Psoriasis, cardiovascular risk factors and metabolic disorders: sex-specific findings of a population-based study.

BACKGROUND: Scientific evidence suggests an association between psoriasis and cardiovascular and metabolic diseases. However, there are hardly any sex-specific results from population-based studies reporting the prevalence of cardiovascular risk factors in patients with psoriasis and point estimates of the association between psoriasis and cardiovascular and metabolic disorders. OBJECTIVE: Aims are to evaluate the sex-specific prevalence of psoriasis and cardiovascular risk factors, and to estimate sex-specific associations between psoriasis and diabetes type 2 (DM) and metabolic syndrome (MetS). METHODS: We used data of 3723 participants (45-75 years, 54.1% women) without coronary heart disease and missing data (psoriasis, DM, MetS) from the Heinz Nixdorf Recall study. Standardized information on health outcomes and risk factors was assessed. We performed descriptive statistics and multiple regression analyses to calculate prevalence rate ratios (PR) and 95% confidence intervals (95% CI). RESULTS: The prevalence of psoriasis was 3.8% (n = 143), with no differences between sex. We observed more often metabolic and cardiovascular risk factors in women with psoriasis compared to women without psoriasis. Interestingly, in men, this pattern was partly reversed. Multiple regression analyses revealed distinctly elevated PRs for DM for both women and men with psoriasis (fully adjusted PR: 2.43; 95% CI: 1.17-5.07, resp. 2.09; 1.16-3.76). Regarding the MetS, the results were inconsistent, showing a positive association between psoriasis and MetS in women (1.84; 1.14-2.98), but a negative association in men, even though with a wide 95% CI (0.69; 0.42-1.12). CONCLUSION: The results of our cross-sectional, population-based analysis show a distinct association between psoriasis and DM, whereas for the MetS the results contrasted between men and women, translating in women with MetS showing a higher and in men a lower chance to be psoriatic. Our results emphasize the urgent need for sex-specific research, studying the effects of psoriasis on metabolic disorders as well as effective sex tailored prevention measures.

2-mm surgical margins are adequate for most basal cell carcinomas in Japanese: a retrospective multicentre study on 1000 basal cell carcinomas.

BACKGROUND: Surgery is the gold standard for basal cell carcinomas (BCC). Current recommended surgical margins for BCCs are determined from studies in Caucasian populations. However, the appropriate surgical margins for BCCs in non-white races are unclear. OBJECTIVES: To investigate the accuracy of preoperative determination of clinical tumour borders and appropriate surgical margins in Japanese patients with BCC. METHODS: The maximum calculated differences in distance between the preoperatively determined surgical margins and the actual histologic tumour side margins were considered as 'accuracy gaps' of clinical tumour borders. Estimated side margin positivity rates (ESMPRs) with narrower (2 and 3 mm) surgical margins were calculated on the basis of the accuracy gaps. RESULTS: Overall, 1000 surgically excised BCCs from 980 Japanese patients were included. The most frequent histologic subtype was nodular BCC (67%). The median accuracy gap was 0.3 mm [interquartile range (IQR): -0.5 to +1 mm]. The ESMPRs with 2- and 3-mm surgical margins were 3.8% and 1.4%, respectively. Only the ESMPRs between the well-defined (n = 921) and poorly defined clinical tumour border groups (n = 79) showed statistical difference [2-mm margin: 3.1% vs. 11.7%, OR: 3.89, 95% confidential interval (CI): 1.41-10.71, P <0.01; 3-mm margin: 0.97% vs. 6.3%, OR: 6.58, 95% CI: 1.67-25.99, P <0.01]. No significant differences in ESMPRs were noted in other subgroups including risk classifications. CONCLUSIONS: The determined clinical tumour border accuracy gaps in this Japanese cohort were negligible. Dermatologic surgeons may use narrower surgical margins with acceptable margin positivity rates. The clarity of clinical tumour borders could be an appropriate guide for selection of different surgical margins in the Japanese cohort.

[Computer-assisted skin cancer diagnosis : Is it time for artificial intelligence in clinical practice?] / Computerassistierte Hautkrebsdiagnose : Wann kommt künstliche Intelligenz in der Praxis an?

BACKGROUND: Artificial intelligence (AI) is increasingly being used in medical practice. Especially in the image-based diagnosis of skin cancer, AI shows great potential. However, there is a significant discrepancy between expectations and true relevance of AI in current dermatological practice. OBJECTIVES: This article summarizes promising study results of skin cancer diagnosis by computer-based diagnostic systems and discusses their significance for daily practice. We hereby focus on the analysis of dermoscopic images of pigmented and unpigmented skin lesions. MATERIALS AND METHODS: A selective literature search for recent relevant trials was conducted. The included studies used machine learning, and in particular "convolutional neural networks", which have been shown to be particularly effective for the classification of image data. RESULTS AND CONCLUSIONS: In numerous studies, computer algorithms were able to detect pigmented and nonpigmented neoplasms of the skin with high precision, comparable to that of dermatologists. The combination of the physician's assessment and AI showed the best results. Computer-based diagnostic systems are widely accepted among patients and physicians. However, they are still not applicable in daily practice, since computer-based diagnostic systems have only been tested in an experimental environment. In addition, many digital diagnostic criteria that help AI to classify skin lesions remain unclear. This lack of transparency still needs to be addressed. Moreover, clinical studies on the use of AI-based assistance systems are needed in order to prove its applicability in daily dermatologic practice.

Estimation of total genetic effects for survival time in crossbred laying hens showing cannibalism, using pedigree or genomic information.

Mortality of laying hens due to cannibalism is a major problem in the egg-laying industry. Survival depends on two genetic effects: the direct genetic effect of the individual itself (DGE) and the indirect genetic effects of its group mates (IGE). For hens housed in sire-family groups, DGE and IGE cannot be estimated using pedigree information, but the combined effect of DGE and IGE is estimated in the total breeding value (TBV). Genomic information provides information on actual genetic relationships between individuals and might be a tool to improve TBV accuracy. We investigated whether genomic information of the sire increased TBV accuracy compared with pedigree information, and we estimated genetic parameters for survival time. A sire model with pedigree information (BLUP) and a sire model with genomic information (ssGBLUP) were used. We used survival time records of 7290 crossbred offspring with intact beaks from four crosses. Cross-validation was used to compare the models. Using ssGBLUP did not improve TBV accuracy compared with BLUP which is probably due to the limited number of sires available per cross (~50). Genetic parameter estimates were similar for BLUP and ssGBLUP. For both BLUP and ssGBLUP, total heritable variance (T2 ), expressed as a proportion of phenotypic variance, ranged from 0.03 ± 0.04 to 0.25 ± 0.09. Further research is needed on breeding value estimation for socially affected traits measured on individuals kept in single-family groups.

Artificial intelligence for detection of microsatellite instability in colorectal cancer-a multicentric analysis of a pre-screening tool for clinical application.

BACKGROUND: Microsatellite instability (MSI)/mismatch repair deficiency (dMMR) is a key genetic feature which should be tested in every patient with colorectal cancer (CRC) according to medical guidelines. Artificial intelligence (AI) methods can detect MSI/dMMR directly in routine pathology slides, but the test performance has not been systematically investigated with predefined test thresholds. METHOD: We trained and validated AI-based MSI/dMMR detectors and evaluated predefined performance metrics using nine patient cohorts of 8343 patients across different countries and ethnicities. RESULTS: Classifiers achieved clinical-grade performance, yielding an area under the receiver operating curve (AUROC) of up to 0.96 without using any manual annotations. Subsequently, we show that the AI system can be applied as a rule-out test: by using cohort-specific thresholds, on average 52.73% of tumors in each surgical cohort [total number of MSI/dMMR = 1020, microsatellite stable (MSS)/ proficient mismatch repair (pMMR) = 7323 patients] could be identified as MSS/pMMR with a fixed sensitivity at 95%. In an additional cohort of N = 1530 (MSI/dMMR = 211, MSS/pMMR = 1319) endoscopy biopsy samples, the system achieved an AUROC of 0.89, and the cohort-specific threshold ruled out 44.12% of tumors with a fixed sensitivity at 95%. As a more robust alternative to cohort-specific thresholds, we showed that with a fixed threshold of 0.25 for all the cohorts, we can rule-out 25.51% in surgical specimens and 6.10% in biopsies. INTERPRETATION: When applied in a clinical setting, this means that the AI system can rule out MSI/dMMR in a quarter (with global thresholds) or half of all CRC patients (with local fine-tuning), thereby reducing cost and turnaround time for molecular profiling.

Direct magnification technique for cerebral angiography in the rat.

RATIONALE AND OBJECTIVES: The authors evaluated the performance of direct magnification radiography (DIMA) with digital image processing for cerebral angiography in the rat. METHODS: A microfocal x-ray unit with a focal spot of 5 microns was used for cerebral angiography in 10 rats. The animals were examined form x 4 up to x 20 magnification after injection of 0.2 mL x-ray contrast medium into the common carotid artery. RESULTS: Direct magnification radiography technology provides high resolution images and enables the visualization of very small vessels with high quality. It allows the peripheral branches of the middle cerebral artery or the ophthalmic artery to be visualized. Superimposition and noise effects can be excluded with digital subtraction and image processing. CONCLUSIONS: The experiments show that DIMA radiography is a suitable technique for cerebral angiography in the rat.

Immunohistochemical characterization of axonal sprouting and reactive tissue changes after long-term implantation of a polyimide sieve electrode to the transected adult rat sciatic nerve.

The development of artificial microstructures suited for interfacing of peripheral nerves is not only relevant for basic neurophysiological research but also for future prosthetic approaches. Aim of the present study was to provide a detailed analysis of axonal sprouting and reactive tissue changes after implantation of a flexible sieve electrode to the proximal stump of the adult rat sciatic nerve. We report here that massive neurite growth after implantation, steadily increasing over a period of 11 months, was observed. Parallel to this increase was the expression of myelin markers like Po, whereas non-myelin-forming Schwann cells did not change. Compared to five weeks post-implantation. where both Schwann-cell phenotypes were intermingled with each other, non-myelin-forming Schwann cells occupied a peripheral position in each microfascicle after 11 months. After an initial increase, hematogenous macrophages were down-regulated in number but maintained close contact with the implant. However, at no time were signs of its degradation observed. It is concluded that the introduced flexible polyimide electrode is suitable for contacting peripheral nerves since it permits substantial neurite growth and offers excellent long-term stability.

Chicken arachnoid granulations: a new model for cerebrospinal fluid absorption in man.

Cerebrospinal fluid (CSF) absorption was investigated chicken and rat using infusion tests into the cisterna magna. Data were analysed according to a mathematical model by Johnson et al. Results in rat predicted a predominant lymphatic mechanism, which was confirmed by rapid outflow of X-ray contrast media into the olfactoric mucosa. In contrast, dynamics measurements suggested CSF drainage via arachnoid granulations in chicken. CSF spaces along the optic nerve were contrasted radiographically resulting in venous drainage. Electron microscopically, villus-like structures were found at the distal optic nerve connecting the subarachnoid space with accompanying veins, resembling human arachnoid granulations. We hypothesize that CSF absorption through arachnoid villi in microsmatic chicken reflects the situation in man very well.

Regeneration of a transected peripheral nerve by transplantation of spinal cord encapsulated in a vein.

