INTRODUCTION — The acute immune-mediated polyneuropathies are classified under the eponym Guillain-Barré syndrome (GBS), after the authors of early descriptions of the disease. Historically, GBS was considered a single disorder, but it is now known to be a heterogeneous syndrome with several variant forms. Most often, GBS presents as an acute monophasic paralyzing illness provoked by a preceding infection. In addition to the demyelinating form, which is the most common type, axonal forms of GBS are well-recognized.

This topic will review the epidemiology, clinical features, and diagnosis of GBS in children. Other aspects of GBS are discussed separately. (See "Guillain-Barré syndrome in children: Treatment and prognosis" and "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis".)

PATHOGENESIS — The pathogenesis of Guillain-Barré syndrome (GBS) is discussed here briefly and reviewed in detail elsewhere. (See "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis".)

One proposed mechanism for GBS is that an antecedent infection evokes an immune response, which in turn cross-reacts with peripheral nerve components because of the sharing of cross-reactive epitopes (molecular mimicry). The end result is an acute polyneuropathy. This immune response can be directed towards the myelin or the axon of peripheral nerve. The main lesions of GBS are acute inflammatory demyelinating polyradiculoneuropathy and, particularly in patients with Campylobacter-associated disease and acute axonal degeneration. (See "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis" and "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'Pathogenesis'.)

Antecedent infections are common with GBS, and are thought to trigger the immune response that leads to acute polyneuropathy. Approximately two-thirds of patients give a history of an antecedent respiratory tract or gastrointestinal infection. Campylobacter infection is the most commonly identified precipitant of GBS and can be demonstrated in as many as 30 percent of cases. Other precipitants include cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, and influenza-like illnesses. GBS can also occur in association with HIV infection, predominantly in those who are not profoundly immunocompromised. A small percentage of patients develop GBS after another triggering event such as immunization, surgery, trauma, or bone-marrow transplantation. (See "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'Antecedent events'.)

While GBS has followed vaccinations, the small risk of GBS associated with influenza vaccination, of approximately one to two excess cases of GBS per million people vaccinated, is substantially less than the overall health risk posed by naturally occurring influenza. Furthermore, the risk of GBS following influenza infection is several times greater than the risk following influenza vaccination. (See "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'Vaccinations'.)

The available evidence suggests that there is no increased risk of GBS associated with the H1N1 influenza vaccine in children [1-3].

EPIDEMIOLOGY — In the post-polio era, Guillain-Barré syndrome (GBS) is the most common cause of acute flaccid paralysis in healthy infants and children [4,5]. GBS occurs worldwide with an annual incidence of 0.34 to 1.34 cases per 100,000 persons aged 18 years or less. [6-8]. While all age groups are affected, the incidence is lower in children than in adults. The incidence increases by approximately 20 percent with every 10-year increase in age beyond the first decade of life. GBS occurs rarely in children younger than two years of age, but can occur even in infants [9,10]. Males are affected approximately 1.5 times more often than females in all age groups.

CLINICAL FEATURES — Guillain-Barré syndrome (GBS) is a clinical syndrome with a number of variant forms. In patients with acute inflammatory demyelinating polyradiculopathy (AIDP), the most common form of GBS, two-thirds develop the neurologic symptoms two to four weeks after what initially appears to be a benign febrile respiratory or gastrointestinal infection [11,12].

The classic presentation of GBS begins with paresthesia in the toes and fingertips followed by lower extremity symmetric or modestly asymmetric weakness that may ascend over hours to days to involve the arms and, in severe cases, the muscles of respiration [13,14]. The predominant symptoms of GBS at presentation in children are pain and gait difficulty [15]. In preschool-aged children, the most common symptoms are refusal to walk and pain in the legs [16].

