A guide to cranial nerve testing for musculoskeletal clinicians Alan Taylor a, Firas Mourad b,c,d, Roger Kerry a and Nathan Hutting e

aFaculty of Medicine and Health Sciences, School of Health Sciences, Physiotherapy and Sport Rehabilitation, University of Nottingham, UK; bFaculty of Medicine and Surgery, Department of Clinical Science and Translation Medicine, University of Rome Tor Vergata, Roma, Italy; cDepartment of Physiotherapy, LUNEX International University of Health, Exercise and Sports, Differdange, Luxembourg; dDepartment of Physiotherapy, Poliambulatorio Physio Power, Brescia, Italy; eDepartment of Occupation and Health, School of Organisation and Development, HAN University of Applied Sciences, Nijmegen, Netherlands

ABSTRACT Background: Neurological examination in musculoskeletal practice is a key element of safe and appropriate orthopedic clinical practice. With physiotherapists currently positioning them- selves as advanced first line practitioners, it is essential that those who treat patients who present with neck/head/orofacial pain and associated symptoms, should have an index of suspicion of cranial nerve (CN) dysfunction. They should be able to examine and determine if CN dysfunction is present, and make appropriate clinical decisions based upon those findings. Methods: This paper summarizes the functions, potential impairments of the nerves, associated conditions, and basic skills involved in cranial nerve examination. Results: A summary of cranial nerve examination is provided, which is based on the function of the nerves, This is intended to facilitate clinicians to feel more confident at understanding neural function/impairment, as well as performing and interpreting the examination. Conclusion: This paper illustrates that CN testing can be performed quickly, efficiently and without the need for complicated or poten- tially unavailable equipment. An understanding of the CN’s function and potential reasons for impairment is likely to increase the frequency of CN testing in orthopedic clinical practice and referral if positive findings are encountered.

KEYWORDS Cranial nerves; impairment; examination; musculoskeletal practice

With physiotherapy clinicians worldwide, assuming first contact roles as ‘advanced clinical practitioners’ (ACP), there is a need for relevant training, knowledge, clinical reasoning, differential diagnosis and triage skills. Above all, it is essential that clinicians have the ability to recognize the key elements of the patient history, and the physical examination which may be indicative of serious pathology or a potential risk of serious adverse events [1]. As such, the ability to per- form a complete neurological work up is paramount.

Neurological examination in musculoskeletal (MSK) practice has always been considered to be a key ele- ment of safe and appropriate clinical practice [2] and is commonly used to identify upper/lower limb and upper motor neuron involvement. However, for rea- sons as yet to be elucidated, it appears that under- graduate training in a range of countries has not adequately prepared a generation of physiotherapists in the rationale for and fundamentals of cranial nerve (CN) examination. Personal experience and recent Twitter polls of over 600 physiotherapists [3], have highlighted that many were either not taught, or do not feel confident in their knowledge, skills and clinical reasoning, with regard to the clinical application of CN examination. Although the scale and distribution of this knowledge deficit remains to be quantified in full, the authors are aware of as yet unpublished data from surveys in Italy and the UK, that are indicative of a shortfall in education and skills in this area of

neurological examination. However to date, there is no published data on the scale of the issue.

Neck pain and associated symptoms are common conditions that lead to pain, impairments, disability and a considerable economic burden [4]. The asso- ciation between neck pain and headache manifesta- tions including, facial pain, jaw pain, muscular dysfunction, visual/balance disturbances, and dizzi- ness has been well documented and debated in the physiotherapy world for decades in a range of domains [5–7].

