Intracranial Pressure Probe Research Articles

The Application of Intraoperative Ultrasound with Burr Hole Probe in Minimally Invasive Diagnosis and Treatment in Neurosurgery

ObjectiveTo summarize the preliminary application experience of intraoperative ultrasound with burr hole probe in minimally invasive neurosurgery and to explore its application value. Methods31 patients who underwent intraoperative ultrasound guided puncture with burr hole probe in our center from August 2018 to May 2024 were collected, including 16 cases of ventriculoperitoneal shunt operation, 6 cases of assisted stereotactic needle biopsy, 3 cases of intracranial pressure probe implantation in lateral ventricle, 3 cases of brain abscess puncture for external drainage, and 3 cases of intracranial cyst puncture and peritoneal drainage. During the procedures, the burr hole probe was used to locate the intracranial targets and guide the puncture. The postoperative CT scans or combined postoperative pathological results could verify the accuracy of puncture. In addition, the intervention effect and recovery status of patients were also recorded. ResultsThe intraoperative ultrasound with burr hole probe could clearly display all the purposed targets and accurately guide the puncture procedures in all cases. All patients achieved satisfactory diagnostic and therapeutic results without new neurological dysfunction and serious complications. ConclusionsThe intraoperative ultrasound with burr hole probe is an effective device for demonstrating intracranial structures. It not only enables minimally invasive and precise diagnosis or treatment of many neurosurgical diseases, but also is simple and safe to operate, which has important promotional value in the neurosurgery.

Risk factors for hemorrhage in patients with long-term aspirin therapy undergoing emergency external ventricular drainage/intracranial pressure probe placement

BackgroundStudies have been inconclusive on the risk for hemorrhage in patients with a history of aspirin use who underwent emergency external ventricular drainage (EVD)/intracranial pressure (ICP) probe placement. The aim of this study was to explore hemorrhage-related risk factors in order to reduce the risk for hemorrhage in these patients. MethodsBetween July 2014 and July 2020, patients were retrospectively divided into EVD/ICP-related hemorrhage and non-hemorrhage groups. The collected data included age, gender, major diagnosis, medical history, imaging examinations, conventional coagulation test data, thromboelastography with platelet mapping (TEG-PM), surgical procedures and discharge conditions. ResultsIn total 94 patients, 21 in the hemorrhage group (15 males, 6 females) and 73 in the non-hemorrhage group (52 males, 21 females) were included. The majority of hemorrhages were recorded in EVD patients (19/21; 90.5%). Platelet AA pathway inhibition rate of ≥75% (sensitivity: 79.45% specificity: 52.38%) (P = 0.014) and SBP ≥125 mmHg (P = 0.006) were significantly related to hemorrhage. When the platelet AA pathway inhibition rate was ≥75% and the during-procedure SBP was ≥125 mmHg, the hemorrhage rate was significantly higher (83.3%) than with SBP <125 mmHg (6.7%) (P < 0.001). When the inhibition rate was <75%, there were no significant differences in the hemorrhage rates between the during-procedure SBP ≥125 mmHg group (17.2%) and the SBP <125 mmHg group (13.2%) (P > 0.05). Multivariate logistic regression analysis revealed that a platelet AA pathway inhibition rate ≥75% (OR = 5.183, 95% CI: 1.683–15.960) and during-procedure SBP ≥125 mmHg (OR = 4.609, 95% CI: 1.466–14.484) were independent risk factors for EVD/ICP-related hemorrhage. ConclusionPatients with long-term aspirin therapy, a platelet AA pathway inhibition rate ≥75% and during-procedure SBP ≥125 mmHg had a significantly higher risk of hemorrhage, which could be reduced by adjusting the SBP to <125 mmHg.

Intraoperative Epiphyseal Perfusion Monitoring Does Not Reliably Predict Osteonecrosis Following Treatment of Unstable SCFE.

