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Telemetric intracranial pressure monitoring in children

Abstract

Purpose

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.

Methods

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.

Results

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 523 days with a median duration of clinical use at 202 days. The most likely consequence of a recording session was non-surgical treatment alteration (shunt valve adjustment or acetazolamide dose adjustment).

Conclusion

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.

Introduction

Repeated intracranial pressure (ICP) measurements are often essential in treatment of patients with complicated cerebrospinal fluid (CSF) disorders. Telemetric ICP monitoring allows continuous ICP measurement in the patient’s home environment. A hospitalised child will often be more inactive than a child at home and telemetric ICP monitoring can therefore be useful to give a more accurate picture of ICP variations in the paediatric patient. Additionally, telemetric ICP monitoring can guide shunt valve settings and ICP lowering medical treatment (acetazolamide) and makes direct observation of treatment effect possible without exposing the child to the risks of repeated invasive procedures.

In 2014, we reported our experience with telemetric ICP monitoring in 21 adult and paediatric cases [1]. Since publishing our initial experience, we have implanted more than 100 telemetric ICP sensors [2]. With very few exceptions, we still reserve telemetric ICP monitoring for patients which are otherwise challenging to manage (often with a history of repeated cabled ICP sensor insertions and several shunt surgeries) and for long-term follow-up of patients with idiopathic intracranial hypertension (IIH).

We have been using the telemetric ICP monitoring system from Raumedic (Raumedic AG, Helmbrechts, Germany) since 2010. Neurosurgeons and researches have used this system in a variety of clinical settings [3,4,5,6,7,8,9]. Few complications have been reported (perifocal edema, cerebral haemorrhage, seizure, intracranial infection, superficial wound infection and technical failure [9, 10]) and the rate of these complications is comparable to insertion of a conventional, cabled ICP sensor [11,12,13]. However, the telemetric ICP sensor is challenged by an implantation period limited to 3 months by the manufacturer as well as an inherent risk of baseline drift. Recently, we reported a median baseline drift of 2.5 mmHg over a median implantation time of 241 days [2]. In recent years, Miethke (Christoph Miethke GmbH & Co. KG, Potsdam, Germany) has developed an ICP sensor reservoir designed for integration into a shunt system. This system has a longer implantation period and higher sampling frequency, but cannot yet provide continuous ICP monitoring or data storage for analysis (Table 1) [14, 15].

Table 1 Different methods of performing ICP measurements and their advantages/disadvantages. ICP can be measured telemetrically by a sensor reservoir (from Miethke/Aesculap) or by a parenchymal sensor (from Raumedic). Both telemetric systems are position independent and can be used to monitor positional ICP changes. The ICP sensor reservoir can, however, only be used as short-term monitoring, whereas the telemetric ICP sensor can be used for long-term monitoring. Another advantage of the telemetric ICP sensor is the continuous home monitoring

Telemetric ICP sensor technology might be a useful alternative to conventional, cabled ICP technology in paediatric patients, but clinical experience is still limited to case reports [5, 7, 8, 16] and small (mixed paediatric and adult) patient cohorts [1, 2, 9, 10, 17]. The objective of this study was to evaluate and summarise our experience with the use of long-term telemetric ICP monitoring in paediatric patients, including advantages and clinical challenges specific to the paediatric patient.

Methods

Telemetric ICP monitoring system

The telemetric ICP monitoring system from Raumedic has been available since 2009. It consists of three parts: (1) a passive sensor implant (NEUROVENT-P-tel), an active reader (Reader TDT1 readP) and a portable storage unit (MPR 1 DATALOGGER). The sensor is MRI conditional for a field strength up to 3 Tesla. ICP monitoring data can be viewed on the storage unit for quick referencing and transferred to a PC using the supplied software (DataView, previous version named Datalog) for further analysis. The sensor implant uses a piezoelectric strain gauge transducer placed on the tip of a parenchymal catheter (length 30.0 mm, diameter 1.7 mm). The catheter connects to the disc-shaped ceramic housing (diameter 31.5 mm, height 4.3 mm) containing the microchip responsible for data processing. The sensor implant is activated and powered by the reader using a radiofrequency technique. Data is transferred to the storage unit through a proprietary cable [9].

The telemetric ICP sensor is usually implanted through a frontal burr hole (contralateral to an existing shunt system if in place), but can also be placed in a parietal location. In paediatric patients, the procedure is performed under general anaesthesia. Generally, sensor explantation is straightforward, but in some cases and particularly after long-term implantation, it might be necessary to pry the sensor free from a bony reaction around its periphery. In rare cases, the transducer tip is stuck in the brain tissue and in these cases, the parenchymal catheter is simply cut—leaving the transducer tip in situ intracranially and removing only the external ceramic housing.

