AUTHOR INFORMATION

Section 1 of 11

Authored by Tarakad S Ramachandran, MD, Chief, Department of Neurology, Crouse Irving Memorial Hospital; Professor, Department of Neurology, State University of New York Upstate Medical University

Coauthored by Richard A Sater, MD, PhD, Consulting Staff, High Point Neurological Associates

Tarakad S Ramachandran, MD, is a member of the following medical societies: American Academy of Clinical Electroencephalographers, American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners, American College of Managed Care Medicine, American College of Physicians, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, and Royal Society of Medicine

Edited by Donald B Sanders, MD, EMG Laboratory Director, Professor of Medicine (Neurology), Division of Neurology, Duke University Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Glenn Lopate, MD, Associate Professor, Department of Neurology, Division of Neuromuscular Diseases, Washington University School of Medicine; Chief of Neurology, St Louis ConnectCar; Consulting Staff, Barnes Jewish Hospital; Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital; and Nicholas Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants

Author's Email:	Tarakad S Ramachandran, MD
Editor's Email:	Donald B Sanders, MD

eMedicine Journal, July 10 2006, VOLUME 7, Number 7

INTRODUCTION

Section 2 of 11

Background: Acute inflammatory demyelinating polyneuropathy (AIDP) is an autoimmune process that is characterized by progressive areflexic weakness and mild sensory changes. Sensory symptoms often precede motor weakness. About 20% of patients end up with respiratory failure. Many variants exist. In the West, the most common presentation is a subacute ascending paralysis. This is associated with distal paresthesias and loss of deep tendon reflexes. Progression is often maximal by the end of 4 weeks, then the condition usually plateaus before slowly improving. In 1859, Landry described 10 cases characterized by ascending paralysis and sensory changes.

During World War I, Guillain, Barré, and Strohl described a series of patients with a similar presentation and decreased or absent deep tendon reflexes. They also described albuminocytologic dissociation in the cerebrospinal fluid (CSF), ie, increased CSF protein in the absence of increased WBCs. This allowed them to differentiate AIDP from poliomyelitis, the most common acute paralytic syndrome of that era. (AIDP often is referred to as Guillain-Barré syndrome [GBS]).

Myelin breakdown and axonal degeneration were observed in nerve biopsies from patients with AIDP by Haymaker and Kernohan in 1949. An allergic etiology was suggested by Krucke in 1955 after he observed lymphocytic infiltrates within biopsy specimens. An autoimmune process was supported by Waksman and Adams when they created the experimental allergic neuritis model by injecting peripheral nerve tissue into rodents.

Pathophysiology: AIDP 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 GBS, axonal degeneration often predominates. Severe GBS 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.

Frequency:

• In the US: 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.

• Internationally: Frequency is not well documented. In rural China, the AMAN variant occurs in clusters during the late summer. Similar outbreaks have been reported in Mexico, Spain, and Jordan.

Mortality/Morbidity: In 3 recent large studies, mortality rate ranged from 2-6%.

• 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.

Race: AIDP occurs in all races and in all regions of the world.

Sex: The male-to-female ratio is 1.1-1.7:1.

Age: 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.

CLINICAL

Section 3 of 11

History:

• AIDP typically manifests as an ascending paralysis.



• Even in these cases, the clinical presentation and course vary. Additionally, many variants exist that differ markedly from classic AIDP in disease onset or course.



• Progressive weakness


• • The hallmark of classic AIDP is progressive weakness that usually begins in the feet before involving all 4 limbs. At presentation, 60% of patients have weakness in all 4 limbs.
  
  
  
  • Weakness plateaus at 2 weeks after onset in 50% of patients and by 4 weeks in over 90%. It is usually symmetric, although mild asymmetry is not uncommon early in the disease course.
  
  
  
  • In the arms, weakness may be worse proximally than distally. At presentation, half of patients have some facial weakness, although only 5% have varying degrees of ophthalmoplegia.
  
  
  
  • Oropharyngeal or respiratory weakness is a presenting symptom in 40% of patients. Improvement in strength usually begins 1-4 weeks after the plateau. About one third of patients require mechanical ventilation because of respiratory failure.
  
  
  
• Sensory symptoms


• • Mild to moderately severe paresthesias in the distal limbs are common and often precede the onset of weakness by 1 or more days.
  