Avascular necrosis (AVN) remains the most dreaded complication of unstable slipped capital femoral epiphysis (SCFE) treatment. Newer closed reduction techniques (with perfusion monitoring) have emerged as a technically straightforward means to address residual SCFE deformity while still minimizing the risk of osteonecrosis. However, limited data exists regarding the reliability of intraoperative epiphyseal perfusion monitoring to predict the development of AVN. The purpose of this study was to evaluate its reliability. We retrospectively reviewed all patients with unstable SCFE who underwent closed or open reduction with epiphyseal perfusion monitoring using an intracranial pressure (ICP) probe from 2015 to 2023 at a single institution with a minimum 6-month radiographic follow-up. Demographic, clinical, and radiographic data were recorded, including duration of symptoms, type of reduction, capsulotomy performed, presence of a waveform on ICP monitoring after epiphyseal fixation, and development of AVN on follow-up radiographs. Our cohort included 33 hips (32 patients), of which 60.6% (n=20) were male. The average age was 12.5±1.8 years, with a median follow-up of 15.8 months. Eleven hips were treated with open reduction using the modified Dunn technique (10 hips) or anterior approach (1 hip), and 22 hips were treated with inadvertent (5 hips) or purposeful closed reduction using the Leadbetter technique (17 hips). Overall, 8 of the 33 hips in our series (24.2%) developed AVN, 6 of which (20%) had a pulsatile waveform on intraoperative epiphyseal perfusion monitoring. The overall rate of AVN after closed reductions was 31.8% (7 of 22 hips); the incidence of AVN after closed reduction with a detectable waveform was 30% (6 of 20 hips). There was no significant association between time to surgery ( P =0.416) or type of reduction ( P =0.218) and the incidence of AVN. In this series, intraoperative epiphyseal perfusion monitoring did not reliably predict the development of osteonecrosis. To our knowledge, this is the first study to report AVN after demonstrable intraoperative epiphyseal perfusion following closed reduction of unstable slips. Level IV: case series-therapeutic study.

Comparison of two minimally invasive surgical approaches for hypertensive intracerebral hemorrhage: a study based on postoperative intracranial pressure parameters

BackgroundIncreased intracranial pressure (ICP) in patients with hypertensive intracerebral hemorrhage (HICH) has been associated with poor prognosis. The transsylvian insular approach (TIA) and the transcortical (TCA) approach are applied for patients with HICH. We aimed to compare the postoperative ICP parameters of TIA and TCA to identify which procedure yields better short-term outcomes in patients with basal ganglia hematoma volumes ranging from 30 to 50 mL.MethodsEighty patients with basal ganglia hematomas 30–50 mL were enrolled in this study. Patients were implanted with ICP probes and divided into TIA and TCA groups according to the procedure. The ICP values were continuously recorded for five days at four-hour intervals. Short-term outcomes were evaluated using the length of hospitalization and postoperative consciousness recovery time.ResultsNo statistically significant differences were found in age, sex, GCS score at admission, hematoma volume, and hematoma clearance rate (p > 0.05). The results showed that postoperative initial ICP, ICP on the first postoperative day, mean ICP, DICP20 mmHg × 4 h, postoperative consciousness recovery time, the length of hospitalization, mannitol utilization rate and the mannitol dosage were lower in the TIA group than in the TCA group (p < 0.05). Postoperative consciousness recovery time was positively correlated with ICP on the first postoperative day, and the length of hospitalization was positively correlated with mean ICP.ConclusionsTIA is more effective than TCA in improving the short-term outcomes of patients with basal ganglia hematoma volumes ranging from 30 to 50 mL according to comparisons of postoperative ICP parameters.

Pressure Time Dose as a Representation of Intracranial Pressure Burden and Its Dependency on Intracranial Pressure Waveform Morphology at Different Time Intervals.

Intracranial pressure (ICP) burden or pressure time dose (PTD) is a valuable clinical indicator for pending intracranial hypertension, mostly based on threshold exceedance. Pulse frequency and waveform morphology (WFM) of the ICP signal contribute to PTD. The temporal resolution of the ICP signal has a great influence on PTD calculation but has not been systematically studied yet. Hence, the temporal resolution of the ICP signal on PTD calculation is investigated. We retrospectively analysed continuous 48 h ICP recordings with high temporal resolution obtained from 94 patients at the intensive care unit who underwent neurosurgery due to an intracranial haemorrhage and received an intracranial pressure probe (43 females, median age: 72 years, range: 23 to 88 years). The cumulative area under the curve above the threshold of 20 mmHg was compared for different temporal resolutions of the ICP signal (beat-to-beat, 1 s, 300 s, 1800 s, 3600 s). Events with prolonged ICP elevation were compared to those with few isolated threshold exceedances. PTD increased for lower temporal resolutions independent of WFM and frequency of threshold exceedance. PTDbeat-to-beat best reflected the impact of frequency of threshold exceedance and WFM. Events that could be distinguished in PTDbeat-to-beat became magnified more than 7-fold in PTD1s and more than 104 times in PTD1h, indicating an overestimation of PTD. PTD calculation should be standardised, and beat-by-beat PTD could serve as an easy-to-grasp indicator for the impact of frequency and WFM of ICP elevations on ICP burden.

Acetazolamide and topiramate lower intracranial pressure through differential mechanisms: The effect of acute and chronic administration.

Diseases of raised intracranial pressure (ICP) cause severe morbidity and mortality. Multiple drugs are utilised to lower ICP including acetazolamide and topiramate. However, the evidence for their use is unclear. We aimed to assess the ICP modulatory effects and molecular effects at the choroid plexus (CP) of acetazolamide and topiramate. Female rats were implanted with telemetric ICP probes for physiological, freely moving 24/7 ICP recordings. Randomised cross-over studies were performed, where rats received acute (24 h) high doses of acetazolamide and topiramate, and chronic (10days) clinically equivalent doses of acetazolamide and topiramate, all via oral gavage. Cerebrospinal fluid (CSF) secretion assays, and RT-qPCR and western blots on in vitro and in vivo CP, were used to investigate drug actions. We demonstrate that acetazolamide and topiramate achieved maximal ICP reduction within 120 min of administration, and in combination doubled the ICP reduction over a 24-h period. Chronic administration of acetazolamide or topiramate lowered ICP by 25%. Topiramate decreased CSF secretion by 40%. Chronic topiramate increased the gene expression of Slc12a2 and Slc4a10 and protein expression of the sodium-dependent chloride/bicarbonate exchanger (NCBE), whereas chronic acetazolamide did not affect the expression of assessed genes. Acetazolamide and topiramate are effective at lowering ICP at therapeutic levels. We provide the first evidence that topiramate lowers CSF secretion and that acetazolamide and topiramate may lower ICP via distinct molecular mechanisms. Thus, the combination of acetazolamide and topiramate may have utility for treating raised ICP.

Abdominal Wall Movements Predict Intra-Abdominal Pressure Changes in Rats: A Novel Non-Invasive Intra-Abdominal Pressure Detection Method.

(1) Background: As increases in intra-abdominal pressure (IAP) result in irreversible tissue damage, monitoring IAP in critically ill patients using the common urinary bladder catheter method is essential. However, this method can result in complications and is not suitable for very low birth weight neonates. The aim of this study was to establish a non-invasive and accurate method to detect IAP changes using an animal model. (2) Methods: IAP changes via intra-abdominal air application (up to 20 mmHg) were measured in 19 Wistar rats via an intra-abdominally placed intracranial pressure probe. Concurrently, abdominal surface tension was measured using a Graseby capsule (GC). (3) Results: A high correlation between abdominal wall distension and IAP (r = 0.9264, CI 0.9249-0.9279) was found for all subjects. (4) Conclusions: IAP changes in rats can be detected non-invasively using a GC. However, further studies are necessary to assess whether IAP changes can be measured using a GC in the neonatal population.

Blood Clots May Compromise Intracranial Pressure Measurement Using Air-Pouch Intracranial Pressure Probes.

Background: Air-pouch balloon-assisted probes have proven to be both simple and reliable tools for intracranial pressure (ICP) monitoring. However, we experienced reproducible falsely high ICP measurements when the ICP probe was inserted into the intracerebral hematoma cavity. Thus, the aim of the experimental and translational study was to analyze the influence of ICP probe placement with regard to measured ICP values. Methods: Two Spiegelberg 3PN sensors were simultaneously inserted into a closed drain system and were connected to two separate ICP monitors thereby allowing for simultaneous ICP measurements. This closed system was also engineered to allow for pressure to be gradually increased in a controlled fashion. Once the pressure was verified using two identical ICP probes, one of the probes was coated with blood in an effort to replicate placement within an intraparenchymal hematoma. Pressures recorded using the coated probe and control probe were then recorded and compared across a range of 0-60 mmHg. In an effort to further the translational relevance of our results, two ICP probes were inserted in a patient that presented with a large basal ganglia hemorrhage that met criteria for ICP monitoring. One probe was inserted into the hematoma and the other into brain parenchyma; ICP values were recorded from both probes and the results compared. Results: The experimental set-up demonstrated a reliable correlation between both control ICP probes. Interestingly, the ICP probe covered with clot displayed a significantly higher average ICP value when compared to the control probe between 0 mmHg and 50 mmHg (p < 0.001); at 60 mmHg, there was no significant difference noted. Critically, this trend in discordance was even more pronounced in the clinical setting with the ICP probe placed within the hematoma cavity having reported significantly higher ICP values as compared to the probe within brain parenchyma. Conclusions: Our experimental study and clinical pilot highlight a potential pitfall in ICP measurement that may result secondary to probe placement within hematoma. Such aberrant results may lead to inappropriate interventions in an effort to address falsely elevated ICPs.

Glucocorticoids modify intracranial pressure in freely moving rats

BackgroundGlucocorticoids (GCs) are widely prescribed for a variety of inflammatory diseases, but they are also used to treat raised intracranial pressure (ICP) caused by trauma or oedema. However, it is unclear if GCs independently modulate ICP and if GCs are involved in normal ICP regulation. In this study, we aimed to assess the ICP modulatory effects of GCs and their molecular consequences on choroid plexus (CP).MethodsAdult female rats were implanted with telemetric ICP probes for physiological, continuous ICP recordings in a freely moving setup. Rats received prednisolone or vehicle via oral gavage in a randomized acute (24 h) ICP study. In a subsequent study rats received corticosterone or vehicle in drinking water for a 4-week chronic ICP study. CP were removed, and the expression of genes associated with cerebrospinal fluid secretion were assessed.ResultsA single prednisolone dose reduced ICP by up to 48% (P < 0.0001), where ICP was reduced within 7 h and was maintained for at least 14 h. Prednisolone increases ICP spiking (P = 0.0075) while not altering ICP waveforms. Chronic corticosterone reduces ICP by up to 44%, where ICP was lower for the entirety of the 4-week ICP recording period (P = 0.0064). ICP daily periodicity was not altered by corticosterone. Corticosterone ICP reduction was not accompanied by ICP spike differences or alteration in ICP spike periodicity. Chronic corticosterone treatment had modest effects on CP gene expression, lowering the expression of Car2 at CP (P = 0.047).ConclusionsGCs reduce ICP in both the acute and chronic setting to a similar degree. Moreover, GCs did not modify the diurnal rhythm of ICP, suggesting the diurnal variation of ICP periodicity is not under explicit control of GCs. ICP disturbances should be considered a consequence of GC therapy. Based on these experiments, GCs may have broader ICP therapeutic uses, but side effects must be taken into consideration.

A Surgical Technique for Percutaneous Intraoperative Monitoring of Proximal Femur Epiphyseal Perfusion

A Surgical Technique for Percutaneous Intraoperative Monitoring of Proximal Femur Epiphyseal Perfusion

Impact of Postural Changes on Sinonasal Pressure After Endoscopic Endonasal Surgery

Postoperative management following endoscopic endonasal surgery (EES) is important to prevent cerebrospinal fluid leak and preserve the integrity of the nasoseptal flap. No consensus regarding an optimal posture in the postoperative period has been established. We hypothesized that sinonasal pressure (SNP) can represent intracranial pressure affecting the sellar floor in the absence of the sellar bone after surgery. This study provides evidence for the effect of postural changes and recommends optimal posture to reduce SNP following EES. The authors conducted a retrospective analysis of 50 patients who underwent reconstruction for skull base defects with nasoseptal flap after EES for resection of suprasellar tumor between March 2020 and August 2020. The Spiegelberg intracranial pressure probe was placed through the nostril over the nasoseptal flap. SNPs were measured in Fowler' (45° tilt) and supine positions, respectively, daily for the first 3days immediately after EES. For the first 3days after surgery, the mean SNP in Fowler' position (24.82mmHg; standard deviation, 12.23mmHg) was lower than that in the supine position (28.42mmHg; standard deviation, 12.33mmHg) (P<0.01). There were no significant differences in mean SNP for age, sex, tumor size, presence of hydrocephalus, and body mass index. There was a significant correlation between Fowler' position and a decrease in SNP measurements. Placing a patient in Fowler' position after surgery can decrease the SNP. We recommend that patients should be placed in a Fowler' position as an optimal position after surgery.

Knockdown of sortilin improves the neurological injury and regional cerebral blood flow in rats after subarachnoid hemorrhage.

Subarachnoid hemorrhage (SAH) is a severe subtype of stroke. Sortilin protein is elevated in cerebrospinal fluid (CSF) of SAH patients. This study explored the mechanism of sortilin in SAH. SAH model was established by occipital cisternal blood injection. Neurological evaluation was performed on SAH rats using the Gracia scoring system and beam-balance tests. Regional cerebral blood flow (rCBF) and intracranial pressure (ICP) changes were measured using a laser Doppler blood flow monitor and an intraparenchymal Camino ICP probe. The correlation between rCBF changes and neurological deficit was analyzed using the Spearman method. Sortilin protein level in rat cerebral cortex and CSF was detected by Western blot. The Garcia score and beam-balance score of rats at 1, 12, 24, 48, and 72 h after SAH were lowered. Blood clots were observed on the ventral surface of the brain in SAH rats, around Willis ring, and ventral surface of brain stem, but no blood clots were found in the control group. At 1, 12, 24, 48, and 72 h after SAH in rats, the severity of SAH was aggravated, rCBF was decreased, and ICP was increased. The changes of rCBF in rat cerebral cortex at 1 and 72 h after SAH were correlated with the Garcia score. Sortilin was highly expressed in the cerebral cortex and CSF of SAH rats. Knockdown of sortilin improved the neurological injury and rCBF in rats. Sortilin was highly expressed in the cerebral cortex and CSF of SAH rats. Sortilin silencing improved neurological injury and CBF in rats.

Predictive Value of Optic Nerve Sheath Diameter for Diagnosis of Intracranial Hypertension in Children With Severe Brain Injury.

