Stroke - Tests and diagnosis

Taking images of the brain is important in diagnosing a stroke. There are essentially two causes of a stroke: a blockage in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. supply (an ischaemic stroke) or a bleed within the brain (a haemorrhagic stroke).

The clinical features of the two may differ. However, it is important to be absolutely certain whether a stroke is ischaemic or haemorrhagic before beginning treatment, because treatment of the two causes is very different and the wrong treatment can be harmful. Because of this, it is always necessary to differentiateThe specialisation of cells or tissues for a specific function. between the two causes by imaging the brain. This is a matter of urgency.[1,2]

Because time is of the essence when treating a stroke, it is vital that healthcare centres not only have the capabilities to take images of the brain, but also specialist expertise to interpret these images

The choice of imaging investigation used depends on the methods available, as well as the likely underlying cause. [1]

The main types of imaging investigations include:

  • Doppler ultrasound, a method for ultrasound scanning of the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. vessels round the brain
  • Computerised tomography (CTA scan that generates a series of cross-sectional X-ray images.), which uses X-rays to provide a 3D view of the body
  • Magnetic resonance imaging (MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field.), which uses magnetic fields to produce detailed images.

Because time is of the essence when treating a stroke, it is vital that healthcare centres not only have the capabilities to take images of the brain, but also specialist expertise to interpret these images.

Since many centres do not have on-site specialists available on a 24-hour basis, a practice called 'telemedicineTelephone or internet use to obtain advice from experts at another site.' has evolved in some parts of the world - sending the images on to a specialist at a different site.[3,4] This is still a relatively new practice, however, and is not available in all countries. Learn more about telemedicine in stroke.

Although imaging tests are the cornerstone of the investigation of a stroke, other tests are important as well. These tests may include:

  • Blood tests - including glucoseA simple sugar that is an important source of energy in the body. and clotting tests
  • Electrocardiography (ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease.) - a tracing of the electrical activity of the heart, to detect abnormal heart rhythms, and rule out a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.
  • Echocardiography - an ultrasound examination of the heart, to assess for bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. clots originating in the heart
  • Lumbar puncture - an examination of the fluid surrounding the brain and spinal cord, to detect a possible subarachnoid haemorrhageBleeding into the subarachnoid space surrounding the brain, the area between two of the three layers (meninges) surrounding the brain and spinal cord (the arachnoid mater and the pia mater). (a bleed around the brain).
References: 
  1. Yew KS and Cheng E. Acute stroke diagnosisThe process of determining which condition a patient may have.. Am Fam Physician. 2009; 80: 33-40.
  2. Donnan GA, Fisher M, Macleod M et al. Stroke. Lancet 2008; 371: 1612-23.
  3. Hess DC, Wang S, Gross H et al. Telestroke: extending stroke expertise into underserved areas.  Lancet Neurol 2006; 5: 275-78.
  4. Audebert H. Telestroke: effective networking. Lancet Neurol 2006; 5: 279-82.