Critical evaluation of the modified Rankin Scale for assessment of the efficacy of mechanical thrombectomy: A retrospective comparison between the modified Rankin Scale and functional independence measure

Abstract

Objective The primary outcome measure used in mechanical thrombectomy (MT) trials is the modified Rankin Scale (mRS). However, the accuracy of mRS might be limited. On the other hand, the functional independence measure (FIM) is a widely used tool to quantify the extent to which patients require assistance during their activities of daily living. The current study aimed to reveal different clinical backgrounds that affect the efficacy of MT measured either by mRS or FIM. Methods Patients who underwent MT at our institution from January 2019 to July 2022 were included and divided into groups based on mRS scores of 0–2 and ≥ 3. Patients were also divided into two groups based on a cut-off value of FIM of ≥ 108, as patients with FIM ≥ 108 are capable of living an independent life. Results The mRS score was 0–2 in 33% of the patients, while the FIM score was ≥ 108 in only 15% of the patients. In the mRS groups, there were significant differences in terms of duration of hospitalization, National Institutes of Health Stroke Scale (NIHSS) scores, achievement of thrombolysis in cerebral infarction (TICI) reperfusion grade of 2b or 3, and postoperative bleeding. Multivariate logistic regression analysis revealed that NIHSS score and achievement of TICI 2b or 3 were significant factors related to mRS 0–2 at discharge. The FIM groups differed significantly in terms of age and, duration of hospitalization, NIHSS score, although multivariate logistic regression analysis revealed that only the NIHSS score was significantly associated with an FIM score of ≥ 108. Conclusion The study showed that the percentage of independent patients is significantly reduced when we evaluated the patients by the FIM. In addition, there are some differences in the clinical background that led to a good outcome between that evaluated by mRS and FIM.