eMedicine Specialties > Physical Medicine and Rehabilitation > Plexopathy

Neoplastic Brachial Plexopathy

Author: Mark A Wren, MD, MPH, Medical Director, Department of Physical Medicine and Rehabilitation, HealthSouth Rehabilitation Hospital of Texarkana
Contributor Information and Disclosures

Updated: Jan 26, 2007

Introduction

Background

Neoplastic brachial plexopathy (NBP) is an uncommon diagnosis in most physiatrists' offices, but the condition bears review as it can mimic symptoms of many common upper limb neuropathies. Approximately 10% of all peripheral nerve lesions involve some type of brachial plexus lesion. Neoplastic invasion of the brachial plexus is an uncommon, though not rare, cause of plexopathy. This article reviews the more common issues associated with physiatric treatment of patients with NBP.

Pathophysiology

Lesions of the brachial plexus occur most often secondary to neoplasms that reach the plexus by direct extension (Pancoast syndrome) or, more commonly, by metastasis through lymphatics from the axilla. Pain in the shoulder, radiating down the limb, may be observed, as well as pain in the medial forearm and hand with lower trunk innervation (C8-T1 roots) in some series. The most common pathophysiology revealed on electrodiagnostic tests is axonal loss. Peripheral pain mechanisms may include lowering of the nociceptor threshold by prostaglandins and other noxious chemical substances and persistent nociceptor stimulation. Compression or infiltration of the nerves of the plexus by a tumor may produce neuralgia and inflammation.

Frequency

United States

Approximately 14% of all upper limb neurologic lesions are due to brachial plexopathy of all types. Neoplastic plexopathies were responsible for 1.4 and 14.5% of symptoms in 2 series of patients who had undergone surgery. Insufficient data have been published to determine the frequency of NBP, but symptomatic NBP has been estimated to occur in 4% of patients with lung cancer and 2% of patients with breast cancer.

International

The international incidence of NBP is unknown.

Mortality/Morbidity

Primary neoplasms of the brachial plexus generally are benign, while secondary neoplasms are malignant. Most secondary tumors are metastatic, contributing to higher mortality.

Sex

Solitary neoplastic lesions of the brachial plexus are more common in females. Neurofibromas demonstrate a male-to-female ratio of 1:1.

Age

Incidence of metastatic neoplasm of the brachial plexus increases with age; thus, the condition is more common in elderly patients.

Clinical

History

Pain is the most common presenting symptom of NBP (seen in 89% of the Kori series). In one series, 17 of 55 patients presented with brachial plexopathy as the initial manifestation of cancer. Patients with NBP may present with shoulder pain and paresthesias with radiation of pain into the medial forearm and/or hand. Symptoms often are related to breast or lung metastases or lymphoma in a generalized plexus involvement, sometimes with a lower trunk predominance. Symptoms may be diffuse but more often involve the C8-T1 dermatomes and myotomes (mimicking ulnar neuropathy or C8 or T1 radiculopathy).

The Pancoast syndrome (superior pulmonary sulcus tumor) usually is caused by carcinoma at the lung apex, encroaching on the lower trunk of the brachial plexus. Patients with this condition frequently are males with a history of cigarette smoking. For primary brachial plexus tumors, usually from the nerve sheath (neurofibromas and schwannomas), slightly higher incidence is noted in the upper brachial plexus; thus, symptoms appear in the C5-C6 dermatomes and myotomes (mimicking C5 or C6 radiculopathy or possibly carpal tunnel syndrome).

Radiation-induced brachial plexopathy (RBP) is another relevant topic since it can be confused with NBP. As treatment may be different for the two conditions, differentiation between RBP and NBP is important, although it may be difficult. As many as 73% of patients who have undergone radiotherapy at more than 60 Gy develop plexopathy. Overall incidence of brachial plexopathy is approximately 1.8% of treated patients; however, several factors play a role in development of the condition, including dose (incidence is higher with doses more than 50 Gy), volume irradiated, and treatment technique, as well as whether chemotherapy is administered concurrently. Emami reports 5% incidence of NBP at 5 years when the patient has been treated at doses of 60 Gy to the entire plexus; however, up to one third of patients with RBP find that the deterioration may stop after several years.

• Some historical findings suggestive of NBP include the following:
  • Onset of limb pain less than 6 months following radiation
  • Rapid progression
  • Horner syndrome (in two thirds of patients with Pancoast syndrome)
  • Severe pain predominant
  • Other metastases
  • Focal mass or neoplasm on biopsy
• The most reliable feature of NBP (in 80% of patients) is early severe unrelenting pain. Fewer than 20% of RBP patients present with pain, and approximately 33% have minimal or no pain throughout the course of the disease. Two thirds of patients with RBP show severe neurologic deficit progression over several years, while in one third of patients, progression spontaneously ceases after 1-3 years (Killer, 1990). More common findings in RBP include the following:
  • Slowly progressive course, duration greater than 4 years
  • Predominant paresthesias
  • Median sensory amplitude decreased early
  • Involvement of the upper trunk or C5-C6 portions of the plexus
  • Conduction block on supraclavicular stimulation
  • Myokymia on needle examination

Physical

Examination findings depend on the specific parts of the plexus involved. As can be inferred from the information above, weakness in the hand intrinsics and sensory loss in the C8 and/or T1 dermatomes may be present with the most common lower trunk involvement. For more widespread involvement, motor and sensory loss may be present throughout the limb.

Less common primary neoplasms may occur and present as limb pain and/or a tender mass, causing radiating paresthesias upon palpation. Sensory and motor deficits may be found corresponding to the tumor's location in the plexus; however, weakness and sensory changes in the lower trunk distribution of patients with Pancoast syndrome are reported in approximately one third of cases.

Causes

The most common causes of NBP are metastatic lesions from breast or lung cancer, and the clinician also should be aware of possible concurrent cervical spine metastases. Primary NBP is less common than secondary metastatic lesions and usually is benign. Neural sheath tumors comprise 67-85% of primary NBP, and benign neurofibromas represent 66% of primary NBP tumors. Most neurofibromas are solitary, fusiform, and supraclavicular, and they are more common in females than males (3:1 in one series). A smaller number of plexus neurofibromas (37-42%) are associated with Von Recklinghausen disease. They can arise or extend intraspinally, and their nerve fibers often are nonfunctional.

Benign schwannomas (eg, neurinomas, neurilemomas) are the second most common type of sheath tumors, comprising about 20%. Approximately 15% of neural sheath tumors are malignant (eg, neurogenic sarcomas, fibrosarcomas). Many of these malignant tumors occur in tumors that initially are benign and undergo malignant transformation, as occurs often in Von Recklinghausen disease. They may develop many years after radiation for Hodgkin disease or breast cancer. Among other types of primary neoplasms, only lymphomas metastasize to the brachial plexus with any appreciable frequency. Rarely, NBP may occur as a paraneoplastic syndrome in patients with Hodgkin lymphoma, encephalomyelitis, and small cell carcinoma of the lung.

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