Patient selection

For this study, we included all patients under the age of 18 years with a telemetric ICP sensor inserted at Rigshospitalet (Copenhagen, Denmark) from September 1, 2013, to December 31, 2017. Follow-up ended June 30, 2018. There were no exclusion criteria. Patients were identified retrospectively in the surgical planning system using a unique registration code. The following data were retrieved from electronic patient records: baseline demographics (age, sex, diagnosis, indication for implantation), surgical information (location, anaesthesia type, complications, explantation procedure) and data concerning ICP monitoring (number of recording sessions, clinical treatment decision made following each ICP recording session, technical problems, reasons for explantation).

Interpretation of collected ICP data

The ICP recording sessions are analysed by a team of hydrocephalus specialists. Telemetric ICP curve analysis is performed using the same criteria as for ICP curves obtained through conventional, cabled ICP sensors, but with attention to the limitations of the telemetric ICP sensor technology (baseline drift, loss of signal, underestimation of amplitude due to low sampling frequency). Particular attention is paid to matching the clinical information to the ICP data, as drift and biological reaction around the sensor may cause discrepancy between measured and actual ICP. It is assessed if average ICP during day-time and night-time is within reference values. Pulse wave amplitude level and presence of B waves (Fig. 3a–c) are noted and a conclusion for the entire ICP recording session in relation to the patient’s symptoms and neuro-imagining is established for clinical decision-making.

Statistics

Data management and statistical analysis were carried out in SAS 9.4 (SAS Institute Inc., Cary, NC, USA). For all data, the median, range and interquartile range are presented. Differences in the clinical treatment decision between diagnoses were detected with a chi-square test. A p value < 0.05 was considered statistically significant.

Glossary/definitions

Sensor implantation period = time from implantation to explantation or end of follow-up.

Duration of clinical use = time from implantation to last ICP recording session performed, in which the telemetric ICP sensor is in clinical use.

ICP recording session = an ICP monitoring session typically consisting of at least 24 h of measurements (including both day and night).

ICP home monitoring = the use of the telemetric ICP monitoring system outside the hospital.

Results

Patient characteristics

During the study period, 20 children had a NEUROVENT-P-tel sensor implanted (male = 13, median age at implantation n = 11 years, range 2–18 years, IQR 7–15). Patients had diagnoses of hydrocephalus (n = 12, age range 2–18), IIH (n = 7, age range 7–17) or arachnoid cyst (n = 1, age 13). Seventeen of the 20 patients had a shunt at implantation (ventriculoperitoneal, 15; ventriculoatrial, 1; or lumboperitoneal, 1).

Sensor implantation and removal

Thirty-two sensors were implanted in the 20 patients (Table 2). During the study period, 12/20 patients had only one sensor implanted, while 8/20 patients had the sensor exchanged: six patients had two sensors implanted and two patients had a total of four sensors implanted. The reasons for re-implantation were technical defects of the sensors.

Table 2 The median implantation period, median reading period and median number of ICP recording sessions for each diagnosis. Patients with hydrocephalus had a shorter median reading period and a shorter median implantation period compared to both patients with IIH and the one patient with an arachnoid cyst

The indications for implantation were diagnostic evaluation (n = 4/32) or therapeutic evaluation (n = 28/32). All surgical implantations were performed in general anaesthesia through either a left (n = 24/32) or right (n = 8/32) frontal burr hole. In total, 17 sensors were explanted during the study period: 12 due to a technical defect (37.5%), one due to a superficial wound infection (3%), one due to skin erosion (3%), while three were removed on patient’s or parents’ request when they were no longer needed for treatment guidance (9.5%). There were no surgical complications related to implantation or explantation procedures. Figure 1 a and b show median implantation period (n = 523 days, range 42–2067, IQR 146–930) and median duration of clinical use (n = 202 days, range 8–1176, IQR 89–525).

