The ASIA impairment scale for spinal injuries may show worsening despite neurological improvement


Ibrahim Gündoğdu (Department of Physical Therapy and Rehabilitation, Ministry of Health Ankara Diskapi Yildirim Beyazit Education and Research Hospital, Ankara, Turkey) and colleagues report in Spinal Cord that the American Spinal Injury Association (ASIA) impairment scale is limited because it could show worsening despite a patient with a spinal cord injury experiencing neurological improvement. Gündoğdu speaks to Spinal News International about the problems of the ASIA impairment scale (AIS).

What are the known limitations of AIS?

AIS has limitations when used as an instrument to measure outcomes that provide an anatomical or neurological assessment for the connectivity of the spinal cord. Its requirement for the improvement of ASIA grades (eg. ASIA B to ASIA C or ASIA D) as a primary outcome endpoint may be too demanding a threshold (ie. it is a relatively insensitive measure for a therapeutic effect).

A candidate therapeutic with a very large effect size could be addressed with such a challenging clinical point. However, detecting sensory and motor changes may require more sensitivity than measuring AIS grade conversion as these requirements could be complicated by a “ceiling” in ASIA motor scores—making it difficult to determine a statistical difference between the ASIA motor scores of spinal cord injury participants in the experimental and control arms of a study.

In addition, there are inter-rater reliability problems when assessing sensory and motor scores, and there are no agreed methods for assessing motor levels in the thoracic cord when using the ASIA scale.

For chronic spinal cord injury studies, ASIA assessments may not be a sufficient tool as an outcome measure, especially for studies on incomplete spinal cord injury where the ASIA motor score is likely to be substantial and highly variable between individuals.

Also, there are factors that could reduce reliability at baseline ASIA assessment, such as concomitant traumatic brain injury, coma, drug effects and ventilator dependency.

What is your clinical e
xperience of using AIS?

We work in a physical therapy and rehabilitation clinic and most of our patients have severe neurological impairments. We assess the spinal cord injury patients with the AIS routinely, and borderline AIS grades and motor level in regions without a key muscle are most problematic when determining AIS classification.

For this reason, after the 2011 revision of the AIS, Aytül Çakcı (scientific committee member; International Spinal Cord Society [ISCOS] 2013 meeting), Müfit Akyüz (scientific committee member of ISCOS, vice president of ISCOS 2013 local organising committee, and vice-president of the Turkish Spinal Cord Diseases Society), Erhan Arif Öztürk, and myself (I was scientific and local organising committee member the ISCOS 2013 meeting) started a clinical AIS training programme. This programme not only included classical questions such as “what is the motor level?” or “what is the AIS grade?” but also questions on probable AIS grade changes in the event of recovery.

What was the m
ethodology of your study?

In our clinical training programme, including analysis of case examples, we realised that there is a mathematical error with the AIS conversion, which comes from its definition in certain conditions. There was no study in the literature analysing lexical and inherent features of AIS that may cause a discrepancy in classification; furthermore, no study explores in which conditions and how it is vulnerable to errors.

Therefore, we decided to show that the AIS scale does not work in a substantial amount of cases by re-analysing a historical cohort from our institution database. However, it was impossible to get data from our institute’s archives as we needed to know the exact time course of natural recovery; our study demanded subsequent follow-up ASIA assessments at predefined stages in relation to the date of injury. Then, we re-analysed the existing data in the literature and showed that our analysis is not only a theory but also an existing problem that needs to be defined and solved.

Now, we have started a prospective study to capture these problematic patients who have certain conditions with their neurological levels. Even though it will take a long time for our centre to gather enough data, we will report our findings once we reached substantial amount of cases. We think that larger prospective studies with close follow-up are needed to detect the extent of the conversion error and to find out if the error is persistent or resolves with the additional recovery in the subacute or chronic phase in larger spinal cord injury centres.

What are the main findings of the study?

The title of our study was “Can spinal cord injury patients show a worsening in ASIA impairment scale classification despite actually having neurological improvement?”. The answer to that question is “yes, they can”.  Another finding was the first definition of “critical conversion zones”, which explains which patients are vulnerable to illogical AIS conversions.

What are the implications of your study?

To the best of our knowledge, there is no study in the literature that has focused on the conflict between AIS grade conversion and neurological changes. We hope that our critique may prove to be helpful when the AIS is refined in the future by the International Standards for Neurological Classification of Spinal Cord Injury Committee and that it will promote further discussion and research on this topic. Our findings may guide clinicians regarding prognosis and treatment decisions, including the consideration of critical conversion zones as a discrepancy factor when grading AIS.