Simplified Motor Score (SMS)
For evaluation of patients in the pre-hospital and acute care setting for possible traumatic brain injury.
The Simplified Motor Score (SMS) has been suggested as a replacement for the GCS in the evaluation of patients for traumatic brain injury.
- A meta-analysis of 5 studies (102,132 total subjects) found that for predicting clinically significant TBI, need for neurosurgery, and need for intubation, the SMS and GCS were statistically equivalent.
- A prospective study involving 126 trauma patients found that the SMS had significantly greater inter-rater reliability (83%) than the GCS (32%) when performed within 5 minutes of each by two ED physicians who were blinded to the other’s assessments.
Points to keep in mind:
- It should be noted that all comparisons of the discriminatory value of the SMS compared to the GCS were retrospective reviews of prospectively collected registry data.
- There is no published data on whether observed differences in performance between the SMS and GCS are truly clinically insignificant as is asserted by the authors of several of the comparative studies.
The Simplified Motor Score allows providers to rapidly assess trauma patients using a score that is significantly simpler than the GCS, has higher inter-rater reliability and comparable sensitivity for significant traumatic brain injury, the need for neurosurgery and/or intubation and death.
Though the composite GCS has been almost universally adopted, there are concerns about its poor reproducibility and the validity of using the composite score. The SMS offers a convenient and viable alternative.
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The Simplifed Motor Score (SMS) is defined as:
- Obeys commands=2
- Localizes to pain=1
- Withdrawals to pain or worse=0.
Patients with a SMS of <2 are at significantly increased risk of having a significant traumatic brain injury and prompt evaluation and head CT imaging is indicated for these patients.
Clinical management decisions should not be based solely on the SMS score, though scores of < 2 are associated with worse clinical outcomes. The threshold for obtaining a head CT in these patients should be low.
As with the GCS, management decisions should be based on the patients overall clinical picture. However the SMS appears to have similar sensitivity to the GCS for predicting patients at risk of significant TBI.
Addition of the selected points; points assigned below:
Facts & Figures
|Withdrawal to pain or worse||0|
- The SMS was initially validated in a retrospective analysis of 8,347 patients in a prospectively maintained trauma registry of a US Level I trauma center that found it comparable to GCS for its ability to predict the need for ED intubation, neurosurgical intervention, traumatic brain injury and mortality. (Gill 2005)
- A secondary analysis of 21,170 patients from a large prospective trauma database found that the SMS also performed comparably to the total GCS with respect to the same 4 key outcome measures (need for ED intubation, neurosurgical intervention, traumatic brain injury and mortality) with a median difference of 5%. (Haukoos 2006)
- A similar analysis of 19,408 patients in the out-of-hospital setting found the SMS had nearly equivalent discriminatory ability (small statistical differences, but no clinically significant [a priori defined as <5% absolute difference in the area under the receiver operating characteristic curve]) compared to the GCS. (Thompson 2011)
- A large retrospective analysis of a statewide trauma registry of 52,412 again found the SMS had comparable sensitivity compared to the GCS for mortality (72.2% vs. 74.6%), traumatic brain injury (40.8 vs 45.4%), need for neurosurgery (52.9% vs. 60%) and intubation (72.7% vs. 75.5%) and conclude the performance of the two score to be “clinically indistinguishable.” (Caterino 2011)
- According a large meta-analysis the SMS was 86-88% sensitive for predicting mortality vs. the GCS which was 90-91% sensitive. Given the large sample size this difference was found to be statistically significant (p = 0.01), though the authors found “the difference to be very small and the clinical significance remained undetermined.” (Singh 2012)
Original/Primary ReferenceGill M, Windemuth R, Steele R, Green SM. A comparison of the Glasgow Coma Scale score to simplified alternative scores for the prediction of traumatic brain injury outcomes. Ann Emerg Med. 2005 Jan;45(1):37-42.
ValidationHaukoos JS, Gill MR, Rabon RE, Gravitz CS, Green SM. Validation of the Simplified Motor Score for the prediction of brain injury outcomes after trauma. Ann Emerg Med. 2007 Jul;50(1):18-24. Epub 2006 Nov 16.Thompson DO, Hurtado TR, Liao MM, Byyny RL, Gravitz C, Haukoos JS.Validation of the Simplified Motor Score in the out-of-hospital setting for the prediction of outcomes after traumatic brain injury. Ann Emerg Med. 2011 Nov;58(5):417-25. doi: 10.1016/j.annemergmed.2011.05.033. Epub 2011 Jul 30.
From the Creator
- Why did you develop the Simplified Motor Scale? Was there a clinical experience that inspired you to create this tool for clinicians?
- The literature evidence is now overwhelming that the Glasgow Coma Scale is unreliable, inaccurate, and unnecessarily complex in that simpler scales are just as predictive. The SMS is the worthwhile part of the GCS statistically distilled out to remove the bloat, and with far better inter-rater reliability.
- What pearls, pitfalls and/or tips do you have for users of the Simplified Motor Scale? Are there cases in which it has been applied, interpreted, or used inappropriately?
- The simplicity of the score avoids the pitfalls of more complex scales.
- What recommendations do you have for health care providers once they have applied the Simplified Motor Scale? Are there any adjustments or updates you would make to the score given recent changes in medicine or imaging?
- No additional recommendations or updates.
- Other comments? Any new research or papers on this topic in the pipeline?
- A study in Annals of Emergency Medicine found that prehospital providers can only calculate the GCS correctly 40% of the time, underscoring its inability to be remembered and applied. (Feldman A, et. al. Randomized Controlled Trial of a Scoring Aid to Improve GCS Scoring by EMS Providers. Ann Emerg Med 2015) A potent argument for a simpler scale.
About the Creator
Steven Green, MD, is a professor of emergency medicine and pediatrics at Loma Linda University, California. He currently is an attending physician in the emergency room and also conducts research on subjects like sedation and emergency protocols.
To view Dr. Steven Green's publications, visit PubMed