Tomasz Lyson

No Specific Brain Protection Against Thermal Stress in Fever

Summary Knowledge about human brain temperature is still very limited, despite evidence demonstrating the critical influence of mild increases in temperature on the ischaemic brain. It has been suggested that in passive and exercise hyperthermia the brain may be protected against thermal damage by a mechanism of selective brain cooling (SBC). It is said to bring about suppression of the temperature of the brain, rendering it significantly lower than trunk and arterial blood temperature. Yet very little is known about the possible role of this mechanism in fever, a condition fundamentally different from “physiological” hyperthermia, especially when it occurs in brain – damaged patients. In our investigation we retrospectively analysed the results of direct recordings of cerebral temperature within the subdural space (Tsd) and within the brain parenchyma (Tbr−16 cases) in 63 unanaesthetized patients following neurosurgical procedures, including 23 with fever >38 °C. The differences between trunk temperature, measured in the rectum (Tre) or in the oesophagus (Tes), and the intracranial temperature, were calculated in all subjects. A statistically significant reduction of these differences, in step with increasing fever, would be compatible with demonstrating a process of selective brain cooling. The offsets Tre−Tsd, Tre−Tbr, and Tes−Tsd were plotted against Tre over a wide range of body temperature and near zero correlation was found. This finding suggests that brain temperature in fever was not selectively suppressed by any specific thermolytic mechanism and that dissipation of the main bulk of cerebral metabolic heat both in normothermia and in fever depends on heat uptake by arterial blood. The results suggest that the brain in fever can be seriously jeopardized by heat stress and no specific cooling mechanism exists, to reduce it below body temperature in feverish neurosurgical patients. Tbr and/or Tsd remained the highest body temperature in 14 out of the 23 patients during fever.

Intracranial Pressure Processing with Artificial Neural Networks: Classification of Signal Properties

Summary¶ Intracranial pressure (ICP) is commonly used by neurosurgeons as a source of valuable information about the current condition of the neurosurgical patient. Nevertheless, despite years of effort, extracting clinically valuable information from the ICP signal is still problematical. Approaches, using current values of ICP, may fail to disclose imminent risk, because unpredictable factors can rapidly change the properties of the signal. An alternative approach is to determine some global characteristics of the signal within a longer time interval and such statistical analyses have been proposed by several authors. A further, rarely considered, problem is assessment of the results obtained from the point of view of their practical utility and/or such classification of the obtained properties of the signal that they correspond to certain clinical states of the patient. While this might be a typical task for discriminant analysis, we approached the analysis using an alternative methodology, that of computational intelligence, implemented in artificial neural networks (ANN). We tested two variants of the ANN algorithms for classification and discrimination of global properties of the ICP signal. In a “dynamic pattern classification” the network was presented with several sections of ICP records together with information from the expert-neurosurgeon, classifying 4 risk groups. In this mode no data pre-processing was carried out, in contrast to our second approach, in which the signal had been pre-processed using published statistical analyses and only these intermediate coefficients were fed into the ANN classifier. The results obtained with both classification methods at their current stage of training were similar and approximated to a 70% rate of judgements consistent with the expert scoring. Nevertheless, the method based on the assessment of global parameters from the ICP record looks more promising, because it leaves the possibility for modification of the set of parameters analysed. The new parameters may include information extracted not only from the ICP signal, but also from other diagnostic modalities, like colour coded Doppler ultrasonography. The ultimate goal of this work is to build up a pseudo-intelligent computer expert system, which would be able to reason from a reduced set of input information, available from a standard monitoring modality, because it had been taught salient links between these data and higher-order data, upon which expert scoring was based.

