Telemetric Intracranial Pressure Sensor Research Articles

Intracranial pressure following surgery of an unruptured intracranial aneurysm—a model for normal intracranial pressure in humans

ObjectiveOptimizing the treatment of several neurosurgical and neurological disorders relies on knowledge of the intracranial pressure (ICP). However, exploration of normal ICP and intracranial pressure pulse wave amplitude (PWA) values in healthy individuals poses ethical challenges, and thus the current documentation remains scarce. This study explores ICP and PWA values for healthy adults without intracranial pathology expected to influence ICP.MethodsAdult patients (age > 18 years) undergoing surgery for an unruptured intracranial aneurysm without any other neurological co-morbidities were included. Patients had a telemetric ICP sensor inserted, and ICP was measured in four different positions: supine, lateral recumbent, standing upright, and 45-degree sitting, at day 1, 14, 30, and 90 following the surgery.ResultsICP in each position did not change with time after surgery. Median ICP was 6.7 mmHg and median PWA 2.1 mmHg in the supine position, while in the upright standing position median ICP was − 3.4 mmHg and median PWA was 1.9 mmHg. After standardization of the measurements from the transducer site to the external acoustic meatus, the median ICPmidbrain was 8.3 mmHg in the supine position and 1.2 mmHg in the upright standing position.ConclusionOur study provides insights into normal ICP dynamics in healthy adults following a uncomplicated surgery for an unruptured aneurysm. These results suggest a slightly wider normal reference range for invasive intracranial pressure than previously suggested, and present the first normal values for PWA in different positions. Further studies are, however, essential to enhance our understanding of normal ICP.Trial registration The study was preregistered at www.clinicaltrials.gov (NCT03594136) (11 July 2018)

Telemetric ICP monitoring in children: a national questionnaire-based study.

Telemetric monitoring of intracranial pressure (ICP) facilitates long-term measurements and home monitoring, thus potentially reducing diagnostic imaging and acute hospital admissions in favour of outpatient appointments. Especially in paediatric patients, telemetric ICP monitoring requires a high level of collaboration and compliance from patients and parents. In this study, we aim to systematically investigate (1) patient and parent perception of telemetric ICP system utility and (2) hospital contact history and thus the potential cost-benefit of telemetric ICP monitoring in paediatric patients with a cerebrospinal fluid disorder. We conducted a nationwide questionnaire study, including paediatric patients with either a current or previous telemetric ICP sensor and their parents. Additionally, a retrospective review of electronic health records for all included children was performed. We included 16 children (age range 3-16 years), with a total of 41 telemetric ICP sensors implanted. Following sensor implantation, the frequency of telephone contacts and outpatient visits increased. No corresponding decrease in hospital admissions or total length of stay was found.The telemetric ICP sensor provided most parents with an improved sense of security and was seen as a necessary and valuable tool in treatment guidance. The size and shape of the sensor itself were reported as disadvantages, while the external monitoring equipment was reported as easy to use but too large and heavy for a child to carry. Though, in quantitative terms, there was no cost-benefit of the telemetric ICP sensor, it contributed to extended parental involvement and a sense of improved safety.

Parent perception of telemetric intracranial pressure monitoring in children - A qualitative case study

IntroductionTelemetric monitoring of intracranial pressure (ICP) in children with a complex cerebrospinal disorder might help parents distinguish acute and potential life-threatening symptoms of hydrocephalus from other illnesses. Research questionWhat is patient and parent perceptions of system utility of telemetric ICP monitoring, and how does a long-term telemetric implant influence daily life of both patients and their families? Material and methodsA qualitative case study design with a focus group interview including parents of children with a complex cerebrospinal fluid disorder and an implanted telemetric ICP sensor. ResultsThree parents participated. Based on thematic analysis, three themes were created: ‘Daily living with telemetric ICP monitoring’, ‘Parenting a child with a CSF disorder’, and ‘The healthy sibling’. The ICP sensor provided the parents with security and made them trust their intuition, while the possibility of home monitoring ensured stability for the entire family and had a calming effect on healthy siblings. Home monitoring was seen as the system's greatest advantages, whereas size, weight, and functionality of the external monitoring equipment were highlighted as disadvantages. Discussion and conclusionAll parents supported the telemetric ICP sensor as a valued tool in treatment guidance of their child and stated that advantages exceeded disadvantages. It was stated that the possibility of conducting ICP measurements at home reduced the need for acute hospital admissions, which consequently led to a more stable daily life for the entire family. Suggestions regarding technical improvements with focus on more compatible external monitoring equipment were raised by all parents included.

