Neuro emergencies Flashcards
What is Guillain-barre syndrome
Disorder causing demyelination and axonal degeneration resulting in acute, ascending and progressive neuropathy, characterised by weakness, paraesthesiae and hyporeflexia.
What is GBS usually preceded by
75% of patients have a history of preceding infection, usually of the respiratory and gastrointestinal tract.
A large number of infections have been linked, including Campylobacter jejuni, Epstein Barr virus, cytomegalovirus, mycoplasma and human immunodeficiency virus
Risk factors for GBS
History of gastrointestinal or respiratory infection from 1-3 weeks prior to the onset of weakness.
Recently, an association has been suggested with the Zika virus
Vaccinations: live and dead vaccines have been implicated.
Malignancies - eg, lymphomas, especially Hodgkin’s disease.
Pregnancy: incidence decreases during pregnancy but increases in the months after delivery.
Presentation of GBS
Weakness Pain Areflexia sensory symptoms autonomic symptoms
Weakness in GBS
In 60% of cases, onset occurs approximately three weeks after a viral illness.
The condition usually presents with an ascending pattern of progressive symmetrical weakness, starting in the lower extremities.
This reaches a level of maximum severity two weeks after initial onset of symptoms and usually stops progressing after five weeks.
Facial weakness, dysphasia or dysarthria may develop.
In severe cases, muscle weakness may lead to respiratory failure.
Pain in GBS
neuropathic pain may develop, particularly in the legs. Back pain may be another feature.
Sensory symptoms in GBS
These can include paraesthesiae and sensory loss, starting in the lower extremities.
Autonomic symptoms in GBS
Involvement of the autonomic system may present, with reduced sweating, reduced heat tolerance, paralytic ileus and urinary hesitancy.
Severe autonomic dysfunction may occur.
Features of GBS on examination
Hypotonia.
Demonstrable altered sensation or numbness.
Reduced or absent reflexes.
Fasciculation may occasionally be noted.
Facial weakness - may be asymmetrical.
Autonomic dysfunction - fluctuations of heart rate and arrhythmias, labile blood pressure and variable temperature.
Respiratory muscle paralysis.
What might a lumbar puncture show in GBS
Most patients have an elevated level of cerebrospinal fluid (CSF) protein, with no elevation in CSF cell counts. The rise in the CSF protein may not be seen until 1-2 weeks after the onset of weakness.
What is a major determinant of need for admission to ITU in GBS
Spirometry - forced vital capacity
Management of GBS
Plasma exchange
IV immunoglobulins
Corticosteroids
DVT prophylaxis
Complications of GBS
Persistent paralysis Respiratory failure requiring mechanical ventilation Hypotension or hypertension Thromboembolism Cardiac arrhythmia Ileus
What is myasthenia gravis
Autoimmune condition that causes muscle weakness that gets progressively worse with activity and improves with rest
Which tumours are associated with myasthenia gravis
Strong link between thymoma
10-20% of patients with myasthenia gravis have a thymoma. 20-40% of patients with a thymoma develop myasthenia gravis.
Pathophys of myasthenia gravis
In around 85% of patients with myasthenia gravis, acetylcholine receptor antibodies are produced by the immune system.
These bind to the postsynaptic neuromuscular junction receptors which blocks the receptor and prevents the acetylcholine from triggering muscle contraction. As the receptors are used more during muscle activity, more of them become blocked up.
This leads to less effective stimulation of the muscle with increased activity. There is more muscle weakness the more the muscles are used. This improves with rest as more receptors are freed up for use again.
Presentation of myasthenia gravis
Most affect proximal muscles and small muscles of head/neck
Extraocular muscle weakness causing double vision (diplopia)
Eyelid weakness causing drooping of the eyelids (ptosis)
Weakness in facial movements
Difficulty with swallowing
Fatigue in the jaw when chewing
Slurred speech
Progressive weakness with repetitive movements
How can fatiguability of muscles be elicited on examination
Repeated blinking will exacerbate ptosis
Prolonged upward gazing will exacerbate diplopia on further eye movement testing
Repeated abduction of one arm 20 times will result in unilateral weakness when comparing both sides
Diagnosis of myasthenia gravis
Acetylcholine receptor (ACh-R) antibodies (85% of patients)
Muscle-specific kinase (MuSK) antibodies (10% of patients)
LRP4 (low-density lipoprotein receptor-related protein 4) antibodies
What is the edrophonium test
Patients are given an IV dose of edrophonium chloride (or neostigmine).
Normally, cholinesterase enzymes in the neuromuscular junction break down acetylcholine.
Edrophonium block these enzymes and stop the breakdown of acetylcholine.
As a result the level of acetylcholine at the neuromuscular junction increases. It briefly and temporarily relieves the weakness. This establishes a diagnosis of myasthenia gravis.
Treatment of myasthenia gravis
Reversible acetylcholinesterase inhibitors (usually pyridostigmine or neostigmine) increases the amount of acetylcholine in the neuromuscular junction and improve symptoms
Immunosuppression (e.g. prednisolone or azathioprine) suppresses the production of antibodies
Thymectomy can improve symptoms even in patients without a thymoma