  
  
  • Proximal sensory changes are uncommon but may occur in more severe cases of AIDP.
  
  
  
• Autonomic dysfunction


• • About two thirds of patients have one or more autonomic abnormalities. Sustained sinus tachycardia is the most common dysfunction. Postural hypotension leading to presyncope or syncope can occur.
  
  
  
  • Sweating dysfunction is common but rarely noted by patients. Urinary retention and constipation are more likely to occur later in the course of AIDP. Autonomic dysfunction is more common in intubated patients.
  
  
  
• Pain


• • Mild lower back and/or hip pain is very common and occasionally precedes the onset of weakness.
  
  
  
  • The pain is severe in about 15% of patients.
  
  
  
• AIDP may vary early in the course. More than 95% of patients eventually have the classic symptoms; other patients may have one of the characterized variants.


• • The Miller-Fisher variant, appearing with ophthalmoplegia, areflexia, and ataxia, is the most common variant and is seen in as many as 5% of patients with AIDP. Although usually seen in adults, this variant is also common in children. Most patients with the Miller-Fisher variant have antibodies against ganglioside GQ1b.
  
  
  
  • Regional variants of GBS, such as pharyngeal-cervical-brachial weakness or only leg weakness, are rare and resemble AIDP in time course.
  
  
  
  • Pure pandysautonomia with little, if any, weakness parallels classic AIDP in time course and antecedent infections. The difference is that this variant is manifested primarily by autonomic failure. Many of these patients also have areflexia.

  • The AMAN variant is seen in China and in developing countries. It presents with weakness only.

  • Acute motor-sensory axonal neuropathy resembles classic GBS in presentation but is related pathologically to AMAN.
  
  
  

Physical: A detailed physical examination can help support the diagnosis of AIDP and/or exclude disorders in the differential diagnosis.

• Weakness


• • Although patients often report only weakness in the legs, careful examination usually demonstrates arm weakness (proximally and distally).
  
  
  
  • Some patients with Miller-Fisher or other regional variants may have weakness of cranial muscles only.
  
  
  
• Deep tendon reflexes


• • Hyporeflexia or areflexia is seen in 70% of patients at presentation and eventually in all patients.
  
  
  
  • A progressive decrease in reflexes is a useful finding that may precede electromyographic (EMG) changes.
  
  
  
• Autonomic dysfunction


• • Fluctuations in heart rate, specifically a sustained sinus tachycardia, are seen often.
  
  
  
  • Some intubated patients also may have bradycardia, especially after vagal stimulation with Valsalva and/or tracheal suctioning maneuvers.
  
  
  
  • Orthostatic hypotension can occur and is likely due to dysfunction of the baroreceptor reflex.
  
  
  
  • At times, the labile blood pressure is observed with severe hypertension that may be due to dysfunction of the afferent limb of the baroreceptor reflex.
  
  
  
  • Urinary retention is common, especially in intubated patients. The rare patient may even develop an ileus.
  
  
  
• Findings that are inconsistent with a diagnosis of AIDP


• • Weakness that remains markedly asymmetric
  
  
  
  • Sharp sensory level
  
  
  
  • Severe bladder or bowel dysfunction at onset
  
  
  
• Diagnostic criteria for GBS include the presence of progressive weakness and areflexia, relative symmetry, mild sensory involvement, cranial nerve involvement, at least partial recovery, autonomic dysfunction, and absence of fever. Cerebrospinal fluid features that strongly support the diagnosis are an increase in protein beyond the first week, cell count <10 (albuminocytological dissociation). Electrophysiologic evidence of conduction slowing, block, prolonged distal latency or F-wave latencies are also strongly supportive (80% of the case), though these abnormalities may be delayed for several weeks. Marked persistent asymmetry of weakness, the presence of a sensory level, bowel/bladder involvement at onset, and a prominent pleocytosis, often cast doubt on the diagnosis, so is the presence of another cause for the neuropathy.

Causes: AIDP is thought to be caused by a dysregulated immune response against myelin. This response may be triggered by several illnesses and conditions. Two thirds of patients with AIDP recall an antecedent upper respiratory or gastrointestinal infection or syndrome from 1-6 weeks prior to the onset of weakness.

• Viral


• • Infection with influenza, coxsackie, Epstein-Barr virus, or cytomegalovirus can cause upper respiratory infection. Immunoglobulin M (IgM) antibodies to each have been identified in some individuals.
  