In a prospective series of 95 children with GBS, the most frequent initial symptoms were gait unsteadiness, neuropathic pain, and inability to walk, occurring in 45, 34, and 24 percent of cases, respectively [17]. By the peak of the illness, the frequency of symptoms was as follows:

●79 percent had neuropathic pain

●60 percent could not walk

●51 percent had autonomic dysfunction

●46 percent had cranial nerve involvement

●24 percent could not use their arms

●13 percent required mechanical ventilation

Cranial neuropathy most commonly affects the facial nerves, causing bilateral facial weakness [17,18]. Pain typically involves the back and the legs [19].

Autonomic dysfunction occurs in approximately one-half of children with GBS, and may include the following [17,20]:

●A variety of cardiac dysrhythmias (asystole, bradycardia, persistent sinus tachycardia, and atrial and ventricular tachyarrhythmias)

●Orthostatic hypotension

●Transient or persistent hypertension

●Paralytic ileus

●Bladder dysfunction

●Abnormal sweating

Rare patients have central nervous system involvement [21].

Physical examination — Physical examination typically reveals symmetric weakness with diminished or absent reflexes and gait abnormalities [13,14]. Sensory symptoms are usually "positive" (eg, pain or paresthesia, reflecting nerve irritability) rather than "negative" (eg, loss of sensation). Early symptoms may be atypical, rendering diagnosis difficult. Some cases present with initial proximal weakness, or less common findings such as sphincter disturbances, raising concerns about a possible spinal cord lesion.

Clinical course — More than 90 percent of patients reach the nadir of their function within two to four weeks [22], followed by return of function occurring slowly over the course of weeks to months.

The clinical course of GBS in children is shorter than in adults and recovery is usually more complete [23-26]. In patients who did not require mechanical ventilation, the median time to recovery of independent walking was 43 to 52 days in children compared with 85 days in adults [27-29].

SUBTYPES OF GUILLAIN-BARRÉ SYNDROME — Historically, Guillain-Barré syndrome (GBS) was considered a single disorder. It is now known to be a heterogeneous syndrome with several variant forms [6,30]. Acute inflammatory demyelinating polyradiculopathy (AIDP) is the most common type. Axonal forms of GBS are also well recognized. Each type of GBS has distinguishing clinical, pathophysiologic and pathologic features. The classic presentation of ascending paralysis is most common, but a number of atypical variants present with local or regional involvement of particular muscle groups or nerves [6,30,31]. Several have prominent cranial nerve involvement, including Miller Fisher syndrome, Bickerstaff brainstem encephalitis, polyneuritis cranialis, and pharyngeal-cervical-brachial weakness. Others include pure sensory neuropathy and acute pandysautonomia.

Acute inflammatory demyelinating polyneuropathy — AIDP is the prototype of GBS, and is the most common form in North America, Europe and most of the developed world, where it accounts for about 85 to 90 percent of cases.

Acute motor axonal neuropathy — Acute motor axonal neuropathy (AMAN) is a pure motor form of GBS. This disorder is distinguished from AIDP by its involvement of predominantly motor nerves and an electrophysiologic pattern suggesting axonal damage. AMAN occurs mainly in northern China, but is also a common form of GBS in other locations, including Japan, Mexico, and South America [32-38]. It is more common in developing nations, has a seasonal incidence, and is associated with a preceding Campylobacter jejuni infection. In a series of 31 Japanese children with GBS classified by electrophysiologic criteria, AIDP, AMAN, and unclassified GBS were seen in 11, 15, and 5 children (35, 48, and 16 percent, respectively) [37].

The presenting clinical features and recovery are similar to those of AIDP [39]. However, more patients have respiratory failure requiring assisted ventilation.

Acute motor-sensory axonal neuropathy — Acute motor-sensory axonal neuropathy (AMSAN) resembles the motor axonal variant but has more sensory symptoms. The course tends to be prolonged and severe [40,41]. The pathology is predominantly axonal lesions of both motor and sensory nerve fibers. This form of GBS is uncommon in children.

