Frank Dewaele

Deep Brain Stimulation in Patients with Refractory Temporal Lobe Epilepsy

Summary:  Purpose: This pilot study prospectively evaluated the efficacy of long‐term deep brain stimulation (DBS) in medial temporal lobe (MTL) structures in patients with MTL epilepsy.

Study of the time course of the clinical effect of propofol compared with the time course of the predicted effect-site concentration: performance of three pharmacokinetic–dynamic models

BACKGROUND In the ideal pharmacokinetic-dynamic (PK-PD) model for calculating the predicted effect-site concentration of propofol (Ce(PROP)), for any Ce(PROP), the corresponding hypnotic effect should be constant. We compared three PK-PD models (Marsh PK with Shüttler PD, Schnider PK with fixed ke0, and Schnider PK with Minto PD) in their ability to maintain a constant bispectral index (BIS), while using the respective effect-site-controlled target-controlled infusion (TCI) algorithms. METHODS We randomized 60 patients to Group M (Marshs model with k(e0)=0.26 min(-1)), Group S1 or Group S2 (Schniders model with a fixed k(e0)=0.456 min(-1) or a k(e0) adapted to a fixed time-to-peak effect=1.6 min, respectively). All patients received propofol at a constant rate until loss of consciousness. The corresponding Ce(PROP), as calculated by the respective models, was set as a target for effect-site-controlled TCI. We observed BIS for 20 min. We hypothesized that BIS remains constant, if Ce(PROP) remains constant over time. RESULTS All patients in Group M woke up, one in Group S1 and none in Group S2. In Groups S1 and S2, BIS remained constant after 11 min of constant Ce(PROP), at a more pronounced level of hypnotic drug effect than intended. CONCLUSIONS Targeting Ce(PROP) at which patients lose consciousness with effect-site-controlled TCI does not translate into an immediate constant effect.

Cerebral haemodynamic physiology during steep Trendelenburg position and CO2 pneumoperitoneum

BACKGROUND The steep (40°) Trendelenburg position optimizes surgical exposure during robotic prostatectomy. The goal of the current study was to elucidate the influence of this patient positioning on cerebral blood flow and zero flow pressure (ZFP), and to assess the validity of different methods of evaluating ZFP. METHODS In 21 consecutive patients who underwent robotic endoscopic radical prostatectomy under general anaesthesia, transcranial Doppler flow velocity waveforms and invasive arterial and central venous pressure (CVP) waveforms suitable for analysis were recorded throughout the whole operative procedure in 14. The ZFP was determined by regression analysis of the pressure-flow plot and by different simplified formulas. The effective cerebral perfusion pressure (eCPP), pulsatility index (PI), and resistance index (RI) were determined. RESULTS While patients were in the Trendelenburg position, the ZFP increased in parallel with the CVP. The PI, RI, gradient between the ZFP and CVP, and the gradient between the CPP and the eCPP did not increase significantly (P<0.05) after 3 h of the steep Trendelenburg position. Using the formula described by Czosnyka and colleagues, the ZFP correlated closely with that calculated by linear regression throughout the course of the operation. CONCLUSIONS Prolonged steep Trendelenburg positioning and CO(2) pneumoperitoneum does not compromise cerebral perfusion. ZFP and eCPP are reliable variables for assessing brain perfusion during prolonged steep Trendelenburg positioning.

A novel implantable vagus nerve stimulation system (ADNS-300) for combined stimulation and recording of the vagus nerve: Pilot trial at Ghent University Hospital

