Sebastian Antes

Telemetric ICP Measurement with the First CE-Approved Device: Data from Animal Experiments and Initial Clinical Experiences

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic(®) NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedics NEUROVENT(®) P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.

Long-term performance of a CE-approved telemetric intracranial pressure monitoring

Telemetric intracranial pressure (ICP) monitoring has been a challenge throughout several decades. Major obstruction was to minimize zero drift of absolute pressure sensors. A new promising product demonstrating in-vitro excellent long-term stability has been tested for its reliability in an animal model with a follow-up of up to 2 years. In “minipigs” sub-dural (Raumedic-STel®, Helmbrechts Germany) and intrapa-renchymal (Raumedic-PTel®) telemetric ICP probes have been inserted. Standard ICP probes (Raumedic Neurovent P®) served as controls. In regular intervals of 3 months the teleme-trically and conventionally measured ICP have been compared. For each control a new conventional ICP probe has been inserted frontally to the telemetric device in the generalized anesthetized minipigs, resulting in overall 38 comparisons. Bland-Altman-plots, Chi2-tests and matched pair T-tests (significance level < 0.05) were used for data-analysis. The zero-shift was −1.7±7.6 mm Hg (limits of agreement: 4.4±1.9 mm Hg) and −3.0±6.0 mm Hg (limits of agreement: 3.6±2.6 mm Hg) in STel and PTel respectively meeting well the devices specification of ±2 mm Hg drift per year. The reliability of both telemetric probes has been proved as quite comparable (p=0.2). These new telemetric ICP probes demonstrate reliable data during at least the first 6 months after implantation.

The use of intraoperative computed tomography navigation in pituitary surgery promises a better intraoperative orientation in special cases.

Objective: The safety of endoscopic skull base surgery can be enhanced by accurate navigation in preoperative computed tomography (CT) and magnetic resonance imaging (MRI). Here, we report our initial experience of real-time intraoperative CT-guided navigation surgery for pituitary tumors in childhood. Materials and Methods: We report the case of a 15-year-old girl with a huge growth hormone-secreting pituitary adenoma with supra- and perisellar extension. Furthermore, the skull base was infiltrated. In this case, we performed an endonasal transsphenoidal approach for debulking the adenoma and for chiasma decompression. We used an MRI neuronavigation (Medtronic Stealth Air System) which was registered via intraoperative CT scan (Siemens CT Somatom). Preexisting MRI studies (navigation protocol) were fused with the intraoperative CT scans to enable three-dimensional navigation based on MR and CT imaging data. Intraoperatively, we did a further CT scan for resection control. Results: The intraoperative accuracy of the neuronavigation was excellent. There was an adjustment of <1 mm. The navigation was very helpful for orientation on the destroyed skull base in the sphenoid sinus. After opening the sellar region and tumor debulking, we did a CT scan for resection control because the extent of resection was not credible evaluable in this huge infiltrating adenoma. Thereby, we were able to demonstrate a sufficient decompression of the chiasma and complete resection of the medial part of the adenoma in the intraoperative CT images. Conclusions: The use of intraoperative CT/MRI-guided neuronavigation for transsphenoidal surgery is a time-effective, safe, and technically beneficial technique for special cases.

Aqueductal stenting with an intra-catheter endoscope—a technical note

IntroductionAqueductoplasty as well as aqueductal stenting is an accepted therapy option in short-segment aqueductal stenosis and isolated fourth ventricle. Over the years, different techniques with only slight modifications by using a conventional neuroendoscope with a working sheath to introduce different instruments have been presented. In summary, the use of Fogarty balloon catheters or flexible endoscopes to pass the narrowed aqueduct is recommended.MethodsThis technical report describes a substantially new technique for this purpose. Six patients underwent aqueductal stenting with a new intracatheter endoscope.ResultsAqueductal stenting was possible in 4 out of 6 cases. No complications occurred. Handling of this new technique was good and easy without a prolonged learning curve. All four stents did work appropriately, and the procedure was considered to be successful. Of the two failures, the technique was abandoned and endoscopic third ventriculostomy (ETV) was performed in one. In the other case, suboccipital shunting was done.ConclusionThis technical report describes a substantially new technique for aqueductal stenting. The combination of an intracatheter miniature endoscope and a prepared ventricular catheter enables careful and elegant aqueductal stenting. Large or flexible endoscopes, balloons, or special instruments to place a stent have become completely obsolete in selected cases.

Pathophysiology of Brainstem Lesions Due to Overdrainage

Overdrainage in hydrocephalus therapy is a common shunt complication responsible for many different side effects. Especially an association with an impairment of upper brainstem structures causing symptoms of a dorsal midbrain syndrome (DMS) has already been described. Yet apart from these known mesencephalic lesions, we found several more brainstem signs and symptoms resulting from overdrainage. Parinauds syndrome was diagnosed in all six patients examined; moreover, parkinsonism, memory disturbances, fluctuations in the level of consciousness, and hypothalamic dysfunctions could be detected in five of six patients. In addition hypersalivation combined with peripheral facial nerve palsy and blepharospasm occurred in two patients each, respectively. We postulate an upward herniation of the midbrain into the tentorial notch causing a secondary aqueductal stenosis as causal. An obstructed Sylvian aqueduct and the occurrence of shunt failure can lead to a bulging or enlargement of the third ventricle resulting in diencephalic lesions. If combined with fourth ventricle outlet occlusion, secondary aqueductal stenosis aggravates the situation with a fourth ventricle entrapment. Symptomatology and proposed pathophysiology are presented.