Patients commonly seek physiotherapy assessment and intervention for neck pain/stiffness and headache. It is well documented that neck pain, headache and orofacial pain are commonly reported as the early signs of arterial dissection leading to stroke [8,9]. Indeed it has been suggested that neck pain and head- ache may precede the onset of obvious frank neurolo- gical symptoms for as long as 14 days [10], thought to be a more obvious factor in clinical reasoning errors associated with major adverse events (MAE). Subtle CN palsy is a known be a pre-ischemic feature of carotid artery dissection due to anatomical proximity of the lower cranial nerves (IX, X and XII) to the carotid sheath. Lower CN lesions should be considered in cases of neck pain/head ache, neuralgic pain, dis- turbed speech, swallowing, coughing, deglutition, sen- sory dysfunctions, taste, or autonomic dysfunctions, dysphagia, pharyngeal pain, cardiac or gastrointestinal

CONTACT Nathan Hutting [email protected] HAN University of Applied Sciences, Nijmegen, The Netherlands

JOURNAL OF MANUAL & MANIPULATIVE THERAPY 2021, VOL. 29, NO. 6, 376–389 https://doi.org/10.1080/10669817.2021.1937813

© 2021 Informa UK Limited, trading as Taylor & Francis Group

compromise, or weakness of the trapezius, sternoclei- domastoid, or the tongue muscles [11]. However, clin- icians should note that there are multiple potential causes for CN impairment [12], and appropriate man- agement requires an early recognition. It is the role of the astute clinician to be able to make sense of the complex presentations that commonly combine, asso- ciated with neck pain, with or without trauma. The key objective of any examination is to filter out those patients who may need referral for further examination or testing, either as urgent or non-urgent cases. It has been suggested that CN examination should be an integral part of that process [13].

In medicine, testing of the CN’s has been documented and practised since the late 1800’s [14] and is an integral part of a complete neurological examination. However, with the development of modern imaging, the clinical examination has been reduced [2]. Conversely, in phy- siotherapy, the suggestion is, that this is not routine and furthermore, there appears to be a perception that these skills are the domain of medical physicians, and somehow outside the skill set of physiotherapists. However, this notion does not fit with the intention for physiotherapists to achieve ‘advanced practice level capabilities’.

Purpose

CN examination appears to be perceived as a challenging examination which may be time consum- ing, difficult to interpret and involves specialized equip- ment or skills e.g. fundoscopy. This article aims to provide clinicians with an introduction and updated guide to the CN’s, placed in a clinical reasoning context, which allows the reader to understand the functions of

the cranial nerves, the rationale for, and application of appropriate CN examination in musculoskeletal cases.

The cranial nerves – what are they, what are their functions and why would you test them?

The cranial nerves are involved in sensations such as vision, smell, hearing, taste and facial sensation, as well as the functions of eye movement, head, face, neck/ shoulder, jaw, tongue and throat functions such as speech, swallowing or gagging. As such, some of the CN’s have motor functions, some have sensory func- tions, and some have mixed functions (see Table 1).

There are many reasons for neural impairment, including insidious mechanisms such as local pressure from space occupying lesions, inflammation, infection, atrophy, or demyelination. For clinicians, gaining a working knowledge of the individual nerve functions is key to understanding, performing and interpreting the testing [2]. Appendix 1 presents lists the functions of, and the more common reasons or mechanisms of impairment at each individual nerve.

A function based approach to CN testing

A basic CN testing can be performed easily and quickly in the clinic without the need for specialized equipment. A Snellen chart (or newspaper) together with a pen light or small flashlight, neurotips, cot- ton wool and tongue depressor (optional) are all that is required to perform the examination. It may be helpful to use a cheat sheet, in clinics where this type of testing is only performed occasionally.

Table 1. Cranial nerves and their functions (Diagonal lines – Sensory function – Smell/Hearing; Horizontal lines – Motor and sensory function of the eyes; Vertical lines – Motor and sensory function of the face/jaw/throat/tongue; Crossed lines – Motor function of the head/neck/shoulders).

Number Name Type Function

I Olfactory Sensory Smell (olfaction) II Optic Sensory Vision (acuity and field) III Oculomotor Motor Eye movements, elevation of eyelid.

