The influence of breathing on cerebrospinal fluid movement in the brain

Transcription

1 The influence of breathing on cerebrospinal fluid movement in the brain A computational study based on in vivo pressure measurements Vegard Vinje Simula Research Laboratory GA Ringstad ME Rognes PK Eide K-A Mardal June 15th, 2018 Cerebrospinal Fluid (CSF) Spinal cord 1

2 We calculate fluid flow in the brain based on in vivo pressure measurements 9 hydrocephalus patients 2

3 We calculate fluid flow in the brain based on in vivo pressure measurements 9 hydrocephalus patients In vivo measurements of pressure gradients in the brain 3

4 We calculate fluid flow in the brain based on in vivo pressure measurements 9 hydrocephalus patients Fourier analysis of the pressure gradient In vivo measurements of pressure gradients in the brain 4

5 We calculate fluid flow in the brain based on in vivo pressure measurements 9 hydrocephalus patients Fourier analysis of the pressure gradient In vivo measurements of pressure gradients in the brain CFD computations of flow 5

6 The cerebrospinal fluid (CSF) surrounds the brain and the spinal cord Brain tissue 6

7 Disturbance of the CSF system may lead to disease CSF absorption Brain tissue CSF production 7

8 Hydrocephalus is characterized by enlarged ventricles 8

9 Treatment may include the insertion of a shunt 9

10 In the classical hypothesis, there are distinct sites for production and absorption of CSF 10

11 However, CSF flow is pulsatile and may enter brain tissue along arteries 11

12 12

13 In addition, CSF and blood exchange water constantly at the capillary level 13

14 Also, studies have proposed the production and absorption within the ventricles to be in balance 14

15 The patients outcome after shunting is hard to predict 15

16 Problem Which patients will benefit from a shunt? 16

17 Characteristics of CSF flow has been used as a predictor for shunting 17

18 In traditional MRI, one cardiac cycle is usually obtained in 6 minutes 18

19 The stroke volume is defined as the area under the flow curve 19

20 Bradley (1996) proposed stroke volume as a predictor for shunting Shunt if... Volume > 20

21 Bradley (1996) proposed stroke volume as a predictor for shunting Shunt if... Volume > μl 21

22 More recent MRI studies have also revealed respiratory CSF motion 50 s Dreha-Kulaczewski et al., 2015 Chen et al.,

23 23

24 Simultaneous measurements of intracranial (ICP) and lumbar (LP) pressure Eide & Sæhle,

25 Pressure differences drive CSF flow Pressure difference calculated by data provided from Eide & Sæhle 25

26 The Fourier transformed confirmed that the cardiac cycle dominates pressure fluctuations 26

27 We use a simplified sinusoidal function consisting of two frequencies 27

28 We use a simplified sinusoidal function consisting of two frequencies where Respiratory Cardiac 28

29 In total, 502 accepted 6-minute windows were found in the 9 patients - For each time window, we find the cardiac and respiratory component of dp/dz and solve for the velocity u(r): 29

30 For each time window, we calculated CSF velocities over time, and the stroke volume L = 7 cm R = 0.2 cm 30

31 In the aqueduct, flow is evenly regulated by cardiac and respiratory cycle Pressure gradient CSF Flux 31

32 In the aqueduct, flow is evenly regulated by cardiac and respiratory cycle Pressure gradient CSF Flux 32

33 In the aqueduct, flow is evenly regulated by cardiac and respiratory cycle Pressure gradient CSF Flux 33

34 Variation within a patient is comparable to variation between patients 34

35 How do these finding affect previous assumptions in prediction of shunting? 35

36 The simulated flow can be split up into two frequencies Cardiac Respiration 36

37 Total flow volume is dominated by respiration Cardiac Respiration 37

38 MRI does not detect variation over time in stroke volume Stroke volume for one patient is acquired over 6 minutes with PC-MRI Our study revealed variation over time in stroke volume 38

39 CSF flow may be dominated by respiration, even though pressure is dominated by the cardiac cycle Pressure gradient CSF Flux In vivo pressure measurements CFD simulations, quantifying flow from a simplified input pressure function 39

40 CSF flow may be dominated by respiration, even though pressure is dominated by the cardiac cycle Pressure gradient CSF Flux In vivo pressure measurements CFD simulations, quantifying flow from a simplified input pressure function 40