Introduction
Originating in the neck's root, traversing through the axilla (underarm), and extending into the upper extremities, the brachial plexus forms a network of nerve fibers. The brachial plexus supplies the skin and muscles of the upper limb. The interconnection of the lower four cervical nerves (C5, C6, C7, C8) and the first thoracic nerve (T1) forms them. Brachial plexopathy, a type of peripheral neuropathy, can be caused by damage to a single nerve or a group of nerves, resulting in peripheral nerve damage. Neoplastic invasion of the brachial plexus is a rare cause of brachial plexopathy. It is an uncommon diagnosis due to its similar symptoms to other common upper limb neuropathies.
What Is Neoplastic Brachial Plexopathy (NBP)?
Neoplastic brachial plexopathy most commonly occurs in patients with a previous history of cancer. They commonly occur secondary to the neoplasm that directly reaches the brachial plexus, such as in Pancoast syndrome (lung tumor along with ipsilateral pain in the shoulder and arm, paresthesias of the muscles of the thenar part of the hand, Horner's syndrome). It also occurs commonly in metastasis through lymph nodes in the axillary lymph.
What Are the Causes of Neoplastic Brachial Plexopathy?
Lung and breast cancer metastasis most commonly cause neoplastic brachial plexopathy, and there is a possible concurrent cervical spine metastasis. They occur through metastasis of either recurrent cancer or through the inoperable, progressing primary tumors and nodes. The brachial plexopathy's primary tumor is rare compared to the secondary metastatic lesion. Neural sheath tumors and benign neurofibromas comprise 67 % to 68 % of primary neoplastic brachial plexopathy. Recent studies show evidence of plexus neurofibromas associated with von Recklinghausen's disease, which can arise and extend through the intraspinal. In 20 % of patients with benign schwannoma causes brachial plexopathy. Neoplastic plexopathy can also occur in patients undergoing post-radiation therapy for Hodgkin's disease and breast cancer.
What Is the Clinical Presentation of Neoplastic Brachial Plexopathy?
The most common symptom of neoplastic brachial plexopathy is pain, occurring in about 80 % of the patients. There is an early onset of severe, relentless pain. The clinical presentation of neoplastic brachial plexopathy is similar to radiation-induced brachial plexopathy. Other symptoms include,
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Pain in the shoulder and neck.
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Pain may radiate down the medial forearm and or hand.
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Predominant paresthesias of the neck and shoulder.
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Tumor infiltrates the spinal column and foramen in the spine's bones, resulting in mixed motor and sensory loss.
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Neurological deficits.
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Opioid analgesics do not relieve severe pain at rest along the distribution of significant nerves.
How Is Neoplastic Brachial Plexopathy Diagnosed?
Laboratory investigations in neoplastic brachial plexopathy to screen the signs of neoplasm include:
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Comprehensive metabolic panel.
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Complete blood count.
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Urine analysis.
Radiologic investigations in NBP (neoplastic brachial plexopathy) include:
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Radiographs of the shoulder, chest, and cervical spine are obtained to check for neoplastic changes.
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MRI (magnetic resonance imaging) has shown 100 % accuracy in detecting neoplastic changes in the brachial plexus. MRI of the brachial plexus is highly sensitive. However, there is a limitation in detecting infiltrating neoplasms and distinguishing neoplastic brachial plexopathy from radiation-induced plexopathy.
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Bone scintigraphy or bone scan helps find evidence of metastasis.
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Using fluoroscopy in the spinal cord successfully assesses the epidural metastasis forcing out through the foramen in the spinal cord.
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Fluorodeoxyglucose (FDG) - positron emission tomography (PET) is used in assessing tumors if the radiographic image is not clear in the MRI and CT (computed tomography) scans. PET assesses the metastasis near or in the brachial plexus.
Other tests in diagnosing neoplastic brachial plexopathy:
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The electrodiagnostic test measures the electrical activity of the nerve, which is used in localizing a lesion. It identifies the pathology and establishes the prognosis.
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Nerve conduction studies and electromyography are the conventional diagnostic tests for differentiating brachial plexopathy.
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The nerve conduction studies may identify axon loss, and it can cause loss of the lower trunk-mediated sensory potentials and reduced amplitude of motor responses. Needle examination identifies the motor unit's potential loss. Neuropraxic lesions are observed more commonly in neoplastic brachial plexopathy. The longer the regrowth distance lesser the favorable prognosis.
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Somatosensory evoked potentials are non-invasive in assessing the sensory impairments associated with neoplastic brachial plexopathy.
Histological findings in neoplastic brachial plexopathy for secondary neoplasms include adenocarcinoma, squamous cell carcinoma, or large cell carcinoma.
How Is Neoplastic Brachial Plexopathy Treated?
Physical therapy plays a huge role in treating patients with NBP. The physical therapists will do the initial thorough assessment and examination and determine the therapeutic goals for the patient. An early passive range of motion is performed to prevent permanent shortening of the muscles. Active assisted and range of motion exercises are incorporated into the treatment program. The physical therapists implement an at-home exercise program incorporating a self-directed range of motion and advise strengthening exercises whenever possible.
Various treatment modalities are involved in physical therapy for pain reduction, such as transcutaneous electrical nerve stimulation (TENS) and ultrasound therapy. But they are contraindicated to be applied directly over the malignant neoplasm. Compressive garments, retrograde massage, and elevation are considered to reduce swelling. The physical therapist advises using a sling or splints to maintain a comfortable position of the injured hand. A sling can also avoid subluxation and edema and reduce additional traction over the brachial plexus.
Paravertebral nerve blocks and other injection procedures are advised according to the tumor's location. Due to their widespread use, selective blocks cannot be applied in the case of neoplastic brachial plexopathy. Medicines to control pain are advised early in the disease.
Non-steroidal anti-inflammatory drugs are recommended to relieve pain and are usually used with other agents. Opioid analgesics are effective at acceptable doses, such as Hydrocodone and Acetaminophen. Topical agents are used in mild symptoms. Anti-seizure medications and antidepressants are used in relieving neuropathic pain. Surgical interventions are advised only in definitive tissue diagnosis in secondary neoplasms. In primary tumors, encapsulation is mostly preferred permitting the surgical excision without damaging the adjacent nerves. Doctors may suggest the patients for occupational therapy, recreational therapy, and speech therapy.
Conclusion
Neoplastic brachial plexopathy is a devastating condition often confused with other upper limb neuropathies. Primary neoplasms are generally benign in brachial plexopathy, and secondary neoplasms are usually malignant. Neoplastic brachial plexopathy is found to occur most frequently in females. As the disease progresses, the patient's goal is adequate pain control. An interdisciplinary approach effectively treats NBP; coordination between the physical therapist, consultant, and other therapies is essential.