The Impact of Valsalva Manoeuvres and Exercise on Intracranial Pressure and Cerebrovascular Dynamics in Idiopathic Intracranial Hypertension

ABSTRACT Idiopathic intracranial hypertension (IIH) is a disease characterised by elevated intracranial pressure (ICP). The impact of straining and exercise on ICP regulation is poorly understood yet clinically relevant to IIH patient care. We sought to investigate the impact of Valsalva manoeuvres (VMs) and exercise on ICP and cerebrovascular haemodynamics in IIH. People with IIH were prospectively enrolled and had an intraparenchymal telemetric ICP sensor inserted. Three participants (age [mean ± standard deviation]: 40.3 ± 13.9 years) underwent continuous real-time ICP monitoring coupled with cerebrovascular haemodynamic assessments during VMs and moderate exercise. Participants had IIH with supine ICP measuring 15.3 ± 8.7 mmHg (20.8 ± 11.8 cm cerebrospinal fluid (CSF)) and sitting ICP measuring −4.2 ± 7.9 mmHg (−5.7 ± 10.7 cmCSF). During phase I of a VM ICP increased by 29.4 ± 13.5 mmHg (40.0 ± 18.4 cmCSF) but returned to baseline within 16 seconds from VM onset. The pattern of ICP changes during the VM phases was associated to that of changes in blood pressure, the middle cerebral artery blood velocity and prefrontal cortex haemodynamics. Exercise led to minimal effects on ICP. In conclusion, VM-induced changes in ICP were coupled to cerebrovascular haemodynamics and showed no sustained impact on ICP. Exercise did not lead to prolonged elevation of ICP. Those with IIH experiencing VMs (for example, during exercise and labour) may be reassured at the brief nature of the changes. Future research must look to corroborate the findings in a larger IIH cohort.

Customized External Cranioplasty for Management of Syndrome of Trephined in Nonsurgical Candidates.

Craniectomies represent a lifesaving neurosurgical procedure for many severe neurological conditions, such as traumatic brain injury. Syndrome of trephined (SoT) is an important complication of decompressive craniectomy, and cranial reconstruction is the definitive treatment. However, many patients cannot undergo surgical intervention because of neurological status, healing of the primary surgical wound, or the presence of concurrent infection, which may prevent cranioplasty. To offer a customized external cranioplasty option for managing skull deformities for patients who could not undergo surgical intervention for definitive cranioplasty. We describe the design and clinical application of an external cranioplasty for a patient with a medical history of intractable epilepsy, for which she underwent multiple right cerebral resections with a large resultant skull defect and SoT. The patient had resolution of symptoms and restoration of a symmetrical skull contour with no complication at 17 months. Customized external cranioplasty can improve symptoms associated with SoT for patients who cannot undergo a definitive cranioplasty. In addition, inset monitoring options, such as electroencephalography or telemetric intracranial pressure sensors, could be incorporated in the future for comprehensive monitoring of the patient's neurological condition.

Long-Term Effect of Decompressive Craniectomy on Intracranial Pressure and Possible Implications for Intracranial Fluid Movements.

Decompressive craniectomy (DC) is used in cases of severe intracranial hypertension or impending intracranial herniation. DC effectively lowers intracranial pressure (ICP) but carries a risk of severe complications related to abnormal ICP and/or cerebrospinal fluid (CSF) circulation, eg, hygroma formation, hydrocephalus, and "syndrome of the trephined." To study the long-term effect of DC on ICP, postural ICP regulation, and intracranial pulse wave amplitude (PWA). Prospective observational study including patients undergoing DC during a 12-mo period. Telemetric ICP sensors (Neurovent-P-tel; Raumedic, Helmbrechts, Germany) were implanted in all patients. Following discharge from the neuro intensive care unit (NICU), scheduled weekly ICP monitoring sessions were performed during the rehabilitation phase. A total of 16 patients (traumatic brain injury: 7, stroke: 9) were included (median age: 55 yr, range: 19-71 yr). Median time from NICU discharge to cranioplasty was 48 d (range: 16-98 d) and during this period, mean ICP gradually decreased from 7.8±2.0 mm Hg to -1.8±3.3 mm Hg (P=.02). The most pronounced decrease occurred during the first month. Normal postural ICP change was abolished after DC for the entire follow-up period, ie, there was no difference between ICP in supine and sitting position (P=.67). PWA was markedly reduced and decreased from initially 1.2±0.7 mm Hg to 0.4±0.3 mm Hg (P=.05). Following NICU discharge, ICP decreases to negative values within 4 wk, normal postural ICP regulation is lost and intracranial PWA is diminished significantly. These abnormalities might have implications for intracranial fluid movements (eg, CSF and/or glymphatic flow) following DC and warrants further investigations.

