Guillain Barre Syndrome - The Creeping Paralysis
Its 7:00 pm on a Friday night. I get a call from the casualty about a 65 year old female who came with complaints of inability to move her legs below the knees since the morning. I roll my eyes as I tell the casualty medical officer to wait. It was probably a case of hysteria. Half an hour passes and I get another call. Same patient. Now she can’t move her hips either. Now I am alarmed. I go down to the casualty to find the patient there scared. She suddenly cannot move her feet. Hiding my alarm, I assure her that she’s going to be okay. Her neurological examination reveals paraparesis with areflexia. Not many causes of this presentation are known. I admit her into the ward. Two days later, she’s in the ICU unable to breathe on her own and dependant on mechanical ventilation because her chest muscles won't work.
What gives?
Guillain Barre syndrome (GBS) was named after Guillain, Barre and Stohl, in 1916 when they presented a paper on ascending paralysis without fever. Today we know GBS to be an acute inflammatory demyelinating polyneuropathy.
The essential problem with GBS is acute flaccid paralysis secondary to damage to the nerves by autoantibodies. Antibodies are formed against gangliosides present in the myelin of nerve sheaths or the gangliosides in the nodes of Ranvier. Now the site of damage dictates the nature of lesion, the types of GBS and also the subsequent clinical features.
There are four different types of GBS that each have slightly varied clinical presentation. Acute inflammatory demyelinating polyneuropathy (AIDP) is the most common type and presents with antibodies against ganglioside GM1a. There are two axonal variants of GBS: acute motor axonal neuropathy (AMAN) and acute motor sensory axonal neuropathy (AMSAN). Both of the axonal variants present with anti - GD1a antibodies. The last major subtype of GBS is called Miller Fisher syndrome and presents with anti GQ1b antibodies.
Each of the subtypes have specific clinical features. The features common to all these subtypes of GBS are
hyporeflexia or areflexia,
absence of bladder or bowel involvement and
absence of constitutional symptoms like fever.
Bladder involvement early on in the disease suggests a different diagnosis. All subtypes also have some amount of autonomic dysregulation which may cause a fluctuation of blood pressure and pulse.
AIDP generally presents with acute onset flaccid paralysis that begins in the lower limb and has a symmetrical ascending pattern. Rapid ascension leads to respiratory muscle paralysis and death. There is no sensory loss in this subtype. AMAN has a similar natural history. AMSAN however presents with sensory involvement.
Millard Fisher syndrome is a subtype of GBS with a triad of features -
ataxia
areflexia and
ophthalmoplegia
Remember that in Miller Fisher syndrome, there is no motor weakness, only ataxia.
GBS has molecular mimicry that underlies its pathology. There are antecedent infections that predispose a patient to develop GBS. Usually there is a history of upper respiratory tract infection or diarrhoea usually 3 weeks before the onset of illness. Campylobacter jejuni is a commonly implicated organism in this condition. So what happens is that the antibodies formed against these infections share an epitope with the gangliosides present on the nerve cells. Depending on the antibodies formed and the duration of exposure, the presentation and severity of the disease changes. Some rare cases occur secondary to certain vaccines as well, the most prominent example being the influenza vaccine given in 1961. Todays vaccines are less likely to produce this effect, but 1 in a million cases still do occur.
Diagnosis of this condition is based on three diagnostic modalities. The most accessible modality is Cerebrospinal fluid analysis. The CSF in GBS presents with cytoabuminological disassociation. That means that albumin levels are high while the number of cells is low or nil. This finding, however, is not very specific and may be seen in many other conditions. The next modality is Nerve Conduction Studies. The nerve conduction study not only identifies GBS but also helps in identifying subtypes of it. It can also be used to assess prognosis. Nerve conduction studies show increased distal latencies and eventually conduction block.
The least used modality for diagnosis is a contrast MRI of the spine. This shows contrast enhancement of the conus medullaris and caudal equina. Most commonly the enhancement occurs in the anterior nerve roots.
The treatment for this condition is simple in its ideology but difficult and expensive to provide. What is the problem? Antibodies against our own cells, right? The solution is elegant : form antibodies against the bad antibodies and remove them. This treatment is called intravenous immunoglobulin or IvIg. The dose of IvIg is calculated at 2g/kg body weight and given over 5 days. The other treatment option is plasmapheresis. In this technique, the blood is just essentially purged of all antibodies in general.
The condition has a unpredictable clinical course. Sometimes, the symptoms stop worsening within a day with barely any weakness. Other times, the symptoms worsen for 4 weeks continuously. In general the demyelinating subtype has a better prognosis that the axonal subtypes.
GBS is now the most common cause of acute flaccid paralysis and must always be considered as a differential in patients who present with paraplegia in an acute setting. Remember that there is no fever and no bowel bladder involvement. CSF findings may be strongly suggestive and NCV is diagnostic.
Author: Narendran Sairam (Facebook)
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