Thoracic Limb Nerves

Thoracic Limb Nerves

1. Radial n.

   • Extensors of elbow, carpus, digits
   • Cutaneous to craniolateral antebrachium and dorsomedial manus
     • medial cutaneous antebrachial n.
   • Common Causes of Injury
     • Trauma on lateral side of humerus
     • Avlusion of brachial plexus
     • Fracture of 1st or 2nd rib
     • Venipuncture to superficial branch
   • Functional Damage
     • Proximal
       • Loss of elbow, carpus (ECR, UL), and digit (CDE, LaDE) extension (paralysed
       • Loss of sensation to craniolateral antebrachium and dorsomedial manus
       • Clinical Signs
         • Dropped Elbow
           • Non weight bearing
         • Knuckled Paw
       • Reflex Tests
         • Pinprick Test to craniolateral antebrachium and dorsomedial manus
         • Triceps reflex test
           • Target: golgi tendon receptors in triceps tendon Interpretation Elbow extends (pass) False positive: excessive pressure on triceps tendon, passive extension of elbow No extension = Negative False negative: not hitting target 
         • Proprioceptive Test (superficial branch)
     • Distal Only
       • Knuckled paw
         • Weight bearing
       • Paralyzed ECR, UL, CDE, LaDE
       • ECR Reflex Test
         • Target: muscle spindle receptors of ECR  Interpretation:  Carpus extends = Pass No carpus extension = Fail False Negative: not stimulating the ECR
   • Tensor fascia lata antebrachii, anconeus , brachioradials, supinator mm.

2. Axillary n.

   • Flexors of the shoulder
     • Caudal group muscles of the shoulder
   • Cutaneous sensation to distal lateral 1/3 brachium
     • Cranial lateral cutaneous brachial n.
   • Common Causes of Injury
     • Procedures approaching shoulder joint
   • Functional Damage
     • Lack of cutaneous sensation to distal lateral 1/3 brachium
     • Atrophy of primary flexors of the shoulder
     • Compensation
       • Secondary flexors of the shoulder
     • Reflex Test
       • Pinprick

3. Suprascapular n.

   • Extensors of the shoulder joint
     • Cranial group muscles of the shoulder
   • Common Causes of Injury
     • Fracture at the neck of the scapula
     • Over abduction
     • Violent Retraction
   • Functional Damage
     • Clinical Signs
       • Prominent scapular spine
       • Atrophy of shoulder extensors
       • Outward Deviated joint
       • Lack of lateral support to shoulder joint
         • Shoulder Slip (Sweeney in horses)
     • No reflex tests
       • Joint = synsarcosis
       • No cutaneous branches
     • Compensation
       • Biceps brachii, brachicephalicus

4. Musculocutaneous

   • Primary flexors of elbow joint
   • Cutaneous sensory to medial antebrachium
     • medial cutaneous antebrachial n.
   • Functional Damage
     • Unable to flex elbow
     • Loss of skin sensation to medial antebrachium
     • Clinical Signs
       • Atrophy to primary flexors of elbow
       • Fails to offer paw
       • Reluctance to go up stairs
     • Compensation
       • Normal gait due lattisimus dorsim (flexion) and triceps brachii (relaxation)
     • Reflex Test
       • Biceps Tendon Reflex Test
         • Target: biceps tendon Interpretation: Pass = elbow flexes False Positive: excessive pressure by index finger on biceps tendon Fail = no elbow flexion False Negative: excessive pressure of the three fingers on the triceps tendon (oppose elbow flexion)
       • Pinprick Test

5. Medial n.

   • Flexors of the carpus and digits
     • Caudomedial group m. of antebrachium
   • Sensory to caudomedial aspect of manus
   • Functional damage (rare)
     • Affected pronator teres, FCR
     • Remaining muscles not affected since innervated by both median and ulnar nerves.
     • Clinical Signs
       • Hyperextended carpus
         • Raised claws
     • Reflex Test
       • Caudomedial Manus

6. Ulnar n.

   • Supplies FCU, SDF, ulnar and lateral part of DDF
   • Sensory to caudal cutaneous antebrachial n.
   • Functional Damage (rare)
     • Affected FCU
     • Reflex Test
       • Pinprick Test
         • Caudal antebrachial region
         • 5th digit