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Clinical case: Brachial Plexus Injury - want to learn more about it?

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Clinical case: Brachial Plexus Injury

After reviewing this case you should be able to describe the following:

  • Electrodiagnostic testing and why was it used in this case.
  • The fatal components of hanging.
  • Why this patient was believed to have had a lower, and specifically, not an upper motor nerve lesion (how it was possible to rule out brain damage due to hypoxia).
  • How and why brachial plexus injury is common obstetrical injury.
  • The anatomical and clinical differences between a dermatome and a cutaneous area innervated by a peripheral nerve. Why this difference is important in this case.

This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden

It has been modified and reviewed by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD.

Case Description

History

The patient was a young man with a history of weakness and numbness in his left arm. A complaint of shortness of breath occurring several months prior to the current clinic visit had prompted a radiographic workup that showed a slightly elevated left hemidiaphragm at the time. However, detailed MRI and MRA neuroimaging at the time failed to show a cause for the elevation.

Physical Exam

Physical exam at the current visit to the clinic showed that the young man had difficulty raising his left arm against resistance above the horizontal plane. The patient also showed slight atrophy of both the left deltoid and supraspinatus muscles, and atrophy and weakness of the intrinsic muscles of the left hand. Full strength and normal muscle mass were, however, demonstrated in the left biceps and triceps brachii muscles.

The sensory exam showed reduced sensation to light touch and pinprick along the upper lateral shoulder, suggesting left C5 ramus nerve compromise. In addition, sensory deficits along the medial aspect of the forearm, hypothenar eminence and the fifth digit, and the hand muscle weakness suggested that the left C8 and T1 spinal nerves were also affected.

Paraclinical Investigations

In support of these three nerves (C5, C8, and T1) being involved in the young man’s condition, an electrodiagnostic study found denervation and early regeneration potentials for the left C5, C8 and T1 nerves at the trunk level of the brachial plexus (Figure 1-2).

Diagnosis & Causes

The patient was initially evasive pertaining to the events preceding his neurological deficits. He repeatedly denied any trauma, and a serological exam failed to reveal evidence of an inflammatory process that could account for his motor deficits. With persistent inquiry, however, the patient finally disclosed that several months ago he had attempted suicide by hanging.

He had used a rope and jumped with it around his neck from a significant height to cause injury. The patient stated that just when the noose tightened, his neck was stretched upward. But having a change of mind, the patient then reached up and grabbed the rope. Nevertheless, he remained suspended on his abducted upper limb before he was able to support himself on his feet and remove the noose.

Management & Evolution

Conservative treatment, including physical therapy, resulted in gradual improvement over several months of the deficits. Psychiatric care was also initiated. 

Anatomical and Medical Considerations

Figure 1. The main photograph (cadaver) shows the roots and trunks of the brachial plexus. The inset shows the area magnified in the larger image. UT, upper trunk; MT, middle trunk; LT, lower trunk.

The brachial plexus is a complex of nerves from C5-T1 that provide motor and sensory innervation to the upper extremity (Figure 1). Injury to the brachial plexus usually results in a pattern of functional deficits that implicates the roots or nerves of the brachial plexus that are compromised.

Figure 2. An illustration showing the brachial plexus origin and its branches.

Erb, or Erb-Duchenne palsy, is the name given to a typical upper brachial plexus injury involving spinal nerve roots C5 and C6. In contrast, Klumpke’s, or Klumpke-Dejerine palsy, affects the lower roots of the brachial plexus (C8, T1). Both these types of lesions usually involve a specific injury mechanism that results in the excessive stretching of either the upper plexus (due to an increase of the angle between the shoulder and head) or the lower plexus (associated with hyper abduction of the arm (Figure 3).

Figure 3. Mechanism of brachial plexus injury. The image on the left shows the mechanism of the left upper brachial plexus injury, whereas the one on the right shows the mechanism for the left lower brachial plexus injury.

In the case described here, the patient had a puzzling neurological deficit consisting of apparently both upper and lower brachial plexus injuries. Based on the radiographic findings and patient history, clinical interpretations led to the reasoned response that initial partial diaphragmatic paralysis was responsible for the shortness of breath experienced by the patient. This paralysis was likely associated with some injury to the C3, C4 and C5 spinal nerves, phrenic nerve (Figure 4).

