UNLABELLED: Vagus nerve stimulation is used to reduce the frequency and intensity of seizures in patients with epilepsy. In the present study four such patients were studied while awake. We analyzed the physiological responses to vagus nerve stimulation over a broad range of tolerable stimulus parameters to identify vagal A-fiber threshold and to induce respiratory responses typical of C-fiber activation. A-fiber threshold was determined by increasing stimulation current until laryngeal motor A-fibers were excited (frequency=30 Hz). With A-fiber threshold established, C-fiber excitation was attempted with physiologically appropriate stimulus parameters (low frequency and high amplitude). RESULTS: A-fiber thresholds were established in all patients, threshold currents ranged between 0.5 and 1.5 mA. Stimulation at lower frequency (2-10 Hz) and higher amplitudes (2.75-3.75 mA) did not produce cardiorespiratory effects consistent with C-fiber activation. It is possible that such effects were not observed because vagal C-fibers were not excited, because C-fiber effects were masked by the 'wakeful drive' to breathe, or because epilepsy or the associated therapy had altered central processing of the vagal afferent inputs.
UNLABELLED: Vagus nerve stimulation is used to reduce the frequency and intensity of seizures in patients with epilepsy. In the present study four such patients were studied while awake. We analyzed the physiological responses to vagus nerve stimulation over a broad range of tolerable stimulus parameters to identify vagal A-fiber threshold and to induce respiratory responses typical of C-fiber activation. A-fiber threshold was determined by increasing stimulation current until laryngeal motor A-fibers were excited (frequency=30 Hz). With A-fiber threshold established, C-fiber excitation was attempted with physiologically appropriate stimulus parameters (low frequency and high amplitude). RESULTS: A-fiber thresholds were established in all patients, threshold currents ranged between 0.5 and 1.5 mA. Stimulation at lower frequency (2-10 Hz) and higher amplitudes (2.75-3.75 mA) did not produce cardiorespiratory effects consistent with C-fiber activation. It is possible that such effects were not observed because vagal C-fibers were not excited, because C-fiber effects were masked by the 'wakeful drive' to breathe, or because epilepsy or the associated therapy had altered central processing of the vagal afferent inputs.
Authors: Atsuko Seki; Hunter R Green; Thomas D Lee; LongSheng Hong; Jian Tan; Harry V Vinters; Peng-Sheng Chen; Michael C Fishbein Journal: Heart Rhythm Date: 2014-04-24 Impact factor: 6.343
Authors: Matthijs Kox; Lucas T van Eijk; Tim Verhaak; Tim Frenzel; Harmke D Kiers; Jelle Gerretsen; Johannes G van der Hoeven; Lilian Kornet; Avram Scheiner; Peter Pickkers Journal: Arthritis Res Ther Date: 2015-06-07 Impact factor: 5.156