Acute Inflammatory Demyelinating Polyradiculoneuropathy

Updated: Jul 26, 2021
  • Author: Emad R Noor, MBChB; Chief Editor: Nicholas Lorenzo, MD, MHCM, CPE, FAAPL  more...
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Overview

Background

Acute inflammatory demyelinating polyneuropathy (AIDP) is an autoimmune process  characterized by progressive areflexic weakness and mild sensory changes. Sensory symptoms often precede motor weakness. About 20% of patients end up with respiratory failure. AIDP is the most common form of Guillain-Barré syndrome (GBS) in North America and Europe (AIDP comprises approximately 90% of cases.) 

GBS refers to a group of heterogeneous but related disorders of peripheral nerves with an acute onset, which is considered to be due to an autoimmune process and is usually postinfectious. The two most common forms of GBS are AIDP and acute motor axonal neuropathy (AMAN), with the latter comprising 10% of GBS cases. [1] In Asia, South America, and Central America, the relative frequency of AMAN is much higher. These variations in the incidence of AIDP and AMAN in different geographic regions may indicate differences in the immunogenetic repertoire and infectious pressures. [2]  

This article discusses the AIDP variant of GBS. 

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Pathophysiology

Acute inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both, and the pathogenesis of these disorders remains elusive.

The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium.

Acute inflammatory demyelinating polyneuropathy is believed to be caused by an immunologic attack that is directed against myelin components. This results in a demyelinating polyneuropathy. Both cellular and humoral immune mechanisms appear to play a role. Early inflammatory lesions consist of a lymphocytic infiltrate that is adjacent to segmental demyelination. Macrophages are more prominent several days later.

The peripheral nerve changes consist of varying degrees of perivascular edema, accumulations of mononuclear cells, and paranodal and less commonly, segmental demyelination. They are often multifocal with some predilection for the nerve roots, sites of entrapment, and distal ends. In the axonal variant of Guillain-Barré syndrome, axonal degeneration often predominates. Severe Guillain-Barré syndrome is often associated with axonal degeneration as well, which results in wallerian degeneration. Axonal degeneration occurs either as a primarily axonal process or as a bystander-type axonal degeneration, associated with demyelination. Rarely, the pathologic process extends into the central nervous system.

As the regeneration occurs, nerve sprouting and increased scarring often results.

With electron microscopy, macrophages are observed stripping off the myelin sheath. Humoral molecules such as antimyelin antibodies and complement likely contribute to the process by directing macrophages to Schwann cells by opsonization. Indeed, complement and antibodies have been found to coat the myelin sheath. The changes are observed in nerve roots, peripheral nerves, and cranial nerves. In acute motor axonal neuropathy (AMAN, an AIDP variant), deposited complement is found at the nodes of Ranvier, while myelin often is left undamaged.

Damage to the myelin sheath leads to segmental demyelination. This results in decreased nerve conduction velocity and, at times, conduction block. In this current review, AIDP refers to the more common demyelinating form unless otherwise specified.

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Epidemiology

Frequency

United States

Acute inflammatory demyelinating polyneuropathy (AIDP) is the most common acquired demyelinating polyneuropathy. The incidence is 0.6–1.7 cases per 100,000 per year. No significant seasonal variation has been noted.

International

International frequency is not well documented. Of two predominant Guillain-Barré syndrome subtypes, a demyelinating subtype (AIDP) predominates in the United States and Europe, and axonal subtype (AMAN) is the predominant form in China. Previous clinical studies suggested that AMAN also occurs in Mexican children. [3] Similar outbreaks have been reported in Mexico, Spain, and Jordan.

Mortality/Morbidity

In three large studies, mortality rate ranged from 2% to 6%.

  • In general, death is due to complications of ventilation. Causes include cardiac arrest, pulmonary embolus, sepsis, bronchospasm, pneumothorax, adult respiratory distress syndrome (ARDS), and dysautonomia.

  • More than 75% of patients have complete or near-complete recovery with no deficit or only mild residual fatigue and distal weakness.

  • Other patients, almost all of whom required ventilation, report severe dysesthesias or moderately severe distal weakness as residual symptoms. About 15% of patients end up with significant neurological residuals.

Demographics

AIDP occurs in all races and in all regions of the world. The male-to-female ratio is 1.1–1.7:1. Patients have ranged in age from 2 months to 95 years.

  • In the United States, age distribution is apparently bimodal, with most patients presenting from 15–35 years or 50–75 years.

  • In China (and other countries), frequent outbreaks in children aged 2–12 years have been reported.

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Prognosis

About 75% of acute inflammatory demyelinating polyneuropathy (AIDP) patients have an excellent recovery and regain their premorbid condition. Some of these patients experience easy fatigability for many years.

Almost all of the remaining patients have mild or moderately severe impairment but remain independent in most functions. Residual complaints include dysesthesias, foot drop, and intrinsic hand muscle weakness.

Severe disability occurs in fewer than 5% of patients, who do not recover full independence. Patients with residual deficits are usually those who required mechanical intubation. Improvement is usually complete by 6 months. In more serious cases, recovery may continue for 18–24 months.

Death occurs in only 2%–6% of patients and is usually due to cardiac arrest, ARDS, pulmonary embolism, severe bronchospasm, pneumonia, or sepsis.

About 10% of patients have a relapse 1–6 weeks after completing immunomodulatory therapy. These patients can be treated with a second course of immunomodulation.

Fewer than 1% of patients have AIDP 1 or more years after onset of symptoms. In some cases, the recurrence follows immunization. This recurrence differs from CIDP.

Sporadic cases of recurrent Guillain-Barré syndrome [4]  and rare cases of recurrent Guillain-Barré syndrome after a long asymptomatic period [5]  have been reported. Some authors consider recurrent Guillain-Barré syndrome a variant of CIDP, while others maintain that they are 2 different entities. Martic et al describe a patient who developed Guillain-Barré syndrome as a child and experienced a full relapse after 19 years with another innocuous episode 10 years later. [6]

Several prognostic factors have been identified, including the following:

  • In general, younger patients have a better prognosis than older patients. Those patients with more severe weakness and those who are intubated have a worse prognosis than those with milder weakness.

  • Diarrhea as an antecedent association often is associated with C jejuni infection. These patients may have a more prolonged recovery.

  • Early improvement in strength during treatment is associated with a more rapid recovery. Low compound muscle action potential (CMAP) amplitudes (< 20% of normal) are considered a bad prognostic indicator.

In spite of therapy with plasma exchange or IVIG, the decrease in mortality has often been attributed to improved aggressive supportive treatment than to any drug treatment. This has included close monitoring with the avoidance of hypoxia, pain, and arrhythmogenic stimuli.

In the presence of dysautonomia, hypoxia can trigger cardiac arrhythmias. Tracheal suction can also at times result in cardiac arrhythmias. Ideally, these patients should be given extra oxygen before tracheal toilet.

Subcutaneous heparin to avoid venous thromboembolism, treatment of pain with analgesics including narcotics, treatment of hypotension and hypertension, as the case be and treatment of severe bradyarrhythmia all go a long way in decreasing mortality. Carbamazepine and gabapentin may help.

Persistent fatigue following Guillain-Barré syndrome is common and may be helped by a graded exercise program. C jejuni is often treated with a course of erythromycin.

Hyponatremia is due to inappropriate antidiuretic hormone secretion (SIADH) is best managed by fluid restriction coupled by the avoidance of hyponatremic fluids. Need for immunization should be reviewed on an individual basis.

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