102 Brachial Plexus Injury and Horner Syndrome

Case 102 Brachial Plexus Injury and Horner Syndrome

Stephen M. Russell

Clinical Presentation

A 35-year-old woman was an unrestrained driver in a car accident. She struck her shoulder against the steering wheel, which caused right-arm weakness and numbness.
She is unable to raise the arm or flex at the elbow.
Painful paresthesias and numbness in the thumb and index finger have also been present since the accident.
Imaging revealed no fractures or rotator cuff tears. Despite physical therapy, she has had no evidence of recovery in the 3 months since the accident.
On examination, she has atrophy of the deltoid, supraspinatus, infraspinatus, and biceps muscles. She cannot flex, abduct, or externally rotate the arm at the shoulder joint. She also cannot flex at the elbow or supinate the forearm.
The rest of her arm and hand muscles are full strength.
She has numbness along the radial forearm and hand, including the thumb and index finger.
She has a positive Tinel’s sign in the right supraclavicular space that radiates to the index finger.

Questions

What is your differential diagnosis for this woman?
What are sensory territories and muscles innervated by C5/C6 (i.e., the upper trunk)?
What diagnostic tests would you order for this patient?
Why wait 3 months prior to performing surgery?
What are the surgical outcomes of brachial plexus surgery?
Are there any surgical options if the injury was longer than 2 years ago?
If this patient had presented instead with numbness on the dorsum of his hand, weakness in the hand intrinsic muscles, as well as ptosis and myosis in one eye, where would the lesion then be localized?
What other anatomic site can give the same eye findings?
How do these eye findings affect prognosis?

Answers

What is your differential diagnosis for this woman?

She has a brachial plexus stretch injury involving C5/C6 and/or the upper trunk (Erb palsy).
Less likely diagnoses would include cerebral contusion or stroke, brachial neuritis, cervical spine fracture or herniated disc, and musculoskeletal injuries to the shoulder and arm.

What are sensory territories and muscles innervated by C5/C6 (i.e., the upper trunk)?
- The location of combined C5/C6 and/or upper trunk sensory loss is depicted in Fig. 102.1.¹
- Patients with an upper trunk (Erb) palsy would be weak in the following muscles: rhomboids, deltoid, supraspinatus, infraspinatus, clavicular head of the pectoralis major, biceps, brachialis, brachioradialis, and possibly the latissimus dorsi.
- In general, patients cannot abduct the shoulder or flex the elbow.¹
What diagnostic tests would you order for this patient?
- It is important to image (magnetic resonance imaging [MRI] or computed tomography [CT] myelogram) the cervical spine to exclude rootlet avulsion because if present, graft repair from avulsed spinal nerves would not be an option.
- Electrodiagnostic evaluation must wait for 3–4 weeks so any signs of muscle denervation would be apparent after wallerian degeneration has occurred.
- A repeat electrodiagnostic test 3 months later may reveal subclinical improvement.
- A radiograph of the shoulder is important to exclude fractures and dislocations.
Why wait 3 months prior to performing surgery?
- A 3-month waiting period is recommended because many patients with brachial plexus stretch injuries recover spontaneously within a few months (neurapraxic injuries), this initial observation period prevents them from undergoing surgery.
- Furthermore, for patients with axonotmetic injuries, providing adequate time for the axons to regenerate across the injury site one can then reliably conclude that an absence of an intraoperative nerve action potential across this injured segment would indicate that a spontaneous recovery would not occur.² Therefore, this segment of injured nerve is replaced with sural nerve grafts.
What are the surgical outcomes of brachial plexus surgery?
- This depends on whether nerve grafts were used. If the upper trunk is scarred but has a positive nerve action potential recording across its injured segment, then only scar tissue is removed and no grafts are used (Fig. 102.2A-C).
- These patients do well, with an 80–90% chance of achieving grade ⅗ or better muscle strength on the Medical Research Council scale.
- Alternatively, when there is an absent nerve action potential recording across the injured segment of nerve, or if the nerve is obviously transected, sural grafts are used to reconstruct the nerve (Fig. 102.2D-F).
- The chance of these patients achieving grade ⅗ or better muscle strength is ~50% (results depend on patient age, surgical delay, distance to recipient muscles, and graft length).^3,4
Are there any surgical options if the injury was longer than 2 years ago?
- Nerve repair rarely works if performed more than 2 years after the injury.
- In these patients, and for those who did not improve much after a previous brachial plexus repair, other surgical options are available, including tendon transfers (e.g., Steindler procedure for arm flexion) and free muscle transfers (e.g., gracilis vascularized flap for elbow flexion).
If this patient had presented instead with numbness on the dorsum of his hand, weakness in the hand intrinsic muscles, as well as ptosis and myosis in one eye, where would the lesion then be localized?
- The lesion described represents a preganglionic brachial plexus injury with Horner syndrome.
- Nerve roots involved include C8 and T1 (and possibly C7).
- Other clinical findings may also include anhidrosis, and serratus anterior paralysis (long thoracic nerve, innervation from C7 root).
- A meningocele may be seen on imaging studies at the level of these cervical roots.
- The sympathetic chain has also been damaged and avulsed; damage is proximal to the dorsal root ganglion.
What other anatomic site can give the same eye findings?
- Horner syndrome can be categorized in three types depending on the level of the injured neurons (Fig. 102.3 for an anatomic illustration).^5–9
- First-order neuron lesions may present with hemisensory loss, dysarthria, dysphagia, ataxia, vertigo, and nystagmus. Anhidrosis affects the ipsilateral side of the body. Causes include the following:
  - Chiari malformations, syringomyelia¹⁰
  - Basal meningitis or skull-base tumors
  - Stroke with Wallenberg syndrome (lateral medullary syndrome)
  - Multiple sclerosis
  - Neck trauma and/or dissection of the vertebral artery
  - Pituitary tumors
- Second-order neuron lesions (as in this case) may present with facial, neck, axillary, shoulder or arm pain, cough, hemoptysis, history of thoracic or neck procedures or trauma, anhidrosis of the ipsilateral face. Causes include the following:
  - Pancoast tumor or cervical rib
  - Birth trauma
  - Aortic dissection
  - Central venous line placement, chest tube placement¹¹
  - Trauma or surgical injury to the neck or upper thorax
  - Hilar lymphadenopathy
  - Middle ear lesions¹²
- Third-order neuron lesions may present with diplopia from sixth nerve palsy, numbness in the distribution of the first or second division of the trigeminal nerve, and pain. Anhidrosis is either absent or limited (fibers travel with the external carotid artery). Causes include the following:
  - Internal carotid artery dissection¹³
  - Raeder’s paratrigeminal syndrome
  - Carotid cavernous fistula
  - Herpes zoster
How do these eye findings affect prognosis?
- Nerve damage proximal to the dorsal root ganglion (demonstrated by the presence of a Horner syndrome) usually cannot be directly surgically repaired.
- This often requires a neurotization procedure, which is more complex and has poorer outcomes.¹⁴
- In a retrospective study on 51 patients, outcomes of neurotization at the level of the brachial plexus show results of ~38% useful recovery.¹⁵