Background and AimsIntracranial Hypertension (ICH) is a life-threatening complication of brain injury. The invasive measurement of intracranial pressure (ICP) remains the gold standard to diagnose ICH. Measurement of Optic Nerve Sheath Diameter (ONSD) using ultrasonography is a non-invasive method for detecting ICH. However, data on paediatric brain injury are scarce. The aim of the study was to determine the performance of the initial ONSD measurement to predict ICH occurring in children with severe brain injury and to describe the ONSD values in a control group.MethodsIn this cross-sectional study, ONSD was measured in children aged 2 months-17 years old with invasive ICP monitoring: before placement of ICP probe and within the 60 min after, and then daily during 3 days. ONSD was also measured in a control group.ResultsNinety-nine patients were included, of whom 97 were analysed, with a median (IQR) age of 8.7 [2.3–13.6] years. The median (IQR) PIM 2 score was 6.6 [4.4–9.7] and the median (IQR) PELOD score was 21 [12–22]. Aetiologies of brain injury were trauma (n = 72), infection (n = 17) and stroke (n = 8). ICH occurred in 65 children. The median (IQR) ONSD was 5.58 mm [5.05–5.85]. ONSD performed poorly when it came to predicting ICH occurrence within the first 24 h (area under the curve, 0.58). There was no significant difference between the ONSD of children who presented with ICH within the first 24 h and the other children, with a median (IQR) of 5.6 mm [5.1–5.9] and 5.4 mm [4.9–5.8], respectively. Infants aged less than 2 years had a median (IQR) ONSD of 4.9 mm [4.5–5.2], significantly different from children aged more than 2 years, whose median ONSD was 5.6 mm [5.2–5.9]. Age, aetiology or ICP levels did not change the results. Thirty-one controls were included, with a median age of 3.7 (1.2–8.8) years. The median (IQR) of their ONSD measurement was 4.5 mm [4.1–4.8], significantly lower than the patient group.ConclusionIn a paediatric severe brain injury population, ONSD measurement could not predict the 24 h occurrence of ICH. Severity of patients, timing and conditions of measurements may possibly explain these results.

Confirming subarachnoid hemorrhage induction in the endovascular puncture mouse model

Background and purposeExperimental studies of subarachnoid hemorrhage (SAH) using the endovascular perforation model routinely use either cerebral blood flow (CBF) or intracranial pressure (ICP) monitoring to confirm SAH induction. We designed this study to test the hypothesis that contralateral CBF is a better marker of SAH induction than ipsilateral CBF. MethodsSixty-eight adult C57BL/6J mice were subjected to endovascular perforation. Mice were monitored using laser Doppler (for relative CBF) or ICP probes. ResultsThe ipsilateral CBF significantly decreased prior to ICP rising. However, reduction of the CBF in the contralateral hemisphere occurred at the same time as the rise in ICP. When CBF is monitored on both hemispheres simultaneously, the drop in ipsilateral CBF precedes the drop in the contralateral CBF. ConclusionsThe most suitable method for confirming puncture and induction of SAH in the endovascular mouse model is by ICP. Monitoring the CBF of the contralateral hemisphere is also able to detect the moment of SAH induction, but is not able to distinguish SAH severity. However, monitoring the ipsilateral CBF is not satisfactory for determining induction of SAH.

Affordable Low-Cost Home-Made Skull Model for Interactive Neurosurgical workshops: Experience with Hands-on Intracranial Pressure Monitoring at 2 International Neurosurgical Conferences

Undergraduate neurosurgery conferences are acknowledged to play an important role in bridging the gap between a limited exposure to neurosurgery within medical schools and a highly competitive application process. Hands-on workshops are attractive for any conference but can be prohibitively expensive, especially for student societies. We describe our method to manufacture a low-cost skull model, which we used for a hands-on intracranial pressure (ICP) monitoring workshop station at 2 international neurosurgical conferences. We describe the workflow for our ICP monitoring workshop using these models. Our model acts as an appropriate substitute for more professional simulators while adequately mimicking the sensation of skull drilling, dural puncture, and intraparenchymal ICP bolt and probe insertion. All tools and resources are accessible from local markets and can be sourced online. A total of GB£100 was spent making 5 skull models and took 2 hours to manufacture by 3 individuals. The ICP monitoring workshop was carried out 3 times over 40 minutes, with each session accommodating 18 or 19 delegates (N= 55). These workshop models have been praised by medical students for increasing exposure and awareness toward neurosurgical procedures and the sophistication of investigations used by the specialty. Consultant neurosurgeons have praised the simulation provided by these models as closely mimicking the procedure in reality.

