Spine · Classification

ASIA Impairment Scale (Frankel Scale)

The ASIA Impairment Scale (AIS) — the ASIA/ISCoS international standard that replaced the older Frankel scale — grades the completeness of a spinal cord injury from A (complete) to E (normal). The make-or-break discriminator is SACRAL SPARING: any preserved sensation at S4-S5 (pinprick or light touch) OR voluntary anal contraction makes the injury INCOMPLETE (AIS B or better); absent both = COMPLETE (AIS A). AIS B is sensory-incomplete (sensation including S4-S5, no motor below the level); AIS C and D are motor-incomplete, separated by a muscle count — C if more than half of key muscles below the level are grade under 3, D if at least half are grade 3 or more; E is normal. The exam is a standardised bedside test of 10 key myotomes (MRC 0-5) and 28 sensory dermatomes (pinprick + light touch), and the AIS grade at 72 hours (once spinal shock has resolved) is the strongest early predictor of functional outcome.

Grades A–EA complete → E normal

Sacral sparingS4-S5 → complete vs incomplete

10 / 28Key myotomes / sensory points (bilateral)

72 h gradeStrongest early outcome predictor

Bottom lineTest S4-S5 sensation and voluntary anal contraction FIRST — they decide complete (A) vs incomplete (B–D). B = sensory only; C = motor incomplete, under half of key muscles ≥ grade 3; D = motor incomplete, at least half ≥ grade 3; E = normal. Wait for spinal shock to resolve (bulbocavernosus reflex returns) before confirming AIS A; grade at 72 h drives prognosis, and early (under 24 h) decompression improves AIS conversion.

Traps that cost marks

Not testing sacral sparing first. S4-S5 sensation (pinprick/light touch) and voluntary anal contraction decide complete (A) vs incomplete (B+) — test them before anything else; missing them mis-grades the whole injury.
Declaring AIS A during spinal shock. All reflexes are absent in spinal shock and the injury can look falsely complete — wait for the bulbocavernosus reflex to return before confirming a complete injury.
Counting from the wrong level. The C-vs-D muscle count is of key muscles below the NEUROLOGICAL level, not the bony injury level.
Muddling C and D. C = fewer than half of key muscles below the level reach grade 3; D = at least half reach grade 3+.
Forgetting B is sensory-only. AIS B has sacral sensation but no motor below the level — any motor below the level makes it C/D.
ZPP confusion. The zone of partial preservation is documented only for complete (AIS A) injuries.

The ASIA Impairment Scale — grades A to E

ASIA Impairment Scale grades A to E, each with a body figure showing the preserved sensory and motor function and the sacral-sparing status — The ASIA Impairment Scale (AIS) / Frankel scale, grades A–E. A — complete, no sensory or motor at S4-S5 (no sacral sparing). B — sensory incomplete (sensation including S4-S5 preserved, no motor below the level). C — motor incomplete, more than half of key muscles below the level grade under 3. D — motor incomplete, at least half of key muscles below the level grade 3 or more. E — normal. Grading depends on the standardised neurological examination, not on imaging appearance.Credit: OrthoVellum illustration

Category: Complete
Definition: No motor or sensory function preserved in sacral segments S4-S5
Key discriminator: No sacral sparing at all

Category: Sensory incomplete
Definition: Sensory but not motor function preserved below the neurological level, including S4-S5
Key discriminator: Sacral sensation present, no motor below the level

Category: Motor incomplete
Definition: Motor function preserved below the level AND more than half of key muscles below the level grade under 3
Key discriminator: Motor incomplete; fewer than half of key muscles reach grade 3

Category: Motor incomplete
Definition: Motor function preserved below the level AND at least half of key muscles below the level grade 3 or more
Key discriminator: At least half of key muscles reach grade 3 or better

Category: Normal
Definition: Motor and sensory function normal (in a patient with prior deficits)
Key discriminator: All myotomes 5/5, all dermatomes intact