Endoscopic trans-nasal approach for biopsy of orbital tumours using image-guided neuro-navigation system

SummaryBackground. Histopathological diagnosis of intraorbital tumours is of crucial value for planning further therapy. The aim of the study was to explore clinical utility of image-guided endoscopy for biopsy of orbital tumours. Method. Trans-nasal endoscopic biopsy of intraorbital mass lesions was performed in 6 patients using a neuro-navigation system (Medtronic Stealth Station Treon plus). The CT and MRI 1 mm slice images were fused by the system in order to visualise both bony and soft tissue structures. The anatomic fiducial registration protocol was used during the procedure. Results. All lesions were precisely localised and the biopsies could be taken from the representative part of the pathological mass. None of the patients developed aggravation of ocular symptoms after the procedure. The operative corridor as well as the size of orbital wall fenestration could be limited to a minimum. The accuracy of neuro-navigation remained high and stable during the entire procedure. Conclusions. The image-guided neuro-navigation system facilitated endoscopic localisation and biopsy of intraorbital tumours and contributed to the reduction of surgical trauma during the procedure. The technique was particularly useful in small, medially located, retrobulbar tumours and in unclear situations when the structure of the lesion resembled surrounding intraorbital tissue.

Normal reference values of ratios of blood flow velocities in internal carotid artery to those in common carotid artery using Doppler sonography.

The ratios of of blood flow velocities in the internal carotid artery (ICA) to those in the common carotid artery (CCA) (VICA/VCCA) are used to identify patients with critical ICA narrowing, but their normal reference values have not been established. We provide reference data for the VICA/VCCA ratios for the peak systolic velocity (PSV), mean velocity (MV), and end‐diastolic velocity (EDV) measured in a large group of healthy subjects.

Isolated sphenoid sinus pathologies--the problem of delayed diagnosis.

Summary Background Isolated sphenoid sinus pathologies are relatively rare. In the majority of cases, symptoms do not arise in the early stages of the disease or are non-specific, therefore making diagnosis difficult. The aim of this study was to investigate the diagnostic process and the reasons for development of complications in patients with isolated sphenoid sinus pathology. Material/Methods The clinical data and observation charts of 32 patients were investigated to determine how long the main symptoms of sphenoid pathology had been present before the patients were referred for medical treatment, and the time that elapsed from the first ambulatory medical assessment to the initial diagnosis. Results Complaints and symptoms of sphenoid sinus pathology had been present for 10.2 months before the diagnosis was established. Although the duration of complaints in “ORL” (diagnosed by otorhinolaryngologist) and “non-ORL” (diagnosed by other specialists) group of patients was similar (10.8 and 9.5 months on average, respectively), unexpectedly, in the “non-ORL” group of patients, the time necessary for making the initial diagnosis was actually shorter than in the “ORL” group (1.8 vs 4.1 months). At the time of hospital admission, endoscopic examination revealed no abnormalities in 31.2% of patients. In 28.1% of patients the pathological process in the sphenoid sinus was diagnosed only after the onset of complications. Conclusions The occult character of the disease and the lack of severe and specific symptoms, rather than the delay in getting extensive diagnostic tests, are responsible for the delayed diagnosis and treatment.

Influence of Smoking Cigarettes on Cerebral Blood Flow Parameters

Introduction: While chronic cigarette smoking can lead to increased risk of stroke, the acute effects of smoking have not been established. We studied the changes in blood flow parameters in the major cerebral arteries caused by smoking one cigarette. Method: Using transcranial color-coded sonography (TCCS), we studied the anterior cerebral artery (ACA), middle cerebral artery (MCA), posterior cerebral artery (PCA), and the internal carotid artery (ICA) of 36 healthy male volunteers before and after they smoked one cigarette. Results: Blood flow velocity increased to a different degree in all but one of the arteries examined after participants smoked a single cigarette: The end diastolic velocity increased significantly by 7.8% in the PCA, 8% in the ACA, and 14.4% in the MCA. The peak systolic velocity increased significantly by 7.5% in the MCA. Blood flow velocity remained unchanged in the ICA only. Blood pressure and heart rate increased as did the flow velocity ratio for the MCA/ICA. The pulsatility index decreased after smoking from 0.92 ± 0.13 to 0.87 ± 0.14 in the MCA, 0.93 ± 0.15 to 0.87 ± 0.13 in the ACA, and 0.95 ± 0.17 to 0.89 ± 0.16 in the PCA. Conclusions: The results suggest that the direct effect of smoking on cerebral circulation includes peripheral vasodilatation with possible constriction of the main trunk of the basal cerebral arteries.

