What Shapes Pulse Amplitude of Intracranial Pressure?

Abstract

The pulsatile component of intracranial pressure (ICP) has been shown to be a predictor of outcome in normal pressure hydrocephalus (NPH) and traumatic brain injury (TBI). Experimental studies have demonstrated that the pulse amplitude of ICP (AMP(ICP)) is dependent on the mean ICP (mICP), and on the pulse amplitude of the cerebral arterial blood volume (AMP(CaBV)), according to the exponential craniospinal compliance curve. In this study, we compared the influence of mICP and AMP(CaBV) on AMP(ICP) in patients with NPH (infusion study) and TBI (spontaneous recording). We retrospectively analyzed 25 NPH and 43 TBI patients with continuous monitoring of ICP and cerebral blood flow velocity (CBFV), as assessed with transcranial doppler. AMP(CaBV) was extracted from the CBFV waveform. The influence of mICP and AMP(CaBV) on AMP(ICP) were determined using partial coefficients a, b, and c of the multiple regression model: AMP(ICP) = a * mICP + b * AMP(CaBV) + c. AMP(ICP) was more dependent on mICP in NPH patients than in TBI patients (partial coefficient a = 0.93 versus -0.03; p < 0.001). On the contrary, AMP(ICP) was more dependent on AMP(CaBV) in patients with TBI than in those with NPH (b = 0.86 versus 0.10; p < 0.001). This study shows that AMP(ICP) depends mostly on changes in mean ICP during cerebrospinal fluid (CSF) infusion studies in patients with NPH, and on changes in cerebral arterial blood volume (AMP(CaBV)) in TBI patients. Further clinical studies will reveal whether AMP(ICP) is a better indicator of clinical severity and outcome than mICP in TBI and NPH patients.

Intraspinal pressure and spinal cord perfusion pressure after spinal cord injury: an observational study

“…10 An RAP around 0 at low ICP (< 15 mm Hg) indicates good cerebrospinal compensatory reserve, whereas RAP close to +1 indicates an exhausted compensatory reserve. Lower RAP values (i.e., negative values) at increased ICP (> 20 mm Hg) are associated with unfavorable outcome in TBI patients, 6,10 indicating terminal cerebrovascular derangement. 3,9 Due to the similarities between ICP and ISP, the PRx and RAP indices might also be used to assess SCI in the same way that they are used in TBI, potentially providing some useful indications concerning autoregulation and compensatory reserve.…”

“…5 Secondary indices of ICP can be descriptive of the cerebrospinal compensatory reserve (RAP index), or-based on the interactions between the slow waves of ICP and ABP-can characterize the status of the cerebrovascular pressure reactivity (PRx index). 3,[6][7][8]10,24 In TBI cases, both ICP and its derived indices are well known to have a strong association with outcome and are part of the clinical assessment for deciding the therapeutic management of a patient. 3,8,9,15,16,24 Based on the inherent similarities with ICP, this observational study aims to qualitatively describe the biophysics of ISP and explore its morphology regarding different components in the time and frequency domains.…”

Real-Time Analysis of Intracranial Pressure Waveform Morphology

“…of Curv T ). Amplitude of P 1 , most likely related to systole of arterial pressure [58], shows a moderate increase during BW in comparison with both dP 2 and dP 3 (hence S.D. of dP 12 , S.D.…”

Pulse Amplitude and Lempel–Ziv Complexity of the Cerebrospinal Fluid Pressure Signal

“…At that time, it was thought that the wave morphology could have potentially important clinical implications. This assumption, however, was pushed aside until recently, when renewed interest in the pulsatile component of ICP dynamics has brought the waveform into the field of discussion once again (2,5,6).…”