  
  
  • Acute infection with either herpes simplex virus or human immunodeficiency virus (HIV) also has been associated with AIDP in some individuals.
    • Patients with HIV-associated AIDP often have a pleocytosis with up to 200 WBC/mL CSF.

    • Rare cases also have been reported after infection with rubella, measles, varicella-zoster, hepatitis B, Q fever, and Hantavirus.
  
  
  
• Bacterial


• • Strains of Campylobacter jejuni that cause enteritis are associated closely with the subsequent development of AMAN.
  
  
  
  • Molecular mimicry between gangliosidelike epitopes of the C jejuni lipopolysaccharide and peripheral nerve gangliosides in nerve is a proposed mechanism.
  
  
  
  • In children, an association exists between AIDP and Mycoplasma pneumoniae infection.
  
  
  
• Other: Rare cases of AIDP in individuals infected with toxoplasma, malaria, or filaria have been reported.



• Vaccination


• • Many cases of AIDP were reported after vaccination for swine influenza (especially in 1976).
  
  
  
  • Several cases have been reported after immunization against rabies, influenza, measles, mumps, or rubella.
  
  
  
• Malignancies and systemic illnesses


• • Case reports document patients with AIDP associated with Hodgkin lymphoma, acute myelogenous lymphoma, Castleman disease, systemic lupus erythematosus, and hypothyroidism.
  
  
  
  • The rarity of these combinations raises doubts on the significance of these associations.
  
  
  
• Pregnancy: Most cases occur during the last trimester or during the first 2 weeks of the postpartum period.



• Bone marrow transplantation



• Surgery: Most patients also had an infection or blood transfusion.

• Other problems to be considered
  Poliomyelitis: Classic poliomyelitis is very rare. However, coxsackievirus and echovirus can cause a similar, milder paralysis, especially in children.
  • Buckthorn shrub poisoning: This plant is found in the southwestern United States and Central America and bears a fruit that causes paralysis by an unknown mechanism. The CSF is usually normal.

  • Critical illness polyneuropathy: Weakness is more common in the setting of sepsis and/or multiorgan failure.

  • Diphtheria: Weakness may follow the pharyngeal infection by 2-3 weeks, beginning with palatal paralysis and, often, paralysis of accommodation. Limb weakness is not common.

  • Hypophosphatemia: An acute areflexic paralysis may follow hypophosphatemia in the setting of total parenteral nutrition, alcohol abuse, or rapid refeeding after starvation. The weakness rapidly responds to phosphate replacement.

  • Malingering and conversion reaction: Bizarre or nonphysiologic abnormalities may be seen on neurologic examination.

  • The antidepressant drug zimeldine, a serotonin reuptake blocker, was reported to be associated with GBS and the drug has been withdrawn.



• Variants
  • A number of entities are related to acute demyelinating neuropathy. Although they are acute, likely inflammatory, and immune mediated, they are not necessarily demyelinating. The acute panautonomic neuropathy is characterized by widespread and severe sympathetic and parasympathetic failure. Acute motor axonal neuropathy (AMAN) results in motor axonal degeneration, with little or no demyelination or inflammation. Many follow Campylobacter jejuni infection. Axonal Guillain-Barré syndrome is at the other end of the spectrum, where the illness predominantly involves the axis cylinder of the somatic nervous system, and is fairly common. Hyperacute axonal polyradiculoneuropathy has a hyperacute course with onset to respiratory failure within 48 hours. These patients have a high mortality rate. Recovery when it occurs, is delayed, very prolonged, and characteristically quite incomplete.

  • Critical illness polyneuropathy has an uncertain relationship to the acute inflammatory neuropathies. Sensory Guillain-Barré syndrome, where sensory symptoms occur in isolation, are rare.

  • The Fisher syndrome is an uncommon variant of AIDP (about 5% of the cases) characterized by the triad of ophthalmoplegia, ataxia, and areflexia. Occasionally papillary abnormalities occur, and many cases are associated with some evidence of more widespread motor involvement. Miller-Fisher variant may be associated with a particular serotype of C jejuni.