ASIA Impairment Scale classification
Grade	Category	Definition	Key discriminator
A	Complete	No motor or sensory function preserved in sacral segments S4-S5	No sacral sparing at all
B	Sensory incomplete	Sensory but not motor function preserved below the neurological level, including S4-S5	Sacral sensation present, no motor below the level
C	Motor incomplete	Motor function preserved below the level AND more than half of key muscles below the level grade under 3	Motor incomplete; fewer than half of key muscles reach grade 3
D	Motor incomplete	Motor function preserved below the level AND at least half of key muscles below the level grade 3 or more	At least half of key muscles reach grade 3 or better
E	Normal	Motor and sensory function normal (in a patient with prior deficits)	All myotomes 5/5, all dermatomes intact

Mnemonic

A-B-C-D-EAB-CDE: the five grades

Absent

Complete — no motor or sensory at S4-S5 (no sacral sparing)

Below sensory only

Sensation preserved including S4-S5, but no motor below the level

Crummy motor

Motor incomplete — more than half of key muscles below the level grade under 3

Decent motor

Motor incomplete — at least half of key muscles below the level grade 3 or more

Excellent

Normal motor and sensory function

Hook:A Absent, B Below-sensory-only, C Crummy motor (under half ≥3), D Decent motor (at least half ≥3), E Excellent (normal).

Check sacral sparing FIRST

The single most important step in the ASIA exam is testing sacral sensation (S4-S5 pinprick/light touch) and voluntary anal contraction first. If either is preserved, the injury is automatically incomplete (AIS B or better) — a finding that changes prognosis dramatically. Absent both = complete (AIS A).

The named incomplete cord syndromes (the pattern the AIS grade doesn't capture)

The AIS grades completeness; it does not describe the clinical pattern of an incomplete injury — and the examiner will ask you to recognise the classic syndromes, each with a distinctive deficit and prognosis:

Central cord syndrome — the commonest incomplete SCI. Typically an older patient with cervical spondylosis who sustains a hyperextension injury (often without fracture), or a younger high-energy injury. Upper limbs are affected more than lower limbs (distal upper-limb/hand weakness worst), with variable sensory loss and bladder dysfunction. Generally a favourable recovery (lower limbs and bladder return before intrinsic hand function). Mechanism: central cord damage where the medially-situated upper-limb corticospinal fibres lie.
Anterior cord syndrome — anterior two-thirds of the cord (anterior spinal artery territory). Motor (corticospinal) and pain/temperature (spinothalamic) lost below the level, with preserved proprioception, vibration and light touch (dorsal columns). The worst prognosis of the incomplete syndromes.
Brown-Séquard (cord hemisection) — ipsilateral motor (corticospinal) and dorsal-column (proprioception/vibration) loss, with contralateral pain/temperature loss (spinothalamic decussates) a few levels below. Often penetrating trauma. The best prognosis of the incomplete syndromes — most regain ambulation and bowel/bladder control.
Posterior cord syndrome — rare; isolated dorsal-column loss (proprioception/vibration) with preserved motor and pain/temperature, producing a sensory ataxia.
Conus medullaris vs cauda equina — the conus (cord termination, ~T12-L1) gives a mixed UMN + LMN picture with early, symmetric bowel/bladder and sexual dysfunction and saddle anaesthesia; the cauda equina (nerve roots below the conus) is a pure LMN, areflexic, asymmetric lesion with radicular leg pain, saddle anaesthesia and later/variable sphincter involvement — a surgical emergency.

Four spinal cord cross-sections showing the damaged region in central cord, anterior cord, Brown-Séquard and posterior cord syndromes. — The classic incomplete cord syndromes that the AIS grade does NOT describe — shown on cord cross-sections with the damaged region in red. Central cord (central, around the canal): arms worse than legs, favourable recovery. Anterior cord (anterior two-thirds): motor and pain/temperature lost with the dorsal columns spared — the worst prognosis. Brown-Séquard (hemisection): ipsilateral motor and proprioception loss with contralateral pain/temperature loss — the best prognosis. Posterior cord (dorsal columns): proprioception and vibration lost (sensory ataxia).Credit: OrthoVellum (AI-generated illustration)

Key muscle groups (myotomes) & motor scoring

The ASIA standard motor examination tests 10 key muscle groups bilaterally, each scored 0–5 on the MRC scale (total motor score 100; 50 per side).

