Neurophysiological investigations of drug resistant epilepsy patients treated with vagus nerve stimulation to differentiate responders from non-responders.

BACKGROUND AND PURPOSE: In patients treated with vagus nerve stimulation (VNS) for drug resistant epilepsy (DRE), up to a third of patients will eventually not respond to the therapy. As VNS therapy requires surgery for device implantation, prediction of response prior to surgery is desirable. It is hypothesized that neurophysiological investigations related to the mechanisms of action of VNS may help to differentiate VNS responders from non-responders prior to the initiation of therapy. METHODS: In a prospective series of DRE patients, polysomnography, heart rate variability (HRV) and cognitive event related potentials were recorded. Polysomnography and HRV were repeated after 1 year of treatment with VNS. Polysomnography, HRV and cognitive event related potentials were compared between VNS responders (≥50% reduction in seizure frequency) and non-responders. RESULTS: Fifteen out of 30 patients became VNS responders after 1 year of VNS treatment. Prior to treatment with VNS, the amount of deep sleep (NREM 3), the HRV high frequency (HF) power and the P3b amplitude were significantly different in responders compared to non-responders (P = 0.007; P = 0.001; P = 0.03). CONCLUSION: Three neurophysiological parameters, NREM 3, HRV HF and P3b amplitude, were found to be significantly different in DRE patients who became responders to VNS treatment prior to initiation of their treatment with VNS. These non-invasive recordings may be used as characteristics for response in future studies and help avoid unsuccessful implantations. Mechanistically these findings may be related to changes in brain regions involved in the so-called vagal afferent network.

Prospective study on the outcome of the sphenoid drill out procedure.

BACKGROUND: Chronic sphenoid sinusitis refractory to both medical therapy and sphenoidotomy requires a more extended intervention based on the principles of salvage surgery. Our aim is to describe the sphenoid drill out technique as a sphenoid salvage intervention and to outline its implications on clinical outcome and quality of life. METHODOLOGY: 12 patients with chronic sphenoiditis undergoing a sphenoid drill out procedure were examined by nasal endoscopy preoperatively and postoperatively for one year. Preoperative and postoperative quality of life questionnaires (RSOM-31 and SF-36) were obtained. RESULTS: All but one patient had a completely patent neostium without scar formation. No major complications occurred after this procedure. All patients reported at least an improvement of their symptoms, 50% of patients were even symptom free at one year after surgery. The median postoperative RSOM-31 score was significantly lower than the preoperative score. Both the physical component summary (PCS) and the mental component summary (MCS) of the SF-36 score improved significantly. None of the patients needed a revision procedure. CONCLUSION: Sphenoid drill out is a safe and effective technique with a high success rate. In patients with chronic sphenoid sinusitis refractory to medical therapy and surgery it could be a valid alternative to revision sphenoidotomy.

Traumatic CSF leaks of the anterior skull base.

Traumatic CSF leaks of the anterior skull base. Skull base fractures are a frequent complication of high-impact trauma; due to the inherent anatomic relationships of the skull base, they may be associated with significant intracranial complications, including CSF leakage, and their detection is therefore important. The ethmoid roof and the cribriform plate region are the sites most vulnerable to fractures and dural tears. Rhinorrhoea is a non-specific finding; the presence of CSF in a sample must be confirmed with beta 2 transferin or beta trace protein. Accurate identification of the leakage site is necessary for a successful surgical treatment. Various modalities are available for this purpose, such as CT scan and MRI. Persistent CSF rhinorrhoea necessitates surgical intervention, due to the risk of meningitis. Continued improvements in endoscopic reconstruction techniques have led to fewer open surgeries for repair. Smaller defects can be closed with fat gasket technique or free grafts, while larger defects necessitate a multilayer closure with local vascularized flaps. These techniques have shown consistently high success rates.

Cerebral haemodynamic physiology during steep Trendelenburg position and CO(2) 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.

Pressure monitoring during neuroendoscopy: new insights.

BACKGROUND: Significant increases in intracranial pressure (ICP) may occur during neuroendoscopic procedures. To detect and prevent serious and sustained increases, ICP should be monitored. At present, controversy exists on the optimal location of the monitoring sensor. Therefore, we conducted an in vitro study to estimate the pressure gradients between the ventricle, the 'gold standard' site, and the rinsing inlet and outlet. METHODS: A head model and a standard endoscope were used. Rinsing was enforced by using a pressurized infusion bag. Using clinically relevant flow rates, pressure was measured at the rinsing inlet and outlet, in the ventricle, and at the distal end of the rinsing channel using a tip sensor or a capillary tube. RESULTS: At a flow of 61 ml min(-1), the steady-state pressures measured at the rinsing inlet, in the ventricle, and at the rinsing outlet were 38, 26, and 12 mm Hg, respectively. At 135 ml min(-1), these increased to 136, 89, and 42 mm Hg. Transendoscopic pressure measurements were always within 1 mm Hg of the ventricular pressure. CONCLUSIONS: During endoscopy, measurements at the rinsing inlet overestimated the ventricular pressure by ∼50 mm Hg during heavy rinsing, whereas measurements at the rinsing outlet underestimated the pressure by ∼50 mm Hg. An electronic tip sensor or a pressure capillary tube placed at the distal end of the lumen of the rinsing channel of the endoscope did not interfere with rinsing flow and produced measurements that were equal to ventricular pressures.

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 (Marsh's model with k(e0)=0.26 min(-1)), Group S1 or Group S2 (Schnider's 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.

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 patient's 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.

Intradural endoscopic closure of dural breaches in a case of post-traumatic tension pneumocephalus.

INTRODUCTION: Post-traumatic tension pneumocephalus can become a life-threatening condition that urges the surgeon to repair the causal breach in the dura. Dural repair via craniotomy may be jeopardised by the fragility of the dura and by its firm adhesions to the bone, especially in aged patients. Transnasal sealing requires the opening of each of the paranasal sinuses or cells that line the frontal base. METHOD: We present the case of a 92-year-old man, in whom an alternative, minimally invasive procedure was chosen. The patient was in a poor general condition and suffered from progressive obtundation till coma, because of a massive tension pneumocephalus, which was not reversed by drainage of the intracranial air via a burr hole, but even increased instead. Through the existing burr hole at the coronal suture, a rigid endoscope was introduced. Because of a massive backward compression of the brain, the endoscope could be passed in front of it to visualize the dural defects at the level of the ethmoidal roof. Pericranium, harvested from around the burr hole, was glued against the defects. The procedure was repeated at the contralateral side. RESULT: After surgery, a gradual decrease of the amount of intracranial air was documented. The patient regained consciousness and was extubated. In spite of this favourable course, he suddenly died two weeks after surgery from combined pulmonary and renal dysfunction. Autopsy documented the efficacious endoscopic sealing of the skull base, which was the least invasive procedure in the given circumstances.

Endovascular treatment of a giant petrous internal carotid artery aneurysm. Case report and review of the literature.

Expansive aneurysms of the petrous internal carotid artery are rare. Compressive and thrombembolic neurological deficits and occasionally extradural haemorrhage in combination with a pulsatile tinnitus are most important and alarming symptoms. Due to its extradural location, subarachnoid haemorrhage does not occur. Treatment is indicated since rupture may be devastating and recurrent ischaemic attacks severely disabling. Because direct neurosurgical access to the petrous internal carotid artery is very difficult, treatments consists of parent vessel occlusion with or without extra-intracranial bypass construction. We present a case of a young man with a giant petrous artery aneurysm provoking a thrombembolic event which was treated successfully with proximal balloon occlusion of the internal carotid artery after a temporary balloon occlusion test.