American Spinal Cord Injury Association (ASIA) Impairment Scale

Original Editor - Daphne Jackson.

Top Contributors - Naomi O'Reilly, Kim Jackson and Tarina van der Stockt  

Introduction

Conduction of Sensory and Motor signals and the autonomic nervous system is affected by spinal cord injury. By systematically examining the dermatomes and myotomes, one can determine the cord segments affected by the spinal cord injury. The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), commonly referred to as the ASIA Exam, was developed by the American Spinal Injury Association (ASIA) as a universal classification tool for Spinal Cord Injury based on a standardized sensory and motor assessment, with the most recent revised edition published in 2011. The impairment scale involves both a Motor and Sensory examination to determine the Sensory Level and Motor Level for each side of the body (Right and Left), the single Neurological Level of Injury (NLI) and completeness of the Injury i.e. whether the injury is complete or incomplete. [1]

International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI)
ISNCSCI Scoring Outlines and ASIA Impairment Scale (AIS)

Sensory Examination

Key Sensory Points, readily located in relation to bony anatomical landmarks in each of the 28 Dermatomes C2 - S5, are tested bilaterally using light touch and pin-prick (sharp-dull discrimination). Equipment common to clinical settings may be used, such as a cotton bud for light touch and a neurotip or safety pin for pin-prick. Appreciation of light touch and pin prick sensation at each of the key points is made in comparison to sensation on the patient’s cheek as a normal frame of reference. [1]

A Three-Point Scale is used for scoring:

0 = Absent
1 = Altered - Impaired or Partial Appreciation, including Hyperesthesia
2 = Normal or Intact - Similar as on the Cheek
NT = Not Testable
International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) Key Sensory Points [1]
Level Description of Key Points for Sensory Testing
C2 1 cm lateral to Occipital Protuberance 
C3 Supraclavicular Fossa at Midclavicular Line
C4 Over Acromioclavicular Joint
C5 Lateral Side Antecubital Fossa just Proximal to Elbow Crease
C6 Dorsal Surface of Proximal Phalanx of the Thumb
C7 Dorsal Surface of Proximal Phalanx of the Middle Finger
C8 Dorsal Surface of Proximal Phalanx of the Little Finger
T1 Medial Side Antecubital Fossa, just Proximal to Medical Epicondyle of Humerus
T2 Apex of Axilla
T3 Midclavicular Line and 3rd Intercostal Space
T4 Midclavicular Line and 4th Intercostal Space at Nipple Line
T5 Midclavicular Line and 5th Intercostal Space Midway between T4 & T6
T6 Midclavicular Line and 6th Intercostal Space at the level of Xiphisternum
T7 Midclavicular Line and 7th Intercostal Space Midway between T6 & T8 - Quarter Distance between Level Xiphisternum & Umbilicus
T8 Midclavicular Line and 8th Intercostal Space Midway between T6 & T10- Half Distance between Level Xiphisternum & Umbilicus
T9 Midclavicular Line and 9th Intercostal Space Midway between T8 & T10 - Three Quarters Distance between Level Xiphisternum & Umbilicus
T10 Midclavicular Line and 10th Intercostal Space at the Level of Umbilicus
T11 Midclavicular Line and 11th Intercostal Space Midway between T10 & T12 - Midway between Level of Umbilicus & Inguinal Ligament
T12 Midclavicular Line Over Midpoint Inguinal Ligament
L1 Midway between Sensory Point at T12 & L1
L2 Anterior-Medial Thigh at the Midpoint drawn connecting Midpoint of Inguinal Ligament & Medial Femoral Condyle
L3 Medial femoral Condyle above the Knee
L4 Medial Malleolus
L5 Dorsal Foot at 3rd Metatarsal Phalangeal Joint
S1 Lateral Aspect Calcaneus
S2 Midpoint Popliteal Fossa
S3 Over Ischial Tuberosity or Infragluteal Fold
S4 - 5 Perianal Area < 1cm Lateral to Mucocutaneous Junction
Deep Anal Pressure
A gentle pressure with the examiner’s finger is applied to the internal, anorectal wall, innervated by the somatosensory components of the pudendal nerve S4/5. Perceived pressure is graded as absent or present. Any reproducible pressure sensation felt in the anal area during this part of the exam signifies that the patient has a sensory incomplete lesion. Evaluation of Deep Anal Pressure is not necessarily required in individuals who have light touch or pin prick sensation at S4-5, as they already have a designation for a sensory incomplete injury. [1]

