5.3 Neurological Screening & Cranial Nerve Assessment
Key Takeaways
- Myotomes, dermatomes, and deep tendon reflexes (biceps C5, brachioradialis C6, triceps C7, patella L4, Achilles S1) are the upper- and lower-quarter screens; the triceps reflex is not C6
- Lower motor neuron lesions cause hyporeflexia and myotomal/dermatomal loss; upper motor neuron lesions cause hyperreflexia, spasticity, Babinski, clonus, and Hoffmann signs
- Cranial nerves I–XII have sport-specific jobs: CN II vision, III/IV/VI extraocular motion and pupils, V face/mastication, VII expression, VIII hearing/balance, IX/X swallow and gag, XI SCM/trapezius, XII tongue
- Cauda equina (saddle anesthesia, bowel/bladder change, bilateral leg symptoms) is an emergency; Cook's myelopathy cluster (gait, Hoffmann, inverted supinator, Babinski, age >45) is 94% sensitive at one of five and highly specific at three of five
- Sideline cranial-nerve screening after head impact is a red-flag filter; full concussion protocol (SCAT and return-to-play) belongs to Domain III and is not a substitute for recognizing herniation, skull fracture, or myelopathy
5.3 Neurological Screening & Cranial Nerve Assessment
A neurological screen is part of PA8 task 0202, not a party trick for head-injury days. You run an upper-quarter or lower-quarter screen whenever the history includes spinal pain, radiating symptoms, numbness, unexplained weakness, headache, head impact, gait change, or any red flag from section 5.1. You also screen the limb you are about to stress so you do not miss a nerve-root or cord problem that a special test cannot fix.
This is still the system. Cervical and lumbar special tests, stingers, and full concussion return-to-play live in later chapters and Domain III. Here you must be able to map a finding to a root, a peripheral nerve, the cord, the brain, or a cranial nerve — and know which of those is an emergency.
Myotomes: Key Muscles Held Long Enough to Matter
A myotome is the muscle group innervated primarily by one spinal root. Test isometrically, compare sides, and hold about 5 seconds so fatigable weakness appears. Pain-limited give-way is not the same as neurologic weakness; write down which you saw.
| Root | Key myotome action (ASIA / common AT screen) | Clinic cue |
|---|---|---|
| C5 | Elbow flexion (biceps, brachialis); also shoulder abduction (deltoid) | Weak biceps plus a diminished biceps reflex |
| C6 | Wrist extension (extensor carpi radialis); elbow flexion still shares C6 | Weak wrist extensors; this is not the triceps |
| C7 | Elbow extension (triceps); wrist flexion | Weak push-up / dip strength |
| C8 | Finger flexion (flexor digitorum profundus, distal grip) | Weak grip, little-finger side of the hand |
| T1 | Finger abduction/adduction (intrinsics, abductor digiti minimi) | Intrinsic wasting in chronic lesions |
| L2 | Hip flexion (iliopsoas) | Trouble lifting the thigh onto a table |
| L3 | Knee extension (quadriceps) | Trouble rising from a chair |
| L4 | Ankle dorsiflexion (tibialis anterior) | Foot slap, weak heel walk |
| L5 | Great-toe extension (extensor hallucis longus) | Weak heel-walk plus 1st-web sensory loss |
| S1 | Ankle plantarflexion (gastrocnemius–soleus); eversion (peroneals) | Weak toe walking; this pairs with the Achilles reflex |
| S2 | Knee flexion (hamstrings) | Often tested with S1 in a lower-quarter screen |
A single weak muscle can be peripheral nerve (long thoracic vs C7, peroneal vs L4/L5). A myotomal pattern plus matching dermatome and reflex is root. That distinction is diagnosis (0203) built on this screen.
