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case_images: (A) Headband placement of sensor over the temple and the relationship to the pterion, brain lobes and middle cerebral artery territory. (B) CT of grade 4 subarachnoid haemorrhage with blood in the basal cisterns, sylvian fissures, fourth and left lateral ventricles. (C) Percutaneous cerebral angiogram demonstrating right lateral ventricular drain (continuous arrow) and radio opaque coil securing the left posterior communicating artery aneurysm (dashed arrow). Comparison of brain pulse monitor and invasive ICP pulse waveforms on (D) Days 1 and (E) Day 2 following SAH. The ICP was higher on Day 1 and associated with a relatively higher P2 amplitude (yellow dot) to P1 (red dot) for both the invasive ICP and non-invasive pulse waveforms. On Day 2 the ICP was lower and the P2 to P1 relative amplitudes were also lower. (F) The brain pulse monitor optical intensity (upper panel) of the left and right brain hemispheres and invasive intracranial pressure (lower panel) demonstrating Lundberg B waves (red arrows).
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case_images: A computed tomography angiogram (CTA) demonstrated a left posterior communicated artery aneurysm, shown in Figure 1B. The patient required intubation and underwent a percutaneous coiling of the aneurysm with insertion of a ventricular drain into the right lateral ventricle that provided invasive intracranial pressure monitoring (Figure 1C). The Lundberg B wave morphology was symmetrical in shape (Figure 1F, lower panel). Slow oscillations of the optical intensity were observed in both brain hemispheres synchronous with the Lundberg B waves (Figure 1F, upper panel). Our subsequent analysis focused on the four dominant Lundberg B waves indicated by red arrows in Figure 1F lower panel where these corresponding optical changes were observed. We used feature extraction to identify and calculate the DS ratio per cardiac cycle for the Day 4 recording period (Figure 1F), for the invasive ICP signal, left, and right brain optical signals. By direct comparison of the DS ratios derived from the brain signals to the maximum invasive ICP reference values (Figure 1F, lower), we found significant, yet low, coefficients of determination R2 (Figure 3C and D, "all" regression line).
case_images: Upper panels: (I) Unfiltered signals demonstrating the right and left-brain optical responses to a Lundberg B wave. Filtered left (II) and right (III) brain pulsatile component. (IV) Concurrent ICP recording of Lundberg B wave. Lower panel: Zoomed view of the periods (A-D) highlighted by the shaded areas of upper panels. Relative amplitudes at 45% and 10% of the pulse period (DS ratio) are marked with red dots; time to the pulse peak (TTP) by the vertical lines.
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case_images: Single pulses for one such event are plotted in Figure 2. Figure 2. For these purposes, we took the early diastolic (systolic) to be at 45% (10%) time elapsed fractions of the cardiac cycle. 
case_images: DS ratio calculated for the ICP, left (A) and right (B) brain signals on Day 4. Green-shaded regions demarcate the rise of Lundberg B waves; peach-shaded regions demarcate post-rise periods. Red points denote values determined from periods of poor pulsatility signal. Scatter plots of the DS ratio of the left (C) and right (D) brain versus maximum invasive ICP levels. DS ratio of ICP correlated against maximum invasive ICP included for reference. Coefficient of determination (R2) and p-value reported for all values ("all"), correlated green shaded regions of Lundberg B wave onset ("rising"), and anti-correlated periods following the waves ("post-rise").
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case_images: These calculated outputs in time are plotted as points in Figures 3A and B) with a rolling average line added for clarity.  By direct comparison of the DS ratios derived from the brain signals to the maximum invasive ICP reference values (Figure 1F, lower), we found significant, yet low, coefficients of determination R2 (Figure 3C and D, "all" regression line). The periods of Lundberg B wave onset and periods following their crest were manually labelled (green and peach regions, respectively) (Figure 3A and B). This is reflected in a stronger linear relationship between Lundberg B waves and DS ratios during the green rising periods (R2 = 0.48 left; 0.81 right; Figure 3C and D) compared to those in the post-rise periods (R2 = 0.07 left; 0.20 right; Figure 3C and D). In every subset of the data ("all", "rising", "post-rise"), the left-side signal DS ratio was higher in value and less correlated than the response observed in the right brain signal (Figure 3C and D).
case_images: (A) Time-to-peak (TTP) calculated from the invasive ICP, left and right brain signals on Day 4. Green-shaded regions demarcate the rise of Lundberg B waves; peach-shaded regions demarcate post-rise periods. Red points denote values determined from periods of poor pulsatility signal. Scatter plots of the TTP of left (B) and right (C) brain versus maximum invasive ICP levels. TTP of ICP correlated against maximum invasive ICP included for reference. Coefficient of determination (R2) and p-value reported for all values ("all"), correlated green shaded regions of Lundberg B wave onset ("rising"), and anti-correlated periods following the waves ("post-rise").
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case_images: The sharp transitions in the ICP TTP seen in Figure 4A) correspond to the Lundberg B waves and are due to the discrete shift from where P1 < P2 to P2 > P1 and back again. The transitions in the brain signals are less distinct owing to the less well-defined sub-peaks in the non-invasive signal.  TTP is like that of the DS ratio analysis, though the difference between the right and left hemispheres is not as pronounced. The TTP rising onset showed the strongest relationship to ICP (right R2 = 0.58; left R2 = 0.44; both p < 0.001; Figure 4B and C), followed by the post-rise onset (right R2 = 0.03, p = 0.078; left R2 = 0.08, p = 0.002).
case_images: Left (A) and right (B) brain pulse monitor tissue oxygen saturation levels (StO2) on Day 4. (C) Invasive ICP (mean values, dark purple line) included for reference. Green shaded regions denote Lundberg B wave onsets. Scatter plots of the StO2% and the maximum invasive ICP levels on the left (D) and the right (E). Coefficients of determination (R2) and p-value are reported.
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case_images: Brain tissue oxygen saturation also demonstrated slow oscillations ranging from 55 to 75% in both hemispheres (Figure 5A-C). The R2 and p-values for the StO2 returns compared to mean invasive ICP values were right R2 = 0.04, p < 0.001; left R2 = 0.01, p = 0.005, respectively (Figure 5D and E). 
case_images: (A) Unfiltered optical signals demonstrating the right and left brain responses to a Lundberg B wave (red arrow). Filtered left (B) and right (D) brain pulsatile component. Left (C) and right (E) brain continuous wavelet transformation (CWT) demonstrating the presence of a high amplitude left cardiac signal (yellow band, [1, 1.5] Hz) and absence (absent band) or reduced amplitude (green band) of the right cardiac signal. (F) Concurrent ICP recording of Lundberg B wave (red arrow).
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case_images: The right brain pulse waveform demonstrated intermittent brief episodes with a reduced or absent brain pulse (Figure 6A), lasting from 15 to 80 seconds. These episodes were frequently but not exclusively associated with the onset of Lundberg B waves (Figure 6F). Application of a Butterworth filter (3rd order, [0.5, 8.5] Hz) shows consistent cardiac pulsatility in the left-brain signal (Figure 6B) compared to that of the right (D). A threshold contour applied to the result shows a consistent band between 1 and 1.5 Hz for the left side (Figure 6C) compared to the right (Figure 6E), which has extremely spotty and inconsistent spectral power in the relevant band.