  • Other unusual variants include the pharyngeal-cervical brachial variant, with deficits limited to these regions alone, and the paraparetic variant, where the weakness is confined to the lower extremities only, as the name implies. Acute sensory neuronopathy is usually associated with autonomic failure. It is likely inflammatory-immune-mediated. The brunt of the attack is borne on the dorsal root ganglia cells.

  • The demonstration in some studies of demyelination in excess of control sera when injected into peripheral nerve, and the demonstration of IgM antibodies that bind to carbohydrate residues of peripheral nerve in 90% of GBS patients at the onset of the disease, support of an antibody as the mechanism of GBS.

  • Over the past decade, great progress has been made in GBS research, and the highlights include (1) the emerging correlations between antiganglioside antibodies and specific clinical phenotypes, notably between anti-GM1/anti-GD1a antibodies and the acute motor axonal variant and anti-GQ1b/anti-GT1a antibodies and the Miller Fisher syndrome; (2) the identification of molecular mimicry between GBS-associated C jejuni oligosaccharides and GM1, GD1a, and GT1a gangliosides as a mechanism for antiganglioside antibody induction; and (3) the development of rodent models of GBS with sensory ataxic or motor phenotypes induced by immunization with GD1b or GM1 gangliosides, respectively (Willison, 2005).



• Comparison of clinical features of GBS with CIDP
  • Patients with CIDP have a more slowly progressive weakness and a protracted course either monophasic or relapsing, and relapses are much more common with CIDP. While a history of viral infection is often obtained with GBS, this is rather uncommon in CIDP. Occurrence of respiratory failure is very uncommon with CIDP. Both conditions are associated with areflexia, typical CSF findings of increased protein, abnormal nerve conduction studies (patchy conduction slowing with GBS and diffuse slowing with CIDP). While prednisone therapy on its own has no proven role in GBS, CIDP patients are sensitive to prednisone therapy.

  • GBS and CIDP have been associated with HIV-1 infection. They are most common in infected patients who are otherwise asymptomatic. In certain cases, GBS may occur with seroconversion. The clinical features of GBS and CIDP in HIV-1 infected patients are similar to patients without HIV-1 infection.

DIFFERENTIALS

Section 4 of 11

Arsenic
Brainstem Gliomas
Brucellosis
Chronic Inflammatory Demyelinating Polyradiculoneuropathy
Diabetic Neuropathy
Lambert-Eaton Myasthenic Syndrome
Leptomeningeal Carcinomatosis
Lyme Disease
Myasthenia Gravis
Organic Solvents
Organophosphates
Periodic Paralyses
Sarcoidosis and Neuropathy
Spinal Cord Hemorrhage
Spinal Epidural Abscess
Systemic Lupus Erythematosus
Thyroid Disease
Toxic Neuropathy

Other Problems to be Considered:

Heavy metal poisoning
Period paralyses, usually hypokalemic
Poliomyelitis
Acute porphyric neuropathy
Buckthorn shrub poisoning
Botulism
Collagen vascular diseases
Critical illness polyneuropathy
Cytomegalovirus (CMV) infection
Diphtheria
EBV virus infection (infectious mononucleosis)
HIV infection
Hypophosphatemia
Lead poisoning
Malingering and conversion reaction
Spinal injury
Tick paralysis and related disorders

WORKUP

Section 5 of 11

Lab Studies:

• Laboratory tests help to support the diagnosis of AIDP and monitor patients with the syndrome. No associated hematologic or urinary findings are characteristic of the diagnosis. The erythrocyte sedimentation rate is normal. Serum protein electrophoresis does not show an abnormality. Hyponatremia due to inappropriate ADH secretion may occur.



• Cerebrospinal fluid


• • Increased CSF protein without an increased WBC count (albuminocytologic dissociation) is observed classically in AIDP. However, this finding is not specific to AIDP.
    • About two thirds of patients have this CSF finding during the first week of symptoms and 82% have it by 2 weeks after symptom onset.

    • Although protein values can be elevated by 10-fold or more, no association exists between protein level and clinical severity.
  
  
  
  • Some patients have oligoclonal banding of the CSF.
  
  
  
  • Myelin basic protein also is increased in some patients.
  
  
  
  • More than 90% of patients have fewer than 10 WBC/mL, with a mean of 3 WBC/mL. If more than 50 WBC/mL are present, an alternative diagnosis should be considered, including HIV, Lyme disease, polio, or other infections. Patients with HIV-associated AIDP often have >50 WBC/mL (mean, 23 WBC/mL).
  