Dermatomes: Map the Skin, Then Name the Pattern
Test light touch first; add sharp/dull or two-point when the story is sensory. Compare sides. Ask the athlete to close the eyes so they do not "help."
| Root | Sensory landmark used in sports medicine |
|---|---|
| C4 | Cape / top of shoulder |
| C5 | Lateral arm |
| C6 | Lateral forearm, thumb, and index finger |
| C7 | Middle finger |
| C8 | Medial hand and little finger |
| T1 | Medial forearm |
| L1 | Groin / upper anterior thigh |
| L2 | Mid anterior thigh |
| L3 | Medial knee |
| L4 | Medial leg and medial ankle |
| L5 | Dorsum of the foot and first web space |
| S1 | Lateral foot and little toe |
| S2 | Posterior thigh |
| S3–S5 | Perineum / saddle — ask and test when cauda equina is possible |
A glove or stocking pattern is peripheral neuropathy or effort/hyperventilation, not a single root. A well-mapped median-nerve distribution is carpal tunnel or an upper-trunk/median lesion, not "C6 and C7." If you cannot describe the pattern in one sentence, you do not yet have a neurologic diagnosis.
Deep Tendon Reflexes — Including the C6/Triceps Trap
Grade 0 (absent), 1+ (diminished), 2+ (normal), 3+ (brisk), 4+ (clonus / pathologic). Compare sides. Use Jendrassik (locked fingers, gentle pull) if a reflex is hard to find, and document that you reinforced it.
| Reflex | Primary root the BOC expects | Muscle tapped |
|---|---|---|
| Biceps | C5 (C5–C6) | Biceps tendon in the cubital fossa |
| Brachioradialis | C6 | Distal radius / brachioradialis tendon |
| Triceps | C7 (C7–C8) | Triceps tendon just above the olecranon |
| Patellar | L4 (L3–L4) | Patellar tendon |
| Achilles | S1 | Achilles tendon |
Trap: calling a C6 reflex the triceps. C6 is brachioradialis (biceps is shared with C5). Triceps is C7. Mixing those two is a classic item. Hyporeflexia at one level plus matching myotome/dermatome supports a lower motor neuron (LMN) root lesion. Hyperreflexia below a spinal level supports upper motor neuron (UMN) / cord disease.
Upper Versus Lower Motor Neuron Signs
| Feature | LMN (root, plexus, peripheral nerve) | UMN (brain, spinal cord) |
|---|---|---|
| Weakness | Myotomal or peripheral-nerve pattern | More pyramidal; often legs and hands, may be bilateral |
| Tone | Normal or decreased (flaccid) | Increased (spastic) |
| Reflexes | Decreased or absent | Increased |
| Babinski / clonus / Hoffmann | Absent (flexor plantar is normal in adults) | Often present |
| Fasciculations / atrophy | May appear | Not the early picture |
| Sensory | Dermatome or peripheral nerve | May be a sensory level; saddle sparing or involvement depends on the lesion |
Babinski: stroke the lateral plantar surface toward the great toe. Adult pathologic response is great-toe extension with fanning of the toes (extensor plantar). Withdrawal from ticklishness is not a Babinski; go slowly and watch the first movement of the hallux.
Clonus: rapid dorsiflexion stretch of the ankle. A beat or two can be physiologic in anxious athletes. Sustained clonus (generally three or more beats that do not fatigue immediately, and certainly unsustained versus sustained is interpreted in context) is a UMN red flag.
Hoffmann: flick the distal middle finger. Pathologic: involuntary flexion of the thumb and/or index. Suggests corticospinal involvement, often cervical. It can be present in some hyperreflexic but otherwise normal people; cluster it, do not crown it.
Inverted supinator (inverted brachioradialis) sign: tap the brachioradialis insertion and the fingers flex instead of the elbow flexing. Another cervical UMN sign used in Cook's cluster.