Intracranial pressure before and after cranioplasty: insights into intracranial physiology.

Decompressive craniectomy (DC) is an emergency neurosurgical procedure used in cases of severe intracranial hypertension or impending intracranial herniation. The procedure is often lifesaving, but it exposes the brain to atmospheric pressure in the subsequent rehabilitation period, which changes intracranial physiology and probably leads to complications such as hydrocephalus, hygromas, and "syndrome of the trephined." The objective of the study was to study the effect of cranioplasty on intracranial pressure (ICP), postural ICP changes, and intracranial pulse wave amplitude (PWA). The authors performed a prospective observational study including patients who underwent DC during a 12-month period. Telemetric ICP sensors were implanted in all patients at the time of DC. ICP was evaluated before and after cranioplasty during weekly measurement sessions including a standardized postural change program. Twelve of the 17 patients enrolled in the study had cranioplasty performed and were included in the present investigation. Their mean ICP in the supine position increased from -0.5 ± 4.8 mm Hg the week before cranioplasty to 6.3 ± 2.5 mm Hg the week after cranioplasty (p < 0.0001), whereas the mean ICP in the sitting position was unchanged (-1.2 ± 4.8 vs -1.1 ± 3.6 mm Hg, p = 0.90). The difference in ICP between the supine and sitting positions was minimal before cranioplasty (1.1 ± 1.8 mm Hg) and increased to 7.4 ± 3.6 mm Hg in the week following cranioplasty (p < 0.0001). During the succeeding 2 weeks of the follow-up period, the mean ICP in the supine and sitting positions decreased in parallel to, respectively, 4.6 ± 3.0 mm Hg (p = 0.0003) and -3.9 ± 2.7 mm Hg (p = 0.040), meaning that the postural ICP difference remained constant at around 8 mm Hg. The mean intracranial PWA increased from 0.7 ± 0.7 mm Hg to 2.9 ± 0.8 mm Hg after cranioplasty (p < 0.0001) and remained around 3 mm Hg throughout the following weeks. Cranioplasty restores normal intracranial physiology regarding postural ICP changes and intracranial PWA. These findings complement those of previous investigations on cerebral blood flow and cerebral metabolism in patients after decompressive craniectomy.

In Reply: Long-Term Effect of Decompressive Craniectomy on Intracranial Pressure and Possible Implications for Intracranial Fluid Movements.

BACKGROUND Decompressive craniectomy (DC) is used in cases of severe intracranial hypertension or impending intracranial herniation. DC effectively lowers intracranial pressure (ICP) but carries a risk of severe complications related to abnormal ICP and/or cerebrospinal fluid (CSF) circulation, eg, hygroma formation, hydrocephalus, and "syndrome of the trephined." OBJECTIVE To study the long-term effect of DC on ICP, postural ICP regulation, and intracranial pulse wave amplitude (PWA). METHODS Prospective observational study including patients undergoing DC during a 12-mo period. Telemetric ICP sensors (Neurovent-P-tel; Raumedic, Helmbrechts, Germany) were implanted in all patients. Following discharge from the neuro intensive care unit (NICU), scheduled weekly ICP monitoring sessions were performed during the rehabilitation phase. RESULTS A total of 16 patients (traumatic brain injury: 7, stroke: 9) were included (median age: 55 yr, range: 19-71 yr). Median time from NICU discharge to cranioplasty was 48 d (range: 16-98 d) and during this period, mean ICP gradually decreased from 7.8 ± 2.0 mm Hg to -1.8 ± 3.3 mm Hg (P = .02). The most pronounced decrease occurred during the first month. Normal postural ICP change was abolished after DC for the entire follow-up period, ie, there was no difference between ICP in supine and sitting position (P = .67). PWA was markedly reduced and decreased from initially 1.2 ± 0.7 mm Hg to 0.4 ± 0.3 mm Hg (P = .05). CONCLUSION Following NICU discharge, ICP decreases to negative values within 4 wk, normal postural ICP regulation is lost and intracranial PWA is diminished significantly. These abnormalities might have implications for intracranial fluid movements (eg, CSF and/or glymphatic flow) following DC and warrants further investigations.

Telemetric intracranial pressure monitoring in children.