Fig. 1
figure1

The telemetric ICP sensor. a Sensor implantation period (time from implantation to explantation or end of follow-up). The sensors are sub-grouped according to diagnoses. The period is divided into 6-month intervals: < 6 months, 6–12 months, 13–18 months and > 18 months. The median implantation period was 523 days (> 17 months, range 42–2067 days, IQR 146–930 days). In total, 17/32 sensors were explanted within the follow-up period. b Duration of clinical use (time from implantation to last monitoring session performed, in which the sensor is in clinical use). The sensors are sub-grouped according to diagnoses. The duration of clinical use is divided in 6-month intervals: < 6 months, 6–12 months, 13–18 months and > 18 months. The median duration of clinical use was 202 days (> 6 months, range 8–1176 days, IQR 89–525). c Number of ICP recording sessions. The number of ICP monitoring sessions per patient is divided into four groups: 1–5 recordings, 6–10 recordings, 11–15 recordings and > 15 recordings. Furthermore, the patients are sub-grouped by diagnoses. Median number of recording sessions per patient was four and in 11/20 patients, six recording sessions or fewer were performed. IIH idiopathic intracranial hypertension

ICP monitoring

A total of 149 ICP recording sessions were conducted (Table 3) with 68 recordings performed as home monitoring sessions. Figure 1c shows the number of ICP recording sessions per patient (median = 4, range 1–35, IQR 2–9). Overall, 33% of the recording sessions resulted in non-surgical treatment alteration (shunt valve adjustment (31%) or acetazolamide dose adjustment (2%)), 21.5% led to surgical shunt revision, 17.5% led to a new ICP recording session, 15% led to no direct action and finally 13.5% resulted in explantation of the sensor. Patients with IIH were more likely to have another ICP recording session compared to the patients with hydrocephalus (IIH 31%, hydrocephalus 11%, p = 0.03), whereas patients with hydrocephalus were more likely to have a non-surgical treatment alteration (shunt valve adjustment/acetazolamide dose adjustment) (IIH 20%; hydrocephalus, 40%; p = 0.02).

Table 3 The result of each ICP recording session according to diagnosis. The results are given as an absolute number and as a percentage. It should be noted that all patients with hydrocephalus had a shunt system implanted, while this was true for only 4/7 patients with idiopathic intracranial hypertension

Cases

The following two cases illustrate the typical clinical use (slightly modified for patient anonymity).

Case 1

A 14-year-old boy with aqueductal stenosis and shunt treated hydrocephalus referred for second opinion with only few and uncomplicated revisions until age 12, when the number of shunt revisions gradually escalated to almost a monthly surgical revision during the last 6 months before referral. ETV (endoscopic third ventriculostomy) was attempted, but the patient continued to be symptomatic with dilated ventricles despite ample flow signal through the ETV. A shunt system with adjustable differential pressure and gravitational valves was inserted, and because of the preceding shunt-history, a telemetric ICP sensor was implanted contralateral to the shunt during the same procedure. Guided by repeated ICP recording sessions, the valves were adjusted to secure a day-time ICP between − 5 and 0 mmHg and a night-time ICP between 5 and 10 mmHg [18]. The patient’s complaints however continued, with severe headaches, low energy level and absence from school, however with periods when he was active, happy and almost asymptomatic. This led to a shunt revision with valve replacement, but intraoperatively, the valves were found to be functional. Postoperative ICP recording sessions were still within accepted ranges and the clinical situation was likewise unchanged. The family requested another type of adjustable valve to be tried, which did not improve the clinical symptoms, but worsened the ICP management to either day-time overdrainage at low settings or night-time underdrainage at high settings (Fig. 2a). By meticulously going over the symptoms and telemetric ICP recording sessions with the patient and his parents, a decision was made to return to the shunt system with adjustable differential pressure and gravitational valves. Valve settings were optimised to achieve small negative values upright and stable throughout day-time and small positive values supine and stable throughout night-time. Scheduled out-patient visits and several sessions of ICP home monitoring (Fig. 2b, c) helped the patient and his parents to accept that ICP was as well managed as possible and that periods with more symptoms vs. periods with less/no symptoms were not reflected in the ICP. It was suspected that many of the remaining symptoms could be attributed to ‘medication overuse headache’ (MOH) [19] and as he was weaned off analgesics eventually his activity level increased, and gradually he returned to school. During the last year and a half, the patient has only been seen for routine visits in the out-patient clinic, is in a stable almost headache-free condition and continues a normal level of daily activities and school attendance.

