Phantom-based prospective analysis of the accuracy of photo registration technology in electromagnetic navigation of the frontal skull base.

OBJECTIVE: This prospective study compared the accuracy of two different company-specific registration methods (Fiagon GmbH, Hennigsdorf, Germany) in the electromagnetic navigation of the frontal skull base. A newly developed photo registration technology (Fiagon tracey©) promises an increase in accuracy and user-friendliness, but there is no phantom-based prospective study comparing the new method with the classic approach of tactile surface registration. MATERIALS AND METHODS: A phantom skull was prepared with 27 markers in the sagittal, axial and coronary planes, and their reference coordinates were determined using a navigational CT (low dose, slice 0.6 mm). Subsequently, 20 runs of automatic photo registration and tactile surface registration were carried out, and the resulting marker coordinates were compared with the reference coordinates. The target registration error (TRE) of the 27 markers was assessed and compared between the two methods using a 2-factor ANOVA with repeated measures. RESULTS: The mean TRE using surface registration was 1.97 mm ± 0.57, while the mean TRE of the automatic photo registration was 1.54 mm ± 0.24 (p < 0.001). In a subgroup analysis limited to markers in anatomical regions of clinical relevance in terms of paranasal sinus surgery, the mean TRE for the photo registration procedure can even be reduced to 1.29 mm (± 0.43) compared to tactile registration (1.80 mm; ±0.50; p=0.01). CONCLUSIONS: Photo registration is a promising new technology in the field of electromagnetic navigation in paranasal sinus surgery. This prospective phantom-based study showed that the photo registration method achieves a significantly lower target registration error (1.29 mm) compared to the surface-based tactile registration procedure (1.80 mm).

[Reducing tinnitus intensity : Pilot study to attenuate tonal tinnitus using individually spectrally optimized near-threshold noise]. / Reduktion der Tinnituslautstärke : Pilotstudie zur Abschwächung von tonalem Tinnitus mit schwellennahem, individuell spektral optimiertem Rauschen.

BACKGROUND: Around 15% of the general population is affected by tinnitus, but no real cure exists despite intensive research. Based on our recent causal model for tinnitus development, we here test a new treatment aimed at counteracting the perception. This treatment is based on the stochastic resonance phenomenon at specific auditory system synapses that is induced by externally presented near-threshold noise. OBJECTIVE: This pilot study will investigate whether individually spectrally adapted noise can successfully reduce chronic tonal/narrow-band tinnitus during stimulation. MATERIALS AND METHODS: Hearing loss (HL) as well as tinnitus pitch (TP) and loudness (TL) were audiometrically measured in 22 adults (46.6±16.3 years; 4 women) with tinnitus. Based on these measurements, up to eight different noise stimuli with five intensities (-20 to +20 dB SL) were generated. These were presented for 40 s each via audiologic headphones in a soundproof chamber. After each presentation, the change in TL was rated on a five-level scale (-2 to +2). RESULTS: We found patients (n = 6) without any improvement in their TL perception as well as patients with improvement (n = 16), where stimulation around the TP was most effective. The groups differed in post-hoc analysis of their audiograms: the effectiveness of our new therapeutic strategy obviously depends on the individual HL, and was most effective in normal-hearing tinnitus patients and those with mild HL. CONCLUSION: Subjective TL could be reduced in 16 out of 22 patients during stimulation. For a possible success of a future therapy, the HL seems to be of relevance.

[Models of tinnitus development : From cochlea to cortex]. / Modelle der Tinnitusentstehung : Von der Cochlea zum Kortex.

The development of subjective tinnitus is still not mechanistically understood and existing models are controversially discussed. In this overview, the authors discuss three of the main models, all of which propose damage to the cochlea as the initial step in tinnitus development. Based on these models, a possible manifestation of tinnitus-related neuronal activity at the perceptually relevant level of the auditory pathway, the auditory cortex, is presented. Furthermore, it is demonstrated that one of the models offers a new view on the phenomenon, which could potentially help patients to better cope with their condition.

The Erlangen Questionnaire: a new 5-item screening tool for obstructive sleep apnea in a sleep clinic population - A prospective, double blinded study.

OBJECTIVE: The aim of this study was to develop and validate a simplified screening tool for identifying obstructive sleep apnea (OSA) in a sleep clinic population. PATIENTS AND METHODS: A total of 160 patients from a sleep clinic population was enrolled in the prospective, double-blinded study. OSA was defined by using diagnostic criteria of the ICSD-3 after overnight polysomnography (n=96) or polygraphy (n=64). The first 60 patients filled out a multi-item questionnaire and formed the development group. Subsequently, the five most predictive factors were selected to create the Erlangen Questionnaire (EQ). For validation of the EQ, the next 100 patients formed the validation group. RESULTS: The following factors were incorporated into the 5-item EQ: (1) ESS > 10, (2) age > 60, (3) gasping and (4) cardiovascular risk factors, (5) witnessed apneas. The EQ had sensitivities of 94.3%, 92.7% and 92.3%, specificities of 50.0%, 33.3% and 22.9%, positive predictive values of 81.5%, 62.9% and 29.6%, and negative predictive values of 78.9%, 78.9% and 89.5% with respect to mild, moderate and severe OSA. CONCLUSIONS: EQ is a compact 5-item-based, concise and easy-to-use screening tool to identify both male and female patients with OSA in a sleep clinic-population and exhibits all essential factors of internal and external validity. The results of the EQ are comparable to the best-validated and most commonly used STOP-Bang questionnaire regarding sensitivity and specificity in a sleep clinic population.

S100B in serum and saliva: a valid invasive or non-invasive biomarker in obstructive sleep apnea?

OBJECTIVE: The aim of this prospective study was to determine whether serum or saliva S100B could be established as an invasive or non-invasive biomarker of cerebrovascular stress due to chronic intermittent hypoxia in obstructive sleep apnea (OSA). PATIENTS AND METHODS: S100B levels in serum and saliva were measured by an enzyme-linked immunosorbent assay (ELISA) in 40 patients with polysomnographically confirmed OSA (n=34) or ronchopathy (n=6) and 20 control subjects (n=20). We also investigated four healthy volunteers (n=4) to determine whether the S100B levels in serum and saliva are dependent on the time of day. RESULTS: Serum S100B was significantly higher in OSA than in healthy control subjects (p=0.007), although it was not related to the severity of OSA and was independent of age, sex, and subjective daytime symptoms. Values of S100B in saliva showed a marked scatter, so there was no significant difference between the OSA group and controls (p=0.62). We did not find that S100B levels in either serum or saliva depended on the time of day (p=0.53; p=0.91). CONCLUSIONS: Serum S100B allows us to discriminate healthy subjects from patients with OSA. However, it does not live up to its promise as a valid invasive predictor of OSA, since it does not correlate with the severity of the disease. Also, S100B in saliva is not suitable for use as a non-invasive biomarker to detect hypoxia-induced cerebrovascular stress in OSA. This finding prevents an S100B saliva-based assessment of risk or possible extent of structural brain damage, ruling out the possibility of non-invasive home monitoring of compliance and therapeutic efficacy in cases of OSA on treatment.