  
  
  • In non-HIV cases, the cells are overwhelmingly lymphocytes, whereas a nonlymphocytic pleocytosis is seen in patients with HIV.
  
  
  
• Blood tests have little role in the diagnosis of AIDP but may help to exclude other conditions and to serially monitor patients with AIDP in the hospital (especially those who are critically ill).


• • Recently, an association has been found between acute axonal motor variants and immunoglobulin G (IgG) directed against ganglioside GM1 and/or GD1a. Furthermore, most patients with the Miller-Fisher variant of AIDP have antibodies directed against ganglioside GQ1b. Some patients with pure sensory variants have antiganglioside GD1b antibodies. These tests are seldom beneficial in classic AIDP, but can help when patients present with variants.
  
  
  
  • Although not necessary for diagnosis, measurement of antiviral or antibacterial antibodies may confirm an association.
  
  
  
  • Measurement of potassium, phosphate, and porphyrin metabolism products may help exclude alternative diagnoses in atypical cases.
  
  
  
  • Some critically ill patients with AIDP develop the syndrome of inappropriate antidiuretic hormone (SIADH) with associated hyponatremia and reduced serum osmolarity.
  
  
  
  • Additionally, liver enzymes sometimes are elevated in AIDP.
  
  
  
  • If intravenous immunoglobulin (IVIg) therapy is anticipated in noncritical cases, immunoglobulin A (IgA) levels should be drawn before treatment.
  
  
  
• Urine tests to exclude heavy metal intoxication may be necessary in some patients.



• Stool cultures may confirm C jejuni enteritis. Patients with this condition may have a more aggressive course and a slightly worse prognosis.

Imaging Studies:

• Imaging is seldom necessary for diagnosing AIDP, but it may be necessary to exclude alternative diagnoses and to monitor critically ill patients.



• MRI of the spine is sometimes necessary to rule out spinal cord and/or nerve root processes that mimic AIDP.


• • Nerve root, cauda equina, or cranial nerve enhancement is observed sometimes on T1-weighted, gadolinium-contrasted scans. This can help diagnose some atypical cases.
  
  
  
  • Cytomegalovirus radiculitis, meningeal carcinomatosis, lymphomatosis, and sarcoidosis may have similar MRI findings.
  
  
  
• Chest radiography in children may reveal a pattern that is consistent with mycoplasmal pneumonia. Additionally, chest and abdominal radiography may be necessary in critically ill patients to evaluate for possible pneumonia and ileus.

Other Tests:

• Electrodiagnostic testing is always necessary to confirm the diagnosis of AIDP.



• Nerve conduction studies (NCS) can document demyelination, the hallmark of AIDP.


• • Early on, findings of NCS studies are often normal. However, 90% are abnormal within 3 weeks of symptom onset.
  
  
  
  • Patients who meet 3 of the 4 NCS criteria listed below have a clear primary demyelinating neuropathy, although patients who meet fewer than 3 criteria still may have AIDP. Severe slowing of conduction velocities may be more consistent with chronic inflammatory demyelinating polyneuropathy (CIDP). Details of electrodiagnostic criteria are provided in Cornblath (1990).
    • Reduced conduction velocity

    • Conduction block or abnormal dispersion

    • Prolonged distal latencies

    • Prolonged F-waves
  
  
  
• Needle EMG can document the extent of denervation.



• Findings of other electrophysiologic tests, such as blink reflexes, phrenic nerve conduction, and somatosensory evoked responses, may be abnormal but do not offer any advantages to typical NCS studies.



• Autonomic tests such as sympathetic skin responses and cardiovagal testing may be indicated in patients with autonomic failure.



• Pulmonary function tests, useful in determining the timing of intensive care unit (ICU) transfers and elective intubation, should be performed in all patients.


• • Transfer to an ICU generally is indicated when forced vital capacity (FVC) is less than 20 mL/kg.
  
  
  
  • Intubation is usually warranted when FVC drops to 15 mL/kg or negative inspiratory pressure drops to less than -25 cm H₂O.
  
  
  
• Electrocardiography (ECG) and cardiac monitoring can be helpful when arrhythmias occur. Other possible abnormalities include atrioventricular block, QRS widening, and T-wave abnormalities.

Procedures:

• Lumbar puncture is performed to obtain CSF for analysis (see Lab Studies).

