CN

• 12 Cranial Nerves & Their Functions

  • Olfactory
  • Optic
  • Occulomotor
  • Trochlear
  • Trigeminal
  • Abducens
  • Facial
  • Acoustic
  • Glossopharyngeal
  • Vagus
  • Spinal Accessory
  • Hypoglossal
• Cranial Nerve I - Olfactory Nerve Assessment


  1. Have client sit in a comfortable position at your eye level

  2. Ask the client to clear the nose to remove any mucus

  3. Close eyes, occlude one nostril, and identify a scented object that you are holding such as soap, coffee, or vanilla

  4. Repeat procedure for the other nostril
• Normal Olfactory Nerve Assessment


  Client correctly identifies scent presented to each nostril
• Abnormal Olfactory Nerve Assessment

  Neurogenic Anosmia - inability to smell or identify the correct scent
• Neurogenic Anosmia may indicate olfactory tract lesion, frontal lobe tumor, congenital, nasal or sinus problems, nerve tissue injury, smoking and use of cocaine
• Cranial Nerve II - Optic Nerve Assessment

  1. Use a Snellen chart to assess vision in each eye

  2. Ask the client to read a newspaper or magazine paragraph to assess near vision

  3. Assess visual fields of each eye by confrontation

  4. Use an ophthalmoscope to view the retina and optic disc of each eye
• Normal Visual Acuity

  Client has 20/20 vision OD (right eye) and OS (left eye) - (distance vision)
• Abnormal Visual Acuity


  Difficulty reading Snellen chart, missing letters, squinting
• Normal Near Vision


  Reads print at 14 inches without difficulty (until the patient is in the late 30s to the late 40s)
• Abnormal Near Vision


  Reads print by holding closer than 14 inches or holds print farther away as in presbyopia, which occurs with aging
• Normal Visual Fields


  Normal peripheral vision
• Abnormal Visual Fields


  Loss of visual fields may be seen in retinal damage or detachment, lesions of the optic nerve, lesions of the parietal cortex
• Normal Retina & Optic Disc by Ophthalmoscope


  Optic disc 1.5 mm, round or slightly oval, well-defined margins, creamy pink with paler physiologic cup, Retina pink
• Abnormal Retina & Optic Disc by Ophthalmoscope


  Papilledema, optic atrophy
• Cranial Nerves III, IV, VI - Oculomotor, Trochlear, Abducens Assessment


  1. Inspect margins of the eyelids of each eye

  2. Assess extraocular movements

  3. Assess pupillary response to light (direct and indirect) and accommodation in both eyes
• Normal Eyelid Inspection


  Eyelid covers about 2 mm of the iris
• Normal Extraocular Movements


  Eyes move in a smooth, coordinated motion in all directions (the six cardinal fields)
• Normal Pupillary Response


  Bilateral illuminated pupils constrict simultaneously, Pupil opposite the one illuminated constricts simultaneously
• Abnormal Eyelid Inspection


  Ptosis (drooping of the eyelid) is seen with weak eye muscles, myasthenia gravis
• Abnormal Extraocular Movements


  Possible causes: cerebellar disorders, increased ICP, paralytic strabismus
• Abnormal Pupillary Response


  Possible causes: oculomotor nerve paralysis, Argyll Robertson pupils, narcotics abuse, CN III damage, lesions of the sympathetic nervous system, PNS or CNS dysfunction, CN V lesion
• Cranial Nerve V - Trigeminal Nerve Assessment

  1. Test motor function: Ask the client to clench the teeth while you palpate the temporal and masseter muscles for contraction

  2. Test sensory function: Touch the forehead, cheeks, and chin with sharp/dull cotton tip and have client identify sensation, repeat with light touch

  3. Test corneal reflex: Ask the client to look away and up while you lightly touch the cornea with a fine wisp of cotton
• Normal Trigeminal Motor Function


  Temporal and masseter muscles contract bilaterally
• Abnormal Trigeminal Motor Function

  Decreased contraction in one or both sides, asymmetric strength in moving the jaw may be seen with lesion or injury of the 5th cranial nerve, pain occurs with clenching of the teeth
• Normal Trigeminal Sensory Function


  Correctly identifies sharp and dull stimuli and light touch to the forehead, cheeks, and chin
• Abnormal Trigeminal Sensory Function

  Inability to feel and correctly identify facial stimuli, lesions of the trigeminal nerve, lesions in the spinothalamic tract or posterior columns
• Normal Trigeminal Corneal Reflex

  Eyelids blink bilaterally
• Abnormal Trigeminal Corneal Reflex


  Absent corneal reflex, lesions of the trigeminal nerve, lesions of the motor part of cranial nerve VII (facial)
• Cranial Nerve VII - Facial Nerve Assessment


  Test motor function: Smile, frown and wrinkle forehead, show teeth, puff out cheeks, purse lips, raise eyebrows, close eyes tightly against resistance
• CN V - TRIGEMINAL


  Testing motor function
• Normal


  • Temporal and masseter muscles contract bilaterally
• Abnormal


  • Decreased contraction in one or both sides
  • Asymmetric strength in moving the jaw may be seen with lesion or injury of the 5th cranial nerve
• Pain occurs with clenching of the teeth
• CN V - TRIGEMINAL


  Testing sensory function
• Normal


  • Correctly identifies sharp and dull stimuli and light touch to the forehead, cheeks, and chin
• Abnormal


  • Inability to feel and correctly identify facial stimuli
  • Lesions of the trigeminal nerve
  • Lesions in the spinothalamic tract or posterior columns
• CN V - TRIGEMINAL


  Testing corneal reflex
• Normal


  • Eyelids blink bilaterally
• Abnormal


  • Absent corneal reflex
  • Lesions of the trigeminal nerve
  • Lesions of the motor part of cranial nerve VII (facial)
• CN VII - FACIAL


  Test motor function