Pupil size and reactivity to light IV Trochlear Motor Eye movement (vertical and a Dduction) V Trigeminal Mixed Chewing, face/mouth sensation.

Corneal reflex (sensory) VI Abducens Motor Eye movements – aBduction VII Facial Mixed Facial expression, eyelid and lip closure, taste. Corneal reflex (motor) VIII Vestibulocochlear (auditory) Sensory Hearing, balance/equilibrium IX Glossopharyngeal Mixed Gagging, swallowing (sensory), taste X Vagus Mixed Gagging, swallowing (motor), speech (sound) XI Accessory Motor Head/neck/shoulder movement XII Hypoglossal Motor Tongue movement, speech (articulation)

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Those who have learned the nerves in order may prefer to test that way. However, physiotherapists are well used to testing function, and for that reason it is logical, to consider grouping the tests together as shown in Table 2.

A step by step guide to testing the cranial nerves

In line with the current move toward Telehealth, the description of testing, has been written as an online Telehealth consultation wherever possible. Tests that additionally can be used in a face-to-face consultation are also included, so that clinicians can choose either option. The summary of the examination presented in Table 2 describes the use of the tests in Telehealth. Appendix 2 gives a summary of the test procedures in a face-to-face consultation.

Following the function based approach to testing outlined above, the examination may proceed as follows:

The senses of smell and hearing

CN I – Olfactory nerve

Test: Ask the patient to close their eyes and one nostril, introduce a familiar smell (soap/perfume/ coffee) and ask the person to identify it (Figure 1). Repeat on the opposite side. Note any side to side differences.

CN VIII – Vestibulocochlear nerve

If you have completed a full subjective history prior to this point, the likelihood is that the patient can hear you.

Test: compare side to side hearing by asking the patient to rub their fingers together close to each ear. Note any side to side differences.

In a face-to-face consultation you can vigorously rub the fingers together near to each ear with the patient’s eyes closed. If there is lateralization or hearing abnormalities, perform the Rinne and Weber tests using the 256-Hz tuning fork.

Rinne’s test (Figure 2a and 2b): The tuning fork is struck and placed on the mastoid process. The patient is requested to indicate when the sound is no longer audible. As soon as the sound is extinguished, the tuning fork is placed next to the external auditory meatus to assess whether it can be heard. In a patient with normal hearing, air conduction should be greater than bone conduction, so the patient should be able to hear the tuning fork.

Weber’s test (Figure 3): place the tuning fork in the middle of the forehead and the sound is heard from there. The sound should be heard equally on both ears.

The examination of the eyes – CN’s II, III, IV and VI

Ask about any visual disturbances e.g. double vision.

Table 2. A function based approach to order and testing (Diagonal lines – Sensory function – Smell/Hearing; Horizontal lines – Motor and sensory function of the eyes; Vertical lines – Motor and sensory function of the face/jaw/throat/tongue; Crossed lines – Motor function of the head/neck/shoulders. OEMS = Extra ocular movements).

Number Name Examination

I Olfactory Identify a familiar smell (soap/perfume) VIII Vestibulocochlear

(auditory) Ask patient if they can hear fingers rubbing (close to ear) or whispered number sequence

II Optic Test each eye with Snellen chart or newspaper. Test visual fields in 4 quadrants

III Oculomotor Check pupil reaction to light (both should constrict). Check all EOMS (H-test). Check accommodation (finger to nose) IV Trochlear H-Test – observe down and in VI Abducens H-Test – observe side to side V Trigeminal Test jaw strength (open mouth) – try to close/move laterally

Check facial sensation – sharp/blunt Test corneal reflex

VII Facial Ask patient to smile, raise eyebrows, puff out cheeks. Check for symmetry. Ask about taste. IX Glossopharyngeal Assess gag reflex with tongue depressor. Ask patient to swallow. X Vagus Ask patient to say ‘Aaaaaaaaah’, observe for symmetrical elevation of palate and uvula XII Hypoglossal Patient protrudes tongue, check for deviation, look for fasciculations.

