Cranial nerve exams are a vital part of the neurological screen following head trauma. While concussions are considered functional injuries (with no structural damage on imaging), signs of cranial nerve dysfunction may point to more serious complications, including:

  • Brain bleeds
  • Skull fractures
  • Cranial nerve palsies or compression
  • Herniation syndromes

A fast, reliable cranial nerve screen helps distinguish a typical concussion from a more severe or emergent condition — which is critical in sports, emergency, and outpatient care settings.

Note that this is a shortened version of the deep-dive by Matt Nelson. 

 

Cranial Nerves Overview (CN I–XII)

There are 12 cranial nerves, and each controls specific sensory or motor functions — many of which are relevant to post-concussion screening.

CNNameFunction
IOlfactorySmell
IIOpticVision
IIIOculomotorEye movement, pupil constriction
IVTrochlearEye movement (superior oblique)
VTrigeminalFacial sensation, chewing
VIAbducensEye movement (lateral rectus)
VIIFacialFacial expression, taste (anterior tongue)
VIIIVestibulocochlearHearing, balance
IXGlossopharyngealTaste, swallowing, gag reflex
XVagusSwallowing, voice, parasympathetic control
XIAccessoryShoulder shrug, head rotation
XIIHypoglossalTongue movement

In concussion care, CN II–XII are typically the primary focus, as CN I (olfaction) is less frequently tested and less reliable post-injury.

How to Perform a Focused Cranial Nerve Screen

This screening version is designed for clinicians working in concussion settings (e.g., PTs, DCs, ATs, MDs) to quickly rule out red flags. Below is a more detailed description of each test, including what is considered normal and abnormal:

CN II (Optic)

  • Visual acuity: Ask the patient to read from a near card or Snellen chart. Normal: clear and equal vision in both eyes. Abnormal: blurry vision, unequal acuity.
  • Visual fields: Test peripheral vision by wiggling fingers in each quadrant while the patient focuses straight ahead. Normal: full peripheral fields. Abnormal: field cuts or asymmetry.
  • Fundoscopy (if trained): Examine the optic disc for papilledema. Normal: clear disc margins. Abnormal: disc swelling may indicate increased intracranial pressure.

CN III, IV, VI (Oculomotor, Trochlear, Abducens)

  • Extraocular movements: Ask the patient to follow your finger in an “H” pattern. Normal: full, smooth, symmetric movement. Abnormal: restricted movement, diplopia, or nystagmus.
  • Pupil reaction: Shine a light into each eye and observe for direct and consensual response. Normal: pupils equal, round, reactive to light. Abnormal: anisocoria, sluggish response, or non-reactive pupil.

CN V (Trigeminal)

  • Sensory testing: Lightly touch the forehead, cheeks, and jaw with a cotton swab or fingertip. Normal: equal sensation. Abnormal: numbness or asymmetry.
  • Motor testing: Have the patient clench their jaw and palpate masseter and temporalis muscles. Normal: strong, symmetrical contraction. Abnormal: weakness or asymmetry.

CN VII (Facial)

  • Ask the patient to perform facial movements: raise eyebrows, smile, puff cheeks, and close eyes tightly. Normal: symmetrical motion across all expressions. Abnormal: drooping on one side, inability to perform specific actions.

CN VIII (Vestibulocochlear)

  • Hearing test: Rub fingers near each ear or use a tuning fork (512 Hz). Normal: equal hearing bilaterally. Abnormal: diminished or absent hearing on one side.
  • Balance assessment: Ask if the patient has dizziness or vertigo. Consider tandem gait or Romberg test for further evaluation. Abnormal findings suggest vestibular involvement.

CN IX & X (Glossopharyngeal & Vagus)

  • Voice quality: Ask the patient to speak. Normal: clear voice. Abnormal: hoarseness or nasal tone.
  • Swallowing: Ask if there is difficulty swallowing. Normal: smooth swallow. Abnormal: coughing or choking.
  • Uvula movement: Ask patient to say “Ahh” and watch for uvula movement. Normal: midline elevation. Abnormal: deviation indicates contralateral weakness.

CN XI (Accessory)

  • Ask the patient to shrug shoulders and turn head against resistance. Normal: strong and symmetrical strength. Abnormal: weakness or asymmetry on one side.

CN XII (Hypoglossal)

  • Ask patient to stick out their tongue. Normal: midline tongue without atrophy. Abnormal: deviation (toward side of lesion), fasciculations, or atrophy.

Tip: Combine efficiency with thoroughness — this screen can be done in under 3–5 minutes if practiced.** Combine efficiency with thoroughness — this screen can be done in under 3–5 minutes if practiced.

 

When to Refer Immediately

Red flag findings during a cranial nerve exam include:

  • Unequal or fixed pupils
  • Slurred speech or dysphagia
  • Facial droop or asymmetry
  • Tongue deviation
  • Ocular misalignment or impaired movement
  • Sudden hearing loss or imbalance

These may suggest:

  • Cranial nerve compression (hematoma, herniation)
  • Brainstem involvement
  • Emergent neurologic pathology beyond simple concussion

If any of these are present, refer immediately for advanced imaging and medical evaluation.

Related Clinical Education

For Practitioners

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REFERENCES:
  1. Silverberg ND, et al. Assessment of mild traumatic brain injury and its sequelae. J Head Trauma Rehabil. 2019;34(3):161–170.
  2. Duhaime A-C, et al. The spectrum of concussion: Diagnosis, pathophysiology, and clinical management. Nat Rev Neurol. 2021;17(1):1–13.
  3. Ellis MJ, et al. Emergency evaluation and management of concussion in children and adolescents. Pediatrics. 2019;144(6):e20192757.