Dexamethasone versus Hyaluronidase as an Adjuvant to Local Anesthetics in the Ultrasound-guided Hydrodissection of the Median Nerve for the Treatment of Carpal Tunnel Syndrome Patients.

Background: Carpal tunnel syndrome (CTS) is one of the most common focal entrapment neuropathies. Although the exact etiology remains unclear, high-pressure-related intracarpal tunnel compression of the median nerve (MN), progressing ischemia, and mechanical strangulation are common mechanisms. The therapeutic managements for CTS depend on the disease severity, varying from a conservative treatment to surgical interventions. Conservative treatment is helpful for most of the patients with mild-to-moderate CTS. Hydrodissection is a minimally invasive procedure of injecting solutions into some anatomical spaces to facilitate dissection and adhesiolysis. Steroids as an anti-inflammatory drugs are used to treat chronic pain conditions. Hyaluronidase as an adhesolysis agent can also be used for epidural injections with local anesthetics (LAs) and steroids for control of chronic back pain.

Aim of the Study: This study was carried out to compare the efficacy of hyaluronidase versus dexamethasone as adjuvants to the mixture of LAs in ultrasound (US)-guided hydrodissection of the median nerve in mild to moderate cases of carpal tunnel syndrome.

Settings and Design: This study was a prospective randomized controlled double-blinded clinical study.

Methods: 40 patients aged from 20 to 60 years old with clinical, electrophysiologic, and ultrasonographic evidence of mild to moderate CTS were included in this study. Each patient was assessed at the baseline (prior to injection) and at 1 week, 1 month, 3 months, and 6 months intervals after injection: (1) The Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) which is a frequently used patient-based questionnaire for measurement of CTS. primary outcome. (2) Median motor and sensory nerve conduction studies (NCS) secondary outcome. (3) Median nerve ultrasonography. The ultrasound examination included measurement of the median nerve cross-sectional area (CSA) at the distal wrist crease (DWC). Also, the median nerve echogenicity, mobility, and vascularity at the DWC were assessed by US. Secondary outcome. All outcome assessments were assessed by single investigator who was blinded to the study details. All patients received US guided hydrodissection of the median nerve at the distal wrist crease. The selected patients were randomly allocated into 2 groups containing 20 patients each according to the study drugs; Group (D) received 5 mL (3 mL plain bupivacaine 0.5% and 2 mL (8 mg) dexamethasone), and Group (H) received 5 mL (3 mL plain bupivacaine 0.5% and 2 mL normal saline containing 300 international units (IU) hyaluronidase. Ultrasound-guided intracarpal injection using ultrasonography (Sono Scape A5; Shinzhen, China) with a 10-18-MHZ linear array transducer was performed by the same physician who was not aware of study groups, the MN was observed at the inlet of the carpal tunnel, 3 ml of solution was injected via the in-plane ulnar approach, to detach the MN from the transverse carpal ligament and an additional 2 ml was injected to separate the MN from underlying flexor tendons. All patients were observed for 30 minutes post injection for possible side effects before discharge. Normally distributed numerical data are presented as mean ± standard deviation, and differences between the groups were compared using the independent Student's t -test. Chi-square test was used for categorical data. Intragroup data at different follow up time points were evaluated using paired Student's t -test. All statistical tests were two-tailed, with P < 0.05 being considered statistically significant.

Results: The demographic data of the patients in both groups were statistically insignificant (P-value >0.05). In the pre-injection time, there were no statistically significant differences between both groups as regards BCTQ (SSS, FSS), electrophysiological studies (SNCV, DML), and sonographic data (CSA, echogenicity score, mobility score, and vascularity score). The comparison between both groups showed that measured parameters as regards BCTQ (SSS, FSS), electrophysiological studies (SNCV, DML), and sonographic data (CSA, echogenicity score, mobility score, and vascularity score) were significantly improved in group H compared with group D in the follow up periods at 1 week, 1 month, 3 months and 6 months post-injection (P-value <0.05). The comparison within each group showed that in group D, the measured parameters; BCTQ (SSS, FSS), electrophysiological studies (SNCV, DML), and sonographic data (CSA, echogenicity score, mobility score, and vascularity score) were statistically significantly improved at 1 week, 1 month and 3 months follow up post-injection times but they were not significantly improved at 6 months post-injection time compared with the pre-injection data (P-value >0.05). While in group H, these measured parameters were statistically significantly improved in the all follow up post-injection times; at 1 week, 1 month, 3 months and even at 6 months periods compared with the baseline pre-injection data (P-value < 0.05).

Conclusion: In this study, it was concluded that MN hydrodissction using hyaluronidase (as an adhesolysis agent) significantly improved patients with mild to moderate CