Numbness and pain in the active patient: Part 1
Nerve root and plexus injuries
by Paul Winston, MD and Corrie Graboski, MD
Vol.16, No.11, November 2008
case presentation

A 31-year-old personal trainer presents to his family physician with right arm pain and weakness. The hand is also burning and tingling at night. He can no longer do push-ups and fears a radial nerve injury. A week before the arm pain appeared, he awoke one night with intense neck pain. He’s recently been doing much higher intensity weight training, with a lot of overhead presses. A visit to a chiropractor brought some temporary relief, and over the next week neck pain improved, but the pain began to burn down the arm, specifically into the tip of his middle finger. He’s noticed that the middle fingertip feels “funny.” He’s too weak to work out, has difficulty lifting his young daughter and can no longer jog or play volleyball due to pain.

Introduction

Numbness, tingling and pain are frequent complaints in the physically active; however, true neurologic injury with objective weakness is thankfully less common. The goal of the physician is to quickly triage which symptoms merit a thorough neurologic workup. The key to diagnosis is an organized approach that localizes the symptoms to a spinal level, myotome, dermatome, plexus or a peripheral nerve. It’s important to first rule out neurologic emergencies due to traumatic spinal cord injury, brain injury or myelopathy caused by a large disc protrusion and to screen for weakness, bowel or bladder changes, saddle anaesthesia and, if appropriate, cranial nerve damage.

Root and plexus injuries

The most commonly reported sports-related nerve injury is the Burner or Stinger.1,2,4 Stingers are most common in impact sports such as rugby. The mechanism is traction of the arm with the head extended away. The patient will feel pain, numbness, and perhaps transient weakness along the C5-C6 dermatomes and myotomes. Usually, it lasts seconds but occasionally symptoms persist.1 It’s essential to eliminate the possibility of partial cord injury before return to play.

The key Stinger examination focuses on the C5-C6 segments. This includes looking for atrophy or fasciculations in the shoulder girdle, impaired sensation to the shoulder, lateral forearm and digits 1 and 2 of the hand. The C5-C6 biceps and brachioradialis reflex should be compared to the ipsilateral C7-C8 triceps reflex, and to the contralateral side. Power testing focuses on the C5-C6 muscles including the deltoid — shoulder abduction, elbow flexion, including testing with the forearm in neutral to look at the C5-C6 radial nerve innervated brachioradialis muscle. Pronation, testing C6-C7 muscles, and supination, flexing a C5-C6 group, may both exhibit weakness, as may the wrist flexors and extensors.

The approach to brachial plexus injuries consists of similar localizing techniques. Any weakness in a radial innervated muscle, such as the triceps, should trigger examination of other muscles that come off the posterior cord, such as the latisimus dorsi, subscapularis and teres major, most internal rotators of the shoulder, as well as the deltoid, a C5-C6 muscle off the posterior cord.

Persistent neurological signs of injury to the plexus or nerve roots after a contact injury should be referred for electrodiagnostic testing. Imaging by MRI or CT scan is also indicated. Compromises to the cervical canal such as congenital stenosis must be ruled out. Painful onset without injury may suggest brachial neuritis. The patient should remain off play until an accurate diagnosis is made.

It’s worth noting that electromyography (EMG) often shows no signs of denervation for up to three weeks following injury, so a stat EMG consult isn’t necessary. The exception to this rule would be if there is suspected nerve root avulsion. In this case, EMG can help with early diagnosis, and referral to a surgeon should be prompt. The EMG can be quite helpful in diagnosing plexus injuries, as MRI may miss focal pathology such as neuropraxic injury.

Scapular winging — a plexus injury

Winging scapula is a neurologic injury most commonly seen in volleyball and baseball players. Patients will complain of pain in the shoulder, weakness and instability. The scapular dysfunction generally involves nerves that originate close to the spinal nerve roots. In the throwing players, it’s not usually true winging, but rather a suprascapular nerve entrapment that causes weakness of the infraspinatus and possibly supraspinatus muscle. True winging is most often caused by injury to the long thoracic nerve that innervates the serratus anterior muscle, and less commonly due to spinal accessory nerve injury, causing trapezius dysfunction.

To differentiate the two most common causes, the clinician must dissect the action of the muscles. For long thoracic nerve injury, resisted forward flexion causes the intact trapezius and rhomboids to wing the scapula medially. To bring out trapezius winging, by contrast, the arms are resisted in abduction, which causes lateral winging due to the unopposed serratus anterior. (Figure 1)

Radiculopathy

Radiculopathy due to disc prolapse or canal stenosis is a common occurrence and likely underreported in the sports literature. It often strikes weightlifters. Accurate diagnosis consists of a history of acute neck or back pain, with subsequent radiation down the limb and subjective weakness and paresthesias. For instance, in a C6 radiculopathy, a typical patient might report sharp burning pain in the neck with pain radiating down the arm to the thumb and index fingers. The pain is worsened with coughing and flexion of the spine. The patient has difficult with elbow flexion and pronation, shoulder abduction and wrist extension, and may notice wasting of the biceps. A thorough examination would find a decreased or absent biceps and brachioradialis reflex, and weakness in the movements mentioned above.

It’s important to note, though, that since nearly every muscle receives innervation from more than one root level, and dermatomes overlap, you’re more likely to see partial impairment of strength, reflexes and sensation.2 In contrast, a crush injury to a peripheral nerve could result in total loss of function and severe wasting. Table 1 offers key findings for each radicular lesion.

