In a patient with C7 tetraplegia, elbow extension is full (grade 5) and wrist flexion is grade 4, but finger flexion (C8) is absent. Sensory testing shows intact light touch at C8 and absent sensation below T1. What is the motor level?

In a patient with C7 tetraplegia, elbow extension is full (grade 5) and wrist flexion is grade 4, but finger flexion (C8) is absent. Sensory testing shows intact light touch at C8 and absent sensation below T1. What is the motor level?

• A. C8
• B. T1
• C. T2
• D. C7

Answer: (D)

Motor level is set by the most caudal key muscle that has at least a 3/5 strength, with all muscles above it functioning at least as well as this level. In this scenario, elbow extension (the C7 key movement) is normal (5/5), while finger flexion (C8) is absent. Since the next more caudal key muscle (C8) does not meet the 3/5 threshold, the most caudal intact motor function is at C7. The wrist (C6) is 4/5, which is better than 3/5 but still roped above the C7 level, so it doesn’t change the conclusion. Sensory testing shows intact sensation at C8 and absent sensation below T1, indicating a sensory level around T1, but the motor level is determined by the most caudal motor function, which here is C7. Therefore, the motor level is C7.

Motor level is set by the most caudal key muscle that has at least a 3/5 strength, with all muscles above it functioning at least as well as this level. In this scenario, elbow extension (the C7 key movement) is normal (5/5), while finger flexion (C8) is absent. Since the next more caudal key muscle (C8) does not meet the 3/5 threshold, the most caudal intact motor function is at C7. The wrist (C6) is 4/5, which is better than 3/5 but still roped above the C7 level, so it doesn’t change the conclusion. Sensory testing shows intact sensation at C8 and absent sensation below T1, indicating a sensory level around T1, but the motor level is determined by the most caudal motor function, which here is C7. Therefore, the motor level is C7.