Fig. 2
figure2

Case 1: a 14-year-old boy with shunt treated hydrocephalus. a Home ICP monitoring; example from day-time curve. Overdrainage documented by markedly negative ICP values which gradually decreased even further. ICP range between − 8 and − 13 mmHg. b Home ICP monitoring; example from day-time curve showing corrected overdrainage with ICP now between − 3 and 2 mmHg. The fluctuations to the right are normal postural changes. Seen together with Fig. 2c, it is documented that this was not at the expense of nocturnal underdrainage. c Home ICP monitoring; example from night-time curve showing an even curve with small alterations related to changed sleep position. Mean ICP is between 2 and 10 mmHg. ICP intracranial pressure

This case shows how ICP home monitoring can be used to guide the clinical management, but just as importantly for patient and family to be able to ascertain that dysregulated ICP was not the explanation for continued symptoms and to point to another treatable cause (MOH).

Case 2

A 15-year-old girl presented with a transient 7th nerve palsy and headache. The following examinations were all normal: BMI, neurological exam, MRI, ophthalmology exam including no papilledema, CSF cytology and serology. Lumbar puncture opening pressure (LPO) with sedation was 250–280 mmH2O. Because of the symptoms and LPO, ‘papilledema-negative-IIH’ was suspected. ICP measured with a cabled ICP sensor for 48 h showed day-time 5 mmHg on average, but with increased amplitude and many small B waves (Fig. 3a) interpreted as moderately abnormal day-time ICP. Night-time ICP was baseline 15 mmHg with an even pattern 50% of the time interrupted by elevation of mean ICP to 25 mmHg and tall B waves in 30–60 min sequences (Fig. 3b). Polysomnography ruled out sleep apnoea and other sleep disturbances. As her vision was not threatened, she was referred for pharmacological treatment with acetazolamide, but never reached therapeutic dose because of side effects and non-compliance. She continued to have relentless headaches, worse in the mornings, preventing her from school and daily activities. It was decided to implant a shunt with a flow-regulation valve. Headaches disappeared for 2 months, but then re-appeared. Meticulous questioning could not reveal any postural or diurnal variation of the headache, so it was uncertain if the headache was caused by insufficient ICP management, overdrainage, shunt malfunction or other causes unrelated to ICP. Because ICP could not be followed through eye examinations, and it was considered likely that repeated ICP measurements could be needed, a telemetric ICP sensor was implanted. ICP home monitoring for 48 h showed normalised day-time ICP, but unchanged night-time ICP. It was assessed that the shunt was functional, but not optimising the patient’s ICP, and the valve was changed to serial adjustable differential pressure and gravitational valves. The valves were adjusted guided by ICP home monitoring sessions with some improvement of symptoms. As the patient’s activity level increased, an additional series of valve adjustments were needed to prevent overdrainage. Although her condition improved, she still had headaches almost daily and it was difficult to distinguish if they were shunt/ICP related or if they originated from other causes. When the telemetric ICP sensor stopped working after 5 months, it was therefore replaced. Guided by ICP recording sessions, a few minor adjustments were made and ICP was now within normal limits both day and night (Fig. 3c, d). The patient had a residual headache, but it was less severe and not daily. She was now able to finish school and start training as a nurse assistant.

Fig. 3
figure3

Case 2: a 15-year-old girl with ‘papilledema-negative-IIH’. a Primary diagnostic ICP measurement (day-time curve) with cabled ICP sensor. Mean ICP is only around 5 mmHg, but amplitude was increased, and many B waves were seen. b Primary diagnostic ICP measurement (night-time curve) with cabled ICP sensor. Nocturnal ICP was baseline 15 mmHg on average with an even pattern 50% of the time interrupted by sequences lasting 30–60 min with elevation of mean ICP to 25 mmHg and tall B waves. c Home ICP monitoring; example from day-time curve showing ICP stable at − 4 mmHg. There is still moderately increased amplitude and some B wave activity, but considerably reduced. d Home ICP monitoring; example from night-time curve. Mean ICP 5–6 mmHg mostly with an even amplitude interrupted by a periodic irregular pattern, which is both shorter in duration and much reduced in ICP and amplitude increase; probably close to normal sleep stage changes. ICP intracranial pressure

This case shows how repeated ICP monitoring may be used to guide treatment in IIH. Quite often, a residual headache persists in this disease even when ICP is optimised. When eye findings cannot be used to infer if ICP is elevated—because of ‘papil-edema-negative-IIH’ as in this case or because of secondary chronic atrophy—repeated documentation of ICP can be particularly useful and can avoid unnecessary surgical or adjustment interventions on the shunt system. As in case 1, it is important for the patient and family to be able to ascertain that the residual headache is not caused by dysregulated ICP.