Miller Fisher syndrome — Miller Fisher syndrome (MFS) is characterized by external ophthalmoplegia, ataxia, and muscle weakness with areflexia [42,43]. Incomplete forms include acute ophthalmoplegia without ataxia, and acute ataxic neuropathy without ophthalmoplegia [6]. Cerebrospinal fluid findings and electrophysiologic features are similar to those in acute inflammatory demyelinating polyneuropathy. Brainstem auditory evoked potentials demonstrate peripheral and central conduction defects [26].

Bickerstaff encephalitis — Bickerstaff encephalitis is a brainstem encephalitis characterized by encephalopathy and hyperreflexia, in combination with such features of MFS as ophthalmoplegia and ataxia. It is not only clinically linked to MFS, but is associated with anti-GQ1b antibodies and can respond to intravenous immunoglobulin (IVIG) and plasma exchange [44-46]. Some experts consider MFS, Bickerstaff encephalitis, and pharyngeal-cervical-brachial weakness with anti-GQ1b antibodies to be overlapping variants of the anti-GQ1b antibody syndrome [47].

Polyneuritis cranialis — Patients with polyneuritis cranialis develop acute bilateral multiple cranial nerve involvement (eg, bilateral facial weakness, dysphagia, and dysphonia) with severe peripheral sensory loss. Patients tend to be younger than those with other GBS subtypes. This variant is associated with preceding cytomegalovirus infection [48].

Cerebrospinal fluid findings and electrophysiologic features of polyneuritis cranialis are similar to those of AIDP. Magnetic resonance imaging (MRI) with gadolinium shows post-contrast enhancement of the cranial nerve roots [49]. More children with this variant require ventilator support than those with the more typical presentation of GBS [50]. However, most eventually recover fully.

Pharyngeal-cervical-brachial weakness — The pharyngeal-cervical-brachial variant of GBS is characterized by acute weakness of the oropharyngeal, neck, and shoulder muscles, with swallowing dysfunction [51-53]. Facial weakness may also be present. Strength and reflexes are usually normal in the lower extremities. This form of GBS may overlap with MFS [52,54]. It is thought to represent a localized form of axonal GBS [6,51,52]. Some patients with pharyngeal-cervical-brachial weakness have immunoglobulin G (IgG) autoantibodies to GT1a, GQ1b, or (less often) to GD1a.

Other variants — There are a number of additional uncommon variants of GBS, including the following:

●Acute pandysautonomia, symptoms of which include diarrhea, vomiting, dizziness, abdominal pain, ileus, orthostatic hypotension, urinary retention, pupillary abnormalities, an invariant heart rate, decreased sweating, salivation, and lacrimation [55]. The deep tendon reflexes are absent or diminished and sensory symptoms may be present [56].

●Pure sensory GBS, with involvement of large sensory fibers leading to significant sensory ataxia [57]. The deep tendon reflexes are absent and there may be minor motor involvement. An association with antibodies to GD1b has been noted.

●Facial diplegia and distal limb paresthesia [54]. This is considered a variant of acute inflammatory demyelinating polyneuropathy [6].

●Sixth nerve palsy and distal paresthesia [54].

●Bilateral lumbar radiculopathy [54].

●Paraparesis, with weakness restricted to the legs at presentation [51,58]. A minority experiences some arm weakness over the course of the illness.

DIAGNOSIS — The initial diagnosis of Guillain-Barré syndrome (GBS) is based upon the clinical presentation. The typical clinical features of GBS are progressive, mostly symmetric or modestly asymmetric muscle weakness and absent or depressed deep tendon reflexes (see 'Clinical features' above). The weakness can vary from mild difficulty with walking to nearly complete paralysis of all extremity, facial, respiratory, and bulbar muscles. However, some GBS variants present with local or regional involvement of particular muscle groups or nerves, and several have prominent cranial nerve involvement; the variable initial presentations can hinder early diagnosis. (See 'Subtypes of Guillain-Barré syndrome' above.)

