An acute inflammatory demyelinating polyradiculopathy, almost certainly autoimmune since antibodies to ganglioside are often found. Some cases are purely motor, others are mixed motor and sensory. About a quarter follow Campylobacter infection, where there is clear homology between bacterial epitopes and gangliosides. Strongly associated with HIV in the tropics.
Usually gradual onset over a few days but rarely can be over a few hours. Diarrhoeal illness a few weeks previously suggests campylobacter. Presents with pain, numbness, paraesthesiae, weakness. Weakness may initially be proximal or distal (distal alone suggests “withering” axonopathy eg toxin). Facial nerves often affected (see Miller Fisher syndrome, below).
Reflexes usually lost early but sometimes persist. Autonomic features may occur (vagal nerve involvement) eg urinary retention, sinus tachycardia, ileus. The degree of paralysis can be extreme – up to 20% require ventilation.
Gradually worsens, peaks at around 2 weeks (by definition, within 4 weeks). Then there is a variable plateau phase. 20% will have persisting disability; fatigue is common. Myelinopathy usually recovers quite rapidly; axonopathy takes months to years. Neuronopathy is where the dorsal root ganglion cell body itself is damaged, and may never recover. [Am Fam Physician 2020]
The diagnosis is often pretty obvious but investigations should be done to rule out other causes. If purely motor, differential includes hypokalaemia, polio, myasthenia gravis, botulism, acute myopathy.
- MRI brain and spinal cord – low threshold! Consider if acute or rapidly progressive, predominantly sensory symptoms (including back pain), predominant sphincter disturbance at presentation, clear sensory or marked motor level. MRI may show enhancing nerves esp cranial nerves, but more usefully excludes:
- a spinal lesion (eg prolapsed disc, haemorrhage or tumour)
- para-sagittal cerebral lesion, which can present as acute painful flaccid paraparesis
- Acute Transverse Myelitis
- Lumbar puncture – Elevated CSF protein has high PPV but not specific (and may be normal within seven days of onset). Pleocytosis eg >50 cells/mm3 suggests another diagnosis. In children, lumbar puncture is not always necessary to make a definite diagnosis, and should be reserved for cases where the diagnosis is in doubt. Oligoclonal bands present in CSF and plasma.
- Nerve conduction studies – may be normal in the first week! Demyelinating pattern. May be useful in children who present with atypical features, normal CSF protein after the first week following presentation or in categorising the subtype of GBS – for example, Acute motor axonal neuropathy (AMAN)
- U&E (hypokalaemia)
- Creatine kinase (myositis)
- Acute and convalescent serum for viral and mycoplasma antibody titres (Mycoplasma pneumoniae, EBV, CMV, Borrelia burgdorferi).
- Throat swab; stool microscopy, culture and sensitivities (Campylobacter jejuni)
- Antiganglioside antibodies (for example, anti-GQ1b antibodies in Miller-Fisher syndrome)
Monitor respiratory ability with serial peak flows.
- Heavy metals and toxins (lead, mercury, arsenic, organophosphates)
- Urinary porphyrins
- Botulinum toxin identification (stool, serum) (but eyes usually involved)
- Diphtheria (but eyes usually involved)
- Drug toxicology screen
- trial of intravenous edrophonium (Tensilon) and/or oral pyridostigmine (minimum of five days) for myasthenia gravis if investigations have been normal or negative
- Enteroviruses incl Poliomyelitis – fever, asymmetry of weakness, lack of sensory involvement, CSF findings and PCR from throat/stool
- In endemic regions, tick bite paralysis closely resembles AIDP. Seasonal, affects young children predominantly. CSF protein is usually normal and the electrophysiological studies are consistent with a pre-synaptic defect at the neuromuscular junction rather than a peripheral neuropathy. The patient usually recovers rapidly after removal of the tick but full return of strength may take several weeks. Failure to detect the tick may result in the death of the patient.
The initial progressive phase lasts 10-30 days. If deterioration continues beyond four weeks, the diagnosis of GBS is pretty much excluded – suggests chronic inflammatory polyneuropathy (CIDP). In rapid, aggressive disease complete quadriplegia can develop in 2-5 days; apart from need for respiratory support, autonomic involvement can provoke life-threatening arrhythmias and hypertension. Aspiration pneumonia is another major risk.
Children should be admitted to PICU if they have:
- flaccid tetraparesis
- severe rapidly progressive course
- reduced vital capacity at or below 20 ml/kg
- bulbar palsy with symptoms
- autonomic cardiovascular instability viz persistent hypertension or labile blood pressure, or arrhythmias.
Plasma exchange is gold standard. Surprisingly, steroids do not appear to have any benefit (cf CIDP), as they can sometimes make things worse or slow the recovery. Perhaps nerve damage at presentation is already programmed/complete? Or do they impair healing? IVIG 0.4g/kg for 5 days (started as soon as possible and ideally within first 2 weeks, although benefit may extend up to 4 weeks) is as effective as plasma exchange (in adults, Cochrane) and probably quicker as well as safer. The conventional dose of immunoglobulin is a total of 2 g/kg, over 3-5 days, whatever protocol that avoids waste best! In kids, 250 ml/kg plasma exchange or roughly a triple-volume exchange probably best.
For pain which is resistant to conventional analgesia, gabapentin and carbamazepine may be useful.
Mortality in childhood GBS is less than 5%. Deaths may be caused by ventilatory failure (rare now), cardiac arrhythmias, dysautonomia and pulmonary embolism. Full recovery within 3-12 months is experienced by 90-95% of children with GBS; that leaves 5-10% with permanent neuro deficits, but most of those tend to have only minor disability.
Miller-Fisher syndrome = ophthalmoplegia with ataxia & absent reflexes. GQ1b antibodies are highly sensitive and specific, found particularly in ocular motor nerves. Beware botulism and diphtheria, which also affect eyes!