Figure 4. An illustration showing the left phrenic nerve origin in addition to its path through neck and thorax before reaching the dome of the left hemidiaphragm.

Physical examination of the patient found atrophy of the intrinsic muscles of the hand and also ipsilateral weakness of the supraspinatus and deltoid muscles. 

The hypothenar and intrinsic muscles of the hand are innervated by branches of the median and ulnar nerves that contain elements from the ventral roots of C8-T1. C5 and C6 innervate the supraspinatus muscle via the suprascapular nerve. The axillary nerve, formed also from roots of the C5-C6 spinal nerves, innervates the deltoid muscle. 

This pattern of involved nerves and the electrodiagnostic findings suggest injury to the C5, C6, C8 and T1 nerve roots. Apparently the C7 and possibly C6 nerve roots were spared in this patient. It seems likely the damage occurred due to successive movements during the attempted hanging episode that initially stretched the upper, and then later the lower components of the brachial plexus. Natural recovery from brachial plexus injuries usually occurs within six months. However, the patient in this case was very non-compliant and thus the authors were unable to determine the degree of recovery in him.

Upper and Lower Brachial Plexus Roots Injury

In Erb’s palsy, the most commonly affected nerves are the suprascapular, musculocutaneous, and axillary. The patient typically presents with loss of sensation in the arm and paralysis and atrophy of the deltoid, biceps, and brachialis muscles. The position of the limb in Erb’s palsy is characterized by: 

  • the arm hangs loosely by the side and is rotated medially
  • the forearm is extended and pronated
  • the arm cannot be elevated from the side
  • the elbow cannot be flexed
  • the forearm cannot be supinated voluntarily

The position of the upper limb is referred to as a "waiter's tip position" (Figure 5).

Figure 5. An illustration showing Erb’s palsy characteristics, which is a common presentation of the upper brachial plexus injuries,.

In lower brachial plexus injuries, the paralysis affects, principally, the intrinsic muscles of the hand, specifically, the interossei, thenar and hypothenar muscles (Figure 6) and the flexors of the wrist and fingers (notably flexor carpi ulnaris and ulnar component of the flexor digitorum profundus).

Figure 6. Cadaver photograph showing intrinsic hand muscles (interossei are not shown because they are deeper to the plane of this dissection). The ulnar nerve innervates these muscles, although the median nerve innervates the thenar muscles via its recurrent branch.

Forearm pronators and wrist flexors may be involved. The classic presentation, known as Klumpke-Dejerine palsy (Figure 7), is the “claw hand,” in which:

  • the forearm is supinated
  • the metacarpophalangeal joints are hyperextended
  • the fingers are flexed

In the case of the patient presented here, he did not show all the signs of either complete upper or lower brachial injury because not all of the spinal nerve roots were affected by the injury (C7 and possibly C6 were spared).

Figure 7. An illustration showing Klumpke-Dejerine palsy characteristics, which is a common presentation of the lower brachial plexus injuries.

Objective Explanations

Objectives

  • Electrodiagnostic testing and why was it used in this case.
  • The fatal components of hanging.
  • Why this patient was believed to have had a lower, and specifically, not an upper motor nerve lesion (how it was possible to rule out brain damage due to hypoxia).
  • How and why brachial plexus injuries are common obstetrical injuries.
  • The anatomical and clinical differences between a dermatome and a cutaneous area innervated by a peripheral nerve. Why this difference is important in this case.

Electrodiagnostic Testing

Electrodiagnostic physicians use electrophysiologic techniques such as needle electromyography (EMG) and nerve conduction studies (NCS) to diagnose, evaluate, and treat people with impairments of the neurologic, neuromuscular, and/or muscular systems. NCS and needle EMG to evaluate nerve and muscle function may specifically be utilized when there is pain in the limbs, weakness from spinal nerve compression, or concern about a neurologic injury or disorder such as occurred in this case.

EMG measures muscle electrical activity in response to motor nerve stimulation of that muscle. During the exam one or more small needle electrodes are inserted into the muscle. The electrical activity of the muscle is then displayed on a computer screen. An audio-amplifier is used so the activity can also be heard.