The objective was to investigate the regeneration of a transected peripheral nerve after transplantation of fragmented embryonic (E14-15) spinal cord cells which were encapsulated within a vein cavity. After 3 months transplantation, axonal regeneration was observed by staining with HE and antibody to neurofilament subtypes in six of 10 rats. In all six animals compound muscle action potentials to electrical stimulation could be recorded and indicated incomplete reinnervation of the fibular and tibial nerve, respectively. A chronic inflammation process around the transplant and a negative result of staining neurofilaments within the vein cavity and the transected nerve were found in animals lacking electrophysiological response to stimulation.

Towards micro electrode implants: in vitro guidance of rat spinal cord neurites through polyimide sieves by Schwann cells.

Our goal is to develop biohybrid neural microprobe implants with sieve electrodes for external stimulation of co-implanted neurons whose axons penetrate through the holes of electrodes and innervate host targets such as denervated muscle fibers. For evaluation of implants, potential scar formation was imitated in fibroblast-spinal cord co-cultures. In vitro neurite extension through flexible 10-microm thick polyimide sieves was inhibited by co-cultured fibroblasts. In contrast, the neurite penetration of sieves could be greatly stimulated by oriented exposure to Schwann cells. To our knowledge this is the first direct proof that Schwann cells display a guidance effect on spinal cord neurons in vitro. The results pave the way for novel biohybrid neuro-implants and provide means to circumvent the obstacle of inhibitory scar formation.

Breakdown of the meningeal barrier surrounding the intraorbital optic nerve after experimental subarachnoid hemorrhage.

PURPOSE: The intraorbital optic nerve sheath meninges contain a perineural subarachnoid space lined by meningeal cell layers and intercellular fibrous tissue. We sought to determine whether functional or structural characteristics, or both, of the optic nerve sheath are influenced by the increased intracranial pressure after the rupture of cerebral aneurysms. METHODS: We infused the great cisterns of cats with either x-ray contrast medium or autologous blood. The cisternal infusions were done under the experimental condition of a sudden 2.5-minute increase in intracranial pressure similar to that recorded after the rupture of cerebral aneurysms in humans. RESULTS: Digital subtraction radiographs of the optic nerves taken during the cisternal infusion of contrast medium at the start showed the opacification of the optic nerve subarachnoid space. After 2 minutes, the contrast medium leaked into the orbit, indicating the breakdown of the meningeal fluid barrier. Ultrastructural investigation of the optic nerve sheath after high-pressure cisternal infusions showed the arachnoid cell layers scattered. The flattened arachnoid cells displayed mainly intracellular and some intercellular, porelike openings. After infusion of blood into the great cistern, erythrocytes were found within porelike openings of the arachnoid cells. CONCLUSIONS: The meningeal fluid barrier of the optic nerve sheath can be destroyed by pressure changes associated with subarachnoid hemorrhage. This disruption might be regarded as a natural optic nerve sheath fenestration that allows outflow of cerebrospinal fluid into the orbit to protect the optic nerve from increased intracranial pressure after aneurysmal rupture.

Subacute hydrocephalus after experimental subarachnoid hemorrhage: its prevention by intrathecal fibrinolysis with recombinant tissue plasminogen activator.

