Physiology & Pathology Flashcards
How and where is CSF produced?
Produced by arterial blood from the choroid plexus of lateral and fourth ventricles via diffusion, pinocytosis and active transfer
Where is CSF absorbed?
Arachnoid villi into venous circulation
What correlates with CSF pressure?
Rate of CSF absorption
What happens to the heart during diastole?
Ventricular filling, atrial contraction
What happens to the heart during systole?
Ventricular contraction, atrial filling
What is the role of the portal vein?
Deliver venous blood to the liver for processing of nutrients and by-products of food digestion
What is the percentage of blood supplied to the liver by the portal vein and hepatic artery?
80% portal vein, 20% hepatic artery
What is the role of the hepatic artery?
Supply oxygenated blood to the liver
What is the role of the hepatic vein?
Drain deoxygenated blood from the liver into the IVC
Where is blood found in a subdural haemorrhage?
Between arachnoid and dura mater
What is the cause of subdural haemorrhage?
Stretching of bridging cortical veins crossing the subdural space
What is a cause of spontaneous subdural haemorrhage?
Anticoagulation medication or arteriorvenous fistula
Where is blood found in an extradural haemorrhage?
Between inner surface of skull and outer layer of dura mater
What is usually the source of bleeing in extradural haemorrhage?
Middle meningeal artery
Where is blood found in a sub-arachnoid haemorrhage?
Subarachnoid space
What are the risk factors of a sub-arachnoid haemorrhage?
Family history, hypertension, heavy alcohol consumption, abnormal connnective tissue, female
What are the symptoms of a sub-arachnoid haemorrhage?
Thunderclap headache, photophobia, miningism, focal neurological deficits
What the the name of the scale to predict survival in sub-arachnoid haemorrhage?
Hunt and Hess scale
What are the common causes of sub-arachnoid haemorrhage?
Ruptured berry aneurysm, perimesencephalic haemorrhage
Where are the common locations of intracerebral haemorrhage?
basal ganglia, diencephalon, thalamic, pontine, cerebellar, lobar
What condition and pathological process commonly causes intracerebral bleeds?
Hypertension due to pathological changes in the vessels
Describe communicating hydrocephalus with obstruction
CSF can exit the ventricular system but flow is impeded between the basal cisterns and the arachnoid granulations
Describe communicating hydrocephalus without obstruction
Group of conditions abnormal CSF dynamics e.g. normal pressure hydrocephalus and choroid plexus papillomas
Describe non-communicating hydrocephalus
CSF cannot exit the ventricular system resulting in dilated ventricles causing mass effect
Describe what happens physiologically when a stroke occurs
Interruption of blood flow results in deprivation of oxygen and glucose in the supplied vascular territory resulting in cellular death via liquefactive necrosis if circulation is not re-established in time
What are the 3 causes of a stroke
Embolism, thrombosis, arterial dissection
In the stroke setting why is CT Brain used?
To exclude intracranial haemorrhage which would preclude thrombolysis, look for ‘early’ features of ischaemia and to exclude other pathologies such as tumor
What is the timing for early hyperacute stroke and what are the features?
Time:0-6 hours
Loss of grey-white matter differentiation and hypoattenuation of deep nuclei
What is the timing for acute stroke and what are the features?
Time: 24hr-1 week
Hypoattenuation and swelling become marked resulting in mass effect
What is the timing for subacute stroke and what are the features?
Time: 1-3 weeks
CT fogging phenomenom
What is the timing for chronic stroke and what are the features?
Time: >3 weeks
Residual swelling passes, negative mass effect
Why is CTA used in stroke?
- Identify thrombus within vessel which may guide thrombolysis or clot retrieval
- Evaluation of carotid and vertebral arteries establishing stroke etiology and assess limitation for endovascular treatment (stenosis, tortuosity)
- Prior to paediatric thrombolysis some guidelines only advise for arterial thrombolysis
What products are used for thrombolysis?
Streptokinase and altreplase (rtPA)
What do thrombolysis products do?
Activate conversion of plasminogen to plasmin an enzyme responsible for breakdown of clot
Which vessels of the brain is mechanical thrombectomy useful in stroke?
Large, anterior circulatory vessels
What is a TICI scale and what does it predict?
Thrombolysis in Cerebral Infarction
Determines response of thrombolytic therapy for ischaemic stroke or post endovascular revascularisation predicting prognosis
In order of occurrence what are the most common brain tumors?
Neuroepithelial, meningioma, metastases, pituitary
Describe appearance and presentation of meningioma
Well defined rounded dural mass with extensive regions of dural thickening. Patients present with headache, paresis and change in mental status
What is vasogenic oedema, its appearance and what is it associated with?
Vasogenic oedema is fluid within the interstitial space with disrupted blood brain barrier. Grey/white matter more pronounced as it affects only white matter. It is associated with brain tumors
What is cytotoxic oedema, its appearance and what is it associated with?
Cystotoxic oedema is fluid within cells from liquefactive necrosis. It involves both grey and white matter so there is less differentiation of grey/white matter. It is associated with infarction
What does FAST stand for?
Facial droop
Arm weakness
Slurred speech
Time 4hrs
What is multinodular goitre?
Multiples thyroid nodules of normal, hyper or hypo function
What is the most common demographic for multinodular goitre?
Females 35-50
What is the role of CT in multinodular goitre and what is the appearance on CT?
Characterising multinodular goitre and enlarged heterogenous thyroid
Patients with multinodular goitre are at risk of what?
Thyrotoxicosis
What is the appearance of metastatic lymph nodes on CT
Round with ill defined margins, cortical hypertrophy, heterogenous enhancement, central necrosis
What is the appearance of non-metastatic lymph nodes on CT?
Smooth and well-defined, homogenous uniform enhancement, no necrosis
What is the appearance of acute sinusitis on CT?
Peripheral mucosal thickening, gas bubbles, obstruction of ostiomeatal complexes
What is the etiology of chronic sinusitis?
Anatomical variants, chronic allergy, chronic infection
Name the 4 types of pneumothorax
Primary spontaneous, secondary spontaneous, iatrogenic, tension
How does a primary spontaneous pneumothorax present and who is most at risk?
Pleuritic chest pain, mild-moderate dyspnea with no underlying lung diseae
Tall/thin people, Marfan syndrome, homocystinuria
How does a secondary spontaneous pneumothorax present and who is most at risk?
No pleuritic chest pain, severe dyspnea
This with cystic lung disease (bullae, emphysema, asthma, ILD, CF) or parenchymal necrosis (lung abscess, necrotic pneumonia, septic emboli, TB)
What can cause an iatrogenic pneumothorax?
Percutaneous biopsy, oesophageal perforation, CVC/NG placement, trauma
What occurs to produce a tension pneumothorax?
Intrapleural air accumulates progressively exerting positive pressure on mediastinal and intrathoracic structures (creates a one way valve)
Define emphysema
Abnormal permanent enlargement of the airspaces distal to the terminal bronchioles accompanied by destruction of the alveolar wall without obvious fibrosis
Panlobar emphysema affects which part of the lungs and what causes it?
Lower zones matching areas of maximal blood flow
A1A deficiency and ritalin lung
Paraseptal emphysema affects which part of the lungs and what causes it?
Peripheral parts adjacent to pleural surfaces
Smoking
Paraseptal emphysema can lead to what?
Subpleural bullae and spontaneous pneumothorax