Cranial Nerves I–XII for Sports Medicine
A sideline or clinic cranial-nerve screen can be done in a few minutes without special equipment. Taylor, Mueller, and colleagues' musculoskeletal CN guide (J Man Manip Ther 2021) and standard neurologic texts agree on the functions below. After head impact you are screening for focal deficit, herniation, skull-base fracture, and cranial neuropathy, not completing a neuropsychology battery.
| CN | Name | Type | Screen in athletes | Sport-relevant failure |
|---|---|---|---|---|
| I | Olfactory | Sensory | Identify coffee or an alcohol wipe in each nostril (not ammonia — that hits trigeminal pain fibers) | Anosmia after occipital blow or cribriform-plate trauma; often deferred on the sideline |
| II | Optic | Sensory | Visual acuity (near card or scoreboard), visual fields by confrontation, pupils (afferent limb of the light reflex; swinging-flashlight for relative afferent pupillary defect) | Acute vision loss, field cut, papilledema is a physician emergency |
| III | Oculomotor | Motor | Adduction, elevation, depression, eyelid opening, pupil constriction (efferent limb) | "Down and out" eye, ptosis, blown pupil — think third-nerve palsy / uncal herniation, not a simple concussion |
| IV | Trochlear | Motor | Depress the adducted eye (superior oblique); look down and in, as if descending stairs) | Vertical diplopia, head tilt |
| V | Trigeminal | Mixed | Light touch in V1/V2/V3; clench jaw (masseter/temporalis); corneal reflex sensory limb | Facial numbness, weak bite; do not confuse with CN VII motor loss |
| VI | Abducens | Motor | Abduction (lateral rectus) | Horizontal diplopia worse looking toward the lesion; CN VI is vulnerable when intracranial pressure rises |
| VII | Facial | Mixed | Raise brows, close eyes against resistance, smile, show teeth; taste anterior two-thirds is optional on the field | Entire hemiface weak = peripheral (Bell's). Forehead spared = central UMN pattern |
| VIII | Vestibulocochlear | Sensory | Finger-rub or whisper hearing; nystagmus; balance (also cerebellar/vestibular overlap) | Hearing loss, Battle sign, hemotympanum → skull-base fracture pathway |
| IX | Glossopharyngeal | Mixed | Swallow, gag sensory limb, voice quality, "ahh" | Dysphagia; isolated IX is uncommon |
| X | Vagus | Mixed | Palate elevation, uvula (deviates away from a unilateral lesion), gag motor, phonation | Hoarseness, nasal regurgitation, uvula asymmetry after penetrating or high cervical trauma |
| XI | Accessory | Motor | Shoulder shrug (trapezius); rotate the head against resistance (sternocleidomastoid turns the head to the opposite side) | Asymmetric shrug; lateral scapular winging pattern from trapezius palsy vs medial winging from long thoracic nerve |
| XII | Hypoglossal | Motor | Protrude the tongue; it deviates toward the lesion | Dysarthria, bite-the-tongue weakness after mandible or high cervical trauma |
Memory that actually helps on items: II sees, III constricts the pupil, III/IV/VI move the globe, V feels the face and chews, VII makes the face move, VIII hears and balances, IX/X swallow and gag, XI shrugs and turns the head, XII sticks out the tongue.
Concussion preview, not the protocol: after a suspected concussion you still glance at pupils, extraocular motion, facial symmetry, hearing, and tongue. Unequal or unreactive pupils, deteriorating consciousness, seizure, repeated vomiting, severe or progressive headache, and focal weakness are EMS, not a quiet SCAT in the locker room. Standardized sideline concussion tools and return-to-play staging are Domain III (task 0303 and related content). Do not pretend a normal CN screen "clears" concussion; concussion is a clinical diagnosis that can exist with intact cranial nerves.
Upper-Quarter Versus Lower-Quarter Screens
Upper-quarter screen (typical): cervical active motion (stop for cord or vascular red flags), myotomes C5–T1, dermatomes C4–T1, reflexes biceps/brachioradialis/triceps, Hoffmann and inverted supinator if myelopathy is in the differential, and a median neurodynamic test if radiculopathy is in the differential.
Lower-quarter screen: lumbar active motion as tolerated, myotomes L2–S2, dermatomes L1–S2 plus saddle when indicated, reflexes patellar and Achilles, Babinski and clonus, and a straight-leg raise or slump if radicular pain is in the story.
