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; however, symptoms may develop decades after treatment. Owing to this prolonged time interval and nonspecific symptoms, often an extensive workup is undergone prior to arriving at the diagnosis of radiation plexopathy.
Sensory symptoms, such as numbness, paresthesia, and dysesthesia, along with swelling and weakness of the arm, are the predominant presenting symptoms. These neurologic symptoms can be progressive and may lead to a weak and edematous arm.
Most radiation plexopathies are painless, but when present, pain symptoms usually are limited to the shoulder and proximal arm. Such pain usually is rated as mild to moderate in intensity. Significant pain complaints are more commonly associated with recurrent tumor than with radiation plexopathy. [4]
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 primarily into the following 2 categories:
-
Neurologic findings are most prominent in the upper trunk or lateral cord distributions, as well as diminished deep tendon reflexes supplied by C5-C6. [11, 12] (A retrospective study by Cai et al of patients with nasopharyngeal carcinoma found that clinical symptoms of radiation-induced brachial plexopathy arose primarily in the upper and middle trunk of the brachial plexus. [13] ) Myokymia is difficult to visualize by inspection or palpation. [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 passive scapulothoracic and glenohumeral joint range of motion secondary to fibrosis of the musculoskeletal tissues from the radiotherapy or due to postsurgical scar tissue. Neurologic damage to the upper trunk of the brachial plexus may result in scapular winging, decreased shoulder external rotation, and abduction. [15] No specific joint tenderness or effusions should be encountered during the examination of the involved extremity.
Causes
Treatment technique, radiation volume,and concomitant use of chemotherapy are associated with development of radiation injury to the brachial plexus. [16, 17]
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. [18] 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.
A study by Sood et al of patients with apical lung tumors who underwent stereotactic body radiation therapy (SBRT) found that during such treatment, the radiation dose received by the brachial plexus can be much higher than the conventionally recommended limits; in some cases, the biologically effective dose in the study exceeded 100 Gy. Nonetheless, by median 17-month follow-up, no cases of brachial plexopathy had occurred. [19]
In the aforementioned study by Cai et al, the incidence of the plexopathy was increased in nasopharyngeal carcinoma patients with lower cervical lymph node metastasis who underwent corresponding radiotherapy. [13]
Tables
Feature |
Tumor Infiltration |
Radiation Fibrosis |
Transient Radiation Injury |
Acute Ischemic Injury |
Incidence of pain |
80% |
18% |
40% |
Painless |
Location of pain |
Shoulder, upper arm, elbow, fourth and fifth fingers |
Shoulder, wrist, hand |
Hand, forearm |
Hand, forearm |
Nature of pain |
Dull ache in shoulder, lancinating pains in elbow and ulnar aspect of hand; occasional paresthesias and dysesthesias |
Ache in shoulder; prominent paresthesias in C-5/C-6 distribution of hand and arm |
Ache in shoulder; prominent paresthesias in C-5/C-6 distribution of hand and arm |
Paresthesias in C-5/C-6 distribution of hand and arm |
Severity |
Moderate to severe (severe in 98%) |
Usually mild to moderate (severe in 20-35%) |
Mild |
Mild |
Course |
Progressive neurologic dysfunction; atrophy and weakness in C-7/T-1 distribution, persistent pain; occasional Horner syndrome |
Progressive weakness; panplexus or upper plexus distribution; Horner syndrome uncommon |
Translate weakness with complete resolution |
Acute nonprogressive weakness and sensory loss |
Study findings |
|
|
|
|
Magnetic resonance imaging |
High signal intensity on T2-weighted images; may enhance with gadolinium |
Low signal intensity on T2-weighted images; generally nonenhancing with gadolinium |
No data |
Normal |
Computed tomography |
Mass; circumscribed or diffuse tissue infiltration |
Diffuse tissue infiltration |
Normal |
Angiography demonstrates subclavian artery segmental obstruction |
Electromyography |
Segmental slowing |
Diffuse myokymia |
Segmental slowing |
Segmental slowing |