PURPOSE Vagus nerve stimulation (VNS) is an established treatment for refractory epilepsy. The ADNS-300 is a new system for VNS that includes a rechargeable stimulus generator and an electrode for combined stimulation and recording. In this feasibility study, three patients were implanted with ADNS-300 for therapeutic VNS. In addition, compound action potentials (CAPs) were recorded to evaluate activation of the vagus nerve in response to VNS. METHODS Three patients were implanted with a cuff-electrode around the left vagus nerve, that was connected to a rechargeable pulse generator under the left clavicula. Two weeks after surgery, therapeutic VNS (0.25-1.25 mA, 500 μs, 30s on, 10 min off and 30Hz) was initiated and stimulus-induced CAPs were recorded. RESULTS The ADNS-300 system was successfully implanted in all three patients and patients were appropriately stimulated during six months of follow-up. A reduction in seizure frequency was demonstrated in two patients (43% and 40% in patients 1 and 3, respectively), while in patient 2 seizure frequency remained unchanged. CAPs could be recorded in patients 1 and 2, proving stimulation-induced activation of the vagus nerve. CONCLUSION This feasibility study demonstrates that the ADNS-300 system can be used for combined therapeutic stimulation (in 3/3 patients) and recording of CAPs in response to VNS (in 2/3 patients) up to three weeks after surgery. Implantation in a larger number of patients will lead to a better understanding of the electrophysiology of the vagus nerve, which in turn could result in more adequate and individualized VNS parameter choice.

Endoscopic Treatment of Temporal Arachnoid Cysts in 34 Patients

INTRODUCTION Arachnoid cysts are lesions present in 1% of the population and usually found in the temporal fossa. Clinical and radiologic presentations can differ greatly. Despite intensive research, it is still debatable which patients will benefit from surgery. OBJECTIVE This study aims to investigate the pretreatment parameters influencing the outcome after neuroendoscopic treatment of temporal arachnoid cysts. MATERIALS AND METHODS A retrospective analysis of 34 patients who underwent an endoscopic fenestration of a temporal arachnoid cyst between July 1991 and December 2013 was performed. RESULTS In symptomatic patients, there was a clinical improvement in 76.4% of cases. The best results were found in treating symptoms related to intracranial hypertension, acute neurologic defects, and macrocrania. Patients with temporal lobe epilepsy improved after cyst fenestration in 33.3% of cases. Behavioral problems and psychomotor retardation remained largely unchanged. Patients with a complex neurologic presentation, often from a congenital syndrome and combined with an intellectual disability, had the least benefit from endoscopic surgery. Radiologic follow-up showed a cyst volume decrease in 91.2% of cases. Complications were present in 29.4%, but were mostly minor and transient. CONCLUSION This study demonstrates that patients with symptoms related to intracranial hypertension, acute neurologic deficits, and macrocrania have the best postoperative outcome. Also, patients with ipsilateral temporal lobe epilepsy seem to be good candidates for endoscopic arachnoid cyst fenestrations. In complex neurologic disorders without one of the previously mentioned symptoms, endoscopy remains less successful.

Frameless Neuronavigation-Guided Endoscopic Total En-Bloc Removal of a Third Ventricular Colloid Cyst: A Case Report on Surgical Technique

A 26-year-old man was referred to our department with recurrent episodes of loss of consciousness. The radiological evaluation of the patients cranium showed a third ventricular colloid cyst with only a slight degree of obstructive hydrocephalus. The complete, en-bloc removal of the cyst was achieved by a frameless neuronavigation-guided endoscopic resection technique. The patient had an uneventful post-operative period and was discharged home on the fourth post-operative day without any neurological or psychological deficit. The surgical technique and pertinent literature are discussed with emphasis on factors that contribute to our successful total en-bloc removal of the third ventricular colloid cyst.

Automatic detection of oesophageal intubation based on ventilation pressure waveforms shows high sensitivity and specificity in patients with pulmonary disease

BACKGROUND Unrecognised endotracheal tube misplacement in emergency intubations has a reported incidence of up to 17%. Current detection methods have many limitations restricting their reliability and availability in these circumstances. There is therefore a clinical need for a device that is small enough to be practical in emergency situations and that can detect oesophageal intubation within seconds. In a first reported evaluation, we demonstrated an algorithm based on pressure waveform analysis, able to determine tube location with high reliability in healthy patients. The aim of this study was to validate the specificity of the algorithm in patients with abnormal pulmonary compliance, and to demonstrate the reliability of a newly developed small device that incorporates the technology. MATERIALS AND METHODS Intubated patients with mild to moderate lung injury, admitted to intensive care were included in the study. The device was connected to the endotracheal tube, and three test ventilations were performed in each patient. All diagnostic data were recorded on PC for subsequent specificity/sensitivity analysis. RESULTS AND DISCUSSION A total of 105 ventilations in 35 patients with lung injury were analysed. With the threshold D-value of 0.1, the system showed a 100% sensitivity and specificity to diagnose tube location. CONCLUSION The algorithm retained its specificity in patients with decreased pulmonary compliance. We also demonstrated the feasibility to integrate sensors and diagnostic hardware in a small, portable hand-held device for convenient use in emergency situations.