Endoscopic Repair of CSF Leaks in the Postero-Superior Wall of the Frontal Sinus – Report of 2 Cases

BACKGROUND Bony defects extending laterally or superiorly within the posterior wall of the frontal sinus are generally deemed too difficult for endoscopic repair in spite of significant progress in surgical endoscopic techniques. PATIENTS AND METHODS We describe a technique of endoscopic repair of posttraumatic cerebrospinal fluid (CSF) leak from the postero-superior aspect of the frontal sinus in a 40- and a 29-year-old male. In both cases after careful assessment of the surgical anatomy the sinus was widely opened transnasally (Draf IIB and Draf III approach, respectively). Angled (45 and 70°) optics and malleable, individually profiled instruments were used to fit specific anatomic variations encountered during the procedure. RESULTS Endoscopic manipulation near the dome of the sinus proved to be very limited in spite of a wide surgical opening. In our cases the site of the leak could be identified and successfully sealed with gentle pressure on the dura mater. The bony defects were repaired with a 2-layer reconstruction technique. There were no signs of recurrence during 6 months follow-up. CONCLUSION With contemporary endoscopic instrumentation, endoscopic closure of CSF leaks in the supero-posterior wall of the frontal sinus is feasible, especially in patients with favourable anatomy of the frontal sinus.

The transmaxillary endoscopic approach to the inferior part of the orbit: How I do it

BackgroundTransmaxillary endoscopic approach to the inferior part of the orbit was demonstrated on cadaveric preparations; however, its clinical application has not been reported. We describe a clinically useful technique of the transmaxillary approach to the lower orbit.MethodsA four-hand technique is essential for extensive preparation within the orbit; therefore, the tools have to be introduced into the maxillary sinus through two ports: either through the canine fossa and antrostomy or through antrostomy using the bi-nostril transseptal approach.ConclusionIntraorbital pathologies located in the inferior retrobulbar space can be successfully operated on using the transmaxillary endoscopic approach.

Endoscopic treatment of adversely located osteomas of the frontal sinus.

Objectives We assess the utility and limitations of an endoscopic technique in the treatment of osteomas that are considered difficult to manage endoscopically, ie, those located superiorly or laterally in the frontal sinus, extending beyond a virtual plane through the lamina papyracea, and we describe the principles of a surgical technique that facilitates removal of such tumors. Methods We performed a retrospective study on 8 patients with symptomatic frontal sinus osteomas, including tumors extending past the commonly recognized limits of endoscopic resection because of their size or site of attachment. Results All tumors were removed by a purely transnasal endoscopic approach. No major complications were observed during or after the operation. All patients experienced improvement or total regression of their symptoms. Conclusions With appropriate instruments and specific endoscopic techniques, it is possible to resect osteomas that not long ago were deemed inaccessible to endoscopic surgeons. The commonly recognized limits of endoscopic treatment of such tumors may be exceeded in some cases; however, favorable anatomic conditions are decisive for a successful operation.

Endoscopic transconjunctival surgical approach to intraconal space of the orbit: First clinical experience

BACKGROUND AND PURPOSE Recently, a transconjunctival, endoscope-assisted (TEA) approach to the medial intra-orbital space was developed based on cadaver preparations, with an ultimate goal of minimizing disturbances of the anatomic structures of the orbit. However, no report on clinical validation of this promising technique was published thus far. We present our experiences with the TEA approach in two patients. MATERIAL AND METHODS In emergency conditions, we approached the lateral retrobulbar space of a 42-year-old male through a 180° incision close to the corneal limbus; a scrap of metal, which had perforated the globe and resided at its posterior wall, was removed endoscopically. Moreover, we used the TEA approach to remove a tumor from the upper intraconal space in a 63-year-old woman. RESULTS In both patients the surgical goal was achieved with no muscle transection and without additional morbidity and complications. CONCLUSIONS Our experiences with TEA approach suggest that the procedure is clinically feasible, produces no co-morbidity and yields good functional and cosmetic results. As a result, the whole circumference of the retrobulbar space can be conveniently explored.