Later on, macrophages are seen, sometimes with myelin stripping. Axons are usually spared. Under electron microscopy, macrophages (which are stripping myelin) are seen beneath the basement membrane and are usually advancing along the minor dense line.

TREATMENT

Section 6 of 11

Medical Care: Advances in supportive medical care have resulted in improved survival rates in AIDP.

• Mechanical ventilatory assistance is required in about one third of patients with AIDP and lasts for an average of 49 days. Intubation should be performed when FVC drops to less than 15 mL/kg or negative inspiratory pressure is worse than -25 cm H₂O. Tracheostomy is usually recommended if mechanical ventilation will be required for more than 2-3 weeks. Bedridden patients need prophylaxis against thromboembolism. Subcutaneous heparin is the most common agent. Some may also need GI prophylaxis with an H2-blocker (or similar agent).



• Enteric nutrition is necessary for patients on mechanical ventilation. Nasogastric tubes or Dubhoff tubes can be used initially. Those requiring more than 2 or 3 weeks or enteric nutrition may require gastrostomy or jejunostomy tube feedings.



• Cardiac monitoring is necessary. Chronic sinus tachycardia often responds to beta-blockers or calcium channel blockers. Bradycardia requires atropine treatment, if symptomatic. Heart block may require temporary pacing. Hypertension responds well to beta-blockers. These treatments should be administered cautiously under the direction of a cardiologist or critical care specialist, since one of the main causes of death is iatrogenic hypotension, especially in patients with autonomic failure.



• Constipation is common in intubated patients with AIDP, and a bowel regimen is usually necessary. Some patients may also require enemas. Ileus is rare. If it occurs, bowel rest is usually necessary and parenteral nutrition can be used during that time.



• Skilled nursing care of intubated patients is necessary to avoid skin breakdown. Special mattresses are available in most intensive care or step-down units. Communication difficulties can lead to frustration and exacerbate depression. Involvement of speech therapy, physical therapy, and occupational therapy is highly recommended. Many patients may require a rehabilitation unit after being weaned off a ventilator.



• Conventional immunosuppressant treatments with corticosteroids have failed to show benefit. But immunomodulation with IVIg and plasmapheresis has led to faster recovery, relatively mild disability, and shorter hospital stays. IV steroid therapy alone is not indicated for the treatment of AIDP. Treatment is less likely to be effective if initiated more than 2 weeks after the onset of symptoms. Some patients with mild weakness, especially those presenting during the plateau, may not require immunomodulatory therapy. Plasmapheresis had shown to cut the respirator time and time to independent ambulation, by about half when treatment was given during the first week of the disease.

Surgical Care: Tracheostomy is necessary in many intubated patients. Those requiring long-term enteral nutrition typically require a gastrostomy or jejunostomy.

Consultations:

• Neurology: For patients on general medicine or other services, neurological consultation is indicated to manage diagnostic studies and to help determine appropriate treatment.



• Critical care: About one third of patients require mechanical ventilation. Any intubated patient or patient who is transferred to an ICU for monitoring should be monitored by a critical care or pulmonary specialist.



• Surgery: Some patients may require tracheostomy or a feeding tube for parenteral nutrition.



• Cardiology: Patients with arrhythmias in addition to sinus tachycardia or major cardiac rhythm abnormalities should be evaluated by a cardiologist.



• Physical medicine and rehabilitation

Diet: No special diet is required.

Activity: Keep patients ambulatory if they are able to walk without assistance. Most patients who are admitted to the hospital require bedrest.

MEDICATION

Section 7 of 11

Immunomodulatory therapy with either IVIg or plasmapheresis has been demonstrated to result in more rapid recovery of AIDP than other treatments or no treatment. Recent large studies have demonstrated that the 2 treatments are equal in efficacy. Bedridden and critically ill patients also require treatment to prevent complications.

The mechanism of action of plasma exchange is not known. Suggested mechanisms include the removal of antibody, complement components, immune complexes, lymphokines, and acute-phase reactants. The generally recommended regimen includes every other day plasma exchange, totaling 6 exchanges in 2 weeks, with 3-3.5 L exchanged per treatment. If venous access is not of sufficient quality to ensure rapid blood withdrawal, a central line should be a consideration (in about 20% of cases).

