Medición de impedancias in-vivo durante la cirugía de implante coclear como predictor de la posición de los electrodos dentro de la cóclea / Impedance measures during in-vivo cochlear implantation predict array positioning / Medição das impedâncias in-vivo durante a cirurgia de implante coclear como preditor da posição dos eletrodos no interior da cóclea

INTRODUCCIÓN: Los implantes cocleares son dispositivos protésicos neuronales utilizados para el tratamiento de las hipoacusias neurosensoriales severas a profundas. La activación de electrodos estimula las células del ganglio espiral y las vías nerviosas. Una estimulación más discreta de subpoblaciones neuronales se puede obtener cuando los electrodos están más cerca de las células ganglionares en la pared del modiolo. La distancia del electrodo al modiolo podría ser una de las múltiples variables que influyen en el resultado del paciente con un implante coclear. Actualmente no hay un protocolo establecido para medir esta distancia. Mediante diversas técnicas de imágenes se puede determinar la posición de la guía de electrodos dentro de la cóclea. La tomografía computada cone beam ha sido validada como una herramienta útil para evaluar la posición de los electrodos luego de la implantación. Tykocinski et al. describieron un modelo de la interfase electrodo-electrolito del implante coclear como una resistencia y un condensador en paralelo, y la resistencia del tejido circundante como una resistencia en serie. Realizando un registro detallado de la forma de la curva de voltaje, los datos pueden usarse para calcular la impedancia clínica o total, la resistencia de acceso, la impedancia de polarización y sus subcomponentes: Resistencia de polarización y capacitancia de polarización. El objetivo de este estudio es determinar si la distancia electrodo modiolar de cada uno de los electrodos podría predecirse a partir de mediciones de impedancia...

INTRODUCTION: Cochlear implants are neuronal prosthetic devices used for the treatment of severe to profound sensorineural hearing loss. The activation of electrodes stimulates spiral ganglion cells and nerve pathways. A more discrete stimulation of neuronal subpopulations can be obtained when the electrodes are closer to the ganglion cells in the modiolus wall. The distance from the electrode to the modiolus could be one of the multiple variables that influence the outcome of the patient with a cochlear implant. Currently there is no established protocol to measure this distance. By means of various imaging techniques, the position of the electrode guide inside the cochlea can be determined. Cone beam computed tomography has been validated as a useful tool to evaluate the position of the electrodes after implantation. Tykocinski et al., described a model of the electrode-electrolyte interface of the cochlear implant as a resistance and a capacitor in parallel, and the resistance of the surrounding tissue as a series resistance. By making a detailed record of the shape of the voltage curve, the data can be used to calculate the clinical or total impedance, the access resistance, the polarization impedance and its subcomponents: polarization resistance and polarization capacitance. The objective of this study is to determine if the electrode distance modiolar of each of the electrodes could be predicted from impedance measurements…

INTRODUCÃO: Os implantes cocleares são dispositivos protéticos neuronais utilizados no tratamento da perda auditiva neurossensorial severa a profunda. A ativação de eletrodos estimula as células ganglionares espirais e as vias nervosas. Uma estimulação mais discreta de subpopulações neuronais pode ser obtida quando os eletrodos estão mais próximos das células ganglionares na parede do modíolo. A distância do eletrodo ao modíolo pode ser uma das múltiplas variáveis que influenciam o resultado do paciente com implante coclear. Atualmente não há protocolo estabelecido para medir essa distância. Por meio de várias técnicas de imagem, a posição do guia do eletrodo dentro da cóclea pode ser determinada. A tomografia computadorizada por feixe cônico foi validada como uma ferramenta útil para avaliar a posição dos eletrodos após o implante. Tykocinski et al. Descreveu um modelo da interface eletrodo-eletrólito do implante coclear como uma resistência e um capacitor em paralelo, e a resistência do tecido circundante como uma resistência em série. Realizando um registo detalhado da forma da curva de tensão, os dados podem ser usados para calcular a impedância clínico ou total, a resistência de acesso, a impedância de polarização e seus subcomponentes: resistência de polarização e capacitância de polarização. O objetivo deste estudo é determinar se a distância modiolar do eletrodo de cada um dos eletrodos poderia ser prevista a partir de medidas de impedância...

