Cauda equina syndrome (CES) has an incidence of 3.4/million people and a prevalence of 8.9/100.000 population with the highest rates recorded in men in their 5th decade of life. Disc herniation is the most common cause in the ages between 40-60 years, spinal fractures in younger ages (less than 40 years) and iatrogenic causes in older adults (more than 60 years of age). 
Lower urinary tract (LUT) dysfunction is quite common at presentation of the CES, with a mean prevalence of approximately 89%, which is second only to sciatica (95% of CES patients). Partial perineal anesthesia rates range between 30-50%, and perineal sensory deficits are strongly associated with LUT dysfunction [1]. Urodynamically, LUT dysfunction in CES typically involves underactive or acontractile bladder with sphincter underactivity, which result in incomplete bladder emptying and stress urinary incontinence [2]. Detrusor overactivity (DO) is not an uncommon finding and can be found in one out of 3 patients [3]. Prolonged and excessive abdominal straining can denote underactive bladder in such patients, whereas incontinence maybe an early symptom too. 
We performed a retrospective study of patients who had been operated for CES at the Neurosurgical Department of a public teaching Hospital, and had been also submitted to urodynamic investigation either at the immediate peri-operative period or in the following months after surgery, in order to investigate a possible role of urodynamic assessment in the patients’ management.

We retrospectively reviewed the charts of patients who had been operated for CES associated with degenerative lumbar disease between 2012-2021 in our hospital. The data analyzed for possible associations included the patients’ neurological status at presentation and hospital admission, the radiological findings (including simple X-ray of the lumbar spine, CT and MRI scans, and the urodynamic findings, if available. Associations were sought between urodynamic findings and the time that had elapsed between presentation of symptoms/diagnosis and the surgical procedure, the clinical signs and symptoms at presentation and the affected levels radiologically. The Mann-Whitney test and the chi-square test were used accordingly.

Twenty-seven patients (n=16 women, 59% and n=11 men, 41) were included in the final analysis as they had complete data. The mean patient age was 59.59±15.55 years. Radiologically, 44% (n=12) of the patients had one affected level, 37% (n=10) had two affected levels, 15% (n=4) had three affected levels and 4% (n=1) had four affected levels. The majority of patients (n=17, 63%) were submitted to a combination of microdiscectomy, hemilaminectomy and instrumentation, followed by 30 (n=8) who had been submitted to microdiscectomy and hemilaminectomy, while the remaining 7% (n=2) had been submitted to microdiscectomy alone. The most common neurological symptoms and signs are presented in Table 1. 
Urologically, the majority of patients (n=12, 44%) were started on clean intermittent catheterizations (CIC), while another 4 (15%) were on indwelling catheter, 3 patients (11%) were on an alpha-blocker, 4 patients were on antimuscarinics, one patient on combination of an alpha-blocker with an antimuscarinic and CIC, and only 3 patients (11%) could freely void without any intervention. The vast majority of patients (92%, n=25) suffered from LUT dysfunction, urinary retention being the most prevalent symptom (48.1%, n=13) followed by abdominal straining to void (37%, n=10), while urodynamic investigation most commonly demonstrated detrusor underactivity (77%, n=21) followed by detrusor overactivity (33.3%, n=9). The presence of detrusor underactivity (DU) was related to the number of affected levels (p<0.05, x2(3) =8.196). Detrusor overactivity was more commonly present in patients with delayed procedures (p<0.05, U=41.0, z=-2.08). By contrast, early procedures were associated with abdominal straining (p<0.05, U=44.0, z=-2.09). In terms of neurological signs, perianal hypo-aesthesia was the single symptom which precipitated the decision for surgery (p<0.05, U=38, z=-2.5), while paresis and rhizalgia were major indications but did not reach statistical significance. Finally, the number of affected levels was not associated with CES and the type of urological management was not related to the type of neurosurgical procedure.

Our study results suggest an association between the time to surgical management of CES and urodynamic outcomes, but also between radiological findings and urodynamic outcomes. The mechanisms by which an early procedure for CES might be associated with detrusor underactivity whereas a late procedure might be more predictive of DO need to be elucidated. However, the sample size was small and follow-up inadequate for robust results. To establish the role of urodynamics in the neurosurgical and urological management of CES further research is warranted, with studies designed prospectively including preoperative and postoperative urodynamic investigations.

In this patient cohort, we could not find associations between limb sensorimotor dysfunctions and urodynamic findings. Associations were found between the time to surgical management of CES and urodynamic outcomes, as well as between number of affected radiological levels and urodynamic outcomes. Thus, cystometric and radiological evaluation could be proposed in patients with high suspicion of CES.
Underactive bladder is the most common urological dysfunction. Compensatory abdominal straining may ensue and persist in cases of degenerative lumbar disease.
Detrusor overactivity is a rather prevalent condition, accounting for up to 1/3 of patients, with a statistically significant association postoperatively with delayed procedure.

Simon Podnar , Bojan Trsinar, David B Vodusek. Bladder dysfunction in patients with cauda equina lesions. Neurourol Urodyn. 2006;25(1):23-31.  doi: 10.1002/nau.20188.
Simon Podnar, David B Vodušek. Lower urinary tract dysfunction in patients with peripheral nervous system lesions. Handb Clin Neurol. 2015;130:203-24.  doi: 10.1016/B978-0-444-63247-0.00012-2
Seo-Young Kim, Hee Chung Kwon, Jung Keun Hyun. Detrusor overactivity in patients with cauda equina syndrome. Spine (Phila Pa 1976). 2014 Jul 15;39(16):E955-61.  doi: 10.1097/BRS.0000000000000410.