You do not need both full screens on every ankle sprain. You do need the relevant quarter, and you need the cord tests when the story is bilateral, gait-clumsy, or progressive.
Cerebellar and Balance (Brief)
- Romberg: feet together, arms at sides, then eyes closed. Excessive sway or a fall with eyes closed points more to proprioceptive or vestibular loss than to midline cerebellum (which often sways with eyes open too). Guard the athlete.
- Tandem gait: heel-to-toe. Ataxia here after head impact is a remove-from-play finding and, if severe or progressive, an emergency finding.
- Finger-to-nose and heel-to-shin: look for dysmetria.
- Rapid alternating movements (pronation/supination): dysdiadochokinesia.
These overlap concussion balance testing (BESS and tandem on SCAT) without replacing that protocol.
Cauda Equina and Cervical Myelopathy
Cauda equina syndrome is compression of the lumbar and sacral nerve roots in the thecal sac, usually by a massive disc herniation, tumor, or trauma. Red flags: saddle anesthesia or hypesthesia, new bladder dysfunction (retention is often earlier than overflow incontinence), bowel dysfunction, sexual dysfunction, bilateral leg pain or weakness, and reduced anal tone. No single symptom is a perfect SnNOut screen; UK GIRFT/NICE-style guidance is a low threshold for emergency MRI because delayed decompression risks permanent incontinence and sexual dysfunction. An athletic trainer who hears "I cannot feel myself wipe" during a lumbar exam does not schedule McKenzie for Thursday.
Cervical myelopathy is cord compression in the neck: clumsy hands, loss of fine motor (buttons, handwriting), gait disturbance, hyperreflexia, and UMN signs in the legs with possible LMN findings at the level of compression. Cook, Brown, Isaacs, Roman, Davis, and Richardson (J Man Manip Ther 2010) clustered five findings — gait deviation, Hoffmann, inverted supinator, Babinski, age >45. In their sample, one of five positives had sensitivity 0.94 and LR− 0.18 (useful to reduce suspicion when none of the cluster is present, interpreted cautiously). Three of five had specificity 0.99 and LR+ 30.9 (post-test probability 94% from a 35% pretest in that surgical-clinic mix). Later reviews (AO Spine RECODE-DCM, 2024) note that individual UMN signs are often specific but insensitive, which is why you cluster and why a single negative Hoffmann never clears a myelopathic history. Refer; do not manipulate a suspected cord.
Worked Example: Root Versus Cord Versus Cranial Nerve
A 17-year-old linebacker reports right-arm burning after a hit that drove his head toward the opposite shoulder. Findings: weak wrist extension and elbow flexion, sensory loss on the thumb, diminished brachioradialis reflex, normal triceps, no Hoffmann, no clonus, normal gait, intact extraocular motion. That is a C6 root / upper-trunk stinger pattern (LMN), not a C7 triceps problem and not myelopathy. Withhold from contact until strength and sensation recover and the cervical exam is safe — details belong in the cervical chapter — but you already used this section's map.
Change the findings: bilateral hand numbness, clumsy gait, positive Hoffmann, sustained clonus. That is cord until imaging, not a burner, and not a "next practice" decision.
Change them again: after a knockout, the left eye will not abduct and diplopia is worse looking left. That is left CN VI, an indication for emergency evaluation, not a quiet return-to-learn sheet alone.
Trap: calling C6 the triceps reflex. Triceps is C7. Brachioradialis is C6. Get that pair right and a surprising number of neuro items fall over.
Which deep tendon reflex is correctly paired with its primary nerve root for an athletic training neurological screen?
After a head impact, an athlete has horizontal diplopia that worsens looking to the left, and the left eye does not abduct. Which cranial nerve is most likely affected?
Which cluster of findings is most consistent with cervical myelopathy (upper motor neuron / spinal cord) rather than a single lumbar nerve-root lesion?