Trauma Team Activation: Which Surgical Capability Is Immediately Required in Polytrauma? A Retrospective, Monocentric Analysis of Emergency Procedures Performed on 751 Severely Injured Patients.

There has been an ongoing discussion as to which interventions should be carried out by an “organ specialist” (for example, a thoracic or visceral surgeon) or by a trauma surgeon with appropriate general surgical training in polytrauma patients. However, there are only limited data about which exact emergency interventions are immediately carried out. This retrospective data analysis of one Level 1 trauma center includes adult polytrauma patients, as defined according to the Berlin definition. The primary outcome was the four most common emergency surgical interventions (ESI) performed during primary resuscitation. Out of 1116 patients, 751 (67.3%) patients (male gender, 530, 74.3%) met the inclusion criteria. The median age was 39 years (IQR: 25, 58) and the median injury severity score (ISS) was 38 (IQR: 29, 45). In total, 711 (94.7%) patients had at least one ESI. The four most common ESI were the insertion of a chest tube (48%), emergency laparotomy (26.3%), external fixation (23.5%), and the insertion of an intracranial pressure probe (ICP) (19.3%). The initial emergency treatment of polytrauma patients include a limited spectrum of potential life-saving interventions across distinct body regions. Polytrauma care would benefit from the 24/7 availability of a trauma team able to perform basic potentially life-saving surgical interventions, including chest tube insertion, emergency laparotomy, placing external fixators, and ICP insertion.

Escalation therapy in severe traumatic brain injury: how long is intracranial pressure monitoring necessary?

Traumatic brain injury frequently causes an elevation of intracranial pressure (ICP) that could lead to reduction of cerebral perfusion pressure and cause brain ischemia. Invasive ICP monitoring is recommended by international guidelines, in order to reduce the incidence of secondary brain injury; although rare, the complications related to ICP probes could be dependent on the duration of monitoring. The aim of this manuscript is to clarify the appropriate timing for removal and management of invasive ICP monitoring, in order to reduce the risk of related complications and guarantee adequate cerebral autoregulatory control. There is no universal consensus concerning the duration of invasive ICP monitoring and its related complications, although the pertinent literature seems to show that the longer is the monitoring maintenance, the higher is the risk of technical issues. Besides, upon 72 h of normal ICP values or less than 72 h if the first computed tomography scan is normal (none or minimal signs of injury) and the neurological exam is available (allowing to observe variations and possible occurrence of new-onset pathological response), the removal of invasive ICP monitoring can be justified. The availability of non-invasive monitoring systems should be considered to follow up patients’ clinical course after invasive ICP probe removal or for substituting the invasive monitoring in case of contraindication to its placement. Recently, optic nerve sheath diameter and straight sinus systolic flow velocity evaluation through ultrasound methods showed a good correlation with ICP values, demonstrating their potential role in place of invasive monitoring or in the early weaning phase from the invasive ICP monitoring.

B-waves are present in patients without intracranial pressure disturbances.