Single pulse analysis of intracranial pressure for a hydrocephalus implant

The intracranial pressure (ICP) waveform contains important diagnostic information. Changes in ICP are associated with changes of the pulse waveform. This change has explicitly been observed in 13 infusion tests by analyzing 100 Hz ICP data. An algorithm is proposed which automatically extracts the pulse waves and categorizes them into predefined patterns. A developed algorithm determined 88%±8% (mean ±SD) of all classified pulse waves correctly on predefined patterns. This algorithm has low computational cost and is independent of a pressure drift in the sensor by using only the relationship between special waveform characteristics. Hence, it could be implemented on a microcontroller of a future electromechanic hydrocephalus shunt system to control the drainage of cerebrospinal fluid (CSF).

Detection of hidden pseudotumour cerebri behind Chiari 1 malformation: value of telemetric ICP monitoring.

Literature shows that pseudotumour cerebri (PTC) can be hidden behind Chiari malformation. The question is how this hidden PTC can be certainly detected. Measurements of intracranial pressure (ICP) performed by lumbar puncture may not be satisfactorily significant. ICP monitoring via ventricular drains with tip sensor might fail episodes with increased ICP due to an infection risk-related temporal restricted implantation duration. Finally, a long-term ICP measurement device without infection risk constraining duration of implantation is required. Our study group together with RWTH Aachen University (Chair for Medical Information Technology/HelmholtzInstitute for Biomedical Engineering), Raumedic AG (Raumedic AG, Helmbrechts, Germany) and RECO (RECOMedical Technology, Pirna, Germany) and sponsored by the German Federal Ministry of Education and Research (BMBF) developed a telemetric device to measure ICP non-invasively which has been licensed in 2010. The so-called P-tel has been validated in animal experiments [16], and clinically, reliability had been proved.

Association of Chiari malformation and vitamin B12 deficit in a family

PurposeA clear etiology of Chiari malformation is still lacking. Some associations between this disorder and genetical variations have been reported. Documented cases of familial Chiari malformation in three consecutive generations are rare. Furthermore, an association of Chiari disorder and vitamin B12 deficit has rarely been described in literature.MethodsIn this study, three generations of a family suffering from Chiari 1 or Chiari 0 malformation have been examined with MRI, clinically and laboratory (hemograms).ResultsChiari malformation could be confirmed in all presented patients: While the F2 generation (children: 1 × ♀, 1 × ♂) and the female F1 generation (mother and sister of mother) suffered from Chiari type 1, the male F0 generation showed Chiari 0 malformation. F0 and F1 generation further presented with syringomyelia (F0: C4-D1; F1: C4-D2). All patients except the grandfather (F0) underwent surgical posterior fossa decompression to relive successfully cerebellar and hydrocephalus associated progressing clinical symptoms. The hemograms of generation 1 and 2 revealed familial vitamin B12 deficit.ConclusionsA hereditary component is discussed in Chiari malformation, yet proved etiology is still lacking. As folic acid plays an important role in the development of the neural tube, vitamin B12 deficit might have some impact on the development of Chiari malformations.

Subdural or Intraparenchymal Placement of Long-Term Telemetric Intracranial Pressure Measurement Devices?

We established a CE-certified telemetric device to measure intracranial pressure (ICP) noninvasively. To evaluate whether subdural or intraparenchymal insertion of such devices should be preferred, we implanted these telemetric ICP measurement devices (Raumedic, Rautel) in both locations. The study was performed in nine minipigs. The telemetric data were validated every 3 months using conventional intraparenchymal ICP measurement probes.The intraparenchymal telemetric device failed in one animal 12 months after insertion. Computed tomography (CT) revealed first hints for failure: Despite the implantation in adult animals, the skull dimensions seemingly increased after implantation, and the sensor tip was dislocated on the tabula interna level. This finding could also be verified by histopathological examination which would explain the reason for mismeasurement. The subdural catheter failed after 9 months. CT and histopathological examination revealed a bony encapsulation of a large catheter part, which had been located correctly initially. We propose that chronic pulsatile stress on the device was the underlying reason for this phenomenon, comparable to that in meningeal arteries.In some of the other animals, failure of subdural catheters could be detected. Histopathological examinations in these cases are still pending. Nevertheless, we assume similar underlying reasons for failure in these subdural probes.In conclusion, we favour intraparenchymal placement of telemetric ICP measurement devices.

Intracranial Pressure–Guided Shunt Valve Adjustments with the Miethke Sensor Reservoir

BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.