No single investigation can confirm or disprove the diagnosis of GBS, particularly early in its course. In a child with a compatible clinical presentation, the diagnosis is contingent on supporting evidence from the clinical examination, cerebrospinal fluid (CSF) analysis, electrodiagnostic studies, magnetic resonance imaging, and/or ancillary investigations (eg, serum immunoglobulin G [IgG] antibodies to GQ1b), with the exclusion of alternative diagnoses by the same means.

Supportive features include the following:

●An elevated CSF protein (>45 mg/dL) with a normal CSF white blood cell count (ie, albuminocytologic dissociation). (See 'Cerebrospinal fluid' below.)

●In the demyelinating forms of GBS, electrodiagnostic studies demonstrating abnormalities including motor conduction block, slowing of motor and sensory nerve conduction, temporal dispersion, and prolonged distal latencies. In the axonal forms of GBS, nerve conduction studies showing decreased amplitude of motor (and possibly sensory) responses, with normal conduction velocities. (See 'Electrodiagnostic studies' below.)

●Contrast enhancement of the spinal nerve roots, cauda equina, or cranial nerve roots on magnetic resonance imaging (MRI). (See 'Magnetic resonance imaging' below.)

●Detection of serum IgG antibodies to GQ1b, supporting the diagnosis of the GBS variants Miller Fisher syndrome, Bickerstaff encephalitis, and pharyngeal-cervical brachial weakness. (See 'Antibodies' below.)

Cerebrospinal fluid — In patients with GBS, lumbar puncture often reveals an elevated CSF protein with a normal CSF white blood cell count. This finding, known as albuminocytologic dissociation, is present in 50 to 66 percent of patients with GBS in the first week after the onset of symptoms and ≥75 percent of patients in the third week [6,59,60]. The elevated protein may be due to increased permeability of the blood-nerve-barrier at the level of the proximal nerve roots. A normal CSF protein is found in one-third to one-half of patients when tested earlier than one week after symptom onset.

In a prospective series of 110 patients with GBS, initial CSF protein elevation varied from 45 to 200 mg/dL (0.45 to 2.0 g/L) in 73 percent of patients, but protein elevation as high as 1000 mg/dL (10 g/L) has been described [59]. As noted, the CSF cell count is typically normal, ie, <5 cells/mm³. However, a minority of patients with GBS has mildly elevated CSF cell counts. In the same series, the CSF cell count was <5, 5 to 10, 11 to 30, and >30 cells/mm³ in 87, 9, 2, and 2 percent of patients, respectively [59].

Concurrent HIV infection or an alternative diagnosis (eg, Lyme disease, poliomyelitis, enterovirus 71 infection, West Nile virus, or malignancy) should be considered in children with acute flaccid paralysis who have a CSF cell count >50/mm³.

Electrodiagnostic studies — Electrodiagnostic studies are the most specific and sensitive tests for diagnosis of GBS, and establish the underlying pathophysiology as either demyelinating or axonal. Performance of a detailed neurophysiologic study enables diagnosis of pediatric GBS in as many as 90 percent of cases during the first week of symptoms [61]. Changes are virtually universal by the second week of illness, by which time a definitive diagnosis can almost always be made. Electrodiagnostic studies are uncomfortable, and can be technically challenging in small children; they should therefore be undertaken only by individuals with appropriate pediatric expertise. (See "Overview of electromyography" and "Overview of nerve conduction studies".)

Peripheral nerve demyelination often primarily affects proximal nerve roots and the terminal segments of motor nerves, and can be accompanied by conduction block [17,61,62]. In some cases, this results in unrecordable motor responses. It may not be possible, on neurophysiologic criteria, to distinguish this situation from extensive axonal degeneration. The prognostic implications of severely reduced compound muscle action potential (CMAP) amplitudes must therefore be interpreted with caution. When peripheral responses are unrecordable, a search for more proximal responses (such as those from stimulation of the phrenic or axillary nerves) may enable identification of a primarily demyelinating process. Electromyographic evidence of acute denervation is always suggestive of severe axonal injury and a worse prognosis [61-63].