It is investigated whether intrathecal fibrinolysis may prevent subacute hydrocephalus after subarachnoid hemorrhage (SAH). In 19 cats, SAH was induced by the intracisternal infusion of 1 ml/kg body weight of fresh autologous blood at a rate of 0.6 ml/min. Eleven of those animals were treated by intrathecal fibrinolysis performed 24 hours after experimental SAH by intracisternal infusion of 3 mg of recombinant tissue plasminogen activator. Included were eight animals suffering from experimental SAH and four healthy animals retained for control. A computed tomographic scan performed 24 hours after the SAH displayed an acute hydrocephalus from the experimental procedure. Cerebrospinal fluid outflow resistance was 71 +/- 5.0 mm Hg/ml/min in the healthy animals, 265 +/- 19.8 mm Hg/ml/min in the nontreated animals 7 days after SAH, and 151 +/- 6.4 mm Hg/ml/min in the recombinant tissue plasminogen activator-treated animals 7 days after SAH (mean +/- standard deviation; changes significant with P less than 0.01). Postmortem planimetry of both lateral ventricles gives a mean of 3.7 +/- 2.7 mm2 in the healthy animals, 11.1 +/- 3.9 mm2 in the nontreated group after SAH (P less than 0.01), and 3.5 +/- 1.1 mm2 in the animals treated with recombinant tissue plasminogen activator. Intracranial pressure monitoring demonstrated marked intracranial pressure waves only in the nontreated animals after SAH. It is concluded that intrathecal fibrinolysis may prevent subacute hydrocephalus after experimental SAH.

Acute changes in the dynamics of the cerebrospinal fluid system during experimental subarachnoid hemorrhage.

Early changes in intracranial pressure (ICP), ICP volume index, and resistance to absorption of cerebrospinal fluid induced by experimental subarachnoid hemorrhage were studied in cats. After SAH, the ICP was slightly elevated, and there was a decrease in the buffering capacity of the intracranial space and a sharp rise in outflow resistance. During infusion of blood into the cisterna magna with a constant infusion rate, an extensive increase in ICP could be demonstrated in contrast to the infusion of saline, which caused only slight elevation of ICP. Furthermore, during blood infusion, the ICP level did not reach a plateau phase of pressure, as was demonstrated during infusion of saline. It is suggested that the marked increase in ICP during blood infusion into the subarachnoid space is caused by intracranial volume loading and the simultaneous increase in cerebrospinal fluid outflow resistance. It is concluded that the reported relationship between increased cerebrospinal fluid outflow resistance and increased ICP supports the hypothesis of a strong increase in ICP during subarachnoid hemorrhage in human subjects.

Navigation-guided opening of the internal auditory canal via the retrosigmoid route for acoustic neuroma surgery: cadaveric, radiological, and preliminary clinical study.

OBJECTIVE: We investigated the usefulness of a microscope-based navigational system (Multi Koordinaten Manipulator; Zeiss, Oberkochen, Germany) for removal of the posterior wall of the internal auditory canal (IAC) via the retrosigmoid route. METHODS: A cadaveric study was performed to assess the navigational localization error for the retrosigmoid approach to the IAC. Computed tomographic findings for 47 acoustic neuroma cases were divided into three groups, on the basis of the relationship between the labyrinth and the sigmoid-fundus line (medial, on the line, or lateral). Furthermore, the shortest distances between the most medial labyrinthine extension and the resection line were measured. In 20 acoustic neuroma operations, the different features and the practicality of the microscope-based navigational system for opening of the IAC were evaluated. RESULTS: The mean anatomic localization errors were 0.67 +/- 0.2 mm (95th percentile, 1.32 mm) for navigation to the IAC and 0.71 +/- 0.37 mm (95th percentile, 1.68 mm) for navigation to the posterior semicircular canal. The average distances between the most medial labyrinthine extension and the resection line were 3.65, 3.36, and 2.0 mm for the lateral, on-the-line, and medial groups, respectively. Direct contouring of structures at risk does not take into account the localization error, nor does it provide reliable navigational information. A novel indirect contouring concept that takes into account the localization error (the safety corridor method) was therefore introduced. CONCLUSION: The value of navigational assistance for opening of the IAC is promising but still limited. Further development is required before the clinical effects of this navigational approach can be evaluated.

Effect of intrathecal fibrinolysis on cerebrospinal fluid absorption after experimental subarachnoid hemorrhage.

