Cranial Nerve Examination Checklist

What does this exam assess?

The Cranial Nerve Exam is a systematic assessment that assesses the functioning of each cranial nerve individually. Utilizing various methods, this examination can generally be conducted with readily available equipment in a hospital setting (Reese et al., 2023).

Let's take a quick look at the functions of each cranial nerve that are assessed in this examination.

• Olfactory nerve (CN I)
  The olfactory nerve is associated with smell, so tests of the olfactory nerve will typically involve asking about changes in the patient's sense of taste or smell or more formal assessment through scent bottles.
• Optic nerve (CN II)
• The optic nerve is assessed through testing of visual acuity, fields, and reflexes. Informal testing may involve asking the patient to read your name badge, whereas formal testing can involve a Snellen eye chart.
• Oculomotor nerve (CN III), trochlear nerve (CN IV), abducens nerve (CN VI)
• The oculomotor, trochlear, and abducens nerves are assessed as they are all involved with the eye's movement.
• Trigeminal nerve (V)
• The trigeminal nerve comprises three divisions: the ophthalmic, maxillary, and mandibular, and the function of each of these branches is tested through a cotton wool test and movement of the facial muscles (Damodaran et al., 2013).
• Facial nerve (CN VII)
• The facial nerve is associated with the muscles for facial expression. So, assessment typically involves asking the patient to make certain facial expressions and assessing the strength of their facial muscles.
• Vestibulocochlear nerve (auditory) (CN VIII)
• The vestibulocochlear nerve is associated with hearing and balance. Hearing can be tested either via gross hearing assessment, i.e., whispered voice test, or formally, via a Rinne's or Weber's test.
• Glossopharyngeal nerve (CN IX)
• The glossopharyngeal nerve innervates the tongue and pharynx and is involved in sensory and motor functions such as swallowing, the gag reflex, saliva production, and speaking.
• Vagus nerve (CN X)
• The vagus nerve is far-reaching and associated with structures from the pharynx to the abdomen. Vagus nerve palsy can be associated with a hoarse voice or asymmetry in the position of the uvula.
• Spinal accessory nerve (CN XI)
• The spinal accessory nerve is associated with both the sternocleidomastoid and trapezius muscles and part of the vagus nerve. When assessing the spinal accessory nerve, it's typical to focus on these muscles rather than the cranial portion of the nerve due to its close association with the vagus nerve (Damodaran et al., 2013).
• Hypoglossal nerve (CN XII)
• The last cranial nerve, the hypoglossal nerve, innervates tongue muscles. Palsy of the hypoglossal nerve is therefore associated with asymmetry or muscle wasting of the tongue.

How does this cranial nerve checklist work?

Based on the Oxford Medical guidelines (Oxford Medical Education, 2015), this cranial nerve checklist breaks the cranial nerve exam down by the cranial nerve number(s) and then even further into subtasks to complete to assess each cranial nerve thoroughly.

We've tried to keep the checklist itself concise for easy use in clinical situations, but for a more thorough description of each of the items on this checklist- take a look at each of the steps given here.

Step 1. Introduction

We have used the commonly employed acronym WIPE to structure the introduction portion of the examination concisely. Following this acronym ensures you complete the key tasks of hand hygiene, introducing yourself, confirming the patient's identity, gaining permission to perform the examination, and ensuring the patient has privacy for the examination.

Step 2. General inspection

The inspection can be very brief, but it involves assessing the patient's surroundings, general appearance, any medical paraphernalia they have with them, and any other nearby equipment or presentation features that may impact the examination.

Step 3. Cranial nerve examination

Next comes the substantive part of this exam, systematically testing the cranial nerves. The exact order of these tests is up to you and may depend on how you were taught to perform the exam and which order you feel most comfortable with. We have given the cranial nerves in order from one to twelve, with nerves that are typically tested together grouped in the checklist (III, IV, VI, IX, and X).

1. Olfactory nerve (CN I)

To test this nerve, question the patient on any recent change in the sense of taste or smell or formally assess their sense of smell using smelling bottles, e.g., coffee or peppermint, occluding one nostril at a time. 

2. Optic nerve (CN II)

Formally test visual acuity using a Snellen chart at 6m, covering one eye. Test peripheral fields by confrontation and check visual neglect. Alternatively, informally assess visual acuity using your name badge.

Reflexes to be tested include the direct pupillary, accommodation, and consensual pupillary reflexes. Ophthalmoscopy tests the red reflex, assesses the optic disc, and scans the retina. Ensure you ask the patient to look up and down to the left and right so you can check the peripheries.

3. Oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN VI)

We can group the third, fourth, and sixth cranial nerves, as these are generally all tested simultaneously. Check for smooth pursuit, strabismus, and the primary position.

4. Trigeminal nerve (CN V)

Assess ophthalmic, maxillary, and mandibular sensory branches with a piece of cotton wool for the trigeminal nerve tests. Inspect for wasting of the masseter and temporalis muscles and check for jaw resistance strength. Check corneal and jaw-jerk reflexes. 

5. Facial nerve (CN VII)

To assess the functioning of the facial nerve, ask the patient to scrunch up their eyes, look upwards and raise their eyebrows, puff out their cheeks, show their teeth, and inspect for facial asymmetry. 