Electrode Position and the Clinical Outcome after Bilateral Subthalamic Nucleus Stimulation

We compared the surgical outcome with electrode positions after bilateral subthalamic nucleus (STN) stimulation surgery for Parkinson's disease. Fifty-seven patients treated with bilateral STN stimulations were included in this study. Electrode positions were determined in the fused images of preoperative MRI and postoperative CT taken at six months after surgery. The patients were divided into three groups: group I, both electrodes in the STN; group II, only one electrode in the STN; group III, neither electrode in the STN. Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn and Yahr stage, and activities of daily living scores significantly improved at 6 and 12 months after STN stimulation in both group I and II. The off-time UPDRS III speech subscore significantly improved (1.6 +/- 0.7 at baseline vs 1.3 +/- 0.8 at 6 and 12 months, P < 0.01) with least L-dopa equivalent daily dose (LEDD) (844.6 +/- 364.1 mg/day at baseline; 279.4 +/- 274.6 mg/day at 6 months; and 276.0 +/- 301.6 mg/day at 12 months, P < 0.001) at 6 and 12 months after STN deep brain stimulation (DBS) in the group I. Our findings suggest that the better symptom relief including speech with a reduced LEDD is expected in the patients whose electrodes are accurately positioned in both STN.

The Significance of Recording Electrode Placement in Test-Retest of Electroneuronography / 대한이비인후과학회지

ENoG is regarded as a valuable method for quantitatively assessing facial nerve function, however it is occasionally discorrelated with clinical findings. So its utility may be diminished, especially in the serial tests. So, we endeavored to find the suitable position of recording electrode in test-retest variability of ENoG. We performed the test five times individually in 18 healthy adults(all males) volunteers. The recording electrodes were placed at 3 different positions(whole nasolabial fold(A), 2/3 portion of the nasolabial fold(B), 1/2 portion of the nasolabial fold(C)). And then we compared the results between action potentials of 3 different positions. The amplitude was more stable at B or C than A. The mean interside variance(ISV) of individuals was less than 50% except one case at A, and there was no significant difference among them(p>or=0.05) except two persons between A and C(p<0.05). In the test-retest variability, the mean was 20.03%(A:20.66+/-10.72%, B:23.75+/-12.60%, C:15.69+/-10.21%). There was more smaller mean and standard deviation at C than others. So, we recommand the 1/2 of the nasolabial fold as the available position in the serial ENoG recordings.

The Significance of Recording Electrode Placement in ENoG Measurement / 대한이비인후과학회지

ENoG is the objective electrophysiologic measurement of the muscle compound action potential(CAP) to assess the rate of degenerated nerve fibers. However, occasional discorrelation with clinical findings may diminish the utility of the ENoG. So, we studied the significance of recording electrode placement, which is considered to affect the result of the ENoG. We performed the interside variance in 20 healthy adults(20 males) volunteers and retest was performed in 6 adults of 20 volunteers. The recording electrode was placed at 3 positions.(whole nasolabial fold(A), 2 / 3 of the nasolabial fold(B), 1 / 2 of the nasolabial fold(C)) And then we compared the results: 1) In the first measurement, the mean CAP was 3.02+/-0.98mV(A), 2.80+/-0.75mV(B), 2.56+/-0.57mV(C) on the right side, 2.70+/-1.02mV(A), 2.50+/-0.90mV(B), 2.33+/-0.86mV(C) on the left side, and there was no significant difference between right and left inter-side amplitude(p>or=0.05). 2) In the first measurement, the mean interside variance(ISV) was 32.7%(37.55+/-16.32%(A), 29.88+/-17.15%(B), and 30.67+/-18.56(C)) and there was no significant difference among them(A, B, C)(p>or=0.05). The minimal individual ISV was 20.35+/-12.44%. There was significant difference between it and the other individual 3 positions(por=0.05). The minimal individual ISV was varied in each testing at 3 positions. And the value was 14.32+/-2.69%. There was no significant difference between it and other 3 postions(p>or=0.05). So we recommand that the recording electrode may be fixed at the bilateral same position of the nasolabial fold. But if there is any indication of facial nerve decompression, you must find the best recording electrode position to get the minimal ISV before operation.