The effect of intrathecal fibrinolysis on cerebrospinal fluid (CSF) absorption was investigated after experimental subarachnoid hemorrhage (SAH). In 11 cats, SAH was induced by intracisternal application of 1 to 4 ml of fresh autologous blood. Thirty minutes after the experimental SAH, the CSF outflow resistance was found to be elevated from a median of 77 mm Hg/ml/min (range 41.3 to 109 mm Hg/ml/min) to a median of 580 mm Hg/ml/min (range 104 to 7000 mm Hg/ml/min). A logarithmic relationship could be demonstrated between the volume of subarachnoid blood and the elevation of the CSF outflow resistance. The intrathecal application of 2 mg of recombinant tissue plasminogen activator (rt-PA), which is a fibrinolytic substance suitable for lysis of subarachnoid blood clots in man, resulted in an almost total restoration of CSF absorption after experimental SAH. The CSF outflow resistance after SAH was lowered by application of rt-PA from a median of 1028.05 mm Hg/ml/min (range 394 to 7000 mm Hg/ml/min) to 79 mm Hg/ml/min (range 56.7 to 223 mm Hg/ml/min). It is concluded that the impairment of CSF absorption after SAH may play an important role in the pathogenesis of post-hemorrhagic vasospasm.

A positron emission tomography study of cerebrovascular reserve before and after shunt surgery in patients with idiopathic chronic hydrocephalus.

OBJECT: In this study the authors use positron emission tomography (PET) to investigate cerebral blood flow (CBF) and cerebrovascular reserve (CVR) in chronic hydrocephalus. METHODS: Ten patients whose mean age was 67 +/- 10 years (mean +/- standard deviation [SD]) were compared with 10 healthy volunteers who were 25 +/- 3 years of age. Global CBF and CVR were determined using (15)O-H2O and PET prior to shunt placement and 7 days and 7 months thereafter. The CVR was measured using 1 g acetazolamide. Neurological status was assessed based on a score assigned according to the methods of Stein and Langfitt. Seven months after shunt placement, five patients showed clinical improvement (Group A) and five did not (Group B). The average global CBF before shunt deployment was significantly reduced in comparison with the control group (40 +/- 8 compared with 61 +/- 7 ml/100 ml/minute; mean +/- SD, p < 0.01). In Group A the CBF values were significantly lower than in Group B (36 +/- 7 compared with 44 +/- 8 ml/100 ml/minute; p < 0.05). The CVR before surgery, however, was not significantly different between groups (Group A = 43 +/- 21%, Group B = 37 +/- 29%). After shunt placement, there was an increase in the CVR in Group A to 52 +/- 37% after 7 days and to 68 +/- 47% after 7 months (p < 0.05), whereas in Group B the CVR decreased to 14 +/- 18% (p < 0.05) after 7 days and returned to the preoperative level (39 +/- 6%) 7 months after shunt placement. CONCLUSIONS: The preliminary results indicate that a reduced baseline CBF before surgery does not indicate a poor prognosis. Baseline CBF before shunt placement and preoperative CVR are not predictive of clinical outcome. A decrease in the CVR early after shunt placement, however, is related to poor late clinical outcome, whereas early improvement in the CVR after shunt placement indicates a good prognosis.

Induction of heat shock protein 70 in the rat brain following intracisternal infusion of autologous blood: evaluation of acute neuronal damage.

