN XI
A
- Rootlets emerge b/t the dorsal and ventral roots from C1-C5.
- rootlets join & enter cranial cavity thru foramen magnum.
- Exits cranial cavity thru jugular foramen
- passes posterior to the IJV
- courses to the SCM and trapezius muscles.
5
Q
Lesions to CN XI
A
- Unilateral damage causes ipsilateral weakness and atrophy of the SCM & trapezius muscles.
- Patients have difficulty turning the head to the contralateral side and shrugging the ipsilateral shoulder.
