Nervous Examination- Cranial Nerves

Intro

• Wash hands, Introduce self, Check patient name and DOB/CHI, explain procedure and gain consent

General/End of bed

• Assess the level of consciousness
• Assess posture and motor activity
  • Any abnormal posturing; involuntary motor behaviours (including resting/intention tremors); any fasciculations (muscle twitches), dystonia (jerks); any restlessness
• Before starting the physical examination, it may be useful to assess the patient using a mini-mental state examination

Examination of the Cranial Nerves

Often easiest to remember by testing in order.

• CN I – Not routinely tested.  Ask if the patient has had any disturbance in their sense of smell
• CN II –
  • Begin by testing visual acuity (with glasses on for neurological exam cf ophthalmology)
  • Test visual fields of each eye by direct confrontation
    • Stand/sit about 1m from the patient, so that you’re at eye-eye level.  Ask the patient to cover an eye and cover your own contralateral (i.e. patient left- examiner right) eye.  Position your finger out at equal distance between you both, outwith your peripheral field in the temporal upper quadrant.  Wiggle your finger and move it towards your centre of vision.  Ask the patient to look directly into your own eye(s) (you do the same) and to say ‘yes’ when they see your finger.
      • Presuming the examiner’s peripheral field is normal, you should both see your finger at the same time
      • Repeat beginning with your finger at the extremes of the lower temporal, upper nasal and lower nasal quadrants (I.e. finger should be roughly tracing an X)
      • Repeat with the other eye
  • Examine the fundus with the ophthalmoscope (see here)
• Reflex- Pupillary light (CNII via pretectal nucleus (superior colliculus in midbrain) to the Edinger-westphal nucleus to CN III) and fixation (also II-III)
  • Observe pupil diameter and symmetry at rest
    • Do this in both bright and dimly lit rooms (this can help distinguish the cause of asymmetrical pupils: if the asymmetry is greatest in dim light, then it is more likely an issue with sympathetic (dilation) innervation of the smaller pupil.
      • Permanent dilation of one side with reactivity of the other eye suggests efferent (CNIII) defect
      • Symmetry at rest with failure to constrict at either eye when light shone on one eye suggests afferent (CNII) defect
  • Check both direct and consensual light reflexes by shining a light in each eye and observing the same and contralateral eye, respectively.
    • You may also want to check for a relative afferent pupillary defect using the swinging light test (rapidly alternating the light between the eyes)
      • A RAPD will dilate the symptomatic eye when light is shone towards it- usually indicates optic nerve or severe retinal pathology rather than CNIII pathology (which is indicated by abnormal light reflexes)
  • Check the accommodation (fixation) reflex by asking the patient to focus on your finger/pen as it moves closer to their face (normally causes constriction)
• CN III, IV and VI
  • Ask the patient to follow your fingers in an H formation.
    • Ask if there is any double vision at any point
  • Look for any asymmetrical eye movements
    • A CNIII palsy will usually be quite obvious (patient’s eye is ‘down and out’ and cannot turn up or in)
    • A CNIV palsy may be more subtle (patient usually complains of diplopia on medial and downward gaze (e.g. reading) which may be compensated by tilting their head towards the lesion- they may have problems with downward and medial gaze)
    • A CNVI palsy usually manifests as problems with lateral gaze
  • Also look for any nystagmus, ptosis
  • Perform the cover tests to evaluate further squints
• CN V
  • Test light touch (cotton wool) over the three distributions, comparing sides
    • Pin Prick sensation is not always examined on the face but you could say that this may be something you would do (particularly if the patient was reporting numbness of the face)
  • Check motor function of CNV(3) by asking the patient to clench their jaw and palpating the masseter and temporalis muscles over the angle of the jaw and temples.  You may also want to check power by asking the patient to move their jaw from side to side against resistance.
  • Ask about any changes of taste and consider testing if appropriate (rarely done in practice)
  • Cranial nerve reflex- Corneal Reflex (CNV(1) to pons (chief sensory nucleus of CNV bilaterally to motor nucleus of CNVII) to CNVII (bilaterally))
    • NB Rarely done in practice as is often uncomfortable for the patient
    • Using a damp cotton wool tip, lightly touch the edge of the cornea.  The patient should blink.
  • Cranial nerve reflex- Jaw Jerk Reflex (CNV(3) to pons (mesencephalic nucleus to motor nucleus of CNV) to CNV(3))
    • Also rarely performed
    • Make sure the patient’s jaw is relaxed and tap just above the chin prominence.  The jaw should jerk in response to stretch.
• CN VII
  • Inspect for any facial asymmetry
  • Motor function
    • Ask the patient to perform the following
      • Raise their eyebrows
      • Scrunch up eyes (against resistance)
      • Show teeth
      • Puff out cheeks (against resistance)
  • NB In UMN lesions the forehead is spared (bilateral innervation)
• CN VIII
  • Perform a rough hearing test e.g. by whispering a number close to the patient’s ear or by rubbing your fingers together and bringing them closer to the ear until the patient can identify them
    • If the patient cannot hear this, consider Rinne’s and Weber’s tests +/- more formal tests e.g. audiometry
  • Also ask about vertigo/dizziness and consider performing the Dix-Hallpike manoeuvre should this be relevant
• CN IX and X
  • Inspect the soft palate in the mouth, the uvula and any asymmetry (the uvula will deviate away from the affected side (stronger muscles on normal side)
  • Cranial Reflex- Gag Reflex (CNIX to nucleus solitarius to spinal trigeminal nucleus to nucleus ambiguus (bilaterally) to CNX (all medulla))
    • NB Rarely performed in clinical practice
    • Using a wooden stick, prod the soft palate.  The soft palate should rise (and the patient gag).
• CN XI
  • Inspect the neck and shoulders for any muscle wasting and ask the patient to turn their head over their shoulder (against resistance- tests contralateral SCM) and shrug their shoulders (against resistance- tests trapezius)
• CN XII
  • Inspect the tongue for any wasting or fasciculations
  • Stick out the tongue and ask the patient to move it from side to side (you can also test against resistance by asking them to push against your hand through the cheek)
    • Deviation will point the tongue away from the lesion (i.e. away from the weakness)

Finish

• Thank the patient, wash hands, document any findings in the notes/explain them to a supervisor, suggest any further tests/management
  • Suggest that ideally, you would also examine the limbs