ABSTRACT
This study prospectively collected the clinical data of patients who received sacral neuromodulation(SNM)variable-frequency stimulation (VFS) mode from June 2020 to December 2020, in order to explore the efficacy and safety of VFS mode in the treatment of refractory lower urinary tract dysfunction. The inclusion criteria were as follows: ①SNM was implanted; ②age ≥18 years old; ③The traditional constant-frequency stimulation (CFS) mode has poor therapeutic effect, and can not be improved after repeated adjustment of stimulation parameters; ④Patients with overactive bladder (OAB) symptoms, who fail to respond to conservative treatment or are intolerant to conservative treatment; ⑤The drugs that affect the lower urinary tract symptoms and pelvic function should not be increased or decreased during the trial; ⑥provision of informed consent. A total of six patients meeting the criteria were included in the study, with three males and three females. The age ranged from 47 to 74 years, with an average age of 55 years. Among those patients, three cases were diagnosed of OAB, two cases were diagnosed of interstitial cystitis, and one case was diagnosed of neurogenic bladder. All patients had received CFS-SNM for an average of 20.6 months before upgrading to VFS mode, and suffered from severe frequency of urination at the same time. Compared with the severity of symptoms during the baseline period and the CFS period, a trend of improvement was found among four patients during the VFS period. The severity of symptoms was mainly based on the average daily urination frequency and OAB-Q score. For the two patients with interstitial cystitis, OAB symptoms worsened during the VFS period, while the VAS score did not change significantly. In general, VFS-SNM is not inferior to CFS-SNM in improving the symptoms of frequent micturition. For patients with interstitial cystitis, multiple sets of VFS parameters can be tried under the premise of satisfactory pain management.
ABSTRACT
The evoked force was observed during repetitive electrical stimulation for 3 min on m. vastus medialis. The stimulus frequency was 0.2 Hz, 10 Hz and 20 Hz. The time to peak of twitch was 90.8 ms at 0.2 Hz stimulation. The changes in the evoked force did not represent a constant or a monotonic pattern but were complex at 10 Hz and 20Hz stimulations. At 10 Hz the evoked force represented an initial transient increment (steep peak), then an abrupt decrement followed by a gradual increase (gentle peak) and then a gradual decrease. At 20 Hz the steep phase did not appeared. The magnitude of potentiation was not necessarily large at 20 Hz. These results suggest that a constant discharge rate of motor units cannot maintain constant force development, and “rate coding” is considered to be necessary for keeping a constant force.