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.