Imaging CPC Flashcards
What are the indications for EEG?
• Epilepsy ○ Likelihood and location of seizure · Level of sleep/sedation · Sleep disorders · Encephalopathy/dementia · Encephalitis · Brain death
What is the role of EEG in epilepsy?
· Not diagnostic
· 1% of normal population have epileptiform abnormalities on EEG
· 15% of epileptics do not show activity
· Can show likelihood of epilepsy or reinforce diagnosis
· Can suggest location of seizure
· Can clarify the seizure types to assist with treatment
· Can assist in diagnosis of non-epileptic events
What is Electro-diagnosis?
· Involves nerve conduction and electromyography
· Used interchangeably
· Nerve conduction
○ Stimulation of electrical impulses at different points along a nerve
○ Can stimulate the motor or sensory nerves
○ Triggers an AP
○ Time relationship to stimulus is measured
○ Size of response is measured
○ Usually only a minor discomfort
· EMG
○ Needle is put into the muscle
○ Record electrical activity of the muscle
○ Muscle is silent at rest
○ Motor units are recruited with effort giving an interference pattern
· Risks:
○ Bleeding in people on anticoagulants
○ Pace makers or central lines- then avoid stimulation around the chest which you usually don’t do anyway
When is electro-diagnosis helpful?
· consider as an extension of clinical examination · Provides some quantitative data · Can localise site of lesion ○ CNS versus PNS ○ Within a peripheral nerve ie wrist versus elbow ○ Conduction block · Can show neuropathic versus myopathic versus neuromuscular junction issues · Can determine type of neuropathy ○ Axonal versus demyelinating (ie GB) ○ Focal (ie carpel tunnel) ○ Mononeuritis multiplex · Can pick up subclinical abnormality
What are some practical considerations when performing nerve conduction?
· nerves closest to the skin are most easily stimulated
· Sensory and motor responses can be measured
· Large fibre neurones preferentially stimulated
What is the Imaging of choice for ischaemic stroke?
CT ○ Performed first because it is fast ○ aim: § Exclude haemorrhage § Identify tumour § Identify complications such as midline shift, hydrocephalus or coning § Confirm infarction § Evaluate vessel disease ○ Non contrast § 60% visible at 6-8 hours § 100% visible at 24 hours
What are the signs of ischaemic stroke on CT?
• May be normal on non-contrast CT • Oedema • Sharp linear borders • Wedge shaped • Loss of grey white differentiation • Hypodensity of grey and white matter • Defines vessel territory • Low attenuation brain tissue • Sulcal effacement • Loss of basal ganglia definition • Small lacunar infarct • Loss of insular ribbon • Dense MCA sign ○ Or other thrombosed vessel
What is CT angiography used for?
• Assess for vessel stenosis or occlusion
When is CT perfusion performed?
• advanced imaging technique
• Performed in a therapeutic window ( up to 3-6 hours)
• Identifies dead brain versus ischaemic brain
○ Ischaemic brain can be revived
• Helps guide management and prognosis
What is the gold standard for imaging of acute stroke?
What are the considerations?
• MRI • Most sensitive in the acute setting • Not all patients are suitable ○ Confused ○ Pace makers • Not available in some settings - ie not 24 hours
What is digital subtraction angiography used for?
- Identify vascular disease
* Deliver treatment
What are the functions of CSF?
• Mechanical ○ Hydrostatic buffer against trauma • Homeostatic ○ Maintains PH ○ Maintains osmolality etc • Immunological ○ Privileged site
Where is CSF produced?
What is the total volume?
Where is it absorbed?
- choroid plexus and brain parenchyma produce it
- Total volume is 130-140 mls
- The body produces about 500mls daily
- Absorbed by the arachnoid villi
What controls the production of CSF?
Increases production: • Ach stimulation • Cholera toxin • Caffeine • Hyptonicity • Hyperthermia
Decreases production: • Ad stimulation • Cardiac glucosides • Hypertonicity • Hypothermia • Glucocorticoids • Acetazolamide • Furosemide • Increased CSF pressure
What is the immunological contents of CSF?
• ABSENT ○ Complement proteins ○ Leukocytes (PMLs) • LOW ○ Antibodies • PRESENT: ○ Lymphocytes