Patient pushes out cheek with tongue, check power by pushing cheek. XI Accessory Check resisted head rotation (sternocleidomastoid) and shoulder elevation (trapezius – upper fibers).

Figure 1. CN I test (identify familiar smell).

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Observe the eyes: Look for size, shape and symme- try (eyelids, pupils).

CN II – Optic nerve. Visual acuity; Ask the patient to read small print

(with glasses on, if they wear them) from a book or newspaper with one eye covered. Note any side to side differences. In a face-to-face consultation, the patient should read from a Snellen chart at 30–40 cm. In cases of severe visual impairment light perception should be tested using a small flashlight.

Field of vision: Ask the patient focus on a target in front of them, then hold out their arm to the side whilst wagging one finger. Ask them to move their arm toward the midline (whilst still wagging the finger), instruct them to tell you when they first see the move- ment of the finger. Repeat this on either side, at shoulder height, above the head and below the chin. Note any side to side differences or reduction in the visual field.

Figure 2. (a) Rinne’s test (tuning fork is struck and placed on the mastoid process). (b) Rinne’s test (fork is placed next to the external auditory meatus).

Figure 3. Weber’s test (fork is placed on the vertex of the head).

Figure 4. CN II test (eye examination).

Figure 5. CN III test (pupil reaction to light).

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In a face-to-face consultation, the patient is instructed to look directly at the examiner’s eye while the non-tested eye remains covered (see Figure 4). A red pen or the examiner’s finger should be brought in from four directions diagonally toward the center of the visual field. The patient should state when the pen/ finger becomes clearly detectable in order to detect any visual field deficits.

CN III – Oculomotor nerve

Ask the patient to outstretch their arm raise their finger, and then move it toward their nose, following with the eyes (accommodation or convergence), note symmetry of movement and side to side differences.

Pupillary reaction to light: In a dimly lit environment, ask the patient to shine a small flashlight one eye (close to the webcam). Note the reaction in the ipsilateral and contralateral eye. Both pupils should constrict in reaction to bright light. A direct response is the constriction that occurs when the pupil is exposed to light. The consen- sual or indirect response refers to the simultaneous con- striction of the opposite pupil. Note any side to side differences. In a face-to-face consultation you can use a small flashlight to test the light reflex (see Figure 5).

CN’s III, IV and VI, Oculomotor, Trochlear and Abducens nerves

Movement of the eyes (extra ocular movements): Ask the patient to draw a H shape 2–3 times with their finger and follow with their eyes.

In a face-to-face consultation, move a pen in an H pattern 30–40 cm in front of the patient. Patients should be asked to follow the target with their eyes without moving their head (see Figure 6). Observe the symmetry of movement in each eye, deviations, lag or nystagmus (an involuntary, rapid and repetitive move- ment of the eyes – either horizontal, vertical or rotary). Note any side to side differences and try to assess direction of deficit.

Examination of the face, jaw, muscles of expression, throat and tongue – CN V, VII, IX, X, XII Observation: Check for facial or neck/shoulder asym- metry. Note wasting, or any side to side differences.

CN V – Trigeminal nerve (sensory)

Check facial sensation – ask the patient to stroke their skin in the distribution of the ophthalmic (scalp, forehead, upper eyelid), maxillary (lower eyelid, cheek, upper lip/teeth) and mandibular divisions (chin jaw lower lip, mouth, lower teeth/ gums).

In a face to face-to-face consultation, the sensory component is tested using a cotton wool ball and blunt tip needle sequentially, while comparing sides (see Figure 7). Note any side to side differences. The corneal reflex is tested with a wisp of cotton touching the cornea gently for triggering the blinking reflex of both eyes.

