Taylor A, Mourad F, Kerry R, Hutting N. A guide to cranial nerve testing for musculoskeletal clinicians. J Man Manip Ther. 2021 Dec;29(6):376-389. doi:10.1080/10669817.2021.1937813. Epub 2021 Jun 29. PMID: 34182898; PMCID: PMC8725776.
Thanks to the authors who allowed us to use the illustrations from their publication.
Dear N.Hutting, F. Mourad, R. Kerry and A. Taylor, if you read these words, thank you very much
Why Should Clinicians Know the Warning Signs of Cranial Nerve Dysfunction?
The authors approach this subject by raising the idea that if physiotherapists, and by extension other clinicians, claim to be able to be consulted as first intention in the musculoskeletal field and in particular in cases of neck pain, headaches or oral pain -maxillofacial, they must be aware of the warning signs to be able to integrate a suspicion of cranial nerve dysfunction into their clinical reasoning. Be able to make a decision in the presence of suggestive signs. When we know the therapeutic wanderings in cases of temporomandibular dysfunctions, the diagnostic errors, as well as the ignorance regarding the classifications of headaches, even in the case of ordered consultations the clinical examination remains essential in order to be able to sort if necessary or to evoke serious pathologies which would have been too quickly eliminated. The authors mention that for reasons that remain mysterious, the majority of physiotherapists are well trained to detect pathologies involving the nervous system of the upper and lower limbs, but very poorly or insufficiently for the cranial nerves. They also carried out a quick survey on Twitter among 600 practitioners, the vast majority of whom mentioned feeling little confident with the examination of cranial nerves.
The authors make an interesting reflection on the neglect of the examination of the cranial nerves since the emergence and development of medical imaging, even though it was an integral part of routine neurological examination. Traces of this testing can be found in literature dating back to the 19th century. The radio-clinical discrepancies are sufficiently documented for this physical examination to be reintegrated into the routine of clinicians, in order to have clinical arguments to make decisions. They also recommend that physiotherapists understand that the clinical examination is not just the responsibility of the doctor.
What Signs May Indicate Cranial Nerve Dysfunction?
It is found in the literature that neck pain, headaches and orofacial pain can be signs suggestive of arterial dissection which may precede a stroke, within 14 days of their appearance. Thus a so-called “subtle” paralysis coming from a dysfunction of the cranial nerves may be a characteristic of pre-ischemia preceding a carotid arterial dissection, due to the anatomical proximity of the lower cranial nerves (IX, X and XII) to the sheath. carotid artery.
Furthermore, the possible presence of a lesion of the lower cranial nerves must be integrated into the clinical reasoning in the following cases:
- Concomitant neck pain and headache
- Neuralgia
- Dysarthria
- Dysfunctional swallowing
- Dysfunctional cough
- Loss of taste
- Dysphagia (difficulty or inability to swallow food, with common aspiration)
- Pharyngeal pain
- Cardiac or gastrointestinal disorders
- Weakness of the trapezius, SCOM or tongue muscles
Why Is It Crucial to Know the Functions of the Cranial Nerves?
The goal, like any clinical examination, is to sort patients who may need further investigation, in order to eliminate serious clinical hypotheses. By knowing the functions of the different cranial nerves, certain information during the interview may arouse the curiosity of the clinician who decides to carry out these tests. Or in cases of worsening of certain signs, or lack of reversibility during treatments in physiotherapy sessions. It is based on the picture found after the testing, its severity, or its speed of worsening, that the clinician decides to refer with a more or less strong sense of urgency.
The authors point out that some cranial nerves have sensory functions, others motor functions, and finally some have a mixed function. They are thus involved in vision, smell, hearing, taste and facial sensitivity. But also in ocular motor skills, movements of the head, face, neck, shoulders, jaw and tongue, and therefore in particular speech and swallowing. We can also read that there are multiple mechanisms that can cause cranial nerve deficiencies, such as local compressions, inflammation, infections, atrophy or demyelination. It appears essential that clinicians acquire some knowledge about these mechanisms, as well as the functions of each nerve so that they can interpret the test results.
How to Perform a Neurological Examination of the Cranial Nerves?
The authors emphasize the fact that contrary to popular belief, performing a neurological examination of the cranial nerves is quick and does not require special equipment. All in all, you need to be equipped with a Snellen chart (or a journal page), a penlight or a small flashlight, neurotips, a piece of cotton and tongue depressor.
In terms of method some will do according to the order of nerves, but grouping by function seems more adequate, faster, more efficient.
Complete Guide to Cranial Nerve Testing
How to Test Smell and Hearing as part of a Cranial Nerve Examination?
