Browse the corpus

Electrodiagnostic testing is an important tool for the diagnosis of acute inflammatory demyelinating polyneuropathy. This activity describes the electrodiagnostic findings of both nerve conduction tests and needle electromyography studies in acute inflammatory demyelinating polyneuropathy. Objectives: Identify the anatomy and physiology of nerve conduction and its relevance to acute inflammatory demyelinating polyneuropathy. Determine the indications for electrodiagnostic testing in patients with symmetric distal weakness. Assess the nerve conduction study findings in patients with acute inflammatory demyelinating polyneuropathy. Improve communication and care coordination among the interprofessional team to better serve patients with acute inflammatory demyelinating polyneuropathy. Access free multiple choice questions on this topic.

Demyelinating neuropathies can be classified as hereditary, toxic, and immune-mediated. Immune-mediated polyneuropathies can be further classified as acute and chronic, depending on the onset. Guillain-Barre syndrome (GBS) is a syndrome with several variants, with acute inflammatory demyelinating polyneuropathy (AIDP) being the most common type of inflammatory neuropathy in North America. The pathophysiology of GBS and its variants appear to be secondary to an inflammatory process leading to molecular mimicry between central and peripheral nervous structural components and microbial/viral antigens. This condition leads to a lack of self-tolerance from the adaptive immune system and activation of neuroinflammatory processes affecting nerve conduction. The microbial and viral antigens may include Campylobacter jejuni, HIV infection, Epstein-Barr (mononucleosis), and Zika virus.[1] Previously, it was speculated that AIDP has links with vaccinations; however, further research has refuted this association. Clinically, AIDP presents with an acute, symmetric, flaccid, and distal weakness that usually starts in the lower extremities and has an ascending pattern as time progresses.[2] The neurological examination may show facial paresis, cranial nerve/bulbar weakness, distal hyporeflexia without signs of upper motor neuron dysfunction, preserved muscle bulk, dysesthesias, allodynia, or neuropathic pain, and loss of light and vibratory sensation in the affected extremities. Motor symptoms and signs tend to predominate over sensory ones. Autonomic symptoms may be present, such as hypertension or hypotension, cardiac arrhythmias, and respiratory failure requiring mechanical ventilation. The latter can present in those with an advanced and severe disease course. It has a monophasic course with varying onset, progression, and recovery degrees. Imaging may show hyperintense and hypertrophic nerves, especially in caudal nerve roots in the lumbar spine.

Clinically, AIDP presents with an acute, symmetric, flaccid, and distal weakness that usually starts in the lower extremities and has an ascending pattern as time progresses.[2] The neurological examination may show facial paresis, cranial nerve/bulbar weakness, distal hyporeflexia without signs of upper motor neuron dysfunction, preserved muscle bulk, dysesthesias, allodynia, or neuropathic pain, and loss of light and vibratory sensation in the affected extremities. Motor symptoms and signs tend to predominate over sensory ones. Autonomic symptoms may be present, such as hypertension or hypotension, cardiac arrhythmias, and respiratory failure requiring mechanical ventilation. The latter can present in those with an advanced and severe disease course. It has a monophasic course with varying onset, progression, and recovery degrees. Imaging may show hyperintense and hypertrophic nerves, especially in caudal nerve roots in the lumbar spine. Further evaluation includes a lumbar puncture, often showing albuminocytologic dissociation (0 cells and high cerebrospinal [CSF] protein without signs of infection). However, some patients may not have positive CSF findings until 3 weeks into the disease course. A smaller percentage of patients may have unremarkable CSF results. In summary, diagnosing AIDP requires a thorough history and physical exam, screening of risk factors, lumbar spine imaging, comprehensive CSF studies to discard alternate diagnoses, and ancillary electrodiagnostic studies.[3] Electrodiagnostic studies can support the diagnosis and prognosticate the patient's course when an AIDP is suspected. They can help localize a lesion (eg, bulbar, peripheral, neuromuscular junction, muscle), and discern the extent of the pathology and etiology (eg, autoimmune, axonal, myopathic, etc). They are considered an extension of the neurological exam, providing valuable information about nerve conduction, muscle-nerve connections, and structural integrity of the myelinated sensory and motor fibers. AIDP can affect axons in more severe cases, which may have a worse prognosis. This topic focuses on the findings typical of acute demyelinating polyneuropathies.

As with all electrodiagnostic studies in any setting and for any indication, the risk of complications is low. However, there is always a small risk of bleeding, infection, or nerve damage due to needle studies.

Acute demyelinating polyneuropathy is a condition often seen in the inpatient setting and sometimes requires outpatient follow-up. Patients frequently complain of pain, weakness, paresthesias, and weakness in the extremities. Imaging, cerebrospinal, and electrodiagnostic studies are routinely ordered. Physicians must be cautious, as imaging findings might not correlate with the patient's symptoms. It is essential to take an interprofessional team including a team of physicians (general neurologists, neuromuscular neurologists, physical medicine and rehabilitation, pain management physicians), therapists (physical and occupational therapists), social workers, and case managers who can work together to coordinate mobilization with outpatient therapy and aggressive multifaceted rehabilitation so we can improve a patient's functional status.[10] If the axonal injury is severe and prolonged, a long and difficult recovery could occur. A coordinated effort between the various medical disciplines and departments can provide the best outcomes for patients.