C-4 Sensory Dermatome Surface Anatomy

Location

The C4 nerve root can be evaluated by testing sensation on the lateral aspect of the base of the neck coursing out to the shoulder

Significance

Loss of sensation should be correlated to the motor exam; in this case the trapezius (shoulder shrug)

Sensory loss involving a more diffuse area, overlapping several dermatomes suggests a peripheral nerve injury.

The most sensitive way of assessing sensory loss is using two-point discrimination.