Relationships between the Spinal Dural Pulsations and the Short-Term Efficacy of Lumbar Epidural Steroid Injection

Background Lumbar spinal stenosis (LSS) causes low back pain, leg pain, numbness in the leg, and neurogenic intermittent claudication. Epidural steroid injection (ESI) has been used for treating spinal stenosis symptoms. We hypothesized that dural pulsation was variable for lumbar spinal stenosis. In cases of the presence of dural pulsation, the pain relief after the ESI was better than in the absence of dural pulsation. This study aimed at investigating the relationships between the presence or absence of spinal dural pulsations and the efficacy of ESI. Methods A total of 71 patients were enrolled in this prospective study. Prior to the ESI, the dural pulsation was measured using a 5-1 MHz array ultrasound transducer. The visual analogue scale (VAS) score was measured pre-ESI and 2 weeks post-ESI and 4 weeks post-ESI. At 4 weeks post-ESI, dural pulsation was rechecked. Results The VAS scores improved after the ESI procedure regardless of the presence or absence of dural pulsation. There was a correlation between the pulsation of the dura and post-ESI VAS scores. However, VAS was not significantly different for different grades of stenosis. Conclusion The ESI was effective in patients with spinal stenosis in short-term follow-up. Dural pulsation of the spinal cord was a positive predictive factor for the ESI effect, but the grade of spinal stenosis severity had no effect on the effectiveness of ESI.


Introduction
Lumbar spinal stenosis (LSS) may be caused by variable factors, with complaints such as low back pain, leg pain, numbness in the leg, and neurogenic intermittent claudication [1,2].Nonsurgical methods such as medication, physical therapy, and epidural steroid injection have been used to treat spinal stenosis symptoms [3,4].Lumbar epidural steroid injection (ESI) has commonly been used in patients with LSS and/or disc herniation [2,[5][6][7][8][9][10][11][12].Te efect of ESI is to ameliorate pain with the combined advantages of local anesthetics delivery and steroid administration.Tere was a previous study on the efcacy of ESI to the severity of LSS [13].Campell et al. [14] reported that the spinal canal dimension is not predictive of the success or failure of epidural steroid injection in patients with spinal stenosis.
Recently, to increase the efect of the procedure or the accuracy of diagnosis, ultrasound has been used in the spine [15][16][17].Pulsation of the spinal cord, dura mater, and cerebrospinal fuid is seen intraoperatively [18].Additionally, periodic pulsations in the central nervous system are caused by pressure changes in the vascular system of the brain and spinal cord and can be seen by magnetic resonance imaging (MRI) [19,20].
In general, pulsatile movements of the dura mater indicate that the cord is free within the subarachnoid space, with no extrinsic compression.Ultrasound has been used to predict surgical success for cervical laminoplasty [16].In addition, intraoperative US has been used to evaluate the decompression status of the spinal cord in patients with cervical compressive myelopathy [21][22][23][24].However, the presence of dural pulsation does not mean that there was no spinal cord compression and is afected by several factors [18,21].Furthermore, it remains unclear whether restoration of dural pulsation is associated with adequate decompression of the spinal cord, or whether dural and spinal cord motions correlate with each other [21].
We hypothesized that dural pulsation was variable depending on the lumbar spinal stenosis grade and that the presence of dural pulsation led to better pain relief after the ESI when compared to cases without pulsation.Tis study aimed at investigating the relationships between the presence or absence of spinal cord dural pulsations and the efcacy of ESI.

Study Design.
A total of 71 patients were enrolled in the present study.We obtained approval from the institutional review board, and the study participants provided written informed consent.
Te LSS grade followed the new grading system [25].Prior to the procedure, the dural pulsation was measured using a 5-1 MHz array ultrasound transducer (CX50 ® , Philips, CA, USA), and the B-mode was checked in the prone position (whether present or not).Pulsatile movements of the spinal cord and dura mater were checked at the narrowest level of the lumbar canal, which was identifed on preoperative MRI and by transverse and longitudinal transducer orientations to the spinal canal.After confrmation of dural pulsation, the information was recorded.
Te ESIs were performed with a CT unit (Big Bore, Philips, USA).Patients were prepared on the radiological table in the prone position, and a wire marking device wire was placed at a suitable location on the low back, and scanning of the pelvis was acquired at 120 kV and 60 mA; the slice diameter and index were 1 mm.Scans were acquired of the undersurface of the posterior lumbar spinous process.From this view, the distance between the introduction angle and the epidural space was measured at the same level of lesion for all subjects.After marking the skin at the appropriate spot near the midline, the area was sterilized and anesthetized.
A 22-gauge Tuohy needle was then advanced partially into the patient, and the needle was then advanced downward onto the outer aspect of the ligamentum favum by using intermittent CT guidance.After placing the needle in the epidural space using the loss-of-resistance technique, 0.5 ml of contrast agent was injected to confrm the epidural space.A combination of 2 ml of preservative-free 1% lidocaine, 1500 units of hyaluronidase, and 4 mg of dexamethasone (1 ml), for a total volume of 3-5 ml, was injected into the epidural space.
Te visual analogue scale (VAS) score was measured preoperatively and 2 weeks and 4 weeks after ESI.Additionally, postprocedure pulsation was measured at fourweek postprocedure follow-up.Te VAS score was evaluated by using the chi-squared test.Correlations between pain relief and the presence or absence of dural pulsation were evaluated using Spearman's rank correlation test.Statistical signifcance was set at P < 0.05.

