Cerebral vasospasm
Sub arachnoid haemorrhage
A subarachnoid haemorrhage (SAH) occurs when an artery in the subarachnoid space at the base of the brain ruptures. The rupture site is usually a weakness in the vessel wall called an aneurysm. SAH hits in the prime of life and 1 in 10,000 of the UK population will be affected. Cerebral vasospasm is a common complication of SAH that contributes significantly to the mortality and morbidity. It is a reaction to the bleed that can reduce brain blood flow to dangerously low levels by triggering an inappropriate constriction of the arteries in the brain.
Vasospasm
Arteries have muscular walls that are able to dilate and constrict in order to regulate blood flow. After a bleed, when clotting blood surrounds an artery, the muscles in the artery wall often tighten excessively. We call this 'vessel spasm' or vasospasm. It typically starts a few days after the bleed, reaches a peak after 10 days, and lasts for three to four weeks. Despite several decades of research and substantial investment from the pharmaceutical industry, as yet there is no effective drug treatment for cerebral vasospasm. Treatment may be provided by aggressive blood pressure raising therapy, which aims to maintain cerebral blood flow through the narrow arteries. This therapy is itself dangerous and a careful balance needs to be maintained at all times. Each patient needs to be carefully monitored but assessing the extent of vasospasm and the intensity of treatment required is very difficult. There is scope to improve our ability to measure vasospasm and to develop safer more effective treatments.
Broad research goals of the neurological physics group in this area:
Description and rationale of approach being taken
Cerebral vasospasm changes from day to day, therefore to be clinically useful any method of assessment must be easily repeatable. Ultrasound measurements of blood flow velocity in the affected arteries are simple and repeatable and they correlate well with other measures of vasospasm including patient symptoms. Unfortunately it is not possible with this technique to distinguish between spasm and high volume flow. This reduces the sensitivity and specificity of the measurement as an index of vasospasm. The ultrasound measurements provide complex data, which contains considerably more information about the blood flow than we are currently able to use. Our approach is to apply principles of fluid dynamics and ultrasonics to help us to interpret this additional information and develop new measures of vasospasm. We are currently testing a number of new measurements in clinical practice.
If you would like more information or would like to contribute to this project please contact Tony Birch, email Tony.birch@suht.swest.nhs.uk| or telephone 023 80796335.