Which finding is most consistent with a C5 radiculopathy?

Which finding is most consistent with a C5 radiculopathy?

• A. Weakness of shoulder abduction due to deltoid weakness
• B. Weakness of finger flexors
• C. Loss of patellar reflex
• D. Weakness of ankle dorsiflexion

Answer: (A)

Cervical radiculopathy at the C5 level typically produces weakness in muscles that receive input from that root, most notably the deltoid responsible for shoulder abduction. When the C5 nerve root is affected, lifting the arm out to the side (abduction) becomes weak because the deltoid’s motor fibers are impaired, and the initial part of the movement can be limited by involvement of nearby C5-innervated muscles like the supraspinatus as well. The other options point to different nerve roots: weakness of finger flexors suggests a lower cervical or even thoracic involvement (C8–T1), loss of the patellar reflex points to L4, and weakness of ankle dorsiflexion points to L4–L5. Therefore, weakness of shoulder abduction from deltoid weakness best fits a C5 radiculopathy.

Cervical radiculopathy at the C5 level typically produces weakness in muscles that receive input from that root, most notably the deltoid responsible for shoulder abduction. When the C5 nerve root is affected, lifting the arm out to the side (abduction) becomes weak because the deltoid’s motor fibers are impaired, and the initial part of the movement can be limited by involvement of nearby C5-innervated muscles like the supraspinatus as well.

The other options point to different nerve roots: weakness of finger flexors suggests a lower cervical or even thoracic involvement (C8–T1), loss of the patellar reflex points to L4, and weakness of ankle dorsiflexion points to L4–L5. Therefore, weakness of shoulder abduction from deltoid weakness best fits a C5 radiculopathy.