Discussion
SCI is a major disabling condition which has an incidence between 14 to 54 cases per million of the population in different areas around the globe, with a significant dominance of the males [2, 19-21]. The most common etiological factors are traffic accidents and falls, according to the previous reports [20-22]. In our study, all patients were male, and our age group was respectively young with a mean age of 32.03 (SD: 6.7) years. The most common etiologies were also those of accidents and falls in our cohort that comprised 12 and 9 patients, respectively. Unfortunately, we cannot provide any incidence rate or demographic distribution data because of the selective nature of the patient group in our study. On the other hand, we can report that as a multidisciplinary neuro-urology working group, we are faced with 2 to 5 refractory NDO cases per year, which makes one case per physician per year for our group. To the best of the authors’ knowledge, a comprehensive nationwide mapping of SCI cases in our country is not available in the literature and consider that such a thorough report is warranted. Fortunately, individuals who have suffered from SCI are usually managed in specialized institutions, thus, such a comprehensive study or prospective trials in selected patients seems possible in these institutions.
The clinical picture of a SCI patient depends on the extent, whether it is complete or partial, and the level of the injury. A complete cervical disruption presents with tetraplegia while a partial lower lumbar injury may only affect a single extremity. Urinary functions are also in the same vein with the overall motor and sensory functions. Injuries of the cervical, thoracic, or lumbar spinal cord usually represent with an NDO and DSD, while sacral injuries virtually always result in an underactive detrusor with a functional or flask external sphincter [11, 23]. Our study comprised only complete suprasacral SCI lesions with refractory NDO and neuropathic pain, which represented our selected subgroup. Medical management options for these patients are comparatively few, thus, several studies were undertaken to increase the therapeutic choices. In experimental fashion, inosine, resiniferatoxin, an E-series prostaglandin 1 receptor antagonist, kynurenine gene transfer via viruses, gamma-aminobutyric acid A and B receptor agonists muscimol and baclofen, a transient receptor potential 1 and a transient receptor potential vanilloid 1 receptor antagonists, an arginase inhibitor, a prostacyclin receptor antagonist, an endothelin-A receptor antagonist, and memantine have been shown to be beneficial [24-33]. Clinical studies have indicated that mirabegron, tetrahydrocannabinol-cannabidiol oral spray, anticholinergic preparations, and gabapentin are effective in the management of neurogenic overactive detrusor [13-18, 34-39]. However, there is still a group of patients who are unresponsive to the combination of an anticholinergic with the ß-adrenergic therapeutic. These patients are considered for Botulinum Toxin injections or surgical options if the injections fail [11, 40]. Additionally, neuropathic pain is also a common component of the treatment for an individual who has suffered an SCI [41]. The management of neuropathic pain justifies the usage of gabapentin in these patients, akin to our study group. In our study, we aimed to utilize gabapentin’s role for the management of both neuropathic pain and the neurogenic overactive detrusor, and our results showed that it has a beneficial effect. Our results are compatible with the previous studies, but with better urodynamic findings, decreased VAS scores, as well as continence status. As a result, we believe that add-on gabapentin therapy can be considered as a salvage option between the combinations of an anticholinergic with ß-adrenergic and Botulinum Toxin injection, and it is also beneficial in the management of the neuropathic pain of these patients.
As an important caution, physicians should be aware of the addictive and abuse potential of gabapentin [42]. Interestingly, to the best of the authors’ knowledge, previous papers that reported the success of gabapentin in the management of overactive bladder did not indicate any cases of addiction or abuse. Considering the follow-up periods of the available papers, future follow-ups must give importance to this point. A total of 11 patients had benefit from gabapentin and continued the treatment. Among them, we also have not observed any signs of addiction or abuse. We believe that the abusive potential may also be related to the individual’s personality or behavior. This is an area of future research and we consider that future follow-ups of the available studies that have used gabapentin may be a matter of interest.
Our study brings encouraging results in the management of an unresponsive NDO due to SCI; however, the study has some shortcomings. Firstly, the cohort is a selected patient group. Therefore, we cannot indicate any demographic information or endorse a common clinical strategy based on our selected patients. The patient follow-up data is also limited after the initial treatment. A review of the patient charts revealed that among a total of 11 patients, only four of them are still being followed-up by our working group. We cannot report any long-term compliance data for the 7 patients who dropped out of our follow-up. Furthermore, we cannot report the success of Botulinum Toxin injections in the unresponsive group in our cohort. Further follow-ups would show the compliance rates and long-term success of gabapentin add-on therapy. The condition of the unresponsive patients is also a matter of interest. Whether a correlation exists between the unresponsiveness of the patients with the clinical course should be evaluated by prospective observational studies. However, we believe that our results hold importance by bringing clinical and urodynamic evidence in favor of the safety and benefits of gabapentin as an option in the treatment of NDO secondary to SCI.
In conclusion; Gabapentin is an option for the treatment of NDO after SCI. The approved usage of the therapeutic for neuropathic pain may justify its usage for such patients outside of clinical trials. We believe that it can also be considered as a salvage option in refractory NDO cases as well as a primary option in patients who have NDO concurrent with neuropathic pain.
Conflict of interest : Authors declared no conflict of interest
Authors’ contribution: OC contributed to data collection and analysis, manuscript writing, and revision. OG contributed to study design, manuscript writing, and revision. TK contributed to literature review, manuscript writing, and revision. CK and AS contributed to data collection and analysis. OM contributed to study design, data analysis, and literature review. All authors approved the final version of the article for submission.
Data avaibility statement: The data that support the findings of this study are openly available in Harvard Dataverse with https://doi.org/10.7910/DVN/PGNNIY.