Treating Hydrocephalus with Retrograde Ventriculosinus Shunt: Prospective Clinical Study

BACKGROUND Since the 1950s, hydrocephalus has been be treated with cerebrospinal fluid (CSF) shunts, usually to the peritoneal cavity or to the right cardiac atrium. However, because of their siphoning effect, these shunts lead to nonphysiologic CSF drainage, with possible comorbidity and high revision rates. More sophisticated shunt valve systems significantly increase costs and technical complexity and remain unsuccessful in a subgroup of patients. In an attempt to obtain physiologic CSF shunting, many neurosurgical pioneers shunted towards the dural sinuses, taking advantage of the physiologic antisiphoning effect of the internal jugular veins. Despite several promising reports, the ventriculosinus shunts have not yet become standard neurosurgical practice. METHODS In this single-center prospective clinical study, we implanted the retrograde ventriculosinus shunt, as advocated by El-Shafei, in 10 patients. This article reports on our operation technique and long-term outcome, including 4 patients in whom this shunt was implanted as a rescue operation. RESULTS Implantation of a ventriculosinus shunt proved to be feasible, warranting physiologic drainage of CSF. However, in only 3 of 14 patients, functionality of the retrograde ventriculosinus shunt was maintained during more than 6 years of follow-up. In our opinion, these shunts fail because present venous access devices are difficult to implant correctly and become too easily obstructed. After discussion of possible causes of this frequent obstruction, a new dural venous sinus access device is presented. CONCLUSION An easy-to-implant and thrombogenic-resistant dural venous sinus access device needs to be developed before ventriculosinus shunting can become general practice.

A non-hydrocephalic goat experimental model to evaluate a ventriculosinus shunt:

The ventriculosinus shunt is a promising treatment for hydrocephalus. Currently, different shunt techniques exist, and it is not clear whether one is preferable. This pilot study reports on a non-hydrocephalic goat model (Saanen breed) that provides opportunities to evaluate and optimize several aspects of the ventriculosinus shunt technique. Analysis of the coagulation properties of 14 goats by a viscoelastic coagulation monitor showed that goats have a hypercoagulable state compared to humans. This property can be partially counteracted by antiplatelet drugs. During implantation of a ventriculosinus shunt, a pulsatile reflux of blood was observed. After implantation, the animals recovered to their preoperative state, and none of them developed a superior sagittal sinus thrombosis. Evaluation of the shunts after 16 days showed an obstructing luminal clot. Several model-related factors may have promoted this obstruction: the absence of hydrocephalus, the hypercoagulability of caprine blood and the smaller dimensions of the caprine superior sagittal sinus. However, the pulsatile reflux of blood, which is caused by the compliance of the shunt system distal to the valve, may have been an important factor as well. In conclusion, the non-hydrocephalic goat model limits animal suffering and simplifies the study protocol. This model allows researchers to evaluate their implantation technique and shunt hardware but not the efficacy of the treatment or shunt survival.

The use of the trendelenburg position in the surgical treatment of extreme cerebellar slump

Background. State-of-the-art treatment for Chiari Malformation I (CM-I) consists of decompression by posterior fossa craniectomy. A rare but severe complication that develops over months to years after this procedure is cerebellar slump. Treatment options for this condition are limited. We present a new and promising approach to treat this rare condition. Methods. The patients were placed in the Trendelenburg position to facilitate ascent of the cerebellum. After almost complete dissolution of neurologic symptoms, surgical reconstruction was performed by tonsillar resection and the creation of a new structural support using a bone graft. Results. Both patients experienced good clinical and morphological outcomes immediately after surgery, and for two years thereafter. Conclusions. Neurological symptoms related to cerebellar or brainstem slump can be adequately reversed by placing the patient in the Trendelenburg position. After uneventful gravitational reversal of the slump, safe surgical reconstruction of the cerebellar support can be performed to securely preserve the anatomical reversal.