Intracranial pressure (ICP) B-waves are defined as short, repeating elevations of ICP of up to 50mmHg with a frequency of 0.5-2 waves/min. The presence of B-waves in overnight recordings is regarded as a pathological phenomenon. However, the physiology of B-waves is still not fully understood and studies with transcranial Doppler, as a surrogate marker for ICP, have suggested that B-waves could be a normal physiological phenomenon. We present four patients without known structural neurological disease other than a coincidentally found unruptured intracranial aneurysm. One of the patients had experienced well-controlled epilepsy for several years, but was included because ICP under these conditions is unlikely to be abnormal. Following informed consent, all four patients had a telemetric ICP probe implanted during a prophylactic operation with closure of the aneurysm. They underwent overnight ICP monitoring with simultaneous polysomnography (PSG) sleep studies at 8weeks after the operation. These patients exhibited nocturnal B-waves, but did not have major structural brain lesions. Their ICP values were within the normal range. Nocturnal B-waves occurred in close association with sleep-disordered breathing (SDB) in rapid eye movement (REM) and non-REM sleep stages. SDB during REM sleep was associated with ramp-type B-waves; SDB during non-REM sleep was associated with the sinusoidal type of B-wave. We propose that B-waves are a physiological phenomenon associated with SDB and that the mechanical changes during respiration could have an essential and previously unrecognised role in the generation of B-waves.

Comparative investigation of different telemetric methods for measuring intracranial pressure: a prospective pilot study

ObjectivesMeasurement of intracranial pressure (ICP) plays an important role in long-term monitoring and neuro-intensive treatment of patients with a cerebral shunt. Currently, only two complete telemetric implants with different technical features are available worldwide. This prospective pilot study aims to examine patients who had both probes implanted at overlapping times for clinical reasons and represents the first in vivo comparison of both measurement methods.Materials and methodsPatients with a primary subarachnoid hemorrhage or a spontaneous intracerebral hemorrhage with ventricular hemorrhage who had received a telemetric ICP probe (Raumedic® NEUROVENT®-P-tel) were included in the study. Conventional external ventricular drainages (EVD) and ventriculoperitoneal shunts with a telemetric ICP probe (Miethke Sensor Reservoir) were implanted in patients with hydrocephalus who required CSF (cerebrospinal fluid) drainage. Absolute ICP values from all systems were obtained. Due to the overlapping implantation time, parallel ICP measurements were performed via two devices simultaneously. ICP measurements via the sensor reservoir were repeated after 3 and 9 months. Differences between the absolute ICP values measured via the NEUROVENT®-P-tel probe, the Miethke sensor reservoir®, and the EVD were analyzed.ResultsSeventeen patients were included in the present study between 2016 and 2018. 63% of all patients were male. In 11 patients the ICP measurements were followed up with both devices for 3 months. ICP measurements of the sensor reservoir showed corresponding trends in 9 cases compared to ICP measurement via the telemetry probe or EVD. Difference in absolute ICP values ranged between 14.5 mmHg and 0.0 mmHg. The average difference of the absolute ICP values in 8 cases was ≤ 3.5 mmHg.ConclusionICP measurements with both systems continuously showed synchronous absolute ICP values, however absolute values of ICP measurement with the different systems did not match.

Complications of elective intracranial pressure monitoring in adult hydrocephalus

Continuous invasive monitoring of intracranial pressure (ICP) can be used in the diagnosis and management of various types of chronic cerebrospinal fluid (CSF) circulation disorders, such as hydrocephalus, shunt dysfunction and idiopathic intracranial hypertension. The risk profile and incidence of adverse events of this surgical procedure in this patient population is not well established. We aimed to investigate and describe the risks of ICP monitoring in adult patients with chronic CSF circulation disorders. We analysed 152 patients undergoing continuous ICP monitoring between 2010 and 2019, mainly for idiopathic normal pressure hydrocephalus. The average duration of ICP monitoring was 17 h 51 min. We observed no major adverse events, such as symptomatic intracranial haemorrhage, intracranial infection, or persistent neurological deficit. Minor complications were seen in 7% of patients and included accidental removal of the ICP probe in 4 patients, inability to remove the probe requiring surgical removal in 2 patients and single generalised seizures in 2 patients. In summary, the risk of serious adverse events and complications from invasive ICP monitoring in chronic CSF circulation disorders in adult patients appears to be low.