The Cranial Nerves: A Review

Dr. Ann GathersDepartment of Biological SciencesThe University of Tennessee at Martin

Health Science Teacher Education SymposiumNashville, TennesseeOctober 1-2, 2007

Athletes and Cranial NervesContact sports have the highest incidence of nerve injuries.

In the US, approximately 1/3 of diagnosed nerve injuries were related to football trauma.

Others included wrestling, weight-lifting, and baseball and softball (regional differences)

12 Pairs of Peripheral Nerves Originate in or near the brain Sensory, Motor, and Mixed Voluntary, Involuntary, and Mixed

VENTRAL VIEWOlfactory (I)Optic (II)Oculomotor (III)Trochlear (IV)Trigeminal (V)Abducens (VI)Facial (VII)Spinal Accessory (XI)Hypoglossal (XII)Vagus (X)Glosso-pharyngeal (IX)Auditory (VIII)

OlfactoryOpticOculomotorTrochlearTrigeminalAbducensFacialAuditoryVagus &GlossopharyngealGlossopharyngeal

Spinal AccessoryHypoglossal

Oh Olfactory (I)OnceOptic (II)One Oculomotor (III)Takes Trochlear (IV)TheTrigeminal (V)AnatomyAbducens (VI)FinalFacial (VII)VeryVestibulocochlear (VIII)GoodGlossopharyngeal (IX)VacationsVagus (X)Seem Spinal accessory (XI)HeavenlyHypoglossal (XII)

Functions

Olfactory (I)Provides sense of smellDamage causes impaired sense of smell

Optic (II)Provides visionDamage causes blindness in visual fieldOptic (II)

Oculomotor (III)Some eye movement, opening of eyelid (innervates all extraocular muscles except lateral rectus & superior oblique)Constriction of pupil (parasympathetic)FocusingDamage: drooping eyelid (ptosis), dilated pupil, double vision (diplopia), difficulty focusing & inability to move eye in certain directions

Trochlear (IV)Provides eye movementDamage causes double vision (diplopia) & inability to rotate eye downward and outward

Trigeminal (V)

Trigeminal (V)Main sensory nerve to face (touch, pain and temperature) and muscles of masticationDamage produces loss of sensation & impaired chewingThree Branches:

OpthalmicMaxillaryMandibular

Abducens (VI)Provides eye movement (lateral rectus)Damage results in inability to rotate eye laterally & at rest eye rotates medially (strabismus = cross-eyed)

Facial (VII)Facial expressionsTaste on anterior 2/3s of tongue, Salivary glands and tear, nasal & palatine glands

Damage: sagging facial muscles (ptosis and corner of mouth droops) and disturbed taste (no sweet & salty sensations)i.e. Unilateral sagging facial muscles Bells Palsy

Auditory/ Vestibulocochlear (VIII)Provides hearing & sense of balanceDamage produces deafness, dizziness, nausea, loss of balance & nystagmus

Glossopharyngeal (IX)Provides control over swallowing, salivation (parotid), gagging, sensations from posterior 1/3 of tongue, control of BP and respiration (receptors in carotid)Damage results in loss of bitter & sour taste & impaired swallowing (dysphagia)

Vagus (X)

Vagus (X)Provides swallowing, speech, regulation of viscera (somatic and visceral)

Damage causes hoarseness or loss of voice, impaired swallowing (dysphagia) i.e. Neurocardiogenic Syncoperelatively new diagnosisfainting spells

Spinal Accessory (XI)Swallowing, head, neck & shoulder movementDamage: impaired head, neck & shoulder movement, head turns towards injured side

Hypoglossal (XII)

Hypoglossal (XII)Tongue movements of speech , food manipulation & swallowing

Damage: inability to protrude tongue if bilateral damage deviation towards injured side & ipsilateral atrophy if unilateral damagei.e. Dysarthriapoor articulation

Thank You