Multi-electrode sequential versus single electrode stimulation to elicit the stapedial reflex during cochlear implantation: Correlation with maximum comfort level.

OBJECTIVES: To assess whether electrical stimulation sequentially delivered through 4 electrodes located in different cochlear areas may elicit the stapedial reflex at lower levels compared to single electrode stimulation and to correlate the sequentially obtained values with the maximum comfort level (C-level). PATIENTS AND METHODS: A retrospective study was performed on 35 post-verbal adult patients (age 19-80 years) consecutively implanted in 2 cochlear implant centers, evaluating the level of stimulation (pulse width) necessary to electrically evoke the stapedial reflex with two different stimulation modalities: single electrode versus sequential 4 electrode stimulation. Threshold values were compared with C-level obtained at activation. RESULTS: The average differences of pulse width and C-level were significantly smaller (P<0.0001) when the stapedial reflex was obtained with the sequential stimulation modality and reached statistical significance for every single electrode (P<0.0001). CONCLUSIONS: Stapedial reflex thresholds obtained with sequential stimulation through 4 different electrodes significantly correlate to the C-level obtained at the first setting and may be helpful in defining the upper limit of the dynamic field during initial CI mapping.

Sudden hearing loss and MTHFR 677C>T/1298A>C gene polymorphisms.

PURPOSE: Sudden hearing loss (SHL) can be caused by vascular disorders favoring impaired cochlear perfusion. A number of inherited prothrombotic risk factors have been considered in the pathogenesis of vascular impairment and the possible role of genetic alterations has recently been suggested. We aimed to investigate the relationship between SHL and MTHFR 677 and 1298 gene polymorphisms. METHODS: DNA genotyping was performed on peripheral blood leukocytes in 45 SHL patients and 135 controls. RESULTS: Wild-type MTHFR (677CC/1298AA) was significantly more frequent in the controls (P=0.01), and gene polymorphisms (677CT, 677TT, 1298AC, 1298CC, compound 677CT/1298AC) were significantly more frequent in the patients (P=0.005; Ptrend=0.001). CONCLUSION: These data suggest that MTHFR gene polymorphisms may be considered as risk factors for SHL and participate on vascular impairment related to this disorder. Further studies, based on large series of patients, are needed to definitely assess the role of this prothrombotic factor in the etiopathogenesis of SHL.

Chromotropic acid-formaldehyde reaction in strongly acidic media. The role of dissolved oxygen and replacement of concentrated sulphuric acid.

The procedure for formaldehyde analysis recommended by the National Institute for Occupational Safety and Health (NIOSH) is the Chromotropic acid spectrophotometric method, which is the one that uses concentrated sulphuric acid. In the present study the oxidation step associated with the aforementioned method for formaldehyde determination was investigated. Experimental evidence has been obtained indicating that when concentrated H(2)SO(4) (18 mol l(-1)) is used (as in the NIOSH procedure) that acid is the oxidizing agent. On the other hand, oxidation through dissolved oxygen takes place when concentrated H(2)SO(4) is replaced by concentrated hydrochloric (12 mol l(-1)) and phosphoric (14.7 mol l(-1)) acids as well as by diluted H(2)SO(4) (9.4 mol l(-1)). Based on investigations concerning the oxidation step, a modified procedure was devised, in which the use of the potentially hazardous and corrosive concentrated H(2)SO(4) was eliminated and advantageously replaced by a less harmful mixture of HCl and H(2)O(2).

The anterior ligament of the human malleus.

The authors have studied the anterior ligament of the malleus (ALM) from a morphological and embryological point of view. Classical textbooks of anatomy stress the correlation between the ALM and the anterior pin of the sphenoid and define the ligament as a residual of Meckel's cartilage. This study demonstrates the y-shaped form of the ligament, one arm of which reaches the capsule of the temporomandibular joint and the other the pin of the sphenoid bone. Meckel's cartilage pilots the fibres of the ligament itself. Several clinical implications may be hypothesised on the basis of this study.

[Smooth pursuit eye movements evoked by head-phone acoustic stimulation]. / Studio dei movimenti oculari di smooth pursuit evocati mediante stimolazioni acustiche in cuffia.

Smooth pursuit eye movement evoked by binaural acoustic stimulation is examined in the present work. The effect of lateralization was achieved by modulating the interaural difference in intensity, within the headphone, following a pendular pattern. The test was performed on 10 healthy subjects; oscillation frequencies of the acoustic target being 0.15, 0.5 and 0.83 Hz, stimulus intensity 65 and 92 dB SPL. The acoustic signal consisted of white noise. Each trial was performed with eyes closed and then with eyes open. The results demonstrate that sinusoidal eye movement can only be obtained in a few subjects when the acoustic target has the lowest velocity and especially at the higher intensity. In all other cases eye movement was characterized by multiple saccades. The variability in eye movement amplitude is reduced and the value of this parameter decreases significantly under open-eye conditions. The data obtained are in agreement with other reports obtained with free field acoustic stimulation and demonstrate that smooth pursuit eye movement is principally an ocular reflex. In conclusion, acoustic smooth pursuit eye movement appears normally to be characterized by multiple saccades whose pattern can be modulated by intensity and oscillation frequency of the acoustic target as well as by the presence of visual inputs and attentional factors.