The Cornerstone of SCI Evaluation

The ASIA (American Spinal Injury Association) Impairment Scale is a cornerstone in the evaluation and management of spinal cord injuries (SCI). This standardized examination provides critical insights into the extent and severity of an SCI, serving as both a diagnostic tool and a predictor of recovery potential. By assessing motor and sensory function across key levels of the spinal cord, the ASIA scale classifies injuries into distinct categories, guiding treatment plans and rehabilitation strategies.

Beyond its diagnostic capabilities, the ASIA scale plays a pivotal role in monitoring progress over time. By identifying preserved motor and sensory function, clinicians can evaluate the likelihood of functional recovery and establish realistic goals. As a universal framework, it also facilitates communication among healthcare providers and serves as a benchmark for clinical research, ensuring consistency in SCI management across disciplines.

In this newsletter, we’ll break down the ASIA exam, explore how to interpret its results, and highlight its significance in treating SCI patients. Whether you're new to this assessment or looking to deepen your understanding, this guide will equip you with the tools to approach SCI care with confidence utilizing the ASIA scale.

Deciphering the ASIA Exam Chart: Sensory, Motor Scores, and Neurological Level of Injury

The ASIA (American Spinal Injury Association) Impairment Scale utilizes the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) form to assess and document spinal cord injuries (SCI). This detailed form organizes sensory and motor evaluations into a standardized framework, culminating in the determination of the neurological level of injury (NLI) and the ASIA Impairment Scale (AIS) grade. Here's how it all comes together:

Sensory Examination:

The sensory assessment evaluates light touch and pinprick sensation across 28 specific dermatomes on each side of the body, from C2 to S4/5. It is crucial to test sensation at precise, designated locations within each dermatome to avoid areas with overlapping innervation, which could lead to inaccurate scoring. These standardized points ensure consistent and reliable results when determining the sensory level of injury.

Each dermatome is scored for both light touch and pinprick sensation using the following scale:

• 0: Absent sensation

• 1: Impaired sensation (includes hypoesthesia or hyperesthesia)

• 2: Normal sensation

Each modality (light touch and pinprick) can score a maximum of 112 points (56 per side), resulting in a combined total sensory score of up to 224 points.

The sensory level of injury is identified as the most caudal spinal level where sensation is normal for both light touch and pinprick on both sides of the body. Accurate identification of this level is critical for determining the neurological level of injury (NLI) and guiding clinical decision-making.

Motor Examination:

The motor assessment evaluates strength in 10 key muscles on each side of the body, corresponding to specific myotomes from C5 to T1 (upper limbs) and L2 to S1 (lower limbs). However, the key muscles tested in the ASIA exam do not always align with typical orthopedic myotomes. It’s important to note these distinctions:

• C5: Elbow flexors, not shoulder abduction.

• C6: Wrist extensors

• C7: Elbow extensors

• C8: Finger flexors, not thumb extension.

• T1: Small finger abductors

For the lower limbs:

• L2: Hip flexors

• L3: Knee extensors

• L4: Ankle dorsiflexors

• L5: Long toe extensors

• S1: Ankle plantarflexors, not ankle evertors.

Scoring: Muscle strength is graded on a six-point scale:

• 0: No visible or palpable contraction

• 1: Palpable or visible contraction

• 2: Full range of motion (ROM) with gravity eliminated

• 3: Full ROM against gravity

• 4: Full ROM against gravity with moderate resistance

• 5: Normal active movement, full resistance

Each muscle can achieve a maximum score of 5 points, leading to a total motor score of 100 points (50 per side).

The motor level of injury is the lowest spinal level with a muscle grade of at least 3, provided that all muscles above that level have a grade of 5.

Neurologic Level of Injury:

The neurological level of injury (NLI) is a critical determination in SCI evaluation. It represents the most caudal spinal segment with intact motor and sensory function on both sides of the body. It is calculated by integrating sensory and motor findings:

1. Identify the sensory level: Find the lowest spinal segment where sensation is normal on both sides of the body for both light touch and pinprick.

2. Identify the motor level: Find the lowest spinal segment where a key muscle is graded at least 3/5 on both sides of the body, provided that all muscles above that level are graded as 5/5.

3. Determine the NLI: The NLI is the spinal segment where both the sensory and motor criteria are met on both sides of the body.

This approach focuses on ensuring that both sensory and motor functions are intact bilaterally at the identified segment, which simplifies the determination of the NLI and avoids confusion.

Zones of Partial Preservation (ZPP):

The zones of partial preservation (ZPP) refer to areas below the neurological level of injury (NLI) where some motor or sensory function remains intact. ZPPs are strong indicators of recovery potential. Patients with intact motor or sensory function in the ZPP have a better chance of regaining additional function over time. Combining the neurological level of injury (NLI) with an understanding of the zones of partial preservation provides a comprehensive picture of the injury:

• NLI identifies the highest segment of intact motor and sensory function, serving as a baseline.

