In an unconscious patient, both somatic sensory and motor functions of spinal cord levels can be tested using tendon reflexes:
A tap on the tendon of the biceps in the cubital fossa tests mainly for spinal cord level C6.
A tap on the tendon of the triceps posterior to the elbow tests mainly for C7.
The major spinal cord level associated with innervation of the diaphragm, C4, is immediately above the spinal cord levels associated with the upper limb.