Discussion

Telemetric ICP monitoring is a developing field and to our knowledge, the present paper is the largest published study in an exclusively paediatric population [1, 2, 5, 7,8,9,10, 16, 17]. In the present evaluation (n = 20), 65% of our paediatric patients monitored with telemetric ICP sensors were boys and median age was 11 years. The majority of patients were diagnosed with hydrocephalus (60%) and in most cases, they had a shunt system at time of sensor implantation (85%). The patients often had a complex medical history with many invasive attempts to improve shunt treatment or adjustments of acetazolamide dose. In the present paper, we report our four main observations using telemetric ICP sensor technology in a paediatric population; firstly, the overall clinical complication rate is low with superficial wound infection and skin erosion being the only complications observed. Secondly, long-term implantation and ICP data acquisition is possible beyond the currently approved 3 months implantation period. Thirdly, based on ICP recording sessions, the majority of patients underwent an optimisation of their treatment (change in shunt valve setting or acetazolamide dose) without being exposed to risks of surgery and general anaesthesia. Finally, the management of the disease and involvement of the patient and the parents is often improved through the possibility of performing repeated ICP recording sessions.

Clinical complications

Out of a total of 32 sensors, only one sensor was explanted due to superficial wound infection and one due to skin erosion within the study period. Previously, Antes et al. reported an overall complication rate of 7.3% within the approved implantation time of 3 months in 247 (incl. 10 paediatric) patients. In the present study, no complications occurred within the first 3 months and the overall clinical complication rate within the complete study period was 6%. In the study by Antes et al., complications were intracerebral haemorrhage (0.4%), new-onset seizures (4.5%), intracranial infection (0.8%) and superficial wound infection (1.6%) [9]. In our series, no intracerebral complications (haemorrhage, seizures or infection) occurred from the surgical implantation, during the immediate postoperative period or during the entire follow-up period.

Sensor implantation, duration of clinical use and ICP recording sessions

The 32 telemetric ICP sensors were implanted for a median period of 523 days. The median duration of clinical use was 202 days. This is more than twice the implantation period recommended by the manufacturer. In our experience, telemetric ICP sensors can be left in situ and used for monitoring as long as the readings are evaluated with special attention to the possibility of baseline drift (see ‘Technical challenges’).

In this exclusively paediatric population, there was a tendency to perform additional ICP measurements as a consequence of an inconclusive ICP recording session. Furthermore, approximately 2/3 of the recording sessions led to a non-invasive treatment alteration (change in shunt valve setting or acetazolamide dose). This could be interpreted as if telemetric ICP monitoring results in fewer unnecessary surgical interventions on shunt systems, thus facilitating a strategy of a ‘non-surgical-watchful-waiting’ philosophy in children. However, it could also simply indicate that the telemetric accessibility to ICP assessment increased the tendency to perform more ICP measurements. We found that an ICP recording session in patients with IIH more often led to a new ICP monitoring instead of an active treatment alteration, compared to patients with hydrocephalus. This could indicate that patients with IIH benefit from several continuous ICP recording sessions in order to obtain the correct treatment [20]. Hence, this patient group might benefit from a telemetric ICP sensor at the beginning of a diagnostic evaluation and in this way avoid possible several invasive ‘one-time’ pressure monitoring sessions (by lumbar puncture or cabled ICP monitoring).

Ethical considerations

Several ethical aspects must be considered before measuring ICP in the paediatric patient. Traditionally ICP is measured either by lumbar puncture or by surgical intracranial insertion of a cabled ICP sensor with subsequent short-term monitoring (maximally a few days) (see Table 1) [14]. The need for repeated ICP measurements leads to repeated invasive procedures, including risks and discomfort associated with sedation/anaesthesia and surgery. The telemetric ICP monitoring facilitates home monitoring which reduces hospitalisation of the child and improves the patients’ (and the parents’) experience, along with a significant cost saving on hospital admissions and imaging requirements [17].

The two cases illustrate how ICP home monitoring can be a useful tool in ICP management, be used to educate patients and their parents to distinguish between ICP-related headache and point to other causes of persisting headache unrelated to ICP dysregulation, and finally be used to guide treatment in IIH, when eye findings and residual headache cannot be used to infer if ICP is still elevated. The drawback is that the easy access to ICP assessment can also lead to an increased demand to control ICP, despite an already well-managed pressure.

