Muscle assessment in brachial plexus injury: A reliability study

Area of Science:

• Neurology
• Orthopedics
• Rehabilitation Medicine

Background:

• Brachial plexus injuries significantly impact motor function.
• Accurate assessment of motor recovery is crucial for surgical intervention success.
• The Medical Research Council (MRC) scale is commonly used to evaluate muscle strength.

Purpose of the Study:

• To evaluate the inter-rater reliability of the MRC method for assessing C5/C6/C7 motor weakness in adults with brachial plexus injuries.
• To determine if MRC scores correlate with functional recovery using Disabilities of the Arm Shoulder and Hand (DASH) and EQ5D scores.

Main Methods:

• Thirty adult patients with C5/C6/C7 weakness post-nerve injury were examined by two experienced clinicians.
• Modified and unmodified MRC scales were used to assess upper limb motor outcome.
• Inter-rater reliability was analyzed using Kappa statistics; correlations with DASH and EQ5D were calculated.

Main Results:

• Poor inter-rater reliability was observed for MRC grades 3-5 in C5/C6/C7 muscles.
• Only Deltoid Posterior and Extensor Carpi Radialis Longus showed substantial reliability (Kappa > 0.6) with the modified MRC.
• Higher MRC scores correlated with lower DASH scores and higher EQ5D overall health ratings.

Conclusions:

• The MRC motor rating scale demonstrates poor inter-rater reliability for assessing C5/C6/C7 muscles in adults with proximal nerve injuries.
• Current findings suggest the need for alternative assessment methods for motor outcomes in this patient population.