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 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).
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.
KeywordsTelemetric; telemetry Children; paediatric ICP; intracranial pressure Hydrocephalus IIH; idiopathic intracranial hypertension Raumedic
Carbonic anhydrase inhibitor, sales name: Diamox
Idiopathic intracranial hypertension
Magnetic resonance imaging
Endoscopic third ventriculostomy
Medication overuse headache
Body mass index
Lumbar puncture opening pressure
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 . Since publishing our initial experience, we have implanted more than 100 telemetric ICP sensors . 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).
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
Cabled (conventional) ICP sensor1
Telemetric ICP (Miethke)
Telemetric ICP (Raumedic)
Max. 20 min
Max. 10 min
24 h—several days
Day and night
Day and night
Hospitalisation or home monitoring
Hospitalisation or home monitoring
Lumbar puncture position may influence measurement
Stationary or position independent
Only measurement lateral horizontal
Limited or full mobilisation
Measurement with positional changes
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.
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 .
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.
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.
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.
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.
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
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
Number of sensors
Implantation period (days)
Reading period (days)
ICP recording sessions
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
No direct action
New ICP monitoring
Shunt valve adjustment
Explantation of sensor
The following two cases illustrate the typical clinical use (slightly modified for patient anonymity).
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).
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.
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.
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%) . 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 . 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).
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) . 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 .
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.
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 .
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 , whereas Antes et al. only reported a technical defect in 2.8% . 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 . 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.
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.
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’.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 6.Kiefer M, Antes S, Schmitt M et al (2011) Long-term performance of a CE-approved telemetric intracranial pressure monitoring. Conf Proc IEEE Eng Med Biol Soc:2246–2249. https://doi.org/10.1109/IEMBS.2011.6090426
- 8.Magnéli S, Howells T, Saiepour D, Nowinski D, Enblad P, Nilsson P (2016) Telemetric intracranial pressure monitoring : a noninvasive method to follow up children with complex craniosynostoses. A case report. Childs Nerv Syst 32:1311–1315. https://doi.org/10.1007/s00381-016-3023-4 CrossRefPubMedGoogle Scholar
- 11.Kasotakis G, Michailidou M, Bramos A, Chang Y, Velmahos G, Alam H, King D, de Moya MA (2012) Intraparenchymal vs extracranial ventricular drain intracranial pressure monitors in traumatic brain injury: less is more? J Am Coll Surg 214:950–957. https://doi.org/10.1016/j.jamcollsurg.2012.03.004 CrossRefPubMedGoogle Scholar
- 12.Dimitriou J, Levivier M, Gugliotta M (2016) Comparison of complications in patients receiving different types of intracranial pressure monitoring: a retrospective study in a single center in Switzerland. World Neurosurg 89:641–646. https://doi.org/10.1016/j.wneu.2015.11.037 CrossRefPubMedGoogle Scholar
- 13.Ma R, Rowland D, Judge A, Calisto A, Jayamohan J, Johnson D, Richards P, Magdum S, Wall S (2018) Complications following intracranial pressure monitoring in children: a 6-year single-center experience. J Neurosurg Pediatr 21:278–283. https://doi.org/10.3171/2017.9.PEDS17360 CrossRefPubMedGoogle Scholar