Repeated intracranial pressure (ICP) measurements are essential in treatment of patients with complex cerebrospinal fluid (CSF) disorders. These patients often have a long surgical history with numerous invasive lumbar or intracranial pressure monitoring sessions and/or ventriculoperitoneal (VP) shunt revisions. Telemetric ICP monitoring might be an advantageous tool in treatment of these patients. In this paper, we evaluate our experience with this technology in paediatric patients. During a 4-year period, we implanted telemetric ICP sensors (Raumedic NEUROVENT-P-tel) in 20 paediatric patients to minimise the number of future invasive procedures. Patients were diagnosed with hydrocephalus, idiopathic intracranial hypertension (IIH) or an arachnoid cyst. Most patients (85%) had a VP shunt at the time of sensor implantation. In total, 32 sensors were inserted in the 20 patients; the cause of re-implantation was technical malfunction of the implant. One sensor was explanted due to wound infection and one due to skin erosion. We experienced no complications directly related to the implantation/explantation procedures. A total of 149 recording sessions were conducted, including 68 home monitoring sessions. The median implantation period was 523days with a median duration of clinical use at 202days. The most likely consequence of a recording session was non-surgical treatment alteration (shunt valve adjustment or acetazolamide dose adjustment). Telemetric ICP monitoring in children is safe and potentially decreases the number of invasive procedures. We find that telemetric ICP monitoring aids the clinical management of patients with complex CSF disorders and improves everyday life for both patient and parents. It allows continuous ICP measurement in the patient's home and thereby potentially reducing hospitalisations, leading to significant cost savings.

Test-Retest Reliability of Outpatient Telemetric Intracranial Pressure Measurements in Shunt-Dependent Patients with Hydrocephalus and Idiopathic Intracranial Hypertension

Some patients with hydrocephalus and idiopathic intracranial hypertension treated for elevated intracranial pressure (ICP) with a cerebrospinal fluid shunt may continue to experience symptoms or develop new symptoms despite valve adjustments. Use of telemetric ICP measurements may help confirm clinical suspicion of cerebrospinal fluid underdrainage or overdrainage in these patients. However, point in time, duration, and activity during the measurements have never been standardized. We devised a simple, repeatable maneuver for outpatient telemetric ICP recording and evaluated its test-retest reliability. Data of patients who underwent ventriculoperitoneal or ventriculoatrial shunt placement and subsequent telemetric ICP sensor implantation were retrospectively reviewed. Telemetric ICP recordings in patients were conducted in a standardized manner: The standing-supine-sitting paradigm requires postural changes in 10-minute intervals over 30 minutes. First, the patient is requested to walk; second, to lay down; third, to sit down with a headrest elevation of 60°. ICP data (in mmHg) were reported as mean ± SD values. Test-retest validity was assessed using Pearson correlation analysis. We evaluated 66 ICP datasets obtained repeatedly with a time difference of at least 24 hours. Overall test-retest reliability was excellent (Pearson correlation coefficient 0.99, P < 0.001), as were the scores for individual postures: standing (correlation 0.98, P < 0.001), supine (correlation 0.98, P < 0.001), and sitting (correlation 0.99, P < 0.001). The sum of square differences of the test-retest measures reflected a comparable validity of all tested positions. We confirmed high test-retest reliability of the standing-supine-sitting paradigm for telemetric ICP measurements in the outpatient setting. High test-retest reliability should be considered as prerequisite for clinical decision making.

Feasibility of Telemetric Intracranial Pressure Monitoring in the Neuro Intensive Care Unit.

Intracranial pressure (ICP) monitoring is crucial in the management of acute neurosurgical conditions such as traumatic brain injury (TBI). However, pathological ICP may persist beyond the admission to the neuro intensive care unit (NICU). We investigated the feasibility of telemetric ICP monitoring in the NICU, as this technology provides the possibility of long-term ICP assessment beyond NICU discharge. In this prospective investigation, we implanted telemetric ICP sensors (Raumedic Neurovent-P-tel) instead of conventional, cabled ICP sensors in patients undergoing decompressive craniectomy. We recorded ICP curves, duration of ICP monitoring, signal quality, and complications. Seventeen patients were included (median age 55 years) and diagnoses were: severe TBI (8), malignant middle cerebral artery infarction (8), and spontaneous intracerebral hemorrhage (1). In total, 3015 h of ICP monitoring were performed, and the median duration of ICP monitoring was 188 h (interquartile range [IQR] 54-259). The ICP signal was lost 613 times (displacement of the reader unit on the skin) for a median of 1.5 min, corresponding to 0.8% of the total monitoring period. When the signal was lost, it could always be restored by realignment of the reader unit on the skin above the telemetric sensor. Sixteen of 17 patients survived the NICU admission, and ICP gradually decreased from 10.7 mm Hg (IQR 7.5-13.6) during the first postoperative day to 6.3 mm Hg (IQR 4.0-8.3) after 1 week in the NICU. All 17 implanted telemetric sensors functioned throughout the NICU admission, and no wound infections were observed. Therefore, telemetric ICP monitoring in an acute neurosurgical setting is feasible. Signal quality and stability are sufficient for clinical decision making based on mean ICP. The low sampling frequency (5 Hz) does not permit analysis of intracranial pulse wave morphology, but resolution is sufficient for calculation of derived indices such as the pressure reactivity index (PRx).

