Gullian Barre/myaesthenia gravis Flashcards
What is GBS?
Immune mediated demyelination of the peripheral nerves which is often triggered by an infection
It is an acute paralytic neuropathy of the peripheral nerves which causes an acute symmetrical ascending weakness (from the feet upwards)
It can also affect the sensory nerves causing a sensory neuropathy
What is guillain barre syndrome caused by?
Triggered by an infection…
- gastroenteritis with campylobacter jejuni
- cytomegalovirus
- epstein barr virus
What is the pathophysiology behind gullain bare syndrome?
Molecular mimicry
Antibodies are made against the antigens on viruses
These antibodies will also attack the proteins on the nerves (either the myelin sheath or axon itself)
Its the damage to the nerve cells which create the problem
What is the presentation of gullain barre syndrome?
Characteristic feature= progressive, symmetrical weakness of all the limbs
The weakness is classically ascending- the legs are affected first
Reflexes are reduced or absent
Sensory symptoms are mild (distal paraesthesia with very few sensory symptoms)
What is the usual clinical course of gullain barre?
They may have had gastroenteritis 4 weeks prior
The symptoms usually start 4 weeks after their infection
At 2-4 weeks the symptoms peak and there is a slow recovery period that can last months to years
How do you diagnose guillain barre syndrome?
The diagnosis is made clinically
Brighton criteria can be used for diagnosis
It can be supported by investigations…
- nerve conduction studies (show reduced signals throughout the nerve)
- lumbar puncture (test for CSF)
What would the lumbar puncture of guillain barre show?
Albuminocytogenic dissociation- this is found in 65% of patients
Protein is raised but WCC remains the same
What is the management of gullain barre?
IV immunoglobulins
Plasma exchange (to remove some of the antibodies)
Supportive care (make sure patient is still well despite weakness)
Importantly they need VTE prophylaxis (LMWH) which prevents blood clots
In very severe cases which have respiratory failure, then patients need intubation and ventilation and admission to ICU
What is the leading cause of death in gullain barre?
Blood clots
What is the prognosis of gullain barre?
80% fully recover
15% left with some neurological disability
5% die
What is myasthenia gravis?
It is an autoimmune condition which causes muscle weakness which gets worse with activity and improves with rest
How does myaesthenia gravis affect females and males differently?
It typically affects women under the age of 40 and men over the age of 60
What does myaesthenia gravis have a link with?
Thymoma’s
= tumours of the thymus gland
10-20% of patients with myaesthenia gravis have a thymoma, 20-40% of patients with a thymoma have myasethenia gravis
What is the pathophysiology behind myasthenia gravis?
In around 85% of patients with myasthenia gravis acetylcholine receptor antibodies bind to the acetylcholine receptors and block them, preventing the acetylcholine from binding to the receptor and trigger muscle contraction
As the receptors are more active during exercise they become more blocked up and this leads to less effective stimulation of the muscle with increased activity, there is more muscle weakness the more the muscles are used.
The antibodies also activate the complement system within the neuromuscular junction which leads to damage at the post synaptic membrane, further worsening the symptoms
2 other antibodies which cause myasthenia gravis, cause the other 15% of cases
These are antibodies against…
- muscle specific kinase
- low density lipoprotein receptor related protein 4 (LRP4)
Musk and LRP4 are important for the formation and creation of acetylcholine receptor, destruction leads to inadequate acetylcholine receptors being created.
How do patients present?
Varies! Can be very mild or severe
The characteristic presentation is weakness which gets worse with increased muscle use but improves with rest
Typically minimal in the morning and worse at the end of the day
Symptoms typically Affect the proximal muscles and the small muscles of the head and neck…
- extraocular muscle weakness- causes double vision- diplopia
- eyelid muscle drooping- causing ptosis
- facial muscle movement weakness
- difficulty in swallowing
- fatigue in jaw
- slurred speech