In NCS, the amount and speed of conduction of an electrical impulse through a nerve is measured. NCS can determine nerve damage and is usually performed at the same time as EMG. Both procedures assist in determining the presence, location, and extent of damage to nerves and muscles.

Fatal Components of Hanging & Lower vs. Upper Motor Nerve Lesions

It is believed that the primary fatal component of suicidal hanging is not from a cervical fracture, airway compression, or sympathetic stimulation, but rather due to internal jugular vein and carotid artery compression. Venous and arterial compression is then followed by airway compression that ultimately leads to global hypoxia. Deaths in attempted hangings are typically associated with respiratory failure or bronchopneumonia. In attempted suicides, motor disorders have been reported and are typically upper motor neuron lesions caused by damage to the basal ganglia due to cerebral anoxia.

Internal jugular vein (green) and carotid artery - lateral-right view

Nerve damage due to anoxia in the patient in this case was excluded during the physical exam because of the atrophy and decreased strength in the involved muscles, indicating that the deficits were lower motor neuron type lesions. Lower motor neuron lesions without ongoing or past inflammatory episodes in a healthy individual are generally caused by trauma. Although the patient initially denied any trauma, it was still high on the differential diagnosis list of the examining physician and was eventually shown to be correct.

Brachial Plexus Injuries in Obstetrics

The generally accepted mechanism of brachial plexus injury in obstetrics is shoulder dystocia. This occurs when, after delivery of the fetal head, the baby's shoulder becomes wedged behind the pubis. Traction to the neck caused by pull of the obstetrician's hand or instruments (e.g., forceps) in such cases result in the neck on the side of the trapped shoulder being stretched and this stretch causes a “strain” on the ipsilateral brachial plexus, resulting in varying degree of injury. The injury most commonly affects the C5 and C6 roots of the brachial plexus, but all roots can be involved.

Although shoulder dystocia is believed to be the common mechanism of birth brachial plexus injury, some injuries appear to occur as a result of intrauterine maladaptation and not birth trauma. Thus, there may be disagreement about the cause of a birth brachial plexus injury in specific cases, which of course has medico-legal implications. Attorneys for aggrieved parents typically blame the obstetrician for the injury, but this may not always be the true pathophysiology in every case. 

Dermatome vs Cutaneous Area Innervated by a Peripheral Nerve

The area of skin supplied by any one spinal nerve, through both its rami constitutes a dermatome and, typically, the dermatome extends around the body from the anterior to the posterior median line (embryologically based). Generally the dermatomes of consecutive spinal nerves overlap markedly. The dermatome pattern for the trunk is simple, that for the limbs is more complex.

T1 dermatome - ventral view

Dermatomes should not be confused with the cutaneous nerves in the limbs, which may contain fibers from more than one spinal nerve and may involve more than one dermatome because of the redistribution of spinal nerves that occur in the brachial and lumbosacral plexuses. Dermatomes are important relative to spinal cord or spinal nerve root injuries whereas the sensory areas supplied by specific peripheral nerves (e.g., ulnar nerve) are important relative to injuries of the extremity in which the nerve is cut or stretched. In the case described here, the roots of some of the spinal nerves of the brachial plexus were stretched or avulsed, so the dermatomes of these nerves were important relative to diagnosing the extent of the injury. 

Clinical case: Brachial Plexus Injury - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 931,206 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Sinha SK, Mishra V, Abdali N, Singh K, Jha MJ, Kumar A. A Rare Case of Angina Pectoris with the Longest Ectopic Left Main Coronary Artery Arising from Right Sinus of Valsalva and a Prepulmonic Course. Case Reports in Cardiology, Volume 2017, Article ID 5483257, 3 pages.
  • Modified by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD

Layout:

  • Abdulmalek Albakkar
  • Adrian Rad

Illustrators:

  • Left phrenic nerve - ventral view - Yousun Koh
  • Internal jugular vein (green) and carotid artery - lateral-right view - Paul Kim
  • T1 dermatome - ventral view - Irina Münstermann
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related diagrams and images

Brachial plexus

Main nerves of the upper extremity

Neurovasculature of the arm and the shoulder

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