Characterisation of Supra- and Infratentorial ICP Profiles

[Brain metastases]

Cerebral metastases in patients with metastatic lung cancer are found in more than 30% of patients at baseline and manifest themselves in two out of three patients during disease evolution. For a long time, the cerebral manifestation of the disease was classified as prognostically unfavorable and hence such patients were regularly excluded from therapy studies. In the context of targeted molecular therapy strategies and established immuno-oncological systemic therapies, the blood-brain barrier no longer represents an insurmountable barrier. However, the treatment of brain metastases requires decision making in a multidisciplinary team within dedicated lung cancer and/or oncology centers. The differentiated treatment decision is based on the number, size and location of the brain metastases, neurology and general condition, comorbidities, potential life expectancy and the patient's wishes, but also tumor biology including molecular targets, extra-cranial tumor burden and availability of a CNS-effective therapy. Systemic therapies as well as neurosurgical and radiotherapeutic concepts are now often combined for optimized and prognosis-improving therapeutic strategies.

Continuous monitoring methods of cerebral compliance and compensatory reserve: a scoping review of human literature

Objective.Continuous monitoring of cerebrospinal compliance (CC)/cerebrospinal compensatory reserve (CCR) is crucial for timely interventions and preventing more substantial deterioration in the context of acute neural injury, as it enables the early detection of abnormalities in intracranial pressure (ICP). However, to date, the literature on continuous CC/CCR monitoring is scattered and occasionally challenging to consolidate.Approach.We subsequently conducted a systematic scoping review of the human literature to highlight the available continuous CC/CCR monitoring methods.Main results.This systematic review incorporated a total number of 76 studies, covering diverse patient types and focusing on three primary continuous CC or CCR monitoring metrics and methods-Moving Pearson's correlation between ICP pulse amplitude waveform and ICP, referred to as RAP, the Spiegelberg Compliance Monitor, changes in cerebral blood flow velocity with respect to the alternation of ICP measured through transcranial doppler (TCD), changes in centroid metric, high frequency centroid (HFC) or higher harmonics centroid (HHC), and the P2/P1 ratio which are the distinct peaks of ICP pulse wave. The majority of the studies in this review encompassed RAP metric analysis (n= 43), followed by Spiegelberg Compliance Monitor (n= 11), TCD studies (n= 9), studies on the HFC/HHC (n= 5), and studies on the P2/P1 ratio studies (n= 6). These studies predominantly involved acute traumatic neural injury (i.e. Traumatic Brain Injury) patients and those with hydrocephalus. RAP is the most extensively studied of the five focused methods and exhibits diverse applications. However, most papers lack clarification on its clinical applicability, a circumstance that is similarly observed for the other methods.Significance.Future directions involve exploring RAP patterns and identifying characteristics and artifacts, investigating neuroimaging correlations with continuous CC/CCR and integrating machine learning, holding promise for simplifying CC/CCR determination. These approaches should aim to enhance the precision and accuracy of the metric, making it applicable in clinical practice.

Link between both infratentorial and supratentorial intracranial pressure burdens and final outcome in patients with infratentorial brain injury

OBJECTIVE

Increased intracranial pressure (ICP) is most likely not being transmitted uniformly within the cranium. The ICP profiles in the supra- and infratentorial compartments remain largely unclear. Increased ICP in the cerebellum, however, is insufficiently captured by supratentorial ICP (ICPsup) monitoring due to compartmentalization through the tentorium. The authors hypothesized that additional infratentorial ICP (ICPinf) monitoring can be clinically valuable in selected patients. The aims of this study were to demonstrate the safety and feasibility of ICPinf monitoring and to investigate the influence of the ICPinf on clinical outcome in a real-world setting.

METHODS

Fifteen consecutive patients with posterior fossa (PF) lesions requiring surgery and anticipated prolonged neurointensive care between June 2019 and December 2021 were included. Simultaneous ICPsup and ICPinf were recorded. ICP burden was defined as a 15-minute interval with a mean ICP > 22 mm Hg. The Glasgow Outcome Scale score was assessed after 3 months.

RESULTS

The mean ICPinf was substantially higher compared with ICPsup throughout the entire period of ICP recording (16.08 ± 4.44 vs 10.74 ± 3.6 mm Hg, p < 0.01). ICPinf was significantly higher in patients with unfavorable outcome when compared with those with favorable outcome (mean 17.2 ± 4.1 vs 11.4 ± 3.5 mm Hg, p < 0.05). Patients with unfavorable outcome showed significantly higher ICPinf burden compared with those with favorable outcome (mean 40.6 ± 43.8 vs 0.3 ± 0.4 hours, p < 0.05). Neither absolute ICPsup nor ICPsup burden was significantly associated with unfavorable outcome (p = 0.13). No monitoring-associated complications occurred.

CONCLUSIONS

Supplementary ICPinf monitoring is safe and reliable. There is a significant transtentorial pressure gradient within the cranium showing elevated ICPs in the PF. Elevated ICP levels in the PF were strongly associated with unfavorable neurological outcome irrespective of ICPsup values.

Comparison of Cerebral Autoregulation Above and Below the Tentorium of the Cerebellum In Neurosurgical Patients with Transtentorial ICP Gradient

INTRODUCTION

Cerebral autoregulation is an essential mechanism for maintaining cerebral blood flow stability. The phenomenon of transtentorial intracranial pressure (ICP) gradient after neurosurgical operations, complicated by edema and intracranial hypertension in the posterior fossa, has been described in clinical practice but is still underinvestigated. The aim of the study was to compare autoregulation coefficients (i.e., pressure reactivity index [PRx]) in two compartments (infratentorial and supratentorial) during the ICP gradient phenomenon.

METHODS

Three male patients, aged 24 years, 32 years, and 59 years, respectively, were involved in the study after posterior fossa surgery. Arterial blood pressure and ICP were invasively monitored. Infratentorial ICP was measured in the cerebellar parenchyma. Supratentorial ICP was measured either in the parenchyma of the cerebral hemispheres or through the external ventricular drainage. Cerebral autoregulation was evaluated by the PRx coefficient (ICM + , Cambridge, UK).

RESULTS

In all patients, ICP was higher in the posterior fossa, and the transtentorial ICP gradient in each patient was 5 ± 1.6 mm Hg, 8.5 ± 4.4 mm Hg, and 7.7 ± 2.2 mm Hg, respectively. ICP in the infratentorial space was 17 ± 4 mm Hg, 18 ± 4.4 mm Hg, and 20 ± 4 mm Hg, respectively. PRx values in the supratentorial and infratentorial spaces had the smallest difference (- 0.01, 0.02, and 0.01, respectively), and the limits of precision were 0.1, 0.2, and 0.1 in the first, second, and third patients, respectively. The correlation coefficient between the PRx values in the supratentorial and infratentorial spaces for each patient was 0.98, 0.95, and 0.97, respectively.

CONCLUSIONS

A high degree of correlation was established between the autoregulation coefficient PRx in two compartments in the presence of transtentorial ICP gradient and persistent intracranial hypertension in the posterior fossa. Cerebral autoregulation, according to the PRx coefficient in both spaces, was similar.

Assessment of Optic Nerve Sheath Diameter and Its Postoperative Regression among Patients Undergoing Brain Tumor Resection in a Tertiary Care Center

Introduction  Bedside measurement of optic nerve sheath diameter (ONSD) using ultrasonography (USG) is a useful method for detecting raised intracranial pressure (ICP). The primary and main objective of this study is to estimate ONSD among patients with brain tumor and its regression post tumor resection to assess the correlation as well as diagnostic accuracy of the same.

Materials and Methods  This prospective observational study was performed in a tertiary health care center over a span of 3 months on 68 adults of either sex, out of which 30 were nonneurosurgical patients, taken as control group. Rest 38 were neurosurgical patients posted for brain tumor resection. Normal ONSD in our population was determined by calculating average ONSD using transorbital USG in individuals of control group. ONSD in neurosurgical patients taken as case group was recorded before surgery, intraoperatively immediately post tumor resection, as well as 12 and 24 hours post surgery. These values were analyzed to see the correlation of ONSD with tumor resection.

Results  The mean (±standard deviation) binocular ONSD in our population was 4.28 ± 0.28 mm. The mean preoperative binocular ONSD in cases using transorbital USG came out to be 5.43 ± 0.37 mm with 88.23% sensitivity and 100% specificity. Postoperatively, transorbital ONSD showed significant regression at 12 and 24 hours as compared with preoperative values ( p -value < 0.05).

