Central nervous system control of micturition in patients with voiding dysfunction and normal controls. An electrophysiologic study

Purpose: The pontine micturition center plays a central role in regulating the micturition reflex, but the precise neural mechanisms are unclear. The cerebral cortex is involved in coordinating micturition but there is little knowledge on specific evolutionary higher brain regions. The present study aimed to investigate whether cortical activation during micturition can be demonstrated by EEG power spectra patterns and to explore whether specific cortical regions involved in the interaction of inhibition and release dur ing the micturition reflex can be discerned. We also aimed to test whether intravesical electrostimulation (IVES) therapy in patients with micturition disorders has an effect on patterns of cortical activity. Methods: The healthy control group was divided into those who were able to void when requested (6 women, 12 men) and those who were not (8 women, 10 m en). These subgroups were compared separately with the 14 patients before a nd after IVES for voiding dysfunction. following IVES all patients were abl e to void spontaneously. Mean age of the patients and healthy volunteers wa s 52 and 30 years, respectively. At the beginning of the study all subjects had a bladder volume of approximately 250 mt as measured by sonography. Th e EEG was obtained at rest and during the attempt to void. In the patients' group EEG was obtained before IVES treatment and at the day of the last st imulation. The measurement period lasted about 6 minutes. At the beginning of the recording the proband was asked to close his/her eyes. During the re sting period after 1 minute the patient was asked to open his/her eyes. Aft er 10 seconds he/she was asked to close his/her eyes again. Then, with eyes still closed, the patient was asked to void. During the entire EEG recordi ng the patient was seated in a comfortable, electrically isolated chair in a darkened room and separated from the examiner by a partition. The subject was asked to relax and not move his/her eyes. The EEG was recorded from th e 19 standard points (10-20 System) versus an averaged mastoid electrode wi th a gold-plated cup electrode (Glass). An EOG was recorded simultaneously to register eye artefacts. The amplification chain was calibrated with a 10 -Hz 100-mu V-SS sinus signal generated with a biosignal amplifier. The tran sitional resistances of ail EEG channels were less than 5 kOhm and establis hed as soon as possible. EEG and EOG signals were amplified and recorded wi th a B.E.S.T. Brain Mapping System. The recording frequency was 256 Hz and the resolution of the analog digital conversion was 12 bit. A high pass and a low pass filter were set to 0.53 Hz and 70 Hz, respectively. All recordi ngs were inspected visually before computer analysis. Artefacts were marked and excluded from the further analysis. None of the EEG recordings showed clinical abnormalities. As expected, the EEGs during voiding attempts showe d some muscle potentials and slow motion artefacts. For each subject two ar tefact-free resting segments of about 20 seconds, one from the resting phas e and one from the voiding attempt, were defined by hand for automated anal ysis. Relative power spectra (mu V-2) were calculated for the defined segme nts. From the spectra the relative alpha band power (7.5-13.0 Hz) was calcu lated for each subject for rest and voiding. Group (patients vs. voiding pr obands vs. probands unable to void) and sex were independent variables. The alpha power of the 17 electrode positions of the 10-20 system (without Fp1 and Fp2) during rest and attempted voiding were repeated measurement varia bles. The frontopolar electrode was not used because of its susceptibility to artefacts. The number of dependent variables was due to the explorative nature of the study. With interactions of variables with more than two fact or levels a Greenhouse-Geisser correction was performed. Interactions were subjected to contrast analysis and Newman-Keuls-Post tests. Results: Significant effects were seen for BEDINGUNG (F-(1,F-46) = 91.07, P < 0.01) and electrode POSITION (F-(16,F-736) = 35.07, P < 0.01). The alpha level was higher at rest than during attempted micturition, which reflects lower activation. Electrode POSITION was not analyzed further because we w ere interested mainly in the groups. There was a significant interaction be tween GROUP and electrode POSITIONS (F-(32,F-736) = 1.83, P < 0.05). The co ntrast analysis showed that this interaction was due to both activation dif ferences in the individual positions of the probands able to void (F-(16,F- 736) = 11.08, P < 0.01), the probands unable to void (F-(16.736) = 12.72, P < 0.01), and the patients (F-(16,F-736) = 14.89, P < 0.01) and to differen ces among the groups. Most of the significant differences were seen between patients (PA) and healthy controls unable to void (MV). With the exception of O2 there were no differences between patients after stimulation therapy (PA) and healthy controls able to void (M). The alpha band power of patien ts after IVES (PA) and controls able to void (M) was similar whereas contro ls unable to void had a markedly higher activation level (less alpha power) . The comparison of the power spectra of the patients before (PA/v) and aft er (PA) stimulation reveals significant differences that are nearly identic al to the differences between groups M and MV. Conclusions: There are typical electrophysiologic cerebral changes during m icturition in healthy volunteers. Intravesical stimulation is not only effe ctive to induce voiding but also induces electrical changes on higher mictu rition centers measurable by EEG.