Role of Tissue Doppler Ultrasonography for Emergency Assessment of Stroke

Abstract

Background: The primary aims of my PhD project were to explore the feasibility of acquiring high quality brain tissue pulsation (BTP) measurements from stroke patients. The impact of artefacts on BTP estimates, and potential differences in BTP amplitude between patients and healthy controls are explored. My secondary aim was to better understand the impact of middle cerebral artery blood flow velocity (MCAv) changes on BTP amplitude.

Methods: A systematic review was conducted to explore existing methods of investigating BTPs using MR techniques. A reduction in MCAv, induced in healthy volunteers through ingestion of caffeine, was used to explore the impact of lowering MCAv on BTP amplitude (measured using a transcranial tissue Doppler [TCTD] system) under controlled conditions. TCTD and physiological measurement data were obtained from stroke patients to investigate the quality of recordings, impact of artefacts on BTP estimates, and impact of stroke on BTP amplitude.

Results: The systematic review confirmed that brain motion varies regionally within the brain, and that BTPs may be altered in the presence of pathology (e.g. Chiari I malformation). The physiological measurement study showed that BTP amplitude increases in response to caffeine. Analysis of healthy volunteer and patient data showed that artefacts tended to increase estimates of BTP amplitude. Analysis of the first 20 gates (which show limited penetration) from 18 ischaemic stroke patients and control subjects suggested a median (IQR) BTP amplitude in ischaemic stroke patients measured through the forehead of 8 μm (5.7, 13.6) compared to 16.2 μm (10.6, 24) in 24 age-matched control subjects. Waveform shapes appeared qualitatively similar to control subjects.

Conclusions: BTP amplitude appears to be lower in stroke patients compared to healthy controls but increases in response to caffeine, which lowers MCAv. Further work is required to better understand the relationship between BTPs and cerebrovascular physiology.