Intracranial Pressure-Guided Shunt Valve Adjustments with the Miethke Sensor Reservoir.

Telemetric intracranial pressure (ICP) monitoring seems to be a promising therapy-supporting option in shunt-treated patients. Benefits become obvious when headaches are unspecific and clinical symptoms cannot be related to possible overdrainage or underdrainage. In this study, we evaluated a new telemetric device to individually adjust shunt valves according to ICP measurements. Between December 2015 and November 2016, 25 patients with suspected suboptimal shunt valve settings underwent insertion of a telemetric ICP sensor (Sensor Reservoir; Christoph Miethke, Potsdam, Germany). Over a 1-year period, a total of 183 telemetric ICP measurements and 85 shunt valve adjustments were carried out. Retrospective statistic analyses focused on valve adjustments, ICP values, and clinical outcomes. ICP-guided valve adjustments positively changed the clinical state in 18 out of 25 patients. Clinical improvement over time was associated with significant changes of the valve settings and ICP values. Interestingly, a therapeutically normalized ICP profile was not automatically associated with clinical improvement. The Sensor Reservoir is an important and valuable tool for shunt-treated patients suffering from drainage-related problems. The possibility to simultaneously recognize and solve shunt problems represents the decisive advantage. Nevertheless, measurements with the Sensor Reservoir did not allow for the determination of default valve settings or universal target ICP values.

Biocompatibility evaluation of a thermoplastic rubber for wireless telemetric intracranial pressure sensor coating

This study investigated the biocompatibility of the experimental thermoplastic rubber Arbomatrix™ that will be used as the protective coating on a novel intracranial pressure (ICP) sensor silicon chip. Arbomatrix™ was benchmarked against biocompatible commercial silicone rubber shunt tubing in the brain via a rat model with 60-day implant duration. A bare silicon chip was also implanted. The results showed similar cellular distribution in the brain–implant boundary and surrounding tissues. Quantitative analysis of neuron and glia density did not show significant difference between implants. Through histological and immunohistochemical evaluation we conclude that Arbomatrix™ is well tolerated by the brain. Due to its exceptional barrier properties Arbomatrix™ has already been shown to be an excellent protective coating for new ICP monitoring chip.

Feasibility of telemetric ICP-guided valve adjustments for complex shunt therapy

The advances in shunt valve technology towards modern adjustable differential pressure (DP) valves and adjustable gravitational assisted valves result in an increasing complexity of therapeutical options. Modern telemetric intracranial pressure (ICP) sensors may be helpful in their application for diagnostic purposes in shunt therapy. We present our first experiences on telemetric ICP-guided valve adjustments in cases with the combination of an adjustable DP valve and adjustable gravitational unit. Four consecutive cases were evaluated in a retrospective review who had received a proGAV adjustable, gravitational assisted DP valve with secondary in-line implantation of an adjustable shunt assistant (proSA), together with a telemetric ICP sensor (Neurovent-P-tel) between December 2010 and June 2012 in our institution. The measured ICP values and the corresponding valve adjustments were analyzed in correlation with the clinical course and the cranial imaging of the patients. No surgery-related complications were observed after implantation of the proSA and the telemetric ICP sensor additional to the proGAV. ICP values could actively be influenced by adjustments of the respective valve units. An increase of the position depending resistance of the proSA resulted in significant attenuated negative ICP values for the standing position, while adjustments of the proGAV could be detected not only in a supine position but also in a standing position. A clinical improvement could be achieved in all cases. The combination of adjustability in the differential pressure valve and the gravitational unit reveals a complex combination which may be difficult to adapt only according to clinical information. Telemetric ICP-guided valve adjustments seem to be a promising tool as an objective measure according to different body positions. Further investigations are needed to select the patients for these costly implants.

