Suprascapular nerve injury

1. What nerve roots does the suprascapular nerve arise from?
2. What muscles does the suprascapular nerve innervate?
3. How is the suprascapular nerve injured?
4. What is the presentation of suprascapular nerve injury?

Answers:
1. C5 and C6, continuing to contribute to the upper trunk.
2. Supraspinatus, followed by the infraspinatus.
3. Forced scapular protraction, penetrating wounds, crutches, traction, rotator cuff injury, Erb's palsy, supraglenoid ganglions, hematoma, entrapment.
4. Weakness in shoulder abduction and external rotation. If there is an injury at the spinoglenoid notch, only the infraspinatus may be affected.