CN V – Trigeminal nerve (motor)

Test jaw strength – ask the patient to place a fist under their jaw and open their mouth against their own resistance. This is a very powerful movement in normal circumstances. Ask if it feels strong. Ask them to resist side to side movement of the jaw. Ask them to clench their teeth together. Observe and palpate (if face to face) the size and contraction of the masseter. Note any side to side differences.

In a face-to-face consultation, the motor compo- nent is assessed by examining the function of the temporalis, masseteric and pterygoid muscles.

CN VII – Facial nerve

Observation of a patient’s face can yield the initial clues of asymmetrical expression. Ask patient to smile/frown, raise eyebrows, puff out cheeks. Check for symmetry. Ask about taste. In a face-to-face

Figure 7. CN V test (sensory component).Figure 6. CN III, IV, VI test (H test for extra-ocular movement and control).

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consultation, ask the patient to close both eyes tightly while you try to force open each eye to test strength. Then, assess the muscles of expression asking the patient to show the teeth, to ‘puff out’ the cheeks palpating them to determine any difference in tone.

CN IX – Glossopharyngeal nerve

Ask patient to swallow (a sip of water). Ask if swallowing feels normal or if they have noticed any difficulty with eating or drinking. In a face-to-face consultation, an

unilateral lesion in the glossopharyngeal nerve can man- ifest as loss of the ipsilateral gag reflex that is triggered with a tongue depressor touching gently the back of the throat on one side (tests CN IX and X together).

CN X – Vagus nerve

Ask patient to open mouth flatten tongue and say ‘Aaaaaaaaah’, observe for symmetrical elevation of the soft palate and central ascent of the uvula. (see Figure 8).

CN IX and X

Ask the patient about their voice (hoarseness). Ask them if their cough sounds normal. In a face-to-face consulta- tion, take note of the patient’s voice during conversation for a hoarse voice or a ‘bovine’ sound (a non-explosive or hollow sound quality) during cough.

CN XII – Hypoglossal nerve

The tongue is carefully inspected for signs of atrophy, asymmetry or fasciculation. Patient protrudes tongue, check for deviation. Look for fasciculations (visible spon- taneous and intermittent muscle contractions). Ask the patient to push out their cheek with their tongue, and check power by pushing against outside of cheek. Note any side to side differences.

In a face-to-face consult, power is examined by hav- ing the patient press the tip of the tongue against each cheek while the examiner tries to dislodge it (Figure 9).

Head neck and shoulder motor function

CN XI – Accessory nerve

Ask the patient to resist head rotation (sternocleido- mastoid) and shrugging of shoulders (upper fibers trapezius).

Figure 9. CN XII test (test tongue against resistance).

Figure 8. CN X test (observation of the soft palate [a] and uvula ([b]).

Table 3. CN subjective questions (Diagonal lines – Sensory function – Smell/Hearing; Horizontal lines – Motor and sensory function of the eyes; Vertical lines – Motor and sensory function of the face/jaw/throat/tongue; Crossed lines – Motor function of the head/ neck/shoulders).

Number Name Subjective Examination Questions

I Olfactory Have you noticed any recent changes of the ability to smell? VIII Vestibulocochlear Have you noticed any recent alteration to your hearing?

Any balance issues, motion sickness or tinnitus linked to eye movements? II Optic Have you noticed any recent difficult reading or alteration to your vision?

Have your extremes/fields of vision altered? III & VI Oculomotor & Abducens Have you noticed any recent alteration to your vision? IV Trochlear Have you noticed any recent alteration to your vision or unsteadiness? V Trigeminal Have you noticed any recent alteration to your ability to eat or chew?

Have you noticed any recent alteration to your facial sensation? VII Facial Have you noticed any recent alteration to your facial features e.g. smile?

Any recent alteration to taste? IX & X Glossopharyngeal & Vagus Have you noticed any recent alteration to eating, taste or ability to swallow.

Does your cough sound the same as usual? Any change in the sound of your voice or hoarseness? XII Hypoglossal Have you noticed any recent alteration to eating, swallowing, speech (articulation) or tongue function? XI Accessory Have you noticed any recent alteration to your head neck or shoulder function?