Magnetic resonance imaging — Spinal MRI with administration of gadolinium frequently shows enhancement of the spinal nerve roots and cauda equina during the first weeks after the onset of GBS in children [64-66]. The enhancement may be diffuse or predominantly involve the ventral (anterior) nerve roots, and less often the dorsal (posterior) roots. In some cases, nerve root enhancement may be delayed and observed only on a repeat MRI. Enhancement of cranial nerve roots may also be seen in some cases, reflecting more diffuse nerve involvement [66,67].

Evidence from uncontrolled retrospective studies suggests that the sensitivity of contrast-enhanced spinal MRI for the diagnosis of childhood GBS is >90 percent [64-66]. Nevertheless, spinal nerve root enhancement is a nonspecific finding that can be seen in a variety of disorders including polyradiculopathy related to HIV or cytomegalovirus infection, chronic inflammatory demyelinating polyneuropathy, arachnoiditis, sarcoidosis, carcinomatous or lymphomatous meningitis, and certain metabolic diseases. Thus, the diagnosis of GBS cannot be made by MRI alone.

Antibodies — Immune reactions directed against epitopes in Schwann cell surface membrane or myelin can cause the acute demyelinating form of GBS, while immune reactions against epitopes contained in the axonal membrane cause the acute axonal forms of GBS. Antibodies against GQ1b, a ganglioside component of nerve, are present in the vast majority of patients with Miller Fisher syndrome. (See 'Miller Fisher syndrome' above and "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'GQ1b syndromes'.)

In clinical practice, commercially available testing for serum IgG antibodies to GQ1b is useful for the diagnosis of Miller Fisher syndrome, having a sensitivity of 85 to 90 percent. Antibodies to GQ1b may also be present in GBS with ophthalmoparesis, Bickerstaff encephalitis, and the pharyngeal-cervical brachial GBS variant, but not in disorders other than GBS [68,69].

Currently, laboratory testing for antibodies to glycolipids other than GQ1b is not performed routinely because of limited clinical utility.

DIFFERENTIAL DIAGNOSIS — Disorders of the central nervous system, peripheral nerve, neuromuscular junction, and muscle may have features that initially resemble Guillain-Barré syndrome (GBS) (table 1). However, consideration of the neurologic examination, clinical course, cerebrospinal fluid profile, and electrodiagnostic findings usually establish the diagnosis of GBS [22].

Chronic inflammatory demyelinating polyneuropathy — There is a temporal continuum between acute inflammatory demyelinating polyneuropathy (AIDP), the demyelinating form of GBS, and chronic inflammatory demyelinating polyneuropathy (CIDP).

●AIDP is a monophasic subacute illness that reaches its nadir within three to four weeks

●CIDP continues to progress or has relapses for longer than eight weeks (see "Chronic inflammatory demyelinating polyneuropathy: Etiology, clinical features, and diagnosis")

●Subacute inflammatory demyelinating polyneuropathy is the term used by some authors for disease that reaches its nadir between four and eight weeks

This arbitrary temporal delineation of inflammatory demyelinating polyneuropathy can occasionally be difficult to ascertain in practice. Only observation of the patient over time can clarify whether the clinical course is that of AIDP or CIDP.

In addition to chronicity, other features may be useful to distinguish GBS (including AIDP) from CIDP:

●While the onset of GBS is usually easily identified, the precise onset of CIDP is typically less clear

●Antecedent events are more frequent with GBS (where they occur in approximately 70 percent of cases) than with CIDP (where they are found in ≤30 percent of cases) (see "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'Antecedent events')

●Certain features are more consistent with an increased likelihood of CIDP in the first weeks after onset of symptoms, including three or more episodes of clinical deterioration, a mild disease course with retained ability to walk independently, and lack of cranial neuropathies [70]

About 2 percent of patients initially diagnosed with AIDP will develop the chronic relapsing weakness of CIDP. (See "Guillain-Barré syndrome in adults: Treatment and prognosis", section on 'Approach to patients who relapse or worsen'.)

