Fasciculation-myokymic activity and prolonged nerve conduction block. A physiopathological relationship in radiation-induced brachial plexopathy

Radiation Plexopathy

Radiation induced brachial plexopathy represents a constellation of symptoms that present in a delayed manner because of peri-plexus progressive fibrosis or direct neural injury with demyelination. Symptom onset is typically delayed months to years after radiotherapy. Patients may report neuropathic pain, weakness, or extremity dysfunction associated with morbidity and diminished quality of life. Reported surgical interventions include plexus neurolysis, nerve transfers, and vascularized free tissue transfer. In this review, we aim to present the practicing hand surgeon with an update and analysis on the current state of the radiation induced brachial plexopathy literature.

Case report: Brachial plexopathy caused by malignant peripheral nerve sheath tumor and review of the literature

Brachial plexopathy (BP) is easily misdiagnosed due to its complexity and varying clinical presentation. Malignant peripheral nerve sheath tumors (MPNST) can accumulate in the brachial plexus and share symptoms with BP, which may hinder the differential diagnosis between BP induced by radiation or metastases, and MPNST-derived BP, in patients with a history of breast cancer and radiation exposure. A 34-year-old Chinese female presented with MPNST. The tumor involved the brachial plexus. She had a history of breast cancer and radiotherapy. The first consideration was radiation- or breast cancer metastasis-derived BP. Clinical examination was performed. Finally, a diagnosis of MPNST of the brachial plexus was made, which guided an accurate treatment plan. This report highlights the importance of correctly diagnosing BP etiology for guiding precise treatment. BP caused by MPNST needs to be considered in clinical practice, and biopsy plays a central role in the differential diagnosis. Complete local surgical resection can prolong survival of patients with MPNST and improve treatment prognosis.

Clinical Evaluation and Management of Cancer Survivors with Radiation Fibrosis Syndrome

OBJECTIVES

To define radiation fibrosis and radiation fibrosis syndrome; review the basics of radiotherapy, the pathophysiology of radiation injury, and the principles of clinical evaluation and management of the common late effects resulting from radiation therapy for cancer treatment.

DATA SOURCES

Peer-reviewed journal articles, book chapters, Internet.

CONCLUSION

There is no cure for radiation fibrosis syndrome, but supportive treatment of its clinical sequelae can potentially result in improved function and quality of life.

IMPLICATIONS FOR NURSING PRACTICE

The sequelae of radiation fibrosis syndrome can often be improved with early detection and supportive care by a multidisciplinary team including cancer rehabilitation physiatrists, oncologists, oncology nurses, nurse practitioners, physical therapists, occupational therapists, and speech and language pathologists.

Fasciculation in amyotrophic lateral sclerosis: origin and pathophysiological relevance

This review considers the origin and significance of fasciculations in neurological practice, with an emphasis on fasciculations in amyotrophic lateral sclerosis (ALS), and in benign fasciculation syndromes. Fasciculation represents a brief spontaneous contraction that affects a small number of muscle fibres, causing a flicker of movement under the skin. While an understanding of the role of fasciculation in ALS remains incomplete, fasciculations derive from ectopic activity generated in the motor system. A proximal origin seems likely to contribute to the generation of fasciculation in the early stages of ALS, while distal sites of origin become more prominent later in the disease, associated with distal motor axonal sprouting as part of the reinnervation response that develops secondary to loss of motor neurons. Fasciculations are distinct from the recurrent trains of axonal firing described in neuromyotonia. Fasciculation without weakness, muscle atrophy or increased tendon reflexes suggests a benign fasciculation syndrome, even when of sudden onset. Regardless of origin, fasciculations often present as the initial abnormality in ALS, an early harbinger of dysfunction and aberrant firing of motor neurons.

Cancer-treatment-induced neurotoxicity--focus on newer treatments

Neurotoxicity caused by traditional chemotherapy and radiotherapy is widely recognized in patients with cancer. The adverse effects of newer therapeutics, such as biological and immunotherapeutic agents, are less well established, and are associated with considerable neurotoxicity in the central and peripheral nervous systems. This Review addresses the main neurotoxicities of cancer treatment with a focus on the newer therapeutics. Recognition of these patterns of toxicity is important because drug discontinuation or dose adjustment might prevent further neurological injury. Knowledge of these toxicities also helps to differentiate treatment-related symptoms from progression of cancer or its involvement of the nervous system. Familiarity with the neurological syndromes associated with cancer treatments enables clinicians to use the appropriate treatment for the underlying malignancy while minimizing the risk of neurological damage, which might preserve patients' quality of life.

Free functioning muscle transfer in radiation-induced brachial plexopathy: case report

Radiation-induced brachial plexopathy is a delayed complication of radiation treatment for tumors involving the neck and chest area and is progressive. A 56-year-old woman presented to us with loss of elbow flexion and weak wrist and finger extension 15 years after she received external beam radiation to the left chest, axilla, and supraclavicular region for treatment of breast cancer. She was managed with a gracilis free muscle transfer for elbow flexion and hand prehension. By 2 years after surgery she regained elbow range of motion of 40° to 110° and improved in hand function. She was able to perform activities of daily living. Disabilities of the Arm, Shoulder, and Hand score improved from 56 to 20.