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Table 4. Cranial nerves, their functions and examination (Diagonal lines – Sensory function – Smell/Hearing; Horizontal lines – Motor and sensory function of the eyes; Vertical lines – Motor and sensory function of the face/jaw/throat/tongue; Crossed lines – Motor function of the head/neck/shoulders).

Number/Name Function Examination

I Olfactory

Smell (olfaction) Identify a familiar smell (soap/perfume)

VIII Vestibulocochlear (auditory)

Hearing, balance/equilibrium Ask patient if they can hear fingers rubbing (close to ear) or whispered number sequence

II Optic

Vision (acuity and field) Test each eye with Snellen chart or newspaper. Test visual fields in 4 quadrants

III Oculomotor

Eye movements, elevation of eyelid. Pupil size and reactivity to light

Check pupil reaction to light (both should constrict). Check all EOMS (H-test). Check accommodation (finger to nose)

IV Trochlear

Eye movement (vertical and aDduction)

H-Test – observe down and in

VI Abducens

Eye movements – aBduction H-Test – observe side to side

V Trigeminal

Chewing, face/mouth sensation. Corneal reflex (sensory)

Test jaw strength (open mouth) – try to close/move laterally Check facial sensation – sharp/blunt

VII Facial

Facial expression, eyelid and lip closure, taste. Corneal reflex (motor)

Ask patient to smile, raise eyebrows, puff out cheeks. Check for symmetry. Ask about taste.

(Continued)

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In a face-to-face consultation, test power manually. Note any side to side differences.

Interpretation of findings

Clinicians should recognize the need to test CN func- tion when patients present with complex or confusing presentations which may be worsening or unrespon- sive to management. If the subjective examination (see Table 3.) raises the index of suspicion and the CN examination reveals side to side differences or abnor- mal responses, which may or may not fit with the overall clinical picture, then this would be an indication to refer on for further examination or appropriate ima- ging/testing.

The urgency of referral will always very much depend on the full clinical picture and the status of the patient’s symptoms (e.g. static or worsening). Ideally, urgent referral should be made using the situa- tion, background, assessment, recommendation (SBAR) method [15] or appropriate variant which is a communication technique that increases patient safety and is current ‘best practice’ to deliver informa- tion in critical situations [16].

It is however, important that clinicians are aware that there is little or no specific data avail- able to support the diagnostic accuracy (i.e. valid- ity and reliability) of a complete CN examination [2]. However, psychometrics from elements of cra- nial nerve examination support at least moderate reliability and validity of cranial nerve examination [17]. This may link to the wide variety and combi- nations of potential pathologies that may lead ultimately to neural impairments. These impair- ments may manifest in a variety of presentations encountered by musculoskeletal clinicians and may be detected via appropriate examination (as an example a case study is presented in Appendix 3). An comprehensive overview of the CN, their functions and examination is presented in Table 4.

Conclusion

CN examination is an important component of the skill set of physiotherapists working in first contact settings where they may encounter patients with neck pain, orofacial pain, headache and associated symptoms. Gaining

Table 4. (Continued).

Number/Name Function Examination

IX Glossopharyngeal Gagging, swallowing (sensory), taste

Assess gag reflex with tongue depressor. Ask patient to swallow.

X Vagus

Gagging, swallowing (motor), speech (sound)

Ask patient to say ‘Aaaaaaaaah’, observe for symmetrical elevation of palate [a] and uvula [b].

XII Hypoglossal

Tongue movement, speech (articulation)

Patient protrudes tongue, check for deviation, look for fasciculations. Patient pushes out cheek with tongue, check power by pushing cheek.

XI Accessory

Head/neck/shoulder movement Check resisted head rotation (sternocleidomastoid) and shoulder elevation (trapezius – upper fibers).

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knowledge and understanding of the CN’s function and potential reasons for impairment i