• ZPP highlights potential for recovery below the level of injury, helping clinicians tailor interventions to maximize outcomes.

ASIA Levels-Your Guide to Creating Realistic Goals and Interventions

The ASIA Impairment Scale (AIS) provides a framework for classifying spinal cord injuries (SCI), helping clinicians tailor interventions, set realistic goals, and identify appropriate adaptive equipment. While each AIS level reflects different degrees of neurological function, there is often significant overlap in goals and strategies, particularly when factoring in functional capabilities. Below is an explanation of each level, with key considerations for intervention, adaptive equipment, and goal-setting.

AIS Level A: Complete Injury

• Definition: No sensory or motor function is preserved in the sacral segments S4-S5.

• Key Diagnostic Feature: The N000N sign, confirming:

  • N: No sensation to light touch at S4-S5.

  • 0: No sensation to pinprick at S4-S5.

  • 0: No deep anal pressure.

  • 0: No voluntary anal contraction.

  • N: No sacral sparing.

• Considerations:

  • Individuals with complete injuries require interventions focused on compensatory strategies, adaptive technology, and secondary complication prevention.

  • Bowel and bladder management is a critical focus, as sacral function is absent. This includes education on catheterization or bowel programs to maintain health and independence.

  • Goals often overlap with other levels when focusing on functional independence, such as transfers or wheelchair mobility, but the lack of motor and sensory recovery changes the emphasis to assistive technology and environmental adaptations.

AIS Level B: Sensory Incomplete

• Definition: Sensory, but not motor, function is preserved below the neurological level of injury, including the sacral segments S4-S5.

• Key Characteristics:

  • Sacral sparing is present, with sensation intact at S4-S5.

  • No motor function is found more than 3 levels below motor level on either side.

  • No voluntary motor function is preserved below the NLI.

• Considerations:

  • Bowel and bladder programs remain necessary, but preserved sensory function can make toileting strategies more intuitive and allow for improved feedback during care.

  • Sensory input can enhance awareness of body position and improve balance, which can be leveraged in rehabilitation.

AIS Level C: Motor Incomplete

• Definition: Motor function is preserved below the NLI, but more than half of the key muscles below the NLI have a grade of less than 3/5 (unable to move against gravity).

• Key Characteristics:

  • Sacral sparing is present, allowing for voluntary anal contraction or motor function found more than 3 levels below motor level AND sacral sparring.

  • Muscle strength is limited, but preserved motor pathways indicate recovery potential.

• Considerations:

  • Goals include maximizing muscle recovery and compensating for weakness through task-specific training and adaptive equipment.

  • Although goals may overlap with other levels (e.g., improving transfers, mobility), rehabilitation here focuses more on strengthening preserved muscles and addressing motor recovery.

AIS Level D: Motor Incomplete

• Definition: Motor function is preserved below the NLI, and at least half of the key muscles below the NLI have a grade of 3/5 or higher (able to move against gravity).

• Key Characteristics:

  • Sacral sparing is present, allowing for voluntary anal contraction or motor function found more than 3 levels below motor level AND sacral sparring.

  • Individuals often demonstrate enough motor function for ambulation, although assistive devices or orthoses may be required.

• Considerations:

  • Patients with a high NLI focus on compensatory strategies, such as powered wheelchairs, upper limb strengthening, and trunk stability for functional independence.

  • For lower NLI, goals include ambulation training with assistive devices, strengthening lower limbs and core, and achieving energy-efficient walking for community mobility.

  • Overlap exists with other levels in managing fatigue, optimizing transfers, and preventing complications, but ASIA D uniquely emphasizes walking potential and functional endurance.

Beyond the AIS Levels: Using the Scale as a Guide, Not a Limit

The ASIA Impairment Scale (AIS) is a powerful tool for assessing the severity of spinal cord injuries (SCI), but it should never be used in isolation to determine the full potential or limits of a patient’s recovery. The AIS levels are guidelines that help classify injury severity and inform early planning, but recovery trajectories and functional abilities are influenced by numerous other factors. Clinicians must take a holistic view, integrating the ASIA level with each patient’s unique presentation to guide interventions and goal-setting.

