eMedicine Specialties > Physical Medicine and Rehabilitation > Plexopathy

Radiation-Induced Brachial Plexopathy

Author: Robert J Kaplan, MD, James E Van Zandt VA Medical Center, Staff Physician, Department of Rehabilitation Medicine
Contributor Information and Disclosures

Updated: Jun 11, 2009

Introduction

Background

Although radiation therapy is used in the treatment of a myriad of neoplastic diseases, it has potentially adverse effects on several organs and systems that are exposed during treatment. Radiation-induced neurotoxicity can involve the central and peripheral nervous systems. Radiation-induced brachial plexopathy can occur when radiotherapy is directed at the chest, axillary region, thoracic outlet, or neck.

Pathophysiology

The radiation dose, treatment technique, and concomitant use of chemotherapy all demonstrate significant association with the development of radiation injury to the brachial plexus. The mechanism is believed to be a combination of localized ischemia and failure of cellular proliferation. The net result is fibrosis of the neural and perineural soft tissues secondary to microvascular insufficiency.

Frequency

United States

The frequency of radiation-induced brachial plexopathy is estimated at 1.8-4.9% and is most common in patients with underlying breast or lung carcinoma.^1,2

International

No satisfactory data have been reported.

Mortality/Morbidity

The natural course of radiation injury to the brachial plexus varies. Two thirds of the patients diagnosed with radiation-induced brachial plexopathy appear to have a stable course over months to years with a gradual worsening of paresthesias and pain. One third of patients deteriorate rapidly and exhibit significant weakness, lymphedema, and pain. No extant studies quantify the degree of disability experienced by patients with this disorder.

Race

No sources in the literature have examined the racial or ethnic distribution of patients with radiation-induced brachial plexopathy.

Sex

Given that breast cancer often is treated with radiation therapy, women experience a greater incidence and prevalence of radiation-induced brachial plexopathy than men.²

Age

No studies have suggested that any given age group is more likely to develop radiation-induced brachial plexopathy. Otherwise, the age range closely parallels that of patients with breast cancer.

Clinical

History

• The interval from the last dose of radiation to the first symptom of plexus disorder varies widely. The average interval range reported is 7.5 months to 6 years.
• Sensory symptoms, such as numbness, paresthesia, and dysesthesia, along with swelling and weakness of the arm, are the predominant presenting symptoms. One series reported that 55% of patients presented with paresthesia, and the remainder had arm swelling and weakness. These neurologic symptoms can be progressive and may lead to a weak and edematous arm.
• Only 18% of patients presented with any significant pain, and pain was a major symptom in only 35% of patients. The pain symptoms usually are limited to the shoulder and proximal arm. Such pain usually is rated as mild to moderate in intensity.
• The physician, therefore, must ask temporally and neurologically focused questions.
  • Address the existence, onset, and pattern of weakness, as well as the presence, quality, and distribution of any altered sensation.
  • Explore the history if the patient also is experiencing pain in the involved extremity.
  • The characteristics of the pain need to be investigated and documented. Also document details of any swelling in the involved extremity.

Physical

Physical examination findings for radiation-induced brachial plexopathy fall into the following 2 categories:

• Neurologic findings are most prominent in the C5-C6 myotomes and dermatomes, as well as diminished deep tendon reflexes supplied by C5-C6. However, Schierle and Winograd reported frequent involvement in the C7 distribution.³ Myokymia is difficult to visualize by inspection or palpation.⁴ In the series by Mondrup and colleagues, 68% of patients with radiation-induced plexopathy presented with upper trunk involvement.¹⁴ The lymphatic-vascular system may reveal prominent lymphedema of the involved extremity without cyanotic or dusky features. There should be no disturbance of arterial or venous circulation in the involved extremity and no changes in the limb to suggest venous insufficiency (varicosities, stasis ulcers, or dermatitis). The Allen test should be negative. Horner syndrome is not present in patients with radiation-induced brachial plexopathy.
• The musculoskeletal examination may reveal decreased scapulothoracic and glenohumeral joint range of motion. This development is not secondary to the plexopathy; rather, it may be experienced if (1) previous surgery was performed in the chest wall or axillary region or (2) the finding is secondary to fibrosis of the musculoskeletal tissues from the radiotherapy. No specific joint tenderness or effusions should be encountered during the examination of the involved extremity.

Causes

Treatment technique (2 vs 3 fields of radiation therapy) and concomitant use of chemotherapy are associated with development of radiation injury to the brachial plexus. No other risk factors or causes have yet been identified.

A 2009 report examined the incidence of brachial plexopathy resulting from the use of stereotactic body radiotherapy to treat apical lesions in early-stage, non – small cell lung cancer.⁵ The study found that grade 2, 3, or 4 plexopathy developed in 7 out of 37 apical lesions exposed to radiotherapy. The report's authors advised that the risk of brachial plexopathy be reduced by keeping the maximum radiation dose to a brachial plexus below 26 Gy in 3 or 4 fractions.

• Search for CME/CE on This Topic »