Beyond the Ashworth Scale: A New Tool for Measuring Spasticity After Stroke
"Discover how the Electric Spastic Ankle Measure (E-SAM) offers a more precise way to assess muscle tone and spasticity in stroke patients, potentially revolutionizing rehabilitation strategies."
Spasticity, characterized by a velocity-dependent increase in tonic stretch reflexes, is a common challenge following upper motor neuron injuries such as stroke and spinal cord injury (SCI). While the condition is well-recognized, accurately measuring spasticity and understanding its components has remained elusive. This is crucial because spasticity can either hinder or help recovery, depending on the context.
Current clinical assessments rely heavily on manual tools like the Ashworth Scale and the Modified Ashworth Scale (MAS). These scales are widely used due to their simplicity, but they have significant limitations in reliability and the ability to provide quantifiable results. The need for more precise and reliable measurement tools has driven the development of instruments designed to quantify spasticity, though many are cumbersome and impractical for clinical settings.
This article explores the Electric Spastic Ankle Measure (E-SAM), a newly developed, portable instrument designed to quantitatively assess the spastic and viscoelastic components of muscle tone. By comparing E-SAM measurements with those obtained via the MAS, researchers aim to demonstrate E-SAM's potential as a more specific and quantitative tool for evaluating spasticity in stroke patients.
Limits of MAS Correlation
A study published in the Journal of NeuroEngineering and Rehabilitation examined the relationship between Ashworth scores and neuromechanical measurements of spasticity following stroke. Its findings revealed no significant correlation between quantitative measures of the neural and muscular components of joint dynamic stiffness and Modified Ashworth Scale scores. This lack of correlation was observed in both the upper and lower extremities, highlighting limitations in using MAS scores as a proxy for neuromechanical stiffness.
Clinical Scales and Emerging Detection
The Modified Ashworth Scale and Modified Tardieu Scale remain established clinical approaches, but a 2019 review reports that they lack reliability and reproducibility. A 2023 Frontiers review assessed the reliability and effectiveness of current clinical measures alongside newer approaches published since 2016. Another study, published February 17, 2026, described current clinical assessments as subjective and device-based detection as cumbersome, proposing a double-threshold method that detects spasticity during flexion and extension. Persistent disparities in recognition, access, and treatment delivery also mean that some patients receive care only after spasticity is well established, while others receive no treatment.
From Generalized Signs to Integrated Models
Historically, spasticity has often been used as a generalized term for a constellation of distinct positive motor signs arising from a central nervous system lesion. A 2026 historical perspective argues that this terminology creates ambiguity when identifying individual impairments. More recent modeling work compares mechanical, neurological, and integrated approaches to understanding spasticity in conditions including stroke and cerebral palsy. Clinical milestones also include the BoTULS multicentre randomized controlled trial, which evaluated the clinical and cost-effectiveness of botulinum toxin type A for upper-limb spasticity after stroke.
How Does E-SAM Work?
The Electric Spastic Ankle Measure (E-SAM) is designed for ease of use and precise measurement. It incorporates an ankle-foot orthosis (AFO) equipped with torque sensors on an upright bar and a goniometer at the ankle joint. A footplate, pivoting on an anterior hinge, completes the setup.
- Viscoelasticity: The initial drop and resistance encountered reflect the viscoelastic properties of the muscle.
- Reactive Contractions: Subsequent peaks indicate reactive contractions of the plantar flexor muscles, revealing spasticity.
- Data Processing: The recorded data is then analyzed to quantify muscle tone and spasticity, providing a detailed assessment.
New Measures and Management Evidence
A validity study of the Electric Spastic Ankle Measure included 114 stroke patients from 7 hospitals and 88 normal individuals. A 2026 review of post-stroke limb spasticity identified several effective interventions, with botulinum toxin injection described as the primary choice for managing focal spasticity. Other recent work emphasizes that developing effective rehabilitation programs requires a deeper understanding of the relationships among spasticity, proprioception, and motor function. Together, these studies extend assessment beyond a single clinical score toward measurement, treatment, and functional interaction.
Practicality Versus Precision
Technology-assisted assessment is motivated in part by the effects of upper-limb spasticity after stroke, which is associated with post-stroke pain and limitations in rehabilitation engagement. Manually controlled instruments are convenient and portable for measuring muscle activity during stretching, but motor-driven instruments provide more controlled and precise measurements of torque and force. Existing clinical scales also have important limitations in reliability and inter-examiner reproducibility. In addition, one quantitative ankle tool was tested only in adult men with stroke and a MAS of 3, so broader generalization would require patients with a wider range of conditions and spasticity severities.
Biomechanical Detail Beyond MAS
A mechanical measurement study found that the average angular velocity used by physical therapists to assess spasticity was 268 ± 77°/s. The NeuroFlexor device showed excellent test-retest reliability for neural and non-neural elastic wrist-resistance components, with ICC values of 0.93 and 0.95, respectively, and good reliability for the viscous component, with an ICC of 0.84. Reviews of quantitative estimation methods report that biomechanical measurements can estimate both neural and non-neural contributions and provide more information for treatment and rehabilitation research than clinical scales. These approaches therefore offer component-level information that a single ordinal score does not provide.
The Future of Spasticity Assessment
The E-SAM device offers a promising step forward in the quantitative assessment of spasticity, potentially enhancing treatment strategies and improving outcomes for stroke patients. While further research is needed to validate these initial findings across a broader population, the E-SAM shows significant potential as a practical tool for both clinical and research applications.
Earlier Detection and Biomarkers
A scientific statement on poststroke spasticity reviews the rationale, established and emerging evidence, and strategic approaches for improving early recognition and intervention. Guidance from the American Academy of Physical Medicine and Rehabilitation characterizes spasticity as a group of symptoms involving muscle tightening or reduced stretchability after injury or disease affecting the brain or spinal cord, including stroke. Recent biomarker research reports that early identification may help predict spasticity risk and enable proactive therapy aimed at preventing severe muscle stiffness. These directions point toward earlier, more individualized rehabilitation planning.
A Widely Used but Limited Standard
The Ashworth Scale or its modified version is described as the most commonly used clinical measure of spasticity after stroke. It is an ordinal test of resistance to passive stretch, making it simple to use in clinical settings. However, the Stroke review identifies poor inter-rater reliability as a key limitation. This creates a broader measurement challenge: a widely adopted tool may remain practical while providing inconsistent results between examiners.