Conclusion  Transorbital ultrasonographic measurement of ONSD could be considered as an indirect indicator of ICP in neurosurgical patients perioperatively. The technique is quick to perform at bedside, feasible in critical patients, and without any harmful effects.

Intracranial pressure monitoring in posterior fossa lesions-systematic review and meta-analysis

Elevated intracranial pressure (ICP) with reduced cerebral perfusion pressure is a well-known cause of secondary brain injury. Previously, there have been some reports describing different supra- and infratentorial ICP measurements depending on the location of the mass effect. Therefore, we aimed to perform a systematic review and meta-analysis to clarify the issue of optimal ICP monitoring in the infratentorial mass lesion. A literature search of electronic databases (PUBMED, EMBASE) was performed from January 1969 until February 2021 according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. Two assessors are independently screened for eligible studies reporting the use of simultaneous ICP monitoring in the supra- and infratentorial compartments. For quality assessment of those studies, the New Castle Ottawa Scale was used. The primary outcome was to evaluate the value of supra- and infratentorial ICP measurement, and the secondary outcome was to determine the time threshold until equalization of both values. Current evidence surrounding infratentorial ICP measurement was found to be low to very low quality according to New Castle Ottawa Scale. Eight studies were included in the systematic review, four of them containing human subjects encompassing 27 patients with infratentorial pathology. The pooled data demonstrated significantly higher infratentorial ICP values than supratentorial ICP values 12 h after onset (p < 0.05, 95% CI 3.82–5.38) up to 24 h after onset (p < 0.05; CI 1.14–3.98). After 48–72 h, both ICP measurements equilibrated showing no significant difference. Further, four studies containing 26 pigs and eight dogs showed a simultaneous increase of supra- and infratentorial ICP value according to the increase of supratentorial mass volume; however, there was a significant difference towards lower ICP in the infratentorial compartment compared to the supratentorial compartment. The transtentorial gradient leads to a significant discrepancy between supra- and infratentorial ICP monitoring. Therefore, infratentorial ICP monitoring is warranted in case of posterior fossa lesions for at least 48 h.

[Invasive intracranial pressure monitoring in posterior cranial fossa after neurosurgery: an exclusive option or a necessity?]

Posterior cranial fossa (PCF) surgery is associated with the risk of increased intracranial pressure (ICP) under tentorium. The last one can lead to severe brainstem syndromes and postoperative complications. The currently recommended method for ICP control with a supratentorial parenchymal sensor or CSF pressure measurement through an external ventricular drainage is ineffective. Indeed, these methods do not show the true situation in the PCF.

OBJECTIVE

To determine the feasibility of ICP sensor insertion into cerebellar parenchyma for PCF edema after neurosurgery.

MATERIAL AND METHODS

We retrospectively analyzed literature data (15 references) and 3 patients after ICP sensor insertion into cerebellar parenchyma for ICP control in PCF.

CONCLUSION

ICP sensor insertion into cerebellar parenchyma is indicated for infratentorial postoperative edema.

B waves: a systematic review of terminology, characteristics, and analysis methods

Background

Although B waves were introduced as a concept in the analysis of intracranial pressure (ICP) recordings nearly 60 years ago, there is still a lack consensus on precise definitions, terminology, amplitude, frequency or origin. Several competing terms exist, addressing either their probable physiological origin or their physical characteristics. To better understand B wave characteristics and ease their detection, a literature review was carried out.

Methods

A systematic review protocol including search strategy and eligibility criteria was prepared in advance. A literature search was carried out using PubMed/MEDLINE, with the following search terms: B waves + review filter, slow waves + review filter, ICP B waves, slow ICP waves, slow vasogenic waves, Lundberg B waves, MOCAIP.

Results

In total, 19 different terms were found, B waves being the most common. These terminologies appear to be interchangeable and seem to be used indiscriminately, with some papers using more than five different terms. Definitions and etiologies are still unclear, which makes systematic and standardized detection difficult.

Conclusions

Two future lines of action are available for automating macro-pattern identification in ICP signals: achieving strict agreement on morphological characteristics of “traditional” B waveforms, or starting a new with a fresh computerized approach for recognition of new clinically relevant patterns.