Technical challenges

The Raumedic telemetric ICP sensor is a CE approved device with an approved implantation time of 3 months. However, by Danish law, we are not obliged to remove the device after this period. To avoid unnecessary surgical risks, we decided from the beginning to leave the device implanted unless a specific clinical need for explantation occurred either for patient safety reasons (e.g. infection, skin erosion, local pain) or because of the patient’s or the parents’ desire. This policy resulted in the majority of implanted sensors being left in situ, which has given us the opportunity to examine the long-term behaviour beyond the manufacturer recommended period for clinical use. In a recent publication (mixed paediatric and adult cases), we document that (1) 89% of the telemetric ICP sensors are functional at the end of the 3 months period, (2) the median duration of clinical use is longer than 6 months and (3) re-implantations of a telemetric ICP sensor through an existing burr hole have a shorter survival, probably related to a biological reaction around the transducer tip [2].

The telemetric ICP monitoring system used in our clinical practice has been commercially available for almost a decade. There is still potential for technical improvements. Based on our current experience, suggestions for improvements could be an enhanced equipment design, increasing the signal sampling frequency and extending implant survival.

The telemetric ICP sensor has no integrated memory or power source, meaning that the child must have the reader fixed externally to the head kept in place directly over the sensor and the storage unit (measuring 200 × 150 × 69 mm (W × H × D), approx. 0.950 kg) must be carried around. Long-term monitoring with the child in its daily environment is the systems upside and we therefore suggest the development of an even more handy wireless system, e.g. one of the following combinations: (1) a passive sensor implant, an active reader externally fixed to a small portable unit (no more than 40 × 30 × 10 mm) with an incorporated wireless unit and a battery, and a storage unit with a wireless unit; (2) an active sensor implant with an incorporated wireless unit, a small passive portable unit (no more than 40 × 30 × 10 mm) with a battery and a storage unit with a wireless unit; (3) an active sensor implant with an incorporated wireless unit and a rechargeable battery and a storage unit with a wireless unit.

Data (mixed paediatric and adult cases) from our research group indicates a technical malfunction percentage at 11% within the first 3 months period [2], whereas Antes et al. only reported a technical defect in 2.8% [9]. A possible explanation for the technical malfunction could be a biological reaction around the transducer tip, most likely due to an inflammatory response. Similar findings and concerns have been published for other types of brain implants, and this has also previously been described as a concern in telemetric ICP monitoring [21, 22]. Sensor material comparable to the density of the brain tissue could lower the reactive response to the implanted foreign body [23]. In the present exclusively paediatric population, no patients had the telemetric ICP sensor explanted due to technical malfunction within the first 3 months. The first sensor explant (due to technical malfunction) happened after 102 days. During the entire study period, 37.5% of the telemetric ICP sensors were explanted due to technical defect. Why children present this different rate of technical malfunction is unclear and further study is needed for clarification.

Limitations

The implantation period was presented with a wide range from 42 to 2067 days. However, only one telemetric ICP sensor had a study implantation period less than 3 months (42 days) and this was due to end of follow-up (June 30, 2018).

The study is based on retrospective data collection and thereby limited to data in patient records. Furthermore, the patient population is relatively small, and extrapolation should be made with caution. The results could however add to the experience of telemetric ICP monitoring in the paediatric patient population.

Conclusion

The telemetric ICP sensor technology is a useful tool in clinical management of the paediatric patient with either a complex history of shunt treated hydrocephalus or complicated IIH (including ‘papilledema-negative-IIH’ and cases with secondary chronic pupil atrophy). The technology might decrease the number of (potentially unnecessary) invasive surgical procedures and facilitates the use of a safe ‘non-surgical-watchful-waiting’ philosophy in the paediatric patient. We recommend continuous development of the technology to complete its full potential. With further technical development and increasing clinical experience, the methodology may provide important steps towards physiologically improved ICP management and even ‘the intelligent shunt’.

Abbreviations

ICP:

Intracranial pressure

CSF:

Cerebrospinal fluid

Acetazolamide:

Carbonic anhydrase inhibitor, sales name: Diamox

IIH:

Idiopathic intracranial hypertension

MRI:

Magnetic resonance imaging

ETV:

Endoscopic third ventriculostomy

MOH:

Medication overuse headache

BMI:

Body mass index

LPO:

Lumbar puncture opening pressure

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Correspondence to Sarah Hornshøj Pedersen.

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Pedersen, S.H., Norager, N.H., Lilja-Cyron, A. et al. Telemetric intracranial pressure monitoring in children. Childs Nerv Syst 36, 49–58 (2020) doi:10.1007/s00381-019-04271-4

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Keywords

  • Telemetric; telemetry
  • Children; paediatric
  • ICP; intracranial pressure
  • Hydrocephalus
  • IIH; idiopathic intracranial hypertension
  • Raumedic