Background: Differentiation between amyotrophic lateral sclerosis (ALS) and cervical spondylotic myelopathy (CSM) not only for those similar clinical features but also for different handling is very important in clinical practice. Considering that EMG of the sternocleidomastoid muscle (SCM) is using for differential diagnosis of these diseases in Iran, present study was aimed to evaluate the sensitivity of sternocleidomastoid muscle electromyography in differential diagnosis of ALS from CSM.

  Methods: We conducted a retrospective cohort study. Subjects (34patients) were identified from suspected ALS or CSM patients who referred to Loqhman hospital and evaluated with using of the sternocleidomastoid muscle electromyography (SCM-EMG) between March 2006 and February 2008 as part of the diagnostic workup. Clinical characteristics and MRI results were derived from subject’s medical records. Follow-up clinical evaluation during two years after initial diagnostic evaluation was available as a gold standard for confirmation the EMG results. We used two way tables for calculating sensitivity.

  Results: SCM-EMG was abnormal in 10 (29.4%) patients, all of whom were subsequently diagnosed with ALS. The sensitivity of SCM-EMG was 0.71 (95% CI, 0.42– 0.91) for the diagnosis of ALS.

  Conclusion: Although our findings suggest that SCM-EMG is an extremely useful adjunct for the diagnosis of ALS, but further studies with larger sample size is needed for its application as a useful test “Ruling in” for the diagnosis of ALS.