Plasmapheresis (PE) is more frequently associated with severe adverse effects requiring cessation of therapy, including a bleeding diathesis. In addition, PE requires special, appropriate equipment and trained personnel. Also, younger children may be at risk for bleeding after insertion of wide catheters. Transient hypotension, which might occur, is corrected by adjusting the inflow-to-outflow ratio. Other common side effects include paresthesias, and rarely hypersensitivity reactions and hypocalcemia.

Drug Category: Immunomodulatory agents -- AIDP is believed to be caused by immune dysregulation resulting from an attack against myelin. Therapy directed at the immune system can result in more rapid recovery. IVIG is especially proven highly effective in children.

Drug Name	IV Immunoglobulin (IVIg) or gamma globulin (many manufacturers) -- IVIg is prepared from serum pooled from many donors by fractionation and purification. Most manufacturers include a detergent step to help prevent spread of viruses. Mechanism of action is poorly understood. However, it is believed to act by down-regulating antibody and cytokine production and by neutralizing antibodies specific for myelin. Also appears to down-regulate pro-inflammatory cytokines, such as IL-1 and gamma-IFN. Other proposed mechanisms are Fc receptor blockade and interference with complement cascade (ie, interfering with opsonization).
Adult Dose	0.4 g/kg/d for 5 d has been used most often Alternative regimen is 1-2 g/kg/d for 2 d
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity; IgA immunodeficiency (if present, low-IgA preparations available) Severe congestive heart disease is relative contraindication
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Common adverse effects include headache and itching—pretreatment with acetaminophen and diphenhydramine help prevent these effects Patients with prior cardiac history are at risk for pulmonary edema—if it occurs, furosemide is drug of first choice Rarer adverse effects include aseptic meningitis, stroke, skin rashes, renal tubular necrosis; hepatitis C has been transmitted by IVIg in past, but current preparations include detergent step Can artificially decrease serum sodium and elevate ESR

Drug Name	Plasmapheresis or plasma exchange -- This treatment entails removing blood from body, spinning it to separate cells from plasma, and replacing cells suspended in fresh frozen plasma, albumin, or saline. Can be performed using either 2 large-bore peripheral IV sites or multiple lumen central line. May not be effective if started more than 2 wk after onset of symptoms.
Adult Dose	Typical protocol: 200-250 mL/kg for each of 4 or 5 exchanges during an 8- to 10-d period
Pediatric Dose	Administer as in adults
Contraindications	Recent myocardial infarction; coronary artery disease; arrhythmias; severe renal failure; severe hepatic failure; bleeding disorder
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Back-to-back plasmapheresis sessions may remove clotting factors and can alter coagulation test results Common adverse effects include headaches Rare cases of myocardial infarction and stroke have been reported

Drug Category: Anticoagulant agents -- Bedridden patients are at risk for deep venous thrombosis. This risk can be reduced by mild anticoagulation.

Drug Name	Heparin -- Given subcutaneously, interacts with antithrombin III to decrease clot proliferation. This can result in decreased incidence of deep venous thrombosis.
Adult Dose	5000 U SC tid
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; subacute bacterial endocarditis; active bleeding; history of heparin-induced thrombocytopenia
Interactions	Digoxin, nicotine, tetracycline, and antihistamines may decrease effects; NSAIDs, aspirin, dextran, dipyridamole, and hydroxychloroquine may increase toxicity
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Some preparations contain benzyl alcohol as preservative and, when used in large amounts, may be associated with fetal toxicity (ie, gasping syndrome); preservative-free heparin recommended in neonates Use with caution in patients with shock or severe hypotension

FOLLOW-UP

Section 8 of 11

Further Inpatient Care:

• Based on the severity of symptoms, patients may require further inpatient services.


• • Patients should have cardiac monitoring to confirm and treat arrhythmias.
  
  
  
  • Pulmonary function tests such as FVC and negative inspiratory pressure should be performed 3-4 times a day until a patient has reached a plateau for several days.
  
  
  
  • Transfer to an ICU is recommended for patients with worsening respiratory effort (ie, FVC <20 mL/kg) or cardiac arrhythmias.
  
  
  
  • Physical therapy should be initiated early to help increase patient activity and mobility. Patients who do not recover quickly benefit by transfer to an inpatient rehabilitation center before returning home.
  
