Intra-detrusor injections (IDI) of botulinum toxin type A (BTXA) have been used for many years in the management of patients with neurogenic detrusor over-activity (NDO). There is anecdotal evidence to suggest that the duration of effect reduces with time in adults. 
In this study we present 10 years of follow up of children and young people (CYP) who have been treated with IDI of BTXA to manage NDO subsequent to spinal cord injury (SCI). The aim of the study was to investigate whether IDI of BTXA is an effective and tolerated management solution for CYP with NDO following SCI.

The study was a retrospective analysis of CYP in a Spinal Cord Injury Centre (SCIC) who have received IDI of BTXA as part of bladder management for NDO. All patients had urodynamically proven NDO.  Age at injury, cause of injury, impairment, bladder management, age at first injection, number of repeat injections, dose and formulation of BTXA, and current bladder management status of patients was recorded. A Kaplan Meier survival curve was created to determine the feasibility of long term treatment with IDI of BTXA.

20 CYP’s (8 female and 12 male) were identified from discharge summaries of the SCIC. The mean current age is 16.6 years (2-26 years), with mean age at injury 8.35 years (0-15 years) and mean time since injury 7.85 years (2-20 years). The aetiology, impairment and bladder management is shown in Table 1. IDI of BTXA were administered through a paediatric cystoscope under general anaesthesia. Onabotulinum toxin type A (50-300 units) and abobotulinum toxin type A (200-750 units) were used based on child’s weight and previous efficacy. The injections were distributed equally around the bladder avoiding the trigone. The mean age at first injection was 11.25 years (6-19 years). The mean number of repeat injections to date is 3.85 (1-12). The outcome for each patient based on last clinic letter is described in Table 1. The maximum follow up is 120 months

The initial results (after 1 or 2 injections) were satisfactory for the majority of the patients based on urodynamics results and patient reporting. Three patients were not re-treated after the first injections either due to inefficacy or patient choice. A further 2 discontinued treatment after 2-5 injections. Patients who have received more than 5 repeat injections reported decreasing efficacy of treatment with shorter duration of effect and increased incontinence. This was more apparent in the patients who manage their bladder with intermittent catheterisation (IC) compared to a supra-pubic catheter (SPC). In patients who have received more than 5 repeat injections, the dose has gradually increased to the maximum permitted dose, and the frequency of injection has increased from annually to every 6 months. 2 patients who have had more than 5 repeated injections have been offered bladder reconstruction surgery due to inefficacy of IDI of BTXA; a further 3 patients are continuing with IDI of BTXA but report reduced duration of effect. The 2 patients who have received more than 10 injections both reported that the treatment has reduced duration of effect with increased incontinence and smaller capacity. One (performing IC) has been offered bladder augmentation (ileocystoplasty) and one (using SPC) is continuing but at the highest dose, and more frequent intervals. The Kaplan Meier survival graph for patients continuing with treatment is shown in Figure 1.

Intra-detrusor injections of botulinum toxin type A are effective in the short term in children and young people with NDO after SCI. However, we have shown in this study that the duration of efficacy appears to diminish with repeated injections suggesting that this treatment may not provide a long term solution to NDO.
This retrospective study has also highlighted the need for further prospective studies which can quantify outcome measures at specified time intervals to evaluate the efficacy and duration of effect of repeated IDI of BTXA