Cranial Nerves 2 Flashcards
Describe the modalities of CN V.
- Special visceral efferent:
from the motor nucleus in the pons to the muscles of mastication (derived from 1st pharyngeal arch) - General somatic afferent: to the mesencephalic, chief sensory and spinal nuclei in the midbrain, pons and medulla oblongata
What is the CN V mesencephalic nucleus for?
Proprioception
What is the CN V chief sensory nucleus for?
Discriminative touch
What is the CN V spinal nucleus for?
Pain and temperature for structures supplied by CN V as well as general conscious sensation for the viscera supplied by CN IX and X
What is the three main divisions of CN V and where do they emerge from?
CN V1 Ophthalmic division (comes out from supraorbital notch/foramen)
CN V2 Maxillary division (infraorbital foramen)
CN V3 Mandibular division (mental foramen)
Describe the pathway of the nerve root of CN V.
The nerve roots emerge from the mid-pons and pass forwards onto the apex of the petrous temporal bone where the trigeminal ganglion lies in a cave of dura mater (Meckel’s cave)
Describe the course of CN V1 and its divisions, along with what they supply.
CN V1 passes anteriorly in the lateral wall of the cavernous sinus to reach the superior orbital fissure
It then divides into:
- The frontal nerve, dividing into supraorbital and supratrochlear, to supply the skin of vertex and upper eyelid/forehead
- Lacrimal, which goes to the lacrimal gland to supply the skin of the lateral upper eyelid and forehead
- Nasocillary nerve, giving off long ciliary nerve(s), anterior and posterior ethmoidal nerves (external nasal nerve comes off anterior ethmoidal to supply tip of nose), before continuing as the infratrochlear nerve to supply skin of medial upper eyelid and root of nose
Describe the course of CN V2 and its divisions, along with what they supply.
CN V2 passes anteriorly in the lateral wall of the cavernous sinus to reach the foramen roundup and pterygopalatine fossa. It then send branches into the orbit via the inferior orbital fissure.
CN V2 divides into:
- The infraorbital nerve emerges from the infraorbital foramen to supply the lower eyelid, cheek, nose, and upper lip
- The zygomatic nerve which divides into the Zygomaticotemporal nerve to supply the anterior temple, and the Zygomaticofacial nerve to supply the skin over the zygoma.
Describe the course of CN V3 and its divisions, along with what they supply.
CN V3 passes through the foramen oval and into the infra temporal fossa where it gives off many branches:
Auriculotemporal
Buccal
Mental
Lingual - general sensation to anterior 2/3 of tongue; carries chords tympani
Muscular
What else does CN V2 supply?
Parts of the nasal cavity, nasopharynx, maxillary sinus, hard and soft palate, upper teeth and gums.
What else does CN V3 supply?
Supplies the general sensation to the floor of the mouth along with the lower teeth and gums.
Supplies general sensation to the anterior 2/3 of the tongue (general somatic afferent) via the lingual nerve.
Tensor tympani muscle in the middle ear, tensor palate, mylohyoid, anterior belly of digastric
Describe the modalities of CN VII.
- General Visceral Efferent (parasympathetic) from the superior salivatory nucleus in the pons to the lacrimal gland, nasal & oral cavities (mucous membranes), sinuses, submandibular & sublingual salivary glands
- Special Visceral Afferent to the solitary nucleus in the medulla oblongata receiving taste from the anterior 2/3 of the tongue (via the chorda tympani nerve)
- Special visceral efferent: from the motor nucleus in the pons to the muscles of fascial expression and a few additional muscles such as the stapedius, stylohyoid and posterior belly of digastric (all derived from 2nd pharyngeal arch)
Describe the course of CN VII and its divisions, along with what they supply.
- CN VII with the nervus intermedius enters the petrous temporal bone at the internal acoustic meatus with CN VIII & the labyrinthine artery
- The motor root emerges (with the nervus intermedius) in the cerebellopontine angle
- CN VII with the nervus intermedius takes a tortuous course through the middle ear while giving off taste & parasympathetic branches
- CN VII sends a branch to stapedius (the muscle that dampens the movement of stapes) before emerging from the stylomastoid foramen to supply (mainly) the muscles of facial expression
- CN VII emerges from the stylomastoid foramen & sends branches to supply the occipitalis & auricular muscles before dividing to form a plexus within the parotid gland that sends branches to the muscles of facial expression (plus the digastric & stylohyoid)
What does facial nerve injury distal to the stylomastoid foramen cause?
Ipsilateral facial muscle paralysis
If injury is within the petrous temporal bone or proximal to it (e.g. Bell’s palsy & acoustic neuroma) then what are the signs?
Ipsilateral facial muscle paralysis occurs plus hyperacusis; taste disturbances (there may also be an effect on the adjacent CN VIII)