Sensory Level

Defined as the most caudal, intact dermatome for both light touch and pin prick (sharp/dull discrimination) sensation. The sensory level is determined by performing an examination of the key sensory points within each of the 28 dermatomes on each side of the body, as above, and may be different for the right and left side.The Sensory Level is the intact dermatome level located immediately above the first dermatome level with impaired or absent light touch or pin-prick sensation, and should be determined for each side of the body as the right and left sides may differ. Up to four sensory levels may be generated for each dermatome; Right Pin-prick, Right Light Touch, Left Pin-prick and Left Light Touch. The overall single sensory level is the most rostral intact sensory point. [1]

Sensory Score

Sensory scores of each dermatome for pin-prick and light touch can be summed across dermatomes and sides of body, right and left, to generate two summary sensory scores: Pin-prick and Light Touch. Normal sensation for each modality is assigned a score of 2. A score of 2 for each of the 28 key sensory points for Light Touch on each side of the body would result in a maximum score of 56 for Light Touch. A score of 2 for each of the 28 key sensory points for Pin-Prick on each side of the body would result in a maximum score of 56 for Pin-Prick. Total Maximum Sensory Score of 112. The sensory score, provide a means of numerically documenting changes in sensory function, but cannot be calculated if any required key sensory point is Not Testable. [1]

Sensory Scoring.jpeg
Sensory Score.jpeg

Motor Examination

Key Motor Functions of the 10 Paired Myotomes C5 - T1 and L2 - S1 are tested bilaterally. Improper positioning and stabilization can lead to substitution by other muscles, and will not accurately reflect the muscle function being graded. [1]

A Six-Point Scale is used for scoring:

0 = Total Paralysis
1 = Palpable or Visible Contraction
2 = Active Movement, Full Range of Motion with Gravity Eliminated
3 = Active Movement, Full Range of Motion Against Gravity
4 = Active Movement, Full Range of Movement against Gravity and Moderate Resistance in a Muscle Specific Position
5 = Normal Active Movement, Full Range of Motion Against Gravity and Full Resistance in a Muscle Specific Position expected from an Unimpaired Person
5* = Normal Active Movement, Full Range of Motion Against Gravity and Sufficient Resistance to be considered normal if identified Inhibiting Factors i.e., pain, disuse were not present
NT = Not Testable i.e., due to Immobilization, Severe pain such that the patient cannot be graded, Amputation of Limb, or Contracture of >50% of the Range of Motion

Patient should be supine for testing, except for the rectal examination that can be performed side-lying, this is to ensure consistency across tests to allow for a valid comparison from acute stage through to rehabilitation. Each key muscle function should be examined in a cephalad-caudal sequence Ensure to stabilize both above and below the joint to prevent any muscle substitution during the testing. Move the joints through their full range of movement prior to completing manual muscle testing (MMT) as above to rule out any pain, spasticity, or contracture which might impact on the motor scores. The hip should not be allowed to actively or passively flex beyond 90° due to the increased kyphotic stress placed on the lumbar spine in any individual with a suspected acute traumatic injury below the T8 level. Instead unilateral, isometric exam should be completed to ensure the contralateral hip remains extended to stabilize the pelvis. [1]

International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) Key Motor Function [1]
Level Key Muscle Function & Muscles Description of Muscle Function Testing Position for Grade 4 or 5
C5 Elbow Flexion
  • Biceps Brachii
  • Biceps Brachialis
Elbow Flexed at 90, Forearm Supinated
C6 Wrist Extension
  • Extensor Carpi Radialis Longus
  • Extensor Carpi Radialis Brevis
Full Wrist Extension
C7 Elbow Extension
  • Triceps Brachii
Shoulder Neutral Rotation, Adducted at 90 Flexion with Elbow at 45 Flexion
C8 Flexion of Middle Finger
  • Flexor Digitorum Profundus
Full Flexed Distal Phalanx with Proximal Finger Joint Stabilised in Extension
T1 Abduction of Little Finger
  • Abductor Digiti Minimi
Full Abduction Fingers
L2 Hip Flexion
  • Iliopsoas
Hip Flexed at 90
L3 Knee Extension
  • Quadriceps
Knee Flexed at 15
L4 Ankle Dorsiflexion
  • Tibialis Anterior
Full Dorsiflexion
L5 Long Toe Extensors
  • Extensor Hallucis Longus
Full Extension 1st Toe
S1 Ankle Plantarflexion
  • Gastrocnemius
  • Soleus
Hip Neutral with Full Knee Extension and Full Ankle Plantarflexion
Voluntary Anal Contraction
The External Anal Sphincter, innervated by the somatic motor components of the Pudendal Nerve S2-4) should be tested on the basis of reproducible voluntary contractions around the examiner's finger, by instructing the patient “squeeze my finger as if to hold back a bowel movement". A contraction is graded as absent or present. A voluntary anal contraction during this part of the exam signifies that the patient has a motor incomplete injury. Examiners should be careful to distinguish between voluntary anal contraction from reflex anal contraction, which tends to be produced only with the Valsalva Maneuver. [1]

