2 - CNs Locations/Funciton/Injury Flashcards
1
CN I
Name: Olfactory
Location: Cribriform plate and ethmoid bone, ventral surface of the brain
Job: Special Sensory - Olfaction - Smell
Injury:
Loss of smell - Anosmia
2
CN II
Name: Optic
Location: Back of eye, ventral side of the brain
Job: Special Sensory - Retina - Vision
Injury:
Blindness - Injury to eye or optic nerve
Hemianopia - Injury to 1/2 visual field of both eyes
Bitemporal Hemianopia - Lesion of of optic chiasm
Homonymous Hemianopia - Loss of field in both eyes contralateral to the side of the lesion (optic tract, lateral geniculate nucleus, entire primary visual cortex, both superior and inferior optic radiation)
Homonymous Quadrantanopia - Loss of 1/4 of a visual field in both eyes, damage to optic radiation or one bank of calcarine fissure (contralateral and inverse to location of lesion)
3
CN III
Name: Oculomotor
Location:
- Nuclei Medial, rostral midbrain tegmentum, (superior colliculus)
- Exit - Anteromedially at the interpeduncular fossa
Job:
Voluntary motor -
*Levator palpebrae superioris muscle - raise eyelid
*4 extraocular muscles:
-medial rectus - adduction
-Superior rectus - elevation best when abducted
-inferior rectus - depression best when abducted
-inferior oblique - elevation when adducted
Parasympathetic -
- pupillary constrictor - Consensual reflex - pupil constricts when light is shown into the opposite eye
- ciliary muscle of lens - accommodation - for near/far
Injury -
*All symptoms to be in the eye ipsilateral to the affected nerve or nucleus
- Difficulty with moving eye up, down and medially
- Lateral strabismus - abducted position of eye at rest due to unopposed lateral rectus
- Diplopia - Double vision
- Ptosis - drooping eyelid
- Fixed, dilated - non reactive pupil
- Cycloplegia - paralysis of accommodation
4
CN IV
Name: Trochlear
Location:
- Nucleus Medial caudal midbrain tegmentum
- Exits DORSAL side of brainstem
Job: Voluntary muscle - Extraocular muscle (superior oblique) - Depression when adducted (looking at tip of nose)
Injury:
Only fibers cross just before exiting:
-Left nucleus controls right eye but left nerve controls left eye
-Right nucleus controls left eye but right nerve controls right eye
- Diplopia
- Affected eye positioned slightly up
- Trouble looking down when adducted (trouble with descending stairs and reading)
5
CN V
Name: Trigeminal
Location:
Touch & Motor Nuclei - Lateral dorsal mid pons
Proprioception Nucleus - Medial dorsal midbrain tegmentum
Nociception & Temp Nuclei - Lateral caudal dorsal medulla
Exit - Anterolaterally from mid pons
Job:
Ophthalmic (V1)
Somatosensory - face, scalp, bridge of nose
maxillary (V2)
Somatosensory - cheek, upper lip, gum, underside of nose
Mandibular (V3) Somatosensory - anterior 2/3 tongue, skin over mandible, temporomandibular joint Voluntary motor - muscles of mastication: -Lateral pterygoid -Medial pterygoid -Masseter -Temporalis
Injury:
- Ipsilateral paresis/paralysis of muscles of mastication
- Ipsilateral loss of sensation in areas of nerve distribution
- Impaired jaw jerk reflex
6
CN VI
Name: Abducens
Location:
- Nucleus Medial dorsal tegmentum of the caudal pons
- Exit anteromedially
Job:
Voluntary Motor: Abducts the eyes (lateral rectus)
Injury:
Medial strabismus - due to unopposed medial rectus
Diplopia
Inability to abduct the ipsilateral eye beyond midline
7
CN VII
Name: Facial
Location:
-Nuclei Medial Caudal Pons
Job:
Somatosensory - Soft palate and pharynx, small area of outer ear
Special sensory - Anterior 2/3 tongue - taste
Voluntary motor - muscles of facial expression
Parasympathetic - Salivary glands; lacrimal glands
- LMNs to muscles of facial expression of the lower face have only contralateral UMN innervation for voluntary movement
- LMNs to muscles of facial expression of the upper face have bilateral UMN innervation for voluntary movement
Injury:
Loss of facial expression entire ipsilateral side of face
LMN injury
Dry eye and mouth
Loss of taste anterior 2/3 tongue - ageusia
Corticobrainstem injury
- Unilateral lesions
- UMN injury
- Paralysis of muscles of facial expression of the contralateral lower face with normal function of muscles of the upper face
- Emotional centers in the brain have direct connections to the LMNs in CN VII Facial. If intact, these other UMNs allow for spontaneous facial expressions in the lower face despite loss of voluntary facial expressions when one corticobrainstem tract is damage.
