Neuromuscular Disorders Flashcards
What is the neurotransmitter in the NMJ?
Acetylcholine
What causes botulism?
Clostridium Botulinum
How does a bacterial infection produce the neuromuscular disorder?
The toxins cleave presynaptic protein preventing vesicles fusing with the membrane.
Acetylcholine isn’t released in NMJ.
How doe botulism present?
Rapid onset weakness with no sensory loss.
Lamberton Eaton Syndrome
Anutoantibodies to the Ca2+ so reduced vesicles released as Ca2+ doesn’t enter presynaptic bulb.
What is the common cause of Lamberton Eaton Syndrome?
Small Cell Carcinoma
What is the most common Neuromuscular disorder?
Myasthenia Gravis
When does myasthenia present in the population
Women 3rd decade
Men 6-7th decade
What causes myasthenia gravis?
Autoimmune antibodies to the acetylcholine receptors on post synaptic plate.
Reduced receptors mean stamina and increased fatigue.
At what percentage loss of receptors do symptoms present?
30%
What is Myasthenia Gravis associated with?
Thymic Hyperplasia
If left untreated how do the muscles in myasthenia gravis react?
Begin to atrophy
In what percentage of patients with myasthenia gravis do ACh antibodies occur?
80-90%
What are the clinical signs of Myasthenia Gravis?
Fluctuating weakness
Extraoccular weakness - drooping eyes double vision
Struggle to speak and chew
Proximal limb weakness
What is the acute treatment for Myasthenia Gravis?
Acetylcholinesterase inhibitors - Pyridostigmine
IV Immunoglobulin
Plasma Exchange
Thymectomy
What is the acute treatment for chronic Myasthenia Gravis?
Steroid
Steroid sparing agents
What is the course of steroid used in chronic Myasthenia Gravis?
High does 40-60mg prednisolone for a month
What steroid sparing agents are used in chronic Myasthenia Gravis?
Azathioprine
Mycophenolate
What drugs should be avoided in a Myasthenia Gravis?
Gentamicin
What is the mortality in Myasthenia Gravis?
3/4%
What are the commonest causes of death in Myasthenia Gravis?
Respiratory failure
Aspiration pneumonia
Side effects of immunosuppression
What are the signs of muscular disease?
Myalgia
Muscle weakness
Wasting
Hypoflexia
What are fasciculations?
Visible fast fine spontaneous twitches
What are some non pathological causes of fasciculations?
Stress fatigue caffeine
What is a pathological cause of fasciculations?
Denervated muscles that are hyper excitable
What grading system is used to determine the power in someone’s limbs?
MRC - Muscle Power Grading
0 - 5
0 = no movement
5 = normal strength ( subjective to the patient)
What investigations are undertaken in a suspected NMJ disease?
Blood test - Creatine Kinase
Muscle Biopsy
MRI - Muscle tissue
Describe the appearance of polymyositis?
Symmetrical rapidly progressing proximal muscle weakness
What investigations are undertaken in polymyositis?
Raised Creatine Kinase
Very reactive to steroid <24 hours
What’s dermatomyositis?
Clinically similar to polymyositis but + Heliotrope rash
If a diagnosis of dermatomyositis is affirmed what should be investigated?
Look for malignancy - 50% have a malignancy
Describe inclusion body myositis.
6th decade
Sow onset weakness
Spares the thumbs
Non treatable
What is the presentation of someone with Myotonic Dystrophy?
Myotonia Cataracts Ptosis Frontal balding Cardiac abnormalities
Myotonia
Inability to relax muscle
Statins can induce this.
Drug myopathy
What are some causes of Rhabdomyolysis?
Crush injuries
Toxins
Post convulsions
Extreme exercise
What is the pathophysiology behind rhabdomyolysis?
Damaged muscles releases Ca2+
Triggers the release of K+ PH4+ and myoglobininto the blood.
Acute renal failure and DIC as result.
What is DIC (rhabdomyolysis)
Disseminated Intravascular coagulation
How does rhabdomyolysis present?
Myalgia
Weakness
Myoglobulinuria