Neurophysiological approach to disorders of peripheral nerve

Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.

Nerve transfer for elbow flexion in radiation-induced brachial plexopathy: a case report

Radiation-induced brachial plexopathy is an uncommon but devastating late complication seen in patients receiving radiation therapy to the chest wall and axilla. Treatment options are unfortunately limited. We report a case of a 59-year-old woman treated with radiation therapy for breast cancer 12 years earlier, who presented with loss of elbow flexion and marked shoulder weakness. Electromyogram and intraoperative stimulation of the musculocutaneous nerve branches were consistent with a proximal motor nerve conduction block. Microsurgical transfer of median and ulnar nerve fascicles to the biceps and brachialis branches of the musculocutaneous nerve, respectively, were performed. The patient recovered MRC grade 4/5 elbow flexion after surgery. The characteristics of this disorder and surgical treatment options are reviewed.

Interspike interval analysis in a patient with peripheral nerve hyperexcitability and potassium channel antibodies

Neuromyotonia or Isaacs' syndrome is a rare peripheral nerve hyperexcitability disorder caused by antibodies against potassium channels of myelinated axons. We present the high-density surface electromyographic (EMG) recordings of a patient with fasciculations and cramps due to neuromyotonia. To characterize the time course of hyperexcitability, we analyzed the interspike intervals (ISIs) between fasciculation potentials, doublet, and multiplet discharges. ISI duration increased within each burst. The ISI histograms found can be explained by the recovery cycle of the myelinated axon and its dependency on the slow potassium conductance. We conclude that ISI analysis is a useful tool to understand the membrane dynamics underlying abnormal motor unit activity.

Metastases to the peripheral nervous system

Cancer metastasis can affect any part of the nervous system. When the peripheral nervous system is involved, the usual targets are cranial nerves, nerve roots and plexi. However, peripheral nerves and muscles can also be affected by compression or infiltration of neoplastic cells. This review focuses in the diagnosis and treatment of metastatic complications of cancer involving plexi, peripheral nerves and muscles.

Une forme inhabituelle de plexopathie brachiale radio-induite tardive

Radiation therapy of the neck or axillary areas for cancer may result in delayed brachial plexus palsy. Differential diagnosis between radiation and tumor brachial plexopathy is difficult. We report the case of a 38-year-old woman, treated by radiation therapy for osteosarcoma of the humeral head 22 years before, who exhibited a rapidly progressive incomplete hand palsy. EMG study revealed a conduction block at the level of the lateral cord. In this case, MRI could not distinguish between a delayed radiation injury and tumor infiltration. The diagnosis was clarified with an ultrasonographic examination. Neurolysis and epineurotomy of the median trunk in the brachial and axillary areas were performed. Histological examination confirmed radiation-induced nerve injury. The characteristics of this uncommon form are reviewed with regard to the previously reported descriptions.

Brachial plexopathies: classification, causes, and consequences

The brachial plexus, which is the most complex structure of the peripheral nervous system, supplies most of the upper extremity and shoulder. The high incidence of brachial plexopathies reflects its vulnerability to trauma and the tendency of disorders involving adjacent structures to affect it secondarily. The combination of anatomic, pathophysiologic, and neuromuscular knowledge with detailed clinical and ancillary study evaluations provides diagnostic and prognostic information that is important to clinical management. Since most brachial plexus disorders do not involve the entire brachial plexus but, rather, show a regional predilection, a regional approach to assessment of plexopathies is necessary.

Segmental neurogenic muscle hypertrophy associated with radiation injury

A 48-year-old man presented with painless left trapezius hypertrophy 20 years after radiotherapy for nasopharyngeal carcinoma. EMG sampling showed myokymic discharges, reduced polyphasic motor unit recruitment and no signs of active denervation. The relationship between radiotherapy, brachial plexopathy and neurogenic muscle hypertrophy is discussed.

Conduction block and continuous motor unit activity in chronic acquired demyelinating polyneuropathy

The term continuous motor unit activity (CMUA) may be used to refer to the involuntary, sustained activity of motor units caused by hyperactivity of peripheral motor nerves. CMUA has been reported in association with acquired neuropathies such as chronic inflammatory demyelinating polyneuropathy. The precise mechanism responsible for the excess muscle activity is not defined, but the activity is believed to originate in the peripheral nerves, perhaps at sites of focal demyelination. We describe a case of an acquired, demyelinating neuropathy associated with distal motor conduction block in which CMUA was observed in muscles innervated by blocked axons. Despite the prolonged disease duration of nearly 40 years, marked clinical and electrophysiological improvement as well as resolution of the CMUA were observed following immunosuppressive therapy. A relationship between the chronic motor conduction block and the excess muscle activity is postulated.

Fasciculations: what do we know of their significance?

Fasciculations are observed in patients with neurogenic disorders and in healthy individuals. Depending on the associated clinical symptoms and signs, they may signify the presence of a variety of disorders of the lower motor neuron. Divergent and occasionally conflicting opinions prevail regarding the aetiology, pathogenesis, clinical significance, neurophysiological characteristics and the physiological site of origin of fasciculations. In this review we examine the published literature and attempt to clarify these issues.