Results
A total of 71 patients including 27 men and 44 women (aged 50-89 years; mean 68.2 years) diagnosed with central LSS were included in the study.Tere was no signifcant difference between dural pulsation presence group and absence group in age, gender ratio, frequency of stenosis level, and stenosis grade.Te levels and sites of the afected regions are shown in Table 1: L4/5 was the most frequently implicated region.
Te VAS score was improved after ESI, regardless of the presence or absence of dural pulsation (Table 2).Tere was a correlation between the pulsation of the dura and the ESI efect (Table 2).In cases of the presence of dural pulsation, VAS score signifcantly reduced than in the absence of dural pulsation group.According to the grade of stenosis, 41 patients (57%) had grade 1 stenosis.Four weeks after the procedure, the VAS score was not signifcantly diferent for diferent grades of stenosis (Table 3).
None of the cases switched from having dural pulsation to having it or vice versa two weeks after the procedure.

Discussion
In our study, the dural pulsation did correlate with the efect of ESI.However, the grade of spinal stenosis had no efect on the efectiveness of ESI.Our results were not consistent with previous study [13,16,21].
Te movement of the dura originates from the pulsation of the posterior spinal artery and produces a low-grade amplitude periodic motion [18].Stenosis of the spinal canal and compression of nerve structures may lead to intermittent neurogenic claudication due to congestion of the epidural venous blood and increased vascular pressure [26].In addition, we hypothesized that neural compression by stenosis could be the cause for the disappearance of dural pulsation.Te absence of dural pulsation was indicative of severe stenosis, and it might not respond well to the ESI.Dural pulsation does clearly not always indicate the absence of compression of the spinal cord [21].
In the present study, pain reduction was diferent from that in the absence group.Te efect of ESI is to ameliorate pain with the combined advantages of local anesthetics delivery and steroids administration [27].We thought that there would be a change in the dural pulsation after procedure.However, there was no change from absence to presence of dural pulsation or the other way.Tis indicates that the role of ESI may be chemical efect rather than 2 Pain Research and Management mechanical decompression.Also, dural pulsation does clearly not always indicate the absence of compression of the spinal cord [21].Te presence of spinal pulsation indicates low tonicity in the spinal cord and favorable circulation in the radicular arteries [28].
In our study, the B-mode US was used.We attempted to determine the dural pulsation easily and efciently.Te Mmode or another mode was applied to lumbar spine in our study.In our study, B-mode was the best modality to fnd dural pulsation in the epidural space.However, further studies are required to determine which mode is the most efcient.
Te present study has several limitations.Te frst is the short initial follow-up period.Second, we did not study the degree of pulsation strength, such as absence, weak, fair, and strong.Tird, the outcome was measured only by the patient's pain score; there was not a functional outcome measurement or measurement of psychological improvement, medication reduction, or disability status.Fourth, multiple level LSS was excluded, although most patients do have more than one level of stenosis.In addition, we have not ruled out comorbid diseases such as cardiac diseases, atherosclerosis, or diabetes mellitus as other decreasing cause of dural pulsation.Finally, this study did not include a variety of other comorbid diseases, mobilization level, exercise level, or activities of daily living, etc., in two groups.
In conclusion, ESI was efective for patients with spinal stenosis.Dural pulsation of the spinal cord could be a positive predictive factor for the ESI efect; however, the severity of spinal stenosis had no efect on the efectiveness of ESI.

Table 2 :
Correlation between the presence or absence of dural pulsation and postprocedure visual analogue scale (VAS) score evaluated by using the chi-squared test.

Table 3 :
Correlation between the grade of spinal stenosis and postprocedure visual analogue scale (VAS) score evaluated by using Pearson coefcient.