History and exam

Key diagnostic factors

common

Key risk factors include preceding viral or bacterial infection.

Progressive symmetrical muscle weakness usually affecting lower extremities before upper extremities and proximal muscles before distal muscles accompanied by paraesthesias in the feet and hands is typical.[87][88][11] The paralysis is typically flaccid with areflexia and progresses acutely over days, with around 80% of patients reaching a nadir by 2 weeks and 97% by 4 weeks.[89] Weakness evolving over >4 to 8 weeks is more consistent with chronic inflammatory demyelinating polyradiculoneuropathy.[87][88]

Paraesthesias in hands and feet occur in most GBS patients and frequently precede the onset of weakness.[5] Paresthesias may extend proximally in the extremities, but sensory abnormalities on examination are usually mild. If a distinct sensory level is noted on examination, this is unlikely to be GBS and is more likely a spinal cord process.

Pain is a common feature of GBS, and may precede muscle weakness; back and leg pain is typical.[91] The presence of back pain and paralysis is easily misinterpreted as cord compression.

Pain is a much more prominent symptom in children than in adults.[92]

Typical signs may include dyspnoea on exertion and shortness of breath, but respiratory muscle weakness can often be asymptomatic. Approximately 20% to 30% of patients develop respiratory muscle weakness requiring mechanical ventilation.[11][94]

Facial weakness and oropharyngeal weakness occurs in around two-thirds of patients.[134][135] Typical signs include slurred speech.

The majority of patients are areflexic on admission, with ankle jerks and knee jerks being the most commonly affected. In some patients the areflexia/hyporeflexia may be present only in the weakest limbs. Plantar reflex should be downgoing or absent but never upgoing. Tone should be flaccid. However, all GBS variants and subtypes can present with hyper-reflexia, although this is rare.[136]

Occurs in around two-thirds of patients.[134][135]

Together with bilateral facial weakness, bulbar dysfunction is associated with increased risk of progression to mechanical ventilation.[125] Oropharyngeal weakness occurs in around 50% of patients.[134] Typical signs include swallowing difficulty.

Occurs in around 15% of patients.[134]

Often occurs after trunk and limb involvement but occurs before in a small number of patients.

Often occurs after trunk and limb involvement but occurs before in a small number of patients.

Often occurs after trunk and limb involvement but occurs before in a small number of patients.

Often occurs after trunk and limb involvement but occurs before in a small number of patients.

Mild dysautonomia is common and results in sinus tachycardia, hypertension, and postural hypotension in approximately two-thirds of patients.[90] Other autonomic symptoms such as urinary retention and ileus can also occur.[93] Bladder disturbance is usually mild or absent early in the disease; if severe, cord compression should be excluded. Life-threatening cardiac arrhythmias are relatively rare.[11]

Autonomic dysfunction in children may be an independent risk factor for mechanical ventilation.[92]

uncommon

GBS may be associated with bilateral tonic pupils and may involve both parasympathetic and sympathetic post-ganglionic neurons.[8] Up to nearly half of patients with Miller-Fisher syndrome have sluggish pupils and mydriasis.[103][102]

Although uncommon, light-fixed dilated pupils in GBS have been described.[137][138] If pupils are fixed and dilated, the possibility of botulism needs to be considered.[139]

Anisocoria (unequal pupils) may occasionally be seen; tends to accompany severe ophthalmoparesis and ptosis.

Ataxia, areflexia, and ophthalmoplegia are the classic triad for Miller-Fisher syndrome (MFS), although not all patients with MFS have ophthalmoplegia.[99][100] Around 30% of patients with MFS develop extremity weakness manifesting as an overlapping syndrome with classic GBS.[5]

Other diagnostic factors

common

May occur in Miller-Fisher syndrome.

Encephalopathy and hyper-reflexia may be the presenting features of Bickerstaff's brainstem encephalitis.

uncommon

Characteristic feature of Miller-Fisher syndrome (MFS). A few patients with MFS present with ataxia and hyporeflexia without ophthalmoplegia.[99]

Risk factors

strong

Two-thirds of patients with GBS have a history of gastroenteritis or influenza-like illness in the weeks before onset of neurological symptoms.[15][69]

Approximately 60% to 70% of acute motor axonal neuropathy and acute motor-sensory axonal neuropathy cases and up to 30% of acute inflammatory demyelinating polyradiculoneuropathy cases are preceded by Campylobacter jejuni infection.[32][33]Campylobacter-associated GBS appears to have a worse prognosis, manifested by slower recovery and greater residual neurological disability.[13] A study in Sweden estimated that the risk of developing GBS during the 2 months following C jejuni infection is approximately 100-fold higher than in the general population.[70]

Cases of GBS were reported following the outbreak of Zika virus in 2013.[43][44][45][20][21] A case control study from French Polynesia found that 98% of patients with GBS harboured anti-Zika virus IgG or IgM, and that the risk of GBS was 0.24 per 1000 Zika virus infections.[71] However, this risk is lower than that associated with Campylobacter jejuni (0.25 to 0.65 per 1000 cases) or cytomegalovirus infections (0.6 to 2.2 per 1000 cases).[5] Guidelines have been updated regarding the risk of GBS following Zika virus infection.[72][73] Several other mosquito-borne viral infections such as dengue, chikungunya, and Japanese encephalitis have been linked to GBS.[46][47][48][49]

There is evidence that hepatitis E virus is a risk factor for the development of GBS.[74][75] Of patients with GBS in the Netherlands, 5% had preceding acute hepatitis E infection; in Bangladesh (where hepatitis E is endemic), this figure was 11%.[76]

weak

There is some suggestion of increased risk of GBS following vaccination.[36] However, one study found no evidence of increased risk of GBS after seasonal influenza immunisation, and cohort studies found no risk of GBS following meningococcal conjugate vaccine A, C, Y, and W135 (MCV4).[39][38] Epidemiological evidence indicates that the relative risk of GBS after immunisation is far lower than that following an infectious disease, especially for influenza.[40][41] There is a comparatively higher risk for pandemic vaccines than for seasonal vaccines.[42] There have been reports of GBS associated with vaccination against coronavirus disease 2019 (COVID-19).[26]

Case reports link GBS with Hodgkin's disease.[77] Less commonly, other malignancies have been associated with GBS.[78][79][80]

Several immune-mediated neurological complications, including GBS, have been reported in patients with cancer who are prescribed checkpoint inhibitors (eg., anti-CTLA-4 antibodies); clinicians should be aware of this risk when using these therapies.[81][82]

Incidence increases with age. For people <30 years of age, the incidence is <1:100,000. For people >75 years of age, incidence is 4:100,000.[30][69] The mean age of onset is approximately 40 years.[15]

Anecdotal: several cases of GBS have been reported in people with HIV.[83][84][85]

GBS has been reported in patients with confirmed COVID-19 infection; more evidence is needed about whether the incidence of GBS in patients with COVID-19 is higher than that in the general population.[23][24][25]

GBS is slightly more common in males, with an estimated male-female ratio of 1.78.[5][12]

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