Other polyneuropathies — Acute polyneuropathies that may mimic GBS include those due to acute severe vitamin B1 deficiency, acute arsenic poisoning, n-hexane (in glue sniffing neuropathy), vasculitis, Lyme disease, tick paralysis, porphyria, sarcoidosis, leptomeningeal disease, paraneoplastic disease, and critical illness.

The combination of data from the clinical setting, appropriate screening laboratory tests (including thiamine level, rheumatologic testing, Lyme titer, spot urine for porphyria), as well as electromyography with nerve conduction studies and cerebrospinal fluid analysis, are usually sufficient to rule out these other, much less common, causes of polyneuropathy. A spot urine test for porphobilinogen in a sample obtained at the time of symptoms will identify the majority of patients with acute porphyria. (See "Acute intermittent porphyria: Pathogenesis, clinical features, and diagnosis".)

Peripheral nerve vasculitis is a potentially life-threatening illness that can be difficult to diagnose. The pattern is that of a mononeuritis multiplex involving sensory and motor fibers in the distribution of individual peripheral nerves. Although the pathology of the disease is asymmetric, the clinical picture can mimic GBS with fairly symmetric ascending weakness when the vasculitis is rapidly progressive with confluent nerve involvement. Vasculitic neuropathies are rare in childhood. (See "Clinical manifestations and diagnosis of vasculitic neuropathies".)

Spinal cord disorders — Acute myelopathies due to spinal cord compression or acute transverse myelitis can be confused with GBS, since reflexes can be depressed in the acute stage of spinal cord disease. Early bowel and bladder dysfunction and a sensory level point to a myelopathy. Imaging with spine MRI is usually helpful in diagnosing acute myelopathy by demonstrating a focal spinal cord lesion.

Severe low back pain is common with GBS and frequently leads to imaging of the lumbar spine; prominent contrast enhancement of the nerve roots on MRI may occur in GBS. (See 'Magnetic resonance imaging' above.)

Neuromuscular junction disorders — Diseases of the neuromuscular junction including botulism and myasthenia gravis can present with acute weakness, but sensory signs or symptoms are lacking. Botulism is associated with large, unreactive pupils and constipation. Electromyography with repetitive nerve stimulation and appropriate laboratory tests help clarify the diagnosis. (See "Diagnosis of myasthenia gravis" and "Lambert-Eaton myasthenic syndrome: Clinical features and diagnosis" and "Botulism".)

Muscle disorders — Acute polymyositis, critical illness myopathy, and critical illness neuropathy can mimic GBS. The myopathy and neuropathy of critical illness present as an acute paralysis, typically in patients receiving intensive care. High-dose intravenous glucocorticoids, neuromuscular blocking drugs, sepsis, and multiorgan failure are thought to play an important role, but the pathophysiology is not well understood. (See "Neuromuscular weakness related to critical illness".)

TREATMENT — The main modalities of therapy for Guillain-Barré syndrome include plasmapheresis and administration of intravenous immune globulin. Even before initiating specific therapy, the clinician must decide when and whether to admit the patient to the intensive care unit (ICU) and whether mechanical ventilation is required. This topic is discussed separately. (See "Guillain-Barré syndrome in children: Treatment and prognosis".)

PROGNOSIS — The severity of Guillain-Barré syndrome in children does not correlate with long-term outcome. As many as 85 percent of children can be expected to have an excellent recovery. In general, the prognosis in affected children is better than adults. (See "Guillain-Barré syndrome in children: Treatment and prognosis", section on 'Prognosis'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Guillain-Barré syndrome".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Guillain-Barré syndrome (The Basics)")

SUMMARY

●Guillain-Barré syndrome (GBS) is often triggered by an antecedent infection that evokes an immune response, which in turn reacts with peripheral nerve components because of the sharing of cross-reactive epitopes (molecular mimicry). The end result is an acute polyneuropathy. This immune response can be directed towards the myelin or the axon of peripheral nerve. Campylobacter infection is the most commonly identified precipitant of GBS. (See 'Pathogenesis' above.)

●GBS is the most common cause of acute flaccid paralysis in healthy infants and children. (See 'Epidemiology' above.)

●Most patients with acute inflammatory demyelinating polyradiculopathy, the most common form of GBS, develop neurologic symptoms two to four weeks after having what initially appears to be a benign febrile respiratory or gastrointestinal infection. The most common symptoms at presentation in children are pain and gait difficulty. Lower extremity symmetric or modestly asymmetric weakness may ascend over hours to days to involve the arms and the muscles of respiration in severe cases. The facial nerve is occasionally affected, resulting in bifacial weakness. Autonomic dysfunction occurs in approximately one-half of children. Physical examination typically reveals lower-extremity predominant, essentially symmetric weakness with diminished or absent reflexes. Most patients reach their clinical nadir within two to four weeks, with subsequent return of function over the course of weeks to months. (See 'Clinical features' above.)

●GBS has several variant forms (see 'Subtypes of Guillain-Barré syndrome' above):

•The classic presentation of ascending paralysis is most common with acute inflammatory demyelinating polyradiculopathy (see 'Acute inflammatory demyelinating polyneuropathy' above) and the axonal forms (see 'Acute motor axonal neuropathy' above and 'Acute motor-sensory axonal neuropathy' above) of GBS.

•Atypical variants present with local or regional involvement of particular muscle groups or nerves. Several have prominent cranial nerve involvement, including Miller Fisher syndrome (see 'Miller Fisher syndrome' above), Bickerstaff brainstem encephalitis (see 'Bickerstaff encephalitis' above), polyneuritis cranialis (see 'Polyneuritis cranialis' above), and pharyngeal-cervical-brachial weakness (see 'Pharyngeal-cervical-brachial weakness' above). Others include pure sensory neuropathy and acute pandysautonomia (see 'Other variants' above).

●The initial diagnosis of GBS is based upon the clinical presentation. The typical clinical features of GBS are progressive, mostly symmetric muscle weakness and absent or depressed deep tendon reflexes (see 'Clinical features' above), although some GBS variants have atypical features (see 'Subtypes of Guillain-Barré syndrome' above). The diagnosis is supported by the finding of cerebrospinal fluid (CSF) albuminocytologic dissociation, characterized by an elevated CSF protein (>45 mg/dL) with a normal CSF white blood cell count. In the demyelinating forms of GBS, electrodiagnostic studies demonstrate a variety of abnormalities including motor conduction block, slowing of motor and sensory nerve conduction, temporal dispersion, and prolonged distal latencies. In the axonal forms of GBS, nerve conduction studies show decreased amplitude of motor (and possibly sensory) responses, with normal conduction velocities. (See 'Diagnosis' above.)

●Disorders of the central nervous system, peripheral nerve, neuromuscular junction, and muscle may have features that initially resemble GBS (table 1). However, the presentation, neurologic examination, clinical course, cerebrospinal fluid profile, and electrodiagnostic findings usually establish the diagnosis of GBS. (See 'Differential diagnosis' above.)

●The main modalities of therapy for GBS are plasmapheresis and intravenous immune globulin. These issues are discussed separately. (See "Guillain-Barré syndrome in children: Treatment and prognosis".)

●As many as 85 percent of children with GBS have an excellent recovery. Prognosis is reviewed in detail elsewhere. (See "Guillain-Barré syndrome in children: Treatment and prognosis".)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Robert Cruse, DO, who contributed to earlier versions of this topic review.