Cranial Nerve Testing

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I had a client present with Horner’s syndrome that made me think it appropriate to check all their cranial nerves. That made me realise I didn’t have a good recall of each cranial nerve function and appropriate test.

So back to the books and I thought that I would share with you what I have learnt.

Firstly yes, there are still 12 paired cranial nerves and here are some ways to clinically test. I was looking for quick tests that could be performed in the clinic, and I may well have missed a couple of easier ones. Please let the group know of your best/easiest test for each CN via the blog. Thanks.

I Olfactory

Sense of smell, but don’t use astringents. Block one nostril and test individually. Could use oil of wintergreen products, vanilla, massage oil.

II Optic

Function of seeing, not eye movement. Technically could use eye chart (visual acuity) or ask to read text, one eye at a time.

Test accommodation (observe pupil constriction as you move your testing finger from far to near client’s eyes).

III Oculmotor

In association with IV (trochlear) and VI (Abducens), the oculomotor innervates muscles moving the eye balls. Abnormality of tracking, bilateral eye symmetry will be quickly noticeable. To specifically test this, observe vertical up and down movements. Complete paralysis leaves the eyeball in the ‘down - and - out’ position.

IV Trochlear

“T” for tricky. The smallest CN it provides crossed innervation to the eye. The Trochlear is the second CN involved in eye movement. Have clients look with their suspect eye towards the midline (adduction), then ask them to look down. This is the function of the superior oblique.

If the lesion is at a nuclei level, the contralateral eye is affected, if peripheral lesion it will be the ipsilateral eye affected.

V Trigeminal

Sensory function (pain, light touch, hot and cold) to the face via three divisions; mandibular, maxillary and ophthalmic. Note that the area of sensation over the angle of the jaw is C2/3, not Trigeminal. Assists in clinical differentiation.

Motor control to muscles of mastication (masseter, temporalis, pterygoids) so test jaw closure.

VI Abducens

Final nerve involved for eyeball movements. Think Abducens = Abducts = moves laterally.

VII Facial

Muscles of facial activity - frown, smile, pucker - you get the idea.....

VIII Auditory (Vestibular/Cochlear)

Combination nerve for hearing and balance. Check with voice or by rubbing fingers off to the side for hearing. Indication of vestibular involvement are vertigo (rotatory), nystagmus and postural deviation. Possible subjective complaints of nausea & vomiting

IX Glossopharyngeal

Both IX and X are physically intimately related and functionally similar. Often same disease affects both. Injuries are not common, and testing is difficult to isolate due to overlapping functions with other CNs. Both IX and X have nuclei in medulla and have both motor and autonomic functions. They exit the skull and travel through neck together. They often innervate the same tissues. Check motor function by light ipsilateral stimulation of gag reflex (elevation and constriction of pharynx).

X Vagus

Longest and most widely distributed. Again difficult to assess other than innervation to soft palate. Observe and enquire about deviation of uvula, nasal quality of speech, difficultly swallowing liquids more than solids and nasal regurgitation of foods.

XI Accessory

Upper trapezius muscle test.

XII Hypoglossal

Focus on motor control of tongue. Look at resting position and symmetry. Observe movements slow and fast, forward/backward, side to side and up down. Check strength against tongue depressor.