OBJECT: Investigation into a potential treatment for the acute period following onset of spontaneous subarachnoid hemorrhage (SAH) is hampered by the lack of a standardized experimental model. For that purpose the authors elaborated on a small-animal model in which computer-controlled intracisternal blood infusion is used and investigated whether this model can reliably reproduce acute neuronal injury after SAH. METHODS: Whole autologous blood (blood-infused group) or isotonic saline (control group) was infused into the cisterna magna or olfactory cistern of rats. The infusions decreased exponentially during a 5-minute period. Throughout the infusion period, intracranial pressure (ICP) was monitored. Neuronal injury was quantified by observing tissue immunoreactivity to a 70-kD heat shock protein (HSP70) and comparing this with the tissue's reaction to hematoxylin and eosin staining. On Days 1, 3, and 5, the CA1, CA3, and dentate gyrus regions of the hippocampus were analyzed, respectively. During saline infusion ICP increased within seconds beyond 80 mm Hg and afterward decreased in accordance with the infusion rate. During the infusion of blood, the same initial pressure peak was found, but the ICP remained increased beyond this pressure level throughout the 5-minute infusion period. The HSP70 immunoreactivity in the saline-infused group was found only on Day 1 in the CA1 region and the dentate gyrus, but not in the CA3. After injection of whole blood, there was HSP70-positive staining in the CA1, CA3, and dentate gyrus regions throughout the observation period. CONCLUSIONS: The controlled cisternal infusion of blood caused neuronal injury that resembled that of previous experimental models that produce SAH by rupture of intracranial vessels with endovascular techniques. Unlike those experiments, the intracisternal infusion technique presented by the authors provides more standardized bleeding with regard to ICP, the volume of subarachnoid blood, and the extent of acute cellular injury.

Far-field responses to stimulation of the cochlear nucleus by microsurgically placed penetrating and surface electrodes in the cat.

OBJECT: A new generation of penetrating electrodes for auditory brainstem implants is on the verge of being introduced into clinical practice. This study was designed to compare electrically evoked auditory brainstem responses (EABRs) to stimulation of the cochlear nucleus (CN) by microsurgically implanted surface electrodes and insertion electrodes (INSELs) with stimulation areas of identical size. METHODS: Via a lateral suboccipital approach, arrays of surface and penetrating microelectrodes with geometric stimulation areas measuring 4,417 microm2 (diameter 75 microm) were placed over and inserted into the CN in 10 adult cats. After recording the auditory brainstem response (ABR) at the mastoid process, the CN, and the level of the inferior colliculus, EABRs to stimulation of the CN were recorded using biphasic, charge-balanced stimuli with phase durations of 80 microsec, 160 microsec, and 240 microsec at a repetition rate of 22.3 Hz. Waveform, threshold, maximum amplitude, and the dynamic range of the responses were compared for surface and penetrating electrodes. The EABR waveforms that appeared for both types of stimulation resembled each other closely. The mean impedance was slightly lower (30 +/- 3.4 kohm compared with 31.7 +/- 4.5 kohm, at 10 kHz), but the mean EABR threshold was significantly higher (51.8 microA compared with 40.5 microA, t = 3.5, p = 0.002) for surface electrode arrays as opposed to penetrating electrode arrays. Due to lower saturation levels of the INSEL array, dynamic ranges were almost identical between the two types of stimulation. Sectioning of the eighth cranial nerve did not abolish EABRs. CONCLUSIONS: Microsurgical insertion of electrodes into the CN complex may be guided and monitored using techniques similar to those applied for implantation of surface electrodes. Lower thresholds and almost equivalent dynamic ranges indicate that a more direct access to secondary auditory neurons is achieved using penetrating electrodes.

Technical considerations regarding accuracy of the MKM navigation system. An experimental study on impact factors.

The purpose of this study was to investigate experimentally, factors determining the navigation accuracy of the MKM navigation system by Zeiss. The MKM consists of an operating microscope mounted to a six-axis motor-driven robot arm and an alpha-workstation. The image-guided surgery device provides navigation information based on calculation of the cartesian coordinates of the robot arm, and coordinates of the focus point assessed by laser assisted measurement. Navigation information (current position, direction and distance to a previously selected target) is optically projected into the microscopic field. Following factors were examined in an experimental setting for their impact on accuracy of the MKM: optical system, mechanical precision of the robot arm, and registration procedure. The robot arm and the optical system of the microscope allow high precision measurements of any focus point (error < 2 mm if the following aspects are considered: the use of auto-focus function instead of manual focusing, positioning of the registration points as a square or a triangle focus point should be selected on a surface that is perpendicular to the optical axis.