Motor Level

The Motor Level is defined by the lowest key muscle function that has a grade of at least 3 (on supine testing), providing the key muscle functions represented by segments above that level are judged to be intact (graded as a 5). The motor level is determined, as above, by examining the key muscle function within each of the 10 myotomes on each side of the body, and may be different for the right and left side. In regions where there is no myotome that are clinically testable i.e., C1 to C4, T2 to L1, and S2 to S5, the Motor Level is presumed to be the same as the Sensory Level, if testable motor function above that level is also normal. [1]

Example 1

If the sensory level is C4, and there is no C5 motor function strength (or strength graded <3), the motor level is C4.

Example 2:

If the sensory level is C4, with C5 key muscle function strength graded as 4, the motor level would be C5 because the strength at C5 is at least 3 with the “muscle function” above considered normal: presumably if there was a C4 key muscle function it would be graded as normal since the sensation at C4 is intact.

Motor Score

Motor scores for each myotome can be summed across myotomes and sides of body, right and left, to generate a single motor score for each of the upper limbs and lower limbs. Normal strength is assigned a grade of 5 for each muscle function. A score of 5 for each of the five key muscle functions of the upper extremity would result in a maximum score of 25 for each extremity, totaling 50 for the upper limbs. A score of 5 for each of the five key muscle functions of the lower extremity would result in a maximum score of 25 for each extremity, totaling 50 for the lower limbs. In previous versions of a total motor score of 100 for all extremities was calculated but construct validity of the Motor Score as a measure of recovery following spinal cord injury and as an outcome measure for clinical trials is greater when Upper Extremity and Lower Extremity Motor Scores are scored independently and not summated together, therefore it is now recommended to consider Upper Extremity and Lower Extremity Scores separately. The Motor Score, provide a means of numerically documenting changes in motor function, but cannot be calculated if any required muscle function is Not Testable. [1]

Motor Scoring.jpg
Motor Score.jpeg

Determination of Neurological Level of Injury

The Neurological Level of Injury is determined by identifying the most caudal segment of the cord with intact sensation and antigravity muscle function strength (Grade 3 or more) on both sides of the body, provided that there is normal, intact sensory and motor function rostrally (Grade 5).

Sensory Level refers to the most caudal, intact dermatome for both light touch and pin-prick sensation (Score = 2).

Motor Level refers to the most caudal myotome with a key muscle function of at least Grade 3 on Motor Examination.

If there is a discrepancy between the most caudal intact section between the four possible levels of Right-Sensory Level, Left-Sensory Level, Right-Motor Level, or Left-Motor Level, the Neurological Level of Injury is considered the most cephalad segment of these four levels. [1]

ASIA Impairment Scale (AIS)

Spinal Cord Injuries are classified in general terms of being neurologically “Complete” or “Incomplete” based upon Sacral Sparing, which refers to the presence of Sensory or Motor Function in the most Caudal Sacral Segments i.e. preservation of light touch or pin prick sensation at S4-5 Dermatome, Deep Anal Pressure or Voluntary Anal Sphincter Contraction. [1]

Complete Injury is defined as the absence of Sacral Sparing i.e. No Sensory and Motor Function at S4-5
Incomplete Injury is defined as presence of Sacral Sparing i.e. Partial preservation of Sensory and/or Motor Function at S4-5
  • Sensory Incomplete: Sacral Sparing of Sensory Function
  • Motor Incomplete: Sacral Sparing of Motor Function or Sacral Sparing of Sensory and Motor Function more than 3 Levels below Injury

The following ASIA Impairment Scale (AIS) designation is used in grading the degree of impairment:

ASIA Impairment Scale (AIS) [1]
Grade Type of Injury Description of Injury
A Complete No Sensory or Motor Function is preserved in the Sacral Segments S4-S5
B Sensory Incomplete Sensory but not Motor Function is preserved below the neurological level and includes the Sacral Segments S4-S5,

AND

No Motor Function is preserved more than three levels below the Motor Level on either side of the body

C Motor Incomplete Motor Function is preserved below the Neurological Level

AND

More than half of key muscle functions below the Neurological Level of Injury have a muscle grade less than 3 (Grades 0-2)

D Motor Incomplete Motor function is preserved below the neurological level

AND

At least half (half or more) of key muscle functions below the NLI have a muscle grade ≥ 3

E Normal If sensation and motor function as tested with the ISNCSCI are graded as normal in all segments

AND the patient had prior deficits

Then the AIS Grade is E.