8
CN VIII
Name: Vestibulocochlear
Location:
2 cochlear nuclei in the caudal pons
4 vestibular nuclei in the caudal pons and rostral medulla
Exit - Laterally at the base of the pons
Job:
Special sensory (hearing - cochlear and balance - vestibular)
-VOR
-Gaze stabilization
Injury:
Deafness - Almost always peripheral due to death of the receptor cells secondary to loud noise or a conduction problem
9
CN IX
Name: Glossopharyngeal
Location:
Ganglia and nuclei in Rostal medulla
Exits lateral rostral medulla
Job: Somatosensory -Posterior 1/3 tongue -Afferent gag reflex -Carotid sinus -Pharynx, Palate, Small area of outer ear
Special Sensory
-Posterior 1/3 tongue
Voluntary Motor
-Swallowing
Parasympathetic
-Salivary gland
Injury:
- Trouble swallowing - dysphagia
- Dry mouth
- Impaired gag reflex
- Loss of taste ipsilateral posterior 1/3 of tongue
- Loss of somatosensation ipsilateral posterior 1/3 tongue
10
CN X
Name: Vagus
Location:
Nuclei - rostral medulla into caudal medulla
Exit - Lateral rostral medulla
Job:
Somatosensory
-Larynx, dura mater, ear, thoracic, abdominal viscera
Special sensory
- Back of throat - taste
- Thoracic and abdominal viscera through transverse colon
Voluntary Motor
- Muscles of pharynx (swallowing)
- Muscles of larynx (vocalization)
- Muscles of upper esophagus (efferent gag reflex)
Parasympathetic
-Smooth/cardiac muscle in thorax and abdomen through transverse colon
Injury:
- Trouble swallowing - dysphagia
- Unilateral damage - hoarseness
- Impaired gag reflex
- Unable to elevate the soft palate on ipsilateral side - soft palate droops on affected side
- Uvula deviates to contralateral side
11
CN XI
Name: Accessory
Location:
- Cranial root - nucleus in caudal portion of medulla
- Spinal root - LMN somas in C1-C5(6)
Job:
Voluntary Motor -
Sternocleidomastoid
Trapezius
12
CN XII
Name: Hypoglossal
Location:
- Nucleus in the medial dorsal tegmentum in the medulla
- Exits between the pyramid and olive
Job: Voluntary motor - Muscles of tongue
Injury -
-Dysarthria - difficulty with moving the tongue results in difficulty articulating speech
- dysphagia - impairments with moving food around
- Tongue deviates toward the weak side (ipsilateral to the injury since a LMN injury and the tongue muscle itself is innervated ipsilaterally)
- Ipsilateral tongue paresis/paralysis with atrophy and/or fasciculations
- Corticobrainstem injury - Damage to a single corticobrainstem tract rostral to the medulla leads to contralateral tongue paresis.
- Dominant contralateral UMN innervation of LMNs
- Deviation to the weak side which is contralateral to the UMN injury
- Limited and later onset atrophy
