+ What are the key components of this patient’s history and physical examination, and why?

Relevant History:

• How did this start? Context? Onset? Was there trauma/injury?
• Unilateral or bilateral?
• Any other motor or sensory deficits?
• Any neck pain, bowel or bladder dysfunction?
• Is there pain?
• Is there a history of diabetes or alcohol consumption?
• Is the patient right hand dominant or left hand dominant?
• What is the patient’s work status?
• Has the patient sought care or workup for this problem before seeing me?
• Functional history and current functional status, including equipment usage?
• Social history?
• Family history?
• Past Medical and Surgical History?
• Medications?

Relevant Physical Examination:

• Vital signs
• Inspection
• Palpation
• Gait analysis
• Range of motion of neck, shoulder, elbow, wrist, fingers
• Manual muscle testing, sensation, reflex examination of bilateral upper limbs
• Special testing: Spurling, Tinel at elbow and wrist

+ What is your differential diagnosis for this patient?

• Brachial plexopathy, cervical radiculopathy, radial neuropathy, vitamin B12 deficiency, alcoholic neuropathy, diabetic polyneuropathy, peripheral polyneuropathy, shoulder/humerus/elbow fracture, cervical myelopathy, stroke, lead toxicity, wrist extensor tendon rupture.

+ What workup would you order to help narrow your differential diagnosis?

• EMG/NCS right upper extremity
• Labs: CMP, CBC, B12, Hemoglobin A1C
• X-ray of right shoulder, humerus, elbow
• Diagnostic ultrasound scan of the right radial nerve

+ Challenge Question

• What are the electrodiagnostic differences and implications of neurapraxia vs. axonotmesis vs. neurotmesis?

+ Challenge Answer

• These are three different Seddon nerve injury classifications.

• Neurapraxia is defined as a conduction block. This is the failure of an action potential to travel beyond a particular location along a nerve while the ability to conduct impulses beyond that spot is normal. This is revealed on nerve conduction studies as loss of amplitude of a CMAP (compound motor action potential) when stimulating proximal to the point of conduction block, and normal amplitude distal to that location. A spot of focal demyelination (conduction block) should resolve within a few weeks and thus carries a good functional prognosis, improving the patient’s strength and nerve conduction study findings (CMAP repair).

• Axonotmesis is defined as axon loss due to crush or stretch injury to a nerve, leaving the epineurium intact but axons destroyed within a nerve (low-amplitude CMAP). Axonotmesis carries a more severe functional prognosis than neurapraxia, as destroyed axons need to regenerate down the nerve path toward their distal muscle fiber targets in order to reinnervate them “from scratch”. This is more difficult and less certain for the body to accomplish. Regeneration typically occurs with axons growing approximately 1 inch per month, so this is a much slower functional recovery, and recovery may only be partial. The CMAP can be electrodiagnostically “repaired” with enough time.

• Neurotmesis is defined as complete nerve transection/severing through the epineurium, and carries the worst functional prognosis of these three nerve injuries. Complete weakness and absent CMAPs of the affected nerve in muscles distal to the site of injury are typically observed. Functional prognosis is very poor, as there is essentially no nerve path for the damaged axons to regrow along to find their distal targets again.

+ Radiology, EMG/NCS, and laboratory workup reveals the following:

• CMP: normal
• CBC: normal
• Vitamin B12: normal
• A1C: 5.8%
• EMG/NCS: Absent SNAP (sensory nerve action potential) to right thumb snuffbox, diminished CMAP to the extensor indicis proprius. Fibrillations and positive sharp waves in the right extensor indicis proprius, extensor digitorum, brachioradialis, supinator. Normal EMG of right triceps, deltoid, pronator teres, abductor pollicis longus, and cervical paraspinals.
• X-rays reveal no acute or subacute bony injury to the right shoulder, humerus, or elbow.
• Diagnostic ultrasound scan of the right radial nerve reveals enlargement and hypoechogenicity of the radial nerve at the spiral groove of the humerus without irregularities of the humeral cortex.

+ How would you manage this patient?

• Occupational therapy with bracing to start.

+ Challenge Question

• What type of bracing and wearing schedule do you recommend?

+ Challenge Answer

• Wrist cock-up splint to improve wrist extension and enable tenodesis effect for grip. Wear during daytime “operational” hours for functional assistance during manual tasks. May remove during sleep. Generally avoid wearing for longer than several hours at a time, and always check skin for rash or breakdown.

+ Is there anything else you would do for this patient?

• Repeat EMG/NCS in 3 months to monitor clinical and electrodiagnostic recovery.
• Gabapentin for neuropathic pain, uptitrate as tolerated, caution against sedation.

+ Anything else?

• Not at this time, thank you.

+ How would you advise the patient to proceed?

• I would continue monitoring for another 3 months, given that his injury was only 4 months ago at this point and has not stabilized neurologically. Continue OT/home exercise program and medications as directed.

+ How would you manage the patient at this point in time?

• I would recommend orthopedic surgery consult for consideration of tendon transfer surgery. I would discuss with the patient the rationale for this procedure and goals. I would answer all questions to the best of my ability and ask if the patient is agreeable to this plan.

+ Explain the purpose and principles of tendon transfer surgery in this patient's case.

• The purpose of a tendon transfer is to utilize intact neuromuscular structures to perform the functions of weak muscles. In other words, one can transfer the tendon from a strong muscle with intact, healthy innervation to the tendon attachment site of a muscle which has been denervated. For example in this case, one might consider transferring the flexor carpi radialis tendon over to the dorsal aspect of the wrist in order to convert the muscle into a wrist extensor, as this patient lacks radial nerve-innervated active wrist extension. This procedure is performed by an orthopedic surgeon. Typically 1 grade of strength is lost in the donor tendon following transfer surgery. For example, a 5/5 grade flexor carpi radialis muscle/tendon may only maintain 4/5 strength after it is transferred over to become a wrist extensor. Tendon transfer surgery is generally considered for functional improvement in cases that have stabilized neurologically and electrodiagnostically.

+ “Doctor, I still can’t work and need to stay on disability. I need you to fill out my disability paperwork.”

• I am so glad to hear your surgery went well, you have regained wrist function, and that you are having minimal pain. If you are still feeling disabled then we need to discuss this further and possibly investigate further. Could you please explain why you can no longer work your previous job?

+ It just doesn’t feel right anymore. Like it’s not how it used to feel when I moved my wrist around.”

• I am so sorry to hear that. Thank you for sharing that with me. If you could please explain further, I am ready to listen. Are you experiencing numbness or tingling? Any new symptoms since we last talked? What you have described so far is common after such a surgery, and can be improved with physical and occupational therapy, a work hardening program to help get you back up to speed with work-related tasks, and even a functional capacity evaluation to see what sorts of tasks you are able to complete, and which ones give you trouble. Let’s continue working together to maximize your function. I want you to know I am here and ready to listen.