Smell - Cranial Nerve I (Olfactory Nerve)
To test the sense of smell, ask the patient to close their eyes and one nostril, then expose them to a known odor (soap, perfume, coffee) and ask them to identify the smell. Note any differences between the two sides.
Hearing - Cranial Nerve VIII (Vestibulo-Cochlear Nerve)
Test hearing by snapping your fingers near each patient's ear with their eyes closed. Note the differences. Use a 256 Hz tuning fork for the Rinne and Weber tests to assess air and bone conduction. For the Rinne test, the tuning fork is vibrated and applied to the mastoid, then to the area around the ipsilateral ear. In a subject who has normal hearing, the sound perceived by air conduction is more effective than the sound perceived by bone conduction.
For the Weber test, the tuning fork is vibrated at the top of the skull, the sound must be perceived equally on both sides.
How to Perform an Eye Exam during a Cranial Nerve Test? Vision and Eye Movement - Cranial Nerves II, III, IV, and VI
Start by asking about the presence of any vision disturbance (diplopia, etc.), then observe the eyes. Their size, shape and symmetry.
Cranial Nerve II - Optic nerve
For vision, you can ask your patient to read a text by hiding one eye then the other. Note the difference. The subject must put on his glasses if he has them. Or else have him read the Snellen diagram from a distance of 30/40cm.
For the visual field, the subject fixes the operator in the eyes. The operator places a finger in front of the field of vision and spreads it while extending the arm to the side. The patient's eyes should not follow the moving finger. When the subject says he no longer sees the finger, it is because it has left his field of vision. Compare the two sides.
Cranial Nerve III - Oculomotor nerve
The patient extends his arm in front of him and raises his finger. He brings his finger towards his face, the eyes follow the movement of the finger to test convergence. Note the difference.
For the pupil's reaction to light, shine a light in front of the eyes and observe miosis (pupil contraction) and mydriasis (pupil dilation). They must be immediate. Otherwise note the differences.
Cranial Nerves III, IV and VI - Oculomotor, Trochlear and Abducens Nerves
Trace an H with your finger, in the air, 30-40 cm from his face. Observe the attitude of the eyes, and the possible appearance of nystagmus. We can try to note the direction of the deficit if there is one.
What Techniques Should I Use for Examining the Face, Jaw, and Tongue?
Start by observing asymmetries of the face, neck and/or shoulders.
Cranial Nerve V - Trigeminal (sensory)
Sensitive test using a piece of cotton and a blunt needle, on different levels of the face. Then the corneal reflex is performed by very lightly touching the cornea to see the blink of both eyes.
Cranial Nerve V - Trigeminal (Motor)
Jaw tightening power. We test the masseters, temporalis and pterygoid muscles.
Cranial Nerve VII - Facial nerve
We test the subject's facial expressions, observing asymmetries: raising/frowning the eyebrows, closing the eyes against resistance, showing the teeth, puffing out the cheeks. Possibly smile with covered teeth, uncovered teeth. Run a tuft.
Cranial Nerve IX - Glossopharyngeal nerve
Ask the patient to swallow and ask if everything seems normal. Thinking about asking him if recently during his diet and hydration nothing seemed difficult to him. Also test the gag reflex by gently inserting a tongue depressor on one side then the other. This evaluates the IX and the X simultaneously.
Cranial Nerve
The subject opens his mouth and says “Aaaaa”. Observe the back of the throat. The soft palate should elevate on both sides equally with the uvula.
Cranial Nerve IX (Glossopharyngeal) and X (Vague)
Note a hoarseness of the voice. Ask the patient about this, see if it is recent. And see if its hoarse when coughing.
Cranial Nerve XII - Hypoglossal nerve
Observe the language carefully. See if atrophy, asymmetry. Check for possible injury, if the subject bites their tongue. Then assess the force by asking the subject to push with their tongue in one cheek, then in the other. The examiner counters the push against the cheek.
How to Test Motor Function of the Head, Neck and Shoulders?
Cranial Nerve XI (Accessory Nerve)
Test muscle strength by counteracting head rotation (SCOM or sternocleido-occipito-mastoid) and shoulder shrugging (upper head of the trapezius) to assess accessory nerve function.
Conclusion
Performing a cranial nerve examination is simple, quick, and does not require specialized equipment. It is crucial for clinicians treating patients with neck, head, or oro-maxillofacial pain to master these tests. Although these tests are not diagnostic in themselves, they provide essential information for suspecting cranial or spinal nerve damage.
[1] Taylor A, Mourad F, Kerry R, Hutting N. A guide to cranial nerve testing for musculoskeletal clinicians. J Man Manip Ther. 2021 From
c;29(6):376-389. doi:10.1080/10669817.2021.1937813. Epub 2021 Jun 29. PMID: 34182898; PMCID: PMC8725776.