CNs 5, 7, 9, 10 - Pharnygeal Arch Set - Motor
pharyngeal arch set, CNs 5, 7, 9, 10
- They are derived from the pharyngeal (aka branchial) arches
- They have special motor and autonomic motor functions
cranial nerves exit from the brainstem
CN 5, the trigeminal nerve exits the mid/lower pons.*
CN 7, the facial nerve exits the pontomedullary junction.*
CN 9, the glossopharyngeal nerve exits the lateral medulla.*
CN 10, the vagus nerve exits the lateral medulla.*
Cranial Nerve Nuclei at Brainstem Levels
Midbrain
- The motor trigeminal nucleus of CN 5.
Nerve Path:
- The motor division of the trigeminal nerve passes laterally to enter cerebellopontine angle cistern.
Pons
- The facial nucleus of CN 7.
- The superior salivatory nucleus of CN 7.
Nerve Path:
- CN 7 sweeps over the abducens nucleus as it exits the brainstem laterally in an internal genu, which generates a small bump in the floor of the fourth ventricle: the facial colliculus
- Fibers emanate from the superior salivatory nucleus, as well.
Medulla
- The dorsal motor nucleus of the vagus, CN 10
- The inferior salivatory nucleus, CN 9
- The nucleus ambiguus, CNs 9 and 10.
Nerve Paths:
- CNs 9 and 10 exit the medulla laterally through the post-olivary sulcus to enter the cerebellomedullary cistern.
- The motor division of the trigeminal nerve innervates the muscles of mastication
- It passes ventrolaterally through the cerebellopontine angle cistern and exits through foramen ovale as part of the mandibular division (CN 5[3]).
Clinical Correlation - Trigeminal Neuropathy
- The facial nucleus innervates the muscles of facial expression
- It spans from the lower pons to the pontomedullary junction.
- The superior salivatory nucleus activates select facial glands.
- It lies just above the pontomedullary junction.
Clinical Correlations -
Nerve Path:
- CN 7 exits the brainstem at the pontomedullary junction and passes through the internal acoustic meatus.
- The sweep over the abducens nucleus is called the internal genu; it generates a small bump in the floor of the fourth ventricle, called the facial colliculus.
- The inferior salivatory nucleus of CN 9 is a small nucleus in the upper medulla.
- The dorsal motor nucleus of the vagus spans the remainder of the medulla.
- Nucleus ambiguus spans the height of the medulla.
Nerve Paths:
- CNs 9 & 10 exit the medulla and cross the cerebellomedullary cistern to exit through the jugular foramen.
- CN 9 functions in salivation, swallow, and cardio-pulmonary function.
- CN 10 functions in gut motility, swallow, and cardio-pulmonary function.
- See this video on palatal weakness.
Additional:
- CNs 9 and 10 exit the medulla laterally through the post-olivary sulcus to enter the cerebellomedullary cistern.
- Jugular foramen contents: CNs 9, 10, and 11 and the internal jugular vein.
- Carotid space contents: CNs 9, 10, 11, and 12, the internal jugular vein, and the internal carotid artery.
- Internal carotid arteriopathy (eg, carotid dissection) with resultant arterial expansion can compress the neighboring cranial nerves (9, 10, 11, and 12) and cause cranial neuropathies.