Large-Scale Referencing of the Telemetric Neurovent-P-tel Intracranial Pressure Sensor in a Porcine Model

The Neurovent-P-tel sensor is a promising device for telemetric intracranial pressure (ICP) measurements in cases of complex hydrocephalus. Data on its accuracy within a broad ICP range are missing. We applied a porcine model for large-scale manipulation of the ICP values. The telemetric ICP sensor was referenced against ICP values measured directly from a water column within a riser tube. A total of 34 comparative ICP measurements within an ICP range from 2 cm H₂O to 31 mm Hg were performed. The mean difference between both measurement techniques was 0.4 mm Hg. The limits of agreement, where 95% of differences between both methods are expected, were from -2.4 to 3.1 mm Hg. The telemetric Neurovent-P-tel sensor system provides good accuracy within a broad range exceeding normal ICP values and might be useful in clinical practice.

A new ventriculoperitoneal shunt with a telemetric intracranial pressure sensor: clinical experience in 94 patients with hydrocephalus.

We have developed a telemetric intracranial pressure sensor (OSAKA telesensor; Nagano Keiki Seisakusyo Co. Ltd., Tokyo, Japan) and investigated the clinical usefulness of new ventriculoperitoneal shunting with an OSAKA telesensor, an on-off valve, and a programmable valve. The OSAKA telesensor was applied in 94 patients at Osaka Medical College between March 1986 and December 1995. Postoperative management, postoperative course, postural change of intracranial pressure (ICP), and zero drift of the OSAKA telesensor were investigated. ICP was measured easily in all patients with no inconvenience. The setting of the programmable valve was adjusted postoperatively 38 times in 25 patients. Postoperative ICP in the upright position was -14.9 +/- 4.5 mm Hg, and the difference in ICP between the supine and the upright position was about 20 mm Hg. The slope of the decrease in ICP with continuous postural changes from the supine to the upright position was steep until about 30 to 45 degrees but became incrementally less or even rose slightly about this angle. The initial slope was steeper when the shunt was open than when the shunt was closed; it was also steeper postoperatively than preoperatively. This initial slope, therefore, may indicate the intracranial compliance. Seven cases of shunt malfunction were diagnosed correctly by ICP measurements. Zero drift of the OSAKA telesensor was easily corrected by comparing the ICP reading from the telesensor with the puncture pressure in the on-off valve. The OSAKA telesensor is very useful in the postoperative care and pathophysiological evaluation of patients with hydrocephalus.

A New Ventriculoperitoneal Shunt with a Telemetric Intracranial Pressure Sensor: Clinical Experience in 94 Patients with Hydrocephalus

A New Ventriculoperitoneal Shunt with a Telemetric Intracranial Pressure Sensor: Clinical Experience in 94 Patients with Hydrocephalus

Intracranial pressure monitoring using a programmable pressure valve and a telemetric intracranial pressure sensor in a case of slit ventricle syndrome after multiple shunt revisions

A case of hydrocephalus showing slit ventricle syndrome after multiple shunt revisions was treated with a programmable pressure valve, and intracranial pressure was monitored with a telemetric sensor. High pressure setting produced positive and normal values of intracranial pressure in this patient. We report our experiences.

Ten-year follow-up on the performance of a telemetric intracranial pressure sensor

Ten-year follow-up on the performance of a telemetric intracranial pressure sensor

Ten-Year Follow-up on the Performance of a Telemetric Intracranial Pressure Sensor

A permanently implanted epidural sensor has permitted long term telemetric intracranial pressure monitoring in selected neurosurgical patients. The sensor, consisting only of an inductance and a pressure-sensitive capacitance, has been implanted in 127 patients. Of these 127 patients, 13 have continued to have the sensor in place for 4 to 9 years (average, 6.8 +/- 0.44 years). The remaining patients were lost to follow-up or the sensor was removed. The sensor has been evaluated from the standpoint of accuracy, longevity, safety, and stability. Longevity was proven by successful monitoring over periods of years (in 1 patient, at least 9 years). The sensor has been a safe tool; the only morbidity has been two asymptomatic perisensor blood clots in 2 patients. There have been no infections in any of the 127 cases. The stability of the sensor was evaluated by measuring base line drift over time. This rate was 1.0 +/- 0.2 mm H2O/day. Causes of the drift and possible solutions are discussed, and the sensor is compared to other epidural telemetric monitoring systems.