CNS Pathology 2 Flashcards
How can we classify diseases involving degeneration of the CNS into four groups?
Dementias - e.g. Alzheimer’s disease (dementias are essentially accelerated aging dieases)
Extrapyramidal Disorders (i.e. movement disorders involving tremours/slow movement) - e.g. Parkinson’s disease
Ataxic Disorders (i.e. poor coordination) - e.g. Fredrick’s Ataxia
Motor Neurone disorders - e.g. Motor neurone disease
Whta are characteristic symptoms of Parkinson’s?
A low frequency tremour (especially at rest or when anxious)
A deadpan expression as a result of rigid muscles (in this case face muscles) - including their tarsal muscle thus they don’t blink as much (dry eye).
Stooped shuffling gait - again as a result of rigid muscle tone ( fancy way of saying because of rigi muscles)
Pill rolling - this is just a term used to describe the tremouring of the hands.
Slow movements
Difficulty initiating movements (akinesia).
In a healthy brain where does majority of the dopamine lie and why?
In the basal ganglia ( as a result of substansia nigra (which are cells that produce dopamine) being located in the basal ganglia).
Which cells produce dopamine and where are they located?
Substansia Nigra cells in the Basal Ganglia
What is the cause of parkinsons?
Decreased amount of dopamine in the brain
What is the cause of most cases (80%) of Parkinson’s?
Idiopathic
What pathology can be seen in the brain of someone with Parkinson’s?
They have diminished amounts of substansia nigra ( the dark areas in the basal ganglia)
Why can’t you just give a patient a pill with dopamine in it to solve the problem of parkinsons?
Dopamine is too big of a molecule to get through the blood brain barrier.
What are some pharmacological treatments for parkinson’s disease?
What are disadvantages of pharmacological treatments for parkinson’s disease?
You can give the px pills containing building blocks of dopamine (L-dopa). The enzyme to make dopamine is all over the body though so by the time the dopamine reaches the blood brain barrier most of it has been used up. Thus the pill also contains an inhibitor that is too big to pass through the blood brain barrier, therefore the dopamine gets to the brain in suffient quantities.
We could give the px a drug that is an inhibitor of the enzyme that breaks down dopamine ( thus it is not reuptaken and stays around longer).
We could give the px dopamine agonists (i.e. things that are like dopamine in the sense that they will stimulate it’s receptors) making the brain think enough dopamine is present.
All drugs become less effective over an extended period of time. All drugs also have side effects
What are some non pharmacological treatments for parkinson’s?
Embryonic stem cells - but this comes with ethical issues
Implantation of modified fibroblasts- so basically fibroblasts produce collagen but we could genetically modify them to produce dopamine.
Xenotransplantation - implanting substansia nigra from other animals
Implanting adult setm cells - as they are pluripotent
Injecting glial derived neutrotrophic factors (GDNF) - these make neurones develop - inject this into basal ganglia.
Deep brain stimulation - Electrical stimulation of basal ganglia by implanted electrodes - this makes cells produce dopamine.
Gene therapy - alter faulty gene via an adenovirus
Why are effects of parkinson’s on vision going to be of retinal origin?
- The basal ganglia are primarily motor
- Dopamine is a neurotansmitter or neuromodulator in retinal amacrine and interplexiform cells.
- In Parkinson’s disease levels of retinal dopamine are decreased
- Parkinson’s disease is also associated with abnormal ERGs.
[Of course there will be effects on eye movements - because parkinson’s affects muscles - think extraoccular muscles]
What are visual defects experienced by Pxs with Alzheimer’s disease?
- Possibly decreased (low contrast) acuity
- Abnormal saccadic (saccadic movements are rapids shifts in gaze) and smooth pursuit eye movements (increased latency & reduced speed- i.e. basically that the px moves their eyes slowly)
- Decreased blinking (because stiffened muscle)
- Large light adapted pupil. Possible anisocoria. Speed and amplitude possibly decreased
- Longer latency and altered waveform of ERG and VEP - i.e. it takes your brain long to process things thus– reduced temporal resolution (i.e. reduced movement resolution).
- Possible (tritan) colour defect
What can lead to akinesia (frozen movement) for Pxs with Parkinson’s and how can this be resolved?
•Irrelevant peripheral visual stimuli (e.g. door frames) can lead to akinesia
•This can often be alleviated by visual stimuli placed in front of the feet.
What symptoms is alzheimer’s characterised by?
AD is characterised by loss of memory, severely impaired judgement, loss of emotional control and eventually results in a complete breakdown of mental function.
[As cortex is affected]
How many stages of alzheimer’s is there and how can they be characterised?
Name three Alzheimer’s risk factors.
What is the neuropathology of Alzheimer’s?
Thinning of the cortex. Sulci have widened and gyri thinned. Loss of tissue may be most severe in the frontal and temporal lobes.
Ventricles enlarge
In general brain weight decreases ( this happens with age but happens at an accelerated rate in Alzheimer’s).
Plaque depositis and neurofibrillary tangles (neurofibrillary tangles are just microtubules in the brain getting tangled up).
(the more plaques and tangles , the more loss of mental function)
