Cranial Nerves Overview

Introduction

• Cranial Nerves: 12 pairs, emerge from the brain, relay information between brain and head/neck, except CN 10 which also connects with internal organs.
• Numbering: Based on exit order from brain (front to back).
• Innervation: Each nerve innervates one side of the body.
• Types: Sensory, Mixed (some predominantly motor).

Detailed Nerve Descriptions

Cranial Nerve 1: Olfactory Nerve

• Type: Sensory
• Function: Sense of smell
• Origin: Olfactory mucosa of nasal cavity
• Termination: Olfactory bulb at the base of frontal lobe
• Assessment: Smell test for each nostril

Cranial Nerve 2: Optic Nerve

• Type: Sensory
• Function: Vision
• Origin: Retina of the eye
• Termination: Thalamus
• Damage: Leads to partial/total blindness
• Assessment: Vision acuity test for each eye

Cranial Nerve 3: Oculomotor Nerve

• Type: Predominantly Motor
• Function: Eye movements, eyelid opening, pupil constriction
• Origin: Midbrain
• Fibers: Somatic and parasympathetic
• Damage Symptoms: Drooping eyelid, dilated pupil, double vision, down-and-out eye deviation
• Assessment: Pupillary response and eye tracking

Cranial Nerve 4: Trochlear Nerve

• Type: Motor
• Function: Controls superior oblique muscle of the eye
• Origin: Midbrain
• Damage Symptoms: Double vision, upward eye deviation, head tilt

Cranial Nerve 5: Trigeminal Nerve

• Type: Mixed
• Origin: Pons
• Divisions:
  • Ophthalmic: Sensory from upper face
  • Maxillary: Sensory from middle face
  • Mandibular: Mixed, sensory from lower face, motor for chewing
• Assessment: Sensation tests, jaw deviation test

Cranial Nerve 6: Abducens Nerve

• Type: Predominantly Motor
• Function: Lateral eye movement
• Origin: Lower pons
• Damage Symptoms: Inward eye turn

Cranial Nerve 7: Facial Nerve

• Type: Mixed
• Function: Facial expression, taste, tear/salivary gland control
• Branches: Five motor branches
• Damage Symptoms: Facial asymmetry, drooping, taste distortion, noise intolerance

Cranial Nerve 8: Vestibulocochlear Nerve

• Type: Sensory
• Divisions:
  • Vestibular: Equilibrium
  • Cochlear: Hearing
• Damage Symptoms: Hearing loss, vertigo, nystagmus

Cranial Nerve 9: Glossopharyngeal Nerve

• Type: Mixed
• Functions: Sensory (pharynx, ear, tongue), motor, parasympathetic
• Damage Symptoms: Swallowing/speaking difficulties, taste distortion

Cranial Nerve 10: Vagus Nerve

• Type: Mixed
• Functions: Major parasympathetic roles, sensory, motor
• Damage Effects: Voice loss, swallowing difficulty, heart rate increase
• Testing: Speech/swallow tests, gag reflex

Cranial Nerve 11: Accessory Nerve

• Type: Mixed
• Roots: Cranial and spinal
• Functions: Controls neck and shoulder muscles
• Damage Symptoms: Shoulder weakness, difficulty turning head

Cranial Nerve 12: Hypoglossal Nerve

• Type: Predominantly Motor
• Function: Tongue movement
• Damage Symptoms: Speech/swallowing issues, tongue deviation