Cranial Nerves Exam

Examination Technique:

• stimulant should be non-irritating.
• test one nostril at a time with the opposite side occluded.
• patient should not be able to see the stimulus.
• cloves ideal stimulant since it preserves it’s scent.
• alternative stimuli at bedside could include soap, toothpaste, perfume, cologne, etc.

Normal Response:
to perceive the scent with either nostril.

Abnormal Response:
unilateral loss is of more concern and could suggest a structural lesion affecting the olfactory bulb or tract or simply due to a blocked nasal passage or deviated septum.
bilateral loss occurs more commonly and could be due to rhinitis or damage to the cribriform plate sustained as a result of trauma.

Examination Technique:

• the examiner places themself approximately 1 meter in front of the patient.
  ask the patient to look to each side, up and down following an “H” pattern.
• pursuit: ask the patient to follow a target such as your finger or a pen with their eyes without moving their head.
• pause at the ends of each direction of gaze to observe for nystagmus.
• assess saccadic eye movements by having the patient make quick horizontal and vertical eye movements.
• optokinetic nystagmus is performed by having the patient follow a series of moving horizontal or vertical stripes and observing for nystagmus.

The hypoglossal nerve is motor to the tongue.

Examination Technique:

• observe for tongue atrophy or enlargement.
• do not overcall tongue fasciculations. It is very difficult to relax the tongue.
• ask the patient to protrude the tongue.
• ask the patient to push the tongue into each cheek or alternatively to protrude the tongue and push it laterally against a tongue depressor.
• ask the patient to move the tongue quickly from side to side.
• if there is facial weakness, correct this by supporting the upper lip on the side of weakness, otherwise there may appear to be deviation of the tongue but once the facial weakness is corrected for, the tongue will no longer appear to deviate.

Normal Response:
the tongue should be able to protrude relatively straight. Minimal degrees of deviation (i.e. only millimeters) affecting only the tip are insignificant.

Abnormal Response:
with tongue weakness, the tongue deviates towards the weak side.

The 9th and 10th nerves are tested together. They are responsible for swallowing, phonation, guttural and palatal articulation (the 7th nerve has a component for labial articulation). The glossopharyngeal nerve also subserves taste to the posterior one-third of the tongue but this is rarely tested.

Examination Technique:

• check palatial elevation by having the patient sustain an “ah.” When observing palatal movement, look at the palate rather than the uvula.
• assess the gag reflex by gentling stroking the soft palate on each side.
• swallowing can be assessed by giving the patient a sip of water and observing them swallow.
• listen to the patient’s speech. Is there a nasal quality?
• assess palatal articulation with a “KA” sound, guttural with a “GO” sound and labial with a “PA” sound.

Normal Response:
the palate should elevate symmetrically, both when sustaining an “AH” and in response to stimulation on either side. Some patients however do not have a gag response and this can be normal if it is absent bilaterally. Patients should also be asked if they feel the stimulus.

Abnormal Response:
with unilateral palatal weakness, the palate fails to elevate on the weak side and the gag reflex will be absent on that side.

Although taste is not typically assessed during a routine neurological examination, the 7th nerve does supply taste to the anterior two-thirds of the tongue and hard and soft palates. This can be tested using salty, bitter, sour or sweet solutions.

Examination Technique

• the tongue is protruded and held gently by the examiner.
• a small sample of solution is applied to one side of the anterior two-thirds of the tongue using a cotton tipped applicator saturated with the solution.
• with the tongue still protruded, the patient should be asked to point to a sign displaying one of the four possible tastes.
• the patient is then given a small sip of water and the test is repeated using an alternate stimulus.
• the reason the tongue is maintained protruded is because if the patient were allowed to put their tongue back in their mouth in order to verbalize their response, they could masticate and transfer the stimulus to the opposite side which could be affected if there was a lesion of the 7th nerve.

The major role of the facial nerve is to innervate the muscles of facial expression. These can be observed while taking the history and then more formally assessed during the neurological examination.

Examination Technique:

• observe for asymmetry – widening of the palpebral fissure or flattening of the nasolabial fold.
• observe for involuntary facial movements (e.g. hemifacial spasm, orofacial dyskinesia, myokymia, or synkinesis).
• ask the patient to wrinkle their forehead by raising their eyebrows and close their eyes tightly. Observe for asymmetry of ability to burry the eyelashes and palpate for differences of ability to resist eye opening. Ask the patient to show their teeth, puff out their cheeks and appose their lips.
• recall that the efferent limb of the corneal reflex (see trigeminal nerve) is through the 7th cranial nerve.

Normal Response:
although patients may have an asymmetric face, there should be no facial weakness.

Abnormal Response:

• lower motor neuron weakness causes weakness of the entire side of the face with equal involvement of upper and lower facial muscles.
• an upper motor neuron lesion of the contralateral supranuclear pathway results in weakness primarily of lower muscles of facial expression. The upper muscles of facial expression (frontalis and orbicularis oculi) are much less affected because the facial nucleus that innervates them receives partial input from the ipsilateral hemisphere.