6. Vestibulocochlear nerve (auditory) (CN VIII)

If hearing loss is detected, perform a gross hearing assessment followed by a Rinne test, Weber's test, otoscopy, and audiometry. 

7. Glossopharyngeal nerve (CN IX) and vagus nerve (CN X)

Assess for dysarthria or dysphonia as part of the glossopharyngeal and vagus nerve testing. Ask the patient to say "aah" and inspect the soft palate and uvula. Perform a swallow assessment or assessment of the gag reflex (Thomas et al., 2022)

8. Spinal accessory nerve (CN XI)

Ask the patient to raise their shoulders, turn their head, and keep them there while you provide resistance. Similarly, perform a head turn against resistance to assess the sternocleidomastoid muscles.

9. Hypoglossal nerve (CN XII)

To test the hypoglossal nerve, inspect the tongue for wasting and fasciculations, ask the patient to protract their tongue and inspect for deviation, and test the tongue strength against each cheek.

Step 4. Closure

Thank the patient for their time, dispose of any protective equipment, and rewash your hands.

Step 5. Next Steps

Lastly, we have left space for you to summarize your findings and add any next steps for your patient based on your findings.

Interpreting the results of the exam

We have provided space in this checklist for you to note any abnormal results, but just commenting on an abnormal result is not enough.

Interpreting the results of a cranial nerve exam requires a comprehensive understanding of both normal and abnormal findings. The key to correctly interpreting the results of a cranial nerve exam is understanding the distinct functions of each of the twelve cranial nerves. This will allow you to narrow down the potential causes of an abnormal result and choose appropriate further tests.

Observation is a crucial aspect of interpretation. Facial expressions, eye movements, and responses to stimuli provide valuable insights into the functioning of cranial nerves, especially those involved in vision, facial expression, and sensory perception. Additionally, quantitative measurements, such as assessing visual acuity or using specific scales for assessing facial muscle strength, add objective data to the interpretation.

Abnormal findings should be documented and necessitate further investigation into their cause- if not already known. The next steps for your patient will look different depending on their examination results, but there are several different options.

Next steps

Following a cranial nerve examination, the following steps involve synthesizing the gathered information to formulate a comprehensive clinical picture and determine appropriate interventions. If abnormalities or asymmetries are identified during the examination, the healthcare professional may decide to conduct further diagnostic tests to pinpoint the underlying cause. Neuroimaging, such as magnetic resonance imaging (MRI) or computed tomography (CT) scans, can provide detailed views of the brain and cranial structures, aiding in identifying lesions, tumors, or other structural anomalies.

Consultation with specialists, such as neurologists or neurosurgeons, may be recommended for a more in-depth evaluation. Laboratory tests, including blood work or cerebrospinal fluid analysis, may be ordered to investigate systemic conditions or infections that could affect cranial nerve function.

Ultimately, the next steps should be informed by the results of the cranial nerve examination, as well as the patient's wishes and your clinical experience.

Research and evidence

Cranial nerve examinations are grounded in extensive research and evidence, reflecting an understanding of neuroanatomy and physiology that has deepened over time. The foundation of cranial nerve examinations lies in the intricate network of twelve pairs of cranial nerves that emerge directly from the brain, each serving distinct sensory and motor functions.

Numerous research studies have elucidated the specific roles of each cranial nerve, providing insights into their pathways, functions, and potential abnormalities. Magnetic resonance imaging (MRI) and other imaging modalities have allowed researchers to visualize the intricate structures associated with cranial nerves, enhancing our knowledge of their anatomical relationships.

These investigations have refined examination techniques and identified correlations between specific cranial nerve abnormalities and various neurological disorders. This evidence-based approach ensures that cranial nerve examinations are not merely routine procedures but are rooted in a robust scientific foundation, allowing healthcare professionals to detect abnormalities, make accurate diagnoses, and implement appropriate interventions.

Despite their long history, medical imaging techniques have somewhat supplanted the cranial nerve examination in recent years (Damodaran et al., 2014). As multiple potential diagnoses lead to an impairment in one or more of the cranial nerves' functions, the diagnostic specificity of the cranial nerve exam is low (Taylor et al., 2021). However, this can be reduced by standardizing the cranial nerve exam procedure to ensure the most reliable results are obtained from the examination.

References

Damodaran O, Rizk E, Rodriguez J, Lee G. (2014) Cranial nerve assessment: a concise guide to clinical examination. Clin Anat. 27(1):25-30. 

Martini, F., Ober, W., Nath, J., Bartholomew, E., & Petti, K. (2017). Visual Anatomy and Pathology. New York: Pearson Education Inc.

Reese V, M Das J, Al Khalili Y. Cranial Nerve Testing. [Updated 2022 Sep 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.

Taylor A, Mourad F, Kerry R, Hutting N. (2021) A guide to cranial nerve testing for musculoskeletal clinicians. J Man Manip Ther. 29(6):376-389. doi: 10.1080/10669817.2021.1937813.

Thomas K, Minutello K, M Das J. Neuroanatomy, Cranial Nerve 9 (Glossopharyngeal) [Updated 2022 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539877/

Cranial Nerve Examination. (2015) Retrieved from Oxford Medical Education:https://oxfordmedicaleducation.com/clinical-examinations/cranial-nerve-examination