Week 3- randoms- genetics, muscular conditions etc Flashcards
What is myasthenia gravis?
Autoimmune disorder of the neuromuscular junction where antibodies are targeted against the acetyl choline receptors.
What does a reduced number of functioning receptors in myasthenia gravis lead too?
Muscle weakness and fatiguability
What do the antibodies in myasthenia gravis do?
Block the binding of acetylcholine and trigger inflammatory cascades that damage the folds of the post-synaptic membrane.
Who gets myasthenia gravis?
Young women and older men.
Clinical features of myasthenia gravis?
Weakness- typically fluctuating
Most commonly- extra ocular weakness, facial and bulbar weakness.
Limb weakness is typically proximal.
What is the treatment for myasthenia gravis?
Acetylcholinesterase inhibitor- means AcH is left in the synaptic cleft for longer- pyridostigmine.
Also immunomodulating
Steroids- good for younger people, bad for older people.
What is the emergency treatment for myasthenia gravis?
Immunoglobulin or plasma exchange.
What is myotonia?
Failure of muscle contraction after use.
What is rhabdomyolysis?
Damage to skeletal muscle leads to leakage of large quantities of toxic intracellular contents into the plasma.
Triad of rhabdomyolysis
Myalgia (muscle pain)
Muscle weakness
Myoglobinuria
How is Duchenne’s muscular dystrophy inherited?
X linked recessive
What clinical signs indicate Duschenne’s muscular dystrophy?
Delay in motor development
Onset of weakness at 3-4 years. Occurs in the pelvic and shoulder girdles.
On examination of a patient with Duschenne’s muscular dystrophy, what might you expect to find?
Calf hypertrophy.
Shoulders back, stomach stuck out posture.
What might Duchenne’s muscular dystrophy be linked too?
Dystrophin deficiency- large scale deletions in 70% of the boys affected. Other mutations involving it in the other 30%.
How would you go about diagnosing Duchenne’s muscular dystrophy?
Look for:
Developmental delay in boys
Muscle weakness- toe walking and Gowers sign
Raised serum CK
What investigations would you do into Duschennes muscular dystrophy?
Serum CK
Electromyography
Muscle biopsy
Molecular genetic testing (carrier testing)
Only boys can be affected if its X linked recessive. True or false?
True- a girl will be a carrier but wont show the disease unlike the boy.
How is Huntington’s disease inherited?
Autosomal dominantly.
Huntingtons disease can only manifest in males. True or false?
False, due to it being autosomal dominant- it affects females too.
Onset of Huntington’s disease?
Usually 30-50 years old.
Symptoms of huntingtons disease
Dementia
Involuntary movement
Progression to severe dependency and death.
Early clinical signs of Huntington’s?
Clumsiness Agitation Irritability Apathy Anxiety Disinhibition Delusions/hallucinations Abnormal eye movements Depression
Later clinical signs of Huntington’s
Dystonia Involuntary movements Trouble with balance and walking Trouble with activities that require manual dexterity Slow voluntary movements Difficulty initiating movements Inability to control speed and force of movement weight loss speech difficulties stubborness
What are senile plaques and what are they associated with?
Associated with Alzheimers disease
They are extracellular protein deposits containing amyloid beta protein (fragment of the APP gene)
What mutations can cause Alzheimers?
APP
Presenilin 1
Presenilin 2
NOTE ON CT SCANS
You are looking at the density of electrons within the structure. The contrast is determined by electron density. Things that are dense in electrons e.g. bone are white on the scanner. Things like gas which are not electron dense are black.
What colour does CSF show up on CT scan?
Dark- not electron dense.
What colour does clotted blood show up?
Its denser than brain so shows up whiter.
Why would you use iodine as a contrast agent on CT scan?
Its electron dense. Allows you to do CT angiography where you look at the blood vessels.
When is it a CT angiogram and when is it a CT venogram?
During and into 30 seconds its a CT angiogram because you are looking at the arteries. After that it is a CT venogram.
NOTE ON MRI
Mechanism- about the interactions with nuclei. If you put giant magnets together- the nuclei will line up either vertically or horizontally. They accept energy and do this. They then give back out that energy when they return to their previous position which allows you to record an image.
To do with proton density.
When is an MRI contraindicated?
Implanted foreign material (e.g. pacemaker)
What most often causes subarachnoid haemorrhage?
Rupture of aneurysms (85%)
Bleed from AVM (10%)
What is a saccular aneurysm?
A true aneurysm with involvement of all layers of the blood vessel. The tunica media becomes interrupted but the tunica intima is generally normal.
How do aneurysms present?
Generally asymptomatic until rupture.
Uncommonly can produce cranial nerve palsies.
How would you diagnose a subarachnoid haemorrhage?
CT scan- however you get false negatives in about 5% of cases and therefore you need to do a lumbar puncture to exclude a subarachnoid haemorrhage.
How would you determine which treatment is best in a subarachnoid haemorrhage?
Could do a CT angiography or an MR angiography to see size of bleed etc.
Treatment of aneurysms
Could do craniotomy and clipping
or endovascular treatment
