Basic and Advanced Investigations

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Learning objectives

  • What are the usual investigations
  • Why they are done

Brain Imaging

Non contrast CT is the imaging of choice for most stroke patients. It is quick, readily accessible and informative in terms of high sensitivity for blood and can rule out some stroke mimics. See Stroke Imaging link for more detailed information. MRI can be useful when diagnosis perhaps shows a hypodense lesion with oedema and the diagnosis as to stroke or tumour is uncertain. Also useful in those with a recent haemorrhagic stroke where you might suspect underlying tumour. The temptation is always to get it as early as possibly but often more useful to wait a few weeks until much of the haematoma has resolved. I would also consider an MRA in any suspicious bleed to look for any vascular lesion such as an Arteriovenous Malformation or Saccular (Berry) Aneurysm where surgical intervention would be contemplated. Always more suspicious in a lobar haemorrhage in a younger patient (under 60). In an older patient with a deep subcortical bleed and a prominent history of hypertension the BP is usually the aetiology. MRI/MRA is also useful for suspected vasculitis or Reversible cerebral vasoconstriction syndrome. A negative MRI-DWI can prove very useful for those where you suspect a functional stroke presentation or Migraine. It can also be invaluable in proving a stroke aetiology in those where the CT scan has been unhelpful and the clinical features could be anterior or posterior circulation or where the CT is unhelpful and you want to prove or disprove a stroke diagnosis. MRV is the imaging of choice for suspicion of a cerebral venous thrombosis.

Clinical Indications for urgent CT i.e. within 1 hour of arrival at hospital

  • Anticoagulant treatment, a known bleeding tendency
  • Depressed level of consciousness
  • Unexplained progressive or fluctuating Symptoms
  • Papilloedema
  • Neck stiffness or fever
  • Severe headache at onset

Other Tests

Investigations should be rational and appropriate. If you find a pathology e.g. dissection there is questionable merit in then going to look for a PFO or doing a thrombophilia screen. Looking for antiphospholipid syndrome in elderly patients without specific indications will just lead to false positives. The more exotic tests should be done in series rather than as a one hit. Most are not urgent and can be done over a few weeks. Always ask if tests are appropriate and will they change management. There needs to be a rationale for tests and unless you are in a large teaching hospital with very easy access to you need to decide who needs what tests. We certainly do not do Echocardiograms on all patients but on those in whom there is evidence to suggest a cardiac aetiology. We look for investigations that will yield important information that will make a substantial difference to management.

Basic Investigations to be done on admission

  • FBC polycythaemia or anaemia can be important findings. If there is anaemia then look at the MCV. If low check Iron studies and consider initial tests to look for GI blood loss or other aetiology. If MCV high check B12 and folate.
  • ESR temporal arteritis, myeloma, vasculitis, malignancy
  • CRP Infection (Chest/Urine/other), SLE, Vasculitis, endocarditis, temporal arteritis
  • Urea and electrolytes often patients have been ill or been found lying in bed dehydrated and come in with an element of Acute kidney injury which usually responds to cautious rehydration. In some cases other causes of uraemia are found and many patents have degrees of chronic kidney disease related to longstanding diabetes or hypertension. A renal vasculitis is a rare cause but may co-exist with a cerebral vasculitis.
  • Fasting lipids Check Cholesterol, LDL, HDL
  • Non Contrast Head CT scan this is the primary imaging modality. Quick, cheap and very accurate for detecting haemorrhage and developed ischaemic stroke and other differentials such as tumours. Ischaemic stroke shows few changes acutely within the first 6 hours. Contrast can be given if a suspected tumour is seen.
  • ECG AF, LVH, STEMI, NSTEMI, Bundle branch block
  • Chest X-Ray Look for Cardiomegaly, enlarged LA, Lung cancer with cerebral metastases acting as a stroke mimic
  • Random glucose Exclude diabetes

Further Investigations depending on Assessment

  • Coagulation screen (clotting + platelets): if you suspect warfarin or a coagulopathy or thrombocytopenia
  • Prolonged INR: needs urgent reversal in Haemorrhagic Stroke or Subdural
  • Liver disease : Give IV Vitamin K 5 mg + FFP
  • Warfarin therapy : Give IV Vitamin K 5 mg + Prothrombin concentrates (Octaplex/Beriplex)
  • Prolonged APTT: Heparin therapy, Lupus anticoagulant, Von Willebrands disease
  • Platelet count: Thrombocytopenia: haemorrhagic stroke especially if levels fall < 20 x 10 9 Consider cause - Acute ITP, HITT syndrome, Drug induced. Stop antiplatelets. Thrombocytosis: raised platelets and thrombotic stroke

Carotid Doppler

  • Should only be done on those with TIA or non disabling stroke who would agree for endarterectomy
  • Consider in suspected carotid dissection though CTA/MRA preferred

Transthoracic Echocardiography

  • Varying availability and some do in all Ischaemic strokes
  • Selective - Cardiac symptoms, Clinical signs/history of cardiac disease, Abnormal ECG
  • Haemorrhagic strokes secondary to endocarditis
  • Bubble test done to look for right to left shunting

24 hour tape or 7 Day tape

Done where there is suspected PAF but AF not detected during admission on ECG or telemetry. If AF does occur during admission it is vital to get a 12 lead ECG or at least a telemetry print out for the records. Have a very high index of suspicion for PAF in any older patient over 60 especially with a large vessel stroke anterior or posterior circulation. In practice I look for PAF in all ischaemic strokes. In high risk patients I would either get several 24 hour tapes or a 7 day monitor. It depends on what you have easiest access too. Multiple old strokes right and left and anterior and posterior circulation make cardioembolism very likely indeed. The reality is that despite best efforts it is not uncommon for the AF to be finally diagnosed when the patient represent with a new stroke and AF.