Someone without a Spinal Cord Injury does not receive an AIS Grade.

Zone of Partial Preservation

The Zone of Partial Preservation is only used with Complete Injuries (AIS A), and refers to the dermatomes and myotomes caudal to the sensory or motor level that remain partially innervated. The extent of the Sensory or Motor Zone of Partial Preservation is determined by the most caudal segment with some sensory or motor function respectively, and should be recorded for both right and left sides and for sensory and motor function. [1]

Example; If the left sensory level is C6, and some sensation extends from C7 through T1, then “T1” is recorded in the right sensory ZPP block on the worksheet.

Classification Steps

Steps in Classification.jpg

Evidence

Reliability

The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) Sensory and Motor examinations are reliable when conducted by a trained examiner. [4] Formal training in the administration of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) Standards has been shown to improve the accuracy of the examiner’s classification. [5] Use of the 2013 Worksheet Revision provides significantly better classification performance and a reduction in misclassification of Motor Level and Neurological Level of Injury since its introduction, except at C2 - 4 Level, which has been suggested may be linked to the body-side based grouping of myotomes and dermatomes on the same horizontal alignment. As such it is recommended that any future revision of the worksheet should maintain the same graphical aspect in the layout. [6]

Validity

The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) are validated for injury classification. [7] Construct validity of the ASIA Motor Score as a measure of recovery following spinal cord injury and as an outcome measure for clinical trials is greater when Upper Extremity and Lower Extremity Motor Scores are scored independently and not summated together. [7]

Patient Explanation

The should initially be completed within 72 hours of an acute stage of a spinal cord injury to aid improved prediction of recovery. As such it can be both an uncomfortable and confusing exam for individuals, particular as they have just gone through a significant trauma. Explaining why we do the test and what is it entails is vital to make the individual more comfortable during the exam.

We want individuals to understand that this test will help us as clinicians determine where the injury to the spinal cord is and determine what level the injury was, how severe it is, and an idea of what we could expect in terms of recovery. Often the International Standards for Neurological Classification of Spinal Cord Injury and ASIA Impairment Scale can give us a different picture to what we can see on CT or MRI.

Resources

International Standards for Neurological Classification of Spinal Cord Injury: Assessment Forms

International Standards for Neurological Classification of Spinal Cord Injury: Sensory and Motor Guides

ASIA E-Learning Centre InSTeP: International Standards

  • To promote the teaching and competent use of the Standards, ASIA with contribution from the International Spinal Cord Society has developed the International Standards Training e-Learning Program or InSTeP.

ASIA E-Learning Centre ASTeP: Autonomic Anatomy & Function

  • The goal of this training for the Autonomic Standards is to learn normal autonomic functions, understand the changes in autonomic functions following spinal cord injury (SCI) and use the Autonomic Assessment to document and classify remaining autonomic neurological function.

References

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 Burns S, Biering-Sørensen F, Donovan W, Graves D, Jha A, Johansen M, Jones L, Krassioukov A, Kirshblum, Mulcahey MJ, Schmidt Read M, Waring W. International Standards for Neurological Classification of Spinal Cord Injury, Revised 2011. Top Spinal Cord Inj Rehabil 2012;18(1):85-99.
  2. UCTeach Ortho. ASIA Impairment Scale. Available from: https://youtu.be/hO9hADODTw8[last accessed 30/10/18]
  3. SCIREWebVideo . Common Errors Made During the ISNCSCI Examination (ASIA Exam). Available from: https://www.youtube.com/watch?v=PpgGzIhCpuI[last accessed 30/10/18]
  4. Marino R, Jones L, Kirshblum S, Tal J, Dasgupta A. Reliability and repeatability of the motor and sensory examination of the international standards for neurological classification of spinal cord injury. J Spinal Cord Med 2008;31(2)166-170.
  5. Schuld C, Wiese J, Franz S, Putz C, Stierle I, Smoor I, Weidner N, EMSCI Study Group, Rupp RR. Effect of formal training in scaling, scoring and classification of the international standards for neurological classification of spinal cord injury. Spinal Cord 2013;51(4):282-8.
  6. Schuld C, Franz S, Brüggemann K, Heutehaus L, Weidner N, Kirshblum SC, Rupp R. International Standards for Neurological Classification of Spinal Cord Injury: Impact of the Revised Worksheet (Revision 02/13) on Classification Performance. The Journal of Spinal Cord Medicine. 2016 Sep 2;39(5):504-12.
  7. 7.0 7.1 Graves D, Frankiewicz RG, Donovan WH. Construct validity and dimensional structure of the ASIA motor scale. J Spinal Cord Med 2006;29(1):39-45.