User’s guide to electromyography

While the MRI may show a structural lesion, the EMG is the only test that may show which muscles have been functionally affected. Unfortunately, the EMG won’t detect purely sensory radiculopathies. The EMG can offer insight into whether nerve injury is still acute, or has entered the repair phase.

Basic knowledge of a few simple concepts can help with interpretation of the EMG report. For instance, the electromyographer will refer to spontaneous activity, such as fibrillations or positive sharp waves. This describes an acute ongoing nerve injury in which muscle fibres fire rhythmically on their own, like a cardiac pacemaker cell, due to their loss of connection from the nerve. In contrast, a chronic or healing nerve injury will show “large, polyphasic motor units, with decreased recruitment.” This refers to the reinnervation of the muscle fibres due to sprouting of nerve axons.

Common mimickers

Numerous soft tissue and bony abnormalities may mimic radicular symptoms.

For instance a rotator cuff injury or tennis elbow may also present with similar superficial features. Piriformis syndrome and tight gluteal muscles often cause pain down the leg. Thoracic outlet syndrome can very rarely be due to true neurologic compression, but is more often a vascular phenomenon. Finally, systemic neurologic conditions, such as multiple sclerosis or Guillain-Barré must be ruled out.

We’ve found that many young women with generalized ligamentous laxity/hypermobility complain of numbness in the arm and hands, but have normal neurologic findings and test results. This is most likely due to traction on the brachial plexus due to drooping shoulders.

Case revisited

Our patient’s family physician feared possible nerve damage or disc herniation damage, and started him on muscle relaxants, a mild narcotic and amitriptyline for sleep, which continued to dull the pain. The case was referred to a sports medicine physician familiar with nerve injuries, who noted atrophy in the triceps and pectoralis muscles. On inquiry, the patient complained that his hard-earned right pectoral muscles had shrunk. The physical examination revealed grade -4/5 strength in the right triceps, wrist and finger extensors, the pectoralis major, and subtle weakness in elbow pronation and wrist flexion, and a sluggish triceps reflex. Sensation was preserved, although the middle finger felt different.

As it was six weeks after the injury, electrodiagnostic tests were performed. There was acute spontaneous activity noted in the right pectoralis major muscle, triceps, flexor carpi radialis, and extensor digiti communis muscles, with a neurogenic recruitment pattern. This represented multiple C7 muscles, in the radial, median and lateral pectoral nerves and different divisions of the brachial plexus, indicating a C7 nerve root injury. The patient was asked to hold off weight training, given a medication for neuropathic pain, and sent for gentle physiotherapy and traction. A CT scan revealed a disc protrusion of the C6-C7 disc pressing on the exiting C7 nerve root.

He returned for a follow-up EMG two months later, as he had some residual weakness. The EMG now showed only a few runs of spontaneous activity, and many polyphasic wave forms, indicating successful reinnervation.

Conclusion

It may seem daunting to localize a lesion; however, having a simple anatomy text or muscle chart on hand can be extremely helpful. Athletes may be used to working through pain, but with nerve injuries extreme caution must be undertaken. The rehabilitation focuses on maintenance of strength and preserving range. A useful rule of thumb is that nerves regenerate at a millimetre per day — an inch per month. There has been no proven way demonstrated to speed this recovery. Recovery may remain incomplete, despite optimal care, and it’s essential to establish that there’s full recovery before resuming sports. Medications such as gabapentin and pre-gabalin can be quite helpful in managing neuropathic pain. Epidural corticosteroids remain controversial but may offer symptomatic relief. The tricyclic anti-depressants can be very useful, if given in sufficient dosage.

Table 1: Key findings for radicular lesions

Root Level

Muscles affected

Sensory Loss/Pain

Reflex

C5
C6

Shoulder — abduction/external/internal rotation
Elbow — flexion/pronation/supination, Wrist flexion

Lateral arm and forearm into the thumb

Biceps Brachioradialis

C7

Triceps, wrist extensors, finger extensors

Posterior arm to middle finger

Triceps

C8
TI

Finger flexion, adduction, abduction

Medial forearm into 4th and 5th digits

L3
L4

Hip flexion, hip adductors, knee extensors, ankle dorsiflexion

Medial knee, calf, foot

Patella tendon

L5

Toes extensors, ankle inversion/eversion, hip abduction

Dorsum of the foot

Medial
hamstring

S1

Ankle plantar flexion, knee flexion, hip extension

Lateral foot

Ankle

 

feature image
Map of human dermatones. In practice, there is considerable overlap between regions.
feature image
Winging due to spinal accessory nerve entrapment in the scalenes
Note the prominent medial border of the right scapula lies laterally at rest. Also note the absent trapezius muscle on the right.
feature image
With arm abduction, the medial winging is prominent as the serratus anterior protraction of the shoulder is unopposed. Electromyography revealed denervation in the sternocleidomastoid as well.

References:

  1. Krivickas L, Wilbourn A. Muscle and Nerve 1998;21:1092-4.
  2. Preston D, Shapiro B. Electromyography and Neuromuscular Disorders. Elsevier 2005.
  3. Safran, M. Am J Sports Med 2004;32(4):1063-76.
  4. Toth C et al. Sports Med 2005;35(8):717-38.
subscription   |   advertising information   |   about us   |   contact us   |   privacy statement   |   legal terms of use   |   Doctors review
Oncology Exchange   |   Relay   |   Health Essentials   |   Our Voice   |   login