  
  

Further Outpatient Care:

• Generally, all patients in whom AIDP is suspected should be admitted for further monitoring and treatment.



• Patients who present with mild neurologic impairment after already reaching a plateau can be treated as outpatients with close supervision.



• Upon discharge, patients require several follow-up visits to ensure that relapses do not occur and to help coordinate home-health services if necessary. Physical and occupational therapy, either in a long-term rehabilitation unit or at home, help many patients return more rapidly to their baseline level of activity.



• Relapses occur (10-20%) following completion of plasma exchange, and these relapses frequently respond to a second course of treatment. Similarly, relapses that follow IVIG therapy also respond to a second course.

Transfer:

• To the ICU when respiratory failure is impending or when cardiac arrhythmias are occurring



• To regional or tertiary hospitals if a community hospital does not have an ICU or is unable to provide IVIg or plasmapheresis therapy

Complications:

• Critically ill patients are susceptible to the same complications as other intubated patients, including pneumonia, sepsis, skin decubiti, deep venous thrombosis, and urinary tract infections. Patients with AIDP have some unique complications that may cause significant morbidity, the most common being pain, labile blood pressure, and increased sensitivity to cardiac medications.

Prognosis:

• About 75% of 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.



• Several prognostic factors have been identified.


• • 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 GBS 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.

Patient Education:

• Guillain-Barré Syndrome Foundation International

MISCELLANEOUS

Section 9 of 11

Medical/Legal Pitfalls:

• The main medicolegal pitfalls involve not anticipating progression of symptoms.


• • This may occur when a patient who has not reached a plateau is not admitted to a hospital.
  
  
  
  • Similarly, admitted patients require cardiac monitoring and FVC and negative inspiratory pressure testing at least 3 times daily.
  
  
  

Special Concerns:

• Plasmapheresis and IVIg have been used in pregnant patients; however, the risks are not well documented.



• In elderly patients, arrhythmias are the most common cause of death. In addition, elderly patients have a higher complication rate.



• The Miller-Fisher variant is more common in children than in adults, representing as many as 20% of cases.

TEST QUESTIONS

Section 10 of 11

CME Question 1: Which of the following is not an electrophysiologic hallmark of acute inflammatory demyelinating polyradiculoneuropathy (AIDP)?

A: Prolonged distal latencies
B: Conduction block or temporal dispersal
C: Decreased F-wave latencies
D: Decreased conduction velocities
E: Normal or slightly reduced compound muscle action potential (CMAP) amplitudes

The correct answer is C: Electrophysiologic evidence of demyelination includes reduced conduction velocity, increased distal latencies, conduction block (and/or temporal dispersal), and increased F-wave latencies (or absent F-waves).

CME Question 2: Which of the following casts doubt on the diagnosis of acute inflammatory demyelinating polyradiculoneuropathy (AIDP)?

A: Persistent asymmetric weakness
B: Distal sensory paresthesias
C: Elevated cerebrospinal fluid (CSF) protein
D: Respiratory failure
E: Facial weakness

The correct answer is A: Although AIDP may present initially with mild asymmetry, persistent marked asymmetry of weakness is more common in poliomyelitis (but not in AIDP). Distal sensory paresthesias, elevated CSF protein, respiratory failure, and facial weakness are common in AIDP.

Pearl Question 1 (T/F): Orthostatic hypotension is the most common autonomic dysfunction seen in acute inflammatory demyelinating polyradiculoneuropathy (AIDP).

The correct answer is False: The most common autonomic abnormality in AIDP is sinus tachycardia.

Pearl Question 2 (T/F): The most common variant of acute inflammatory demyelinating polyradiculoneuropathy (AIDP) is the Miller-Fisher syndrome.

The correct answer is True: The Miller-Fisher syndrome consists of the triad of ataxia, areflexia, and ophthalmoplegia.

Pearl Question 3 (T/F): Antecedent syndromes may precede onset of acute inflammatory demyelinating polyradiculoneuropathy (AIDP).

The correct answer is True: The 2 most common antecedent syndromes are upper respiratory infection and enteritis.

Pearl Question 4 (T/F): Electrodiagnostic features of demyelination have been defined.

The correct answer is True: These include reduced conduction velocity, prolonged distal latency, conduction block or temporal dispersal, and prolonged or absent F-waves.

BIBLIOGRAPHY

Section 11 of 11

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