Neoplastic Brachial Plexopathy Clinical Presentation

Updated: Jan 04, 2016
  • Author: Mark A Wren, MD, MPH; Chief Editor: Robert H Meier, III, MD  more...
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Presentation

History

Pain is the most common presenting symptom of NBP (seen in 89% of the Kori series). [4] 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).

A Korean case study described thoracic outlet syndrome caused by schwannoma of the brachial plexus, initially suspicious for C8-T1 radiculopathy by electromyography (in the absence of contralateral limb studies to show low amplitudes); however, MRI of the brachial plexus later revealed a mass confirmed to be schwannoma. [5]

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. [6] 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
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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.

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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.

Kamenova et al examined the cause of BP in 28 breast cancer patients suffering from homolateral arm pain and neurologic deficits. [7] In 26 patients, BP arose at the same time that supraclavicular, axillary, or chest wall metastases developed. The metastases resulted either from recurrent cancer (21 patients; found a median of 34 months after primary breast cancer treatment) or from progressing, inoperable primary tumors and nodes (5 patients). Nineteen patients developed arm edema at the same time that locoregional metastases appeared.

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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