Recognizing the Overlap Across AIS Levels

Even though ASIA A (complete injury) and ASIA D (motor incomplete) represent opposite ends of the spectrum, significant overlap can exist in the functional needs and goals of patients, depending on factors such as the neurological level of injury (NLI), comorbidities, and recovery potential. For example:

• ASIA D Requiring More Assistance than ASIA A or B:
  A patient with a high NLI (e.g., C4) classified as ASIA D may have preserved motor function in lower limbs but lack sufficient trunk and upper limb strength for functional independence. This could result in significant challenges with transfers, balance, and mobility, requiring powered wheelchair use and caregiver assistance for ADLs. In contrast, a patient with a lower thoracic ASIA A injury (e.g., T10) may have full upper limb strength and trunk control, enabling them to independently perform transfers, navigate a manual wheelchair, and manage ADLs effectively using compensatory strategies.

How the ASIA Scale Guides Goal Setting and Interventions

• Set Individualized Goals: Goals should be tailored to the patient’s specific functional status, neurological level of injury (NLI), and recovery potential rather than solely their ASIA classification. For example:

  • An ASIA A patient with a mid-thoracic injury may focus on strengthening their upper body for independent wheelchair mobility and developing strategies for self-care tasks like grooming and dressing.

  • An ASIA D patient with a high thoracic injury might focus on improving dynamic sitting balance, strengthening functional lower limb muscles, and using orthotics or assistive devices for partial ambulation.

• Dynamic Reassessment: Regularly evaluate progress, as recovery is often unpredictable and non-linear. Even small improvements in motor or sensory function can significantly shift priorities, such as transitioning from compensatory strategies to recovery-based interventions or adjusting assistive device recommendations.

• Comprehensive Approach: Address all aspects of recovery, including preventing secondary complications (e.g., spasticity, pressure ulcers), optimizing use of preserved muscle function, developing compensatory techniques, and supporting the patient’s psychological and social well-being to enhance quality of life.

The ASIA Impairment Scale is an invaluable resource for understanding and classifying SCI, but its true utility lies in guiding, not defining, clinical practice. A patient-centered, adaptable approach that integrates all factors—beyond just the ASIA level—ensures that each individual receives the care and strategies they need to maximize their recovery and independence.

Check Your Understanding-

Question 1:

Voluntary Anal Contraction: Absent
Deep Anal Pressure: Present

Based on the ASIA examination chart, what is this patient’s ASIA Impairment Scale (AIS) classification?

A. AIS A

B. AIS B

C. AIS C

D. AIS D

Question 2: Based on the patient’s ASIA classification and neurological level of injury, which of the following would be the most realistic short-term rehabilitation goal?

A. Independent ambulation using bilateral ankle-foot orthoses (AFOs).

B. Independent manual wheelchair propulsion with focus on strengthening upper extremities.

C. Independent toileting without assistive devices.

D. Regaining full motor function below the level of injury.

Question 3: A patient wishes to achieve the goal of independently transferring from their wheelchair to a standard-height bed. Based on the following ASIA classifications and neurological levels of injury, which patient is the most likely to achieve this goal?

A. AIS D with a C3 neurological level
B. AIS B with a C6 neurological level
C. AIS A with a T12 neurological level
D. AIS C with a C5 neurological level

Correct Answers with Explanation:

Correct Answer: B

Explanation: This patient is classified as AIS B (Sensory Incomplete) because sensory sparing, including at the sacral level (S4-S5), is present via deep anal pressure (DAP), but there is no motor sparing more than 3 levels below the below motor level on either side.

Correct Answer: B

Explanation: As an AIS B patient with preserved sensory but no significant motor function below the neurological level, this individual is unlikely to ambulate or regain full motor function. Strengthening the upper extremities for independent manual wheelchair propulsion is a realistic and functional goal based on their preserved motor function at C5-C6.

Correct Answer: C

Explanation: AIS D with a C3 neurological level (Limited functional movement due to lack of innervation to key upper extremity muscles; unlikely to assist meaningfully in transfer tasks). AIS B with a C6 neurological level (Some innervation to wrist extensors but lack of triceps strength and hand grip; transfer may require assistance or adaptive strategies). AIS A with a T12 neurological level (Full upper limb function and some trunk stability; most likely to perform the transfer independently with use of intact muscles).
AIS C with a C5 neurological level (Partial biceps and deltoids, but limited triceps or hand function/likely poor tenodesis grip; challenging to achieve independent transfers without significant compensation)

References:

1. Physio-pedia. (n.d.). American Spinal Injury Association (ASIA) Impairment Scale. Retrieved January 16, 2025, from https://www.physio-pedia.com/American_Spinal_Injury_Association_(ASIA)_Impairment_Scale

Disclaimer:

I am a current Doctor of Physical Therapy (DPT) student sharing information based on my formal education and independent studies. The content presented in this newsletter is intended for informational and educational purposes only and should not be considered professional medical advice. While I strive to provide accurate and up-to-date information, my knowledge is based on my current academic and clinical rotations and ongoing learning, not extensive clinical practice.