Muscle: Elbow flexors (biceps)
Action tested: Flex elbow against gravity and resistance
MRC 0–5: 0 nil → 5 normal

Muscle: Wrist extensors (ECRL/ECRB)
Action tested: Extend wrist
MRC 0–5: 0 nil → 5 normal

Muscle: Elbow extensors (triceps)
Action tested: Extend elbow
MRC 0–5: 0 nil → 5 normal

Muscle: Finger flexors (FDP, middle finger)
Action tested: Flex middle finger DIPJ
MRC 0–5: 0 nil → 5 normal

Muscle: Small finger abductors (ADM)
Action tested: Abduct little finger
MRC 0–5: 0 nil → 5 normal

Muscle: Hip flexors (iliopsoas)
Action tested: Flex hip
MRC 0–5: 0 nil → 5 normal

Muscle: Knee extensors (quadriceps)
Action tested: Extend knee
MRC 0–5: 0 nil → 5 normal

Muscle: Ankle dorsiflexors (tibialis anterior)
Action tested: Dorsiflex ankle
MRC 0–5: 0 nil → 5 normal

Muscle: Long toe extensors (EHL)
Action tested: Extend the great toe
MRC 0–5: 0 nil → 5 normal

Muscle: Ankle plantar flexors (gastrocsoleus)
Action tested: Plantarflex ankle
MRC 0–5: 0 nil → 5 normal

The ten key muscle groups
Myotome	Muscle	Action tested	MRC 0–5
C5	Elbow flexors (biceps)	Flex elbow against gravity and resistance	0 nil → 5 normal
C6	Wrist extensors (ECRL/ECRB)	Extend wrist	0 nil → 5 normal
C7	Elbow extensors (triceps)	Extend elbow	0 nil → 5 normal
C8	Finger flexors (FDP, middle finger)	Flex middle finger DIPJ	0 nil → 5 normal
T1	Small finger abductors (ADM)	Abduct little finger	0 nil → 5 normal
L2	Hip flexors (iliopsoas)	Flex hip	0 nil → 5 normal
L3	Knee extensors (quadriceps)	Extend knee	0 nil → 5 normal
L4	Ankle dorsiflexors (tibialis anterior)	Dorsiflex ankle	0 nil → 5 normal
L5	Long toe extensors (EHL)	Extend the great toe	0 nil → 5 normal
S1	Ankle plantar flexors (gastrocsoleus)	Plantarflex ankle	0 nil → 5 normal

Mnemonic

C5–T1, L2–S1The 10 key myotomes, top to bottom

Elbow flexion

Biceps

Wrist extension

ECRL/ECRB

Elbow extension

Triceps

Finger flexion

FDP (middle finger)

Finger abduction

Abductor digiti minimi

Hip flexion

Iliopsoas

Knee extension

Quadriceps

Ankle dorsiflexion

Tibialis anterior

Great-toe extension

EHL

Ankle plantarflexion

Gastrocsoleus

Hook:Five upper-limb (C5→T1) then five lower-limb (L2→S1), tested both sides, each 0–5. Don't skip L4 (ankle dorsiflexion).

Sensory examination & dermatomes

Each of 28 key sensory points is tested bilaterally for pinprick (sharp/dull) and light touch (cotton wisp), scored 0 (absent), 1 (impaired) or 2 (normal). Total sensory score 112 (56 per side, pinprick and light touch combined).

Dermatome map of the body labelled by spinal level (C3 to L5) used for the ASIA sensory examination — The dermatome map underpinning the ASIA sensory examination - each labelled level (C2-S5) corresponds to a key sensory point tested for pinprick and light touch. The neurological level is the most caudal dermatome with normal (grade 2) sensation (and antigravity strength) bilaterally; the S4-S5 dermatome (perianal) is the all-important sacral-sparing check.Credit: Hy9etb, CC BY 3.0, via Wikimedia Commons

The S4-S5 dermatome must be tested explicitly — it determines sacral sparing and therefore complete vs incomplete status.
Anal sensation is recorded separately but contributes to the sacral-sparing assessment.
The neurological level is the most caudal segment with normal sensation (grade 2) AND antigravity strength (grade 3 or more) on both sides.

Zone of partial preservation & key terminology

Neurological level

Definition: Most caudal segment with normal sensation AND motor grade 3 or more on both sides
Clinical relevance: May differ left vs right; record the most rostral

Zone of partial preservation (ZPP)

Definition: Dermatomes/myotomes below the neurological level that remain partially innervated (COMPLETE injuries only)
Clinical relevance: Recorded for AIS A; gives prognostic information on potential recovery

Sacral sparing

Definition: Any preserved sensation (pinprick or light touch) at S4-S5 OR voluntary anal contraction
Clinical relevance: Present = incomplete; absent = complete — the fundamental discriminator

Complete injury

Definition: No sacral sparing; AIS grade A
Clinical relevance: ZPP documented; worst prognosis

Incomplete injury

Definition: Sacral sparing present; AIS grade B, C or D
Clinical relevance: Potential for further recovery; outcome depends on the 72-hour AIS grade

Key terminology in ASIA classification
Term	Definition	Clinical relevance
Neurological level	Most caudal segment with normal sensation AND motor grade 3 or more on both sides	May differ left vs right; record the most rostral
Zone of partial preservation (ZPP)	Dermatomes/myotomes below the neurological level that remain partially innervated (COMPLETE injuries only)	Recorded for AIS A; gives prognostic information on potential recovery
Sacral sparing	Any preserved sensation (pinprick or light touch) at S4-S5 OR voluntary anal contraction	Present = incomplete; absent = complete — the fundamental discriminator
Complete injury	No sacral sparing; AIS grade A	ZPP documented; worst prognosis
Incomplete injury	Sacral sparing present; AIS grade B, C or D	Potential for further recovery; outcome depends on the 72-hour AIS grade

Caution

The ASIA exam should be interpreted after spinal shock has resolved (return of the bulbocavernosus reflex). During spinal shock all reflexes are absent and the injury may falsely appear complete. Serial examinations over the first 48–72 hours are essential — an initial AIS A that converts to an incomplete grade has a fundamentally different prognosis.

Spinal shock vs neurogenic shock — and the acute-SCI management the AIS grade implies

The two "shocks" are constantly confused and constantly examined — they are completely different things:

Spinal shock is a neurological phenomenon — transient loss of all cord function and reflexes (flaccid areflexia, absent bulbocavernosus reflex) below the level immediately after injury, resolving over days to weeks. The bulbocavernosus reflex (S2-S4) is the first to return and marks its end; only then can a complete injury be confirmed.
Neurogenic shock is a haemodynamic/distributive shock from loss of sympathetic outflow in injuries above ~T6 → hypotension WITH bradycardia (and warm, vasodilated peripheries) — distinct from haemorrhagic shock (which gives tachycardia). Treat with fluids, vasopressors/inotropes, and atropine for symptomatic bradycardia.

Acute haemodynamic target

AANS/CNS guidance recommends maintaining MAP ~85–90 mmHg for about 5–7 days and avoiding hypotension (systolic under 90 mmHg) to optimise spinal-cord perfusion — alongside early (under 24 h) decompression.

Steroids (the NASCIS/methylprednisolone controversy)

high-dose methylprednisolone is no longer routinely recommended — the NASCIS II/III benefits were marginal/post-hoc and outweighed by complications (pneumonia, sepsis, GI bleeding); current AANS/CNS guidance does not endorse it as a standard of care.

Autonomic dysreflexia (the later complication)

in injuries at or above ~T6, a noxious stimulus below the level (a distended bladder, constipation, pressure sore) triggers a massive sympathetic discharge → severe paroxysmal hypertension, pounding headache, flushing and sweating above the level, with reflex bradycardia. It is an emergency (stroke/seizure risk): sit the patient upright, loosen constrictions, find and remove the trigger (relieve the bladder/disimpact the bowel) and give a short-acting antihypertensive (e.g. GTN, nifedipine) if the blood pressure persists.

Prognostic significance

Axial T2 cervical MRI showing symmetric anterior cord hyperintensity (owl-eyes / snake-eyes sign) of spinal cord injury — Axial T2 cervical MRI showing the 'owl-eyes' (snake-eyes) sign - symmetric hyperintensity in the anterior cord - a marker of cord signal change after injury. Intramedullary cord signal change, and especially HAEMORRHAGE, adds prognostic information beyond the clinical AIS grade and predicts poorer motor recovery (Flanders 1996).Credit: Hellerhoff, CC BY-SA 4.0, via Wikimedia Commons

The AIS grade at 72 hours is the strongest early predictor of outcome. AIS A at 72 hours carries a low probability of functional ambulation; AIS C–D carry a meaningful chance of walking.
Conversion from AIS A to incomplete occurs in a minority; even limited distal recovery can be functionally significant (e.g. regaining C7 wrist extension enables a tenodesis grip).
AIS B with sacral PINPRICK preservation (not just light touch) carries a better motor-recovery prognosis than light touch alone.
AIS D patients are most likely to achieve community ambulation; the lower-limb motor score predicts walking ability.
Lower cervical injuries (C5–C7) have better functional outcomes than higher cervical levels at the same AIS grade, because preserved proximal upper-limb function enables self-care.

Guidelines, registries & global practice

ASIA / ISNCSCI (International)

Key recommendation on AIS: Use the AIS (A–E) as the standard classification at admission and 72 hours
Notes: Adopted worldwide; free training modules online

NICE NG41 (UK)

Key recommendation on AIS: Document the ASIA grade at presentation and at 72 hours; refer to a specialist SCI centre
Notes: UK pathway; the classification principle is universal

AANS/CNS (US)

Key recommendation on AIS: Early MRI; AIS grade guides prognosis; decompression within 24 h for SCI
Notes: STASCIS-informed; supports early surgery

AO Spine International

Key recommendation on AIS: Adopted ASIA/ISNCSCI; recommends uniform documentation across sites
Notes: Multicentre studies use the AIS as the primary outcome

Major guidance for SCI classification and management
Guideline / body	Key recommendation on AIS	Notes
ASIA / ISNCSCI (International)	Use the AIS (A–E) as the standard classification at admission and 72 hours	Adopted worldwide; free training modules online
NICE NG41 (UK)	Document the ASIA grade at presentation and at 72 hours; refer to a specialist SCI centre	UK pathway; the classification principle is universal
AANS/CNS (US)	Early MRI; AIS grade guides prognosis; decompression within 24 h for SCI	STASCIS-informed; supports early surgery
AO Spine International	Adopted ASIA/ISNCSCI; recommends uniform documentation across sites	Multicentre studies use the AIS as the primary outcome

Global epidemiology: traumatic SCI incidence is roughly 10–80 per million per year by region; falls (now the leading cause in many high-income countries, overtaking road traffic) and road traffic crashes dominate, with young adult males the peak group.
Registry evidence: the NSCISC (US), Rick Hansen SCI Registry (Canada) and Australasian networks collect AIS-grade data and consistently confirm the 72-hour AIS grade as the dominant predictor of functional independence.
Resource variation: the AIS exam needs only a pin and a cotton wisp, making it feasible anywhere — examiners expect you to perform it with minimal equipment even where MRI and urgent decompression are limited.

Viva practice

Exam viva

Practise clinical reasoning and management decisions out loud

Viva scenarioStandard

Clinical prompt

“A 28-year-old man is brought to the emergency department after diving into shallow water. He cannot move his arms or legs. On examination, he has no sensation or voluntary movement below the clavicles. Pinprick at the perianal region is absent and he has no voluntary anal contraction. How do you classify this injury and what is the immediate management?”

Viva scenarioAdvanced

Clinical prompt

“A 42-year-old woman falls from a horse and sustains a T12 burst fracture. At 72 hours she has preserved pinprick at S4-S5 on the right, voluntary anal contraction, and her lower-limb key muscles show L2 grade 3, L3 grade 3, L4 grade 2, L5 grade 1, S1 grade 1 on the left and L2 grade 4, L3 grade 4, L4 grade 3, L5 grade 2, S1 grade 1 on the right. What is her AIS grade?”

Exam cheat sheet

The points that win marks

Sacral sparing decides everything — test S4-S5 sensation and voluntary anal contraction first (present = incomplete; absent = complete/AIS A).
A complete, B sensory-incomplete, C/D motor-incomplete (under vs at-least half of key muscles ≥ grade 3), E normal.
The C/D threshold counts key muscles below the NEUROLOGICAL level, not the injury level.
Wait for spinal shock to resolve (bulbocavernosus reflex) before confirming AIS A.
The 72-hour AIS grade is the strongest early outcome predictor; MRI haemorrhage predicts poor recovery; early (under 24 h) decompression improves AIS conversion.
ZPP is documented only for complete (AIS A) injuries.

Exam day cheat sheet

ASIA Impairment Scale — one-screen revision

The five AIS grades

A = Complete: no motor or sensory at S4-S5 (no sacral sparing)
B = Sensory incomplete: sensation preserved including S4-S5, no motor below the level
C = Motor incomplete: fewer than half of key muscles below the level reach grade 3
D = Motor incomplete: at least half of key muscles below the level reach grade 3 or more
E = Normal: all sensation and motor intact

The examination essentials

10 key myotomes (C5–T1, L2–S1) scored MRC 0–5 bilaterally (total 100)
28 key dermatomes tested pinprick + light touch, scored 0–2 bilaterally (total 112)
S4-S5 sacral sensation and voluntary anal contraction — test FIRST, it changes everything
Neurological level = most caudal segment with normal sensation AND motor grade 3+ both sides

Prognosis & pitfalls

AIS grade at 72 hours is the best early outcome predictor
Spinal shock must resolve (bulbocavernosus reflex) before confirming AIS A
AIS C/D have meaningful ambulation potential; AIS A rarely regain walking
Early (under 24 h) decompression improves AIS conversion; MRI haemorrhage predicts poor recovery

Evidence Base

Evidence

Reference for the 2011 revision of the International Standards for Neurological Classification of Spinal Cord Injury

LoE 5

Kirshblum SC, Waring W, Biering-Sorensen F, et al. • J Spinal Cord Med (2011)

Key Findings:

Details the 2011 ISNCSCI revision — the current AIS grading (A–E) with sacral sparing as the discriminator for complete vs incomplete injury.
Defines the standard 10-myotome motor examination and 28-dermatome sensory grid used worldwide.
Clarifies definitions including the neurological level and the zone of partial preservation (complete injuries).

Clinical implication: The internationally agreed reference standard for classifying spinal cord injury, adopted by all major spine and rehabilitation societies.

Limitation: Consensus standard updated periodically; inter-rater reliability depends on examiner training.

Source: J Spinal Cord Med 2011;34(6):547-54

Verify on PubMed (PMID 22330109)

How to read this evidence

According to PubMed, the current AIS definitions come from Kirshblum et al. 2011 (DOI); the primacy of the clinical examination for prognosis from Kirshblum & O'Connor 1998 (Arch Phys Med Rehabil 1998;79(11):1456-66, PMID 9821910); the ASIA motor score's link to ambulation from Waters et al. 1994 (Arch Phys Med Rehabil 1994;75(7):756-60, PMID 8024420); the prognostic value of MRI haemorrhage/oedema from Flanders et al. 1996 (DOI); and the early-decompression benefit (19.8% vs 8.8% ≥2-grade AIS improvement) from the STASCIS study, Fehlings et al. 2012 (DOI).

ASIA Impairment Scale classification

Grade