4.1 Guillain Barré Syndrome Flashcards
Summarise the case
- Complex critically ill paediatric patient
- Severe neurological pathology with threatened airway and failure of
ventilation needing urgent multidisciplinary input from senior clinicians - Parents are Jehovah’s Witnesses
What abnormality do you note in the blood results?
- Normocytic anaemia
- Platelets are high, depicting inflammation
- Low magnesium
What are the causes of normocytic anaemia?
- Decreased production of normal-sized red blood cells
(e.g. anaemia of chronic disease, aplastic anaemia) - Increased production of HbS as seen in sickle cell disease
- Increased destruction or loss of red blood cells
(e.g. haemolysis, post-haemorrhagic anaemia ) - An uncompensated increase in plasma volume
(e.g. pregnancy, fluid overload) - B2 (riboflavin) and B6 (pyridoxine) deficiency
What are the causes of hypomagnesaemia?
- Decreased magnesium intake
° Starvation
° Alcohol dependence
° Total parenteral nutrition
- Decreased magnesium intake
- Redistribution of magnesium from extracellular to intracellular space
° Treatment of diabetic ketoacidosis
° Alcohol withdrawal syndrome
° Refeeding syndrome
° Acute pancreatitis
- Redistribution of magnesium from extracellular to intracellular space
- Gastrointestinal magnesium loss
° Diarrhoea, vomiting, and nasogastric suction
° Hypomagnesaemia with secondary hypocalcaemia (HSH)
- Gastrointestinal magnesium loss
- Renal magnesium loss
° Renal tubular defects
- Renal magnesium loss
interpret the arterial blood gas.
- Compensated respiratory acidosis
- Type 2 respiratory failure
- Normal glucose and lactate
- Anion gap 21
What is anion gap? How do you calculate it?
- Anion gap is the difference
in the measured cations
and the anions in serum.
- Anion gap is the difference
° Measured cations: Na+, K+, Ca2+, and Mg2+
° Unmeasured cations:
serum proteins (normal) and paraproteins (abnormal)
° Measured anions: Cl−, H2Po4 −, HCo3 −
° Unmeasured anions: sulphates and some serum proteins
- Used to determine the cause of metabolic acidosis
- Expressed as mEq/L
_________________
- Anion gap = (Na + K) − (Cl + HCo3)
What are the causes for a raised AG
- Lactic acidosis/ketoacidosis/alcohol abuse
- Toxins: methanol/aspirin/cyanide
- Renal failure causes
high anion gap acidosis by
decreased acid excretion and
decreased HCO3 − reabsorption.
- Renal failure causes
Accumulation of sulphates, phosphates, urate,
and hippurate accounts for the high anion gap.
What is the significance of a high anion gap?
- The anion gap is affected by
changes in unmeasured ions.
- The anion gap is affected by
A high anion gap indicates acidosis
(e.g. in uncontrolled diabetes,
there is an increase in ketoacids
i.e. an increase in unmeasured anions)
and a resulting increase in the anion gap.
- Bicarbonate concentrations decrease
in response to the need to buffer
the increased presence of acids
(as a result of the underlying condition).
- Bicarbonate concentrations decrease
The bicarbonate is consumed by the
unmeasured anion
(via its action as a buffer),
resulting in a high anion gap.
comment on the CSF analysis.
Increase protein in the absence of organisms
is called albumino cytological dissociation
Why is there increase in CSF protein?
The increase in CSF protein is due to
widespread inflammation of the nerve roots.
What would you expect the CSF glucose to be?
Normal—i.e. approx. 2/3 of plasma glucose
What is the differential diagnosis?
- Guillain Barre Syndrome (GBS)
- Myasthenia Gravis
- Multiple Sclerosis
- Transverse myelitis
- Encephalitis
- Meningitis
- Space-occupying lesion
- Sepsis
What is the likely diagnosis?
My diagnosis is Guillain Barre Syndrome. The history of prodromal infection
and the course of presentation favour my diagnosis. There is often history
of campylobacter or cytomegalovirus infections or vaccinations (influenza,
polio, rabies, and rubella).
What is the pathogenesis GBS?
It is postulated that the immune responses
directed towards the infecting organisms
cross-react with neural tissues
resulting in widespread segmental
demyelination of peripheral nerves.
How will you differentiate this from myasthenia gravis?
Differences in Myasthenia (the following are features of myasthenia):
- Early involvement of muscle groups
including extra-ocular, levator, pharyngeal jaw,
neck, and respiratory muscles.
- Early involvement of muscle groups
Sometimes presents without limb weakness
- Excessive fatigability and variation
of symptoms and signs throughout the
day are common
- Excessive fatigability and variation
- Reflexes are preserved and sensory features,
dysautonomia, and bladder dysfunction are absent
- Reflexes are preserved and sensory features,
- Electrophysiological study shows
normal nerve conduction and presence
of decremental response to repetitive nerve stimulation
- Electrophysiological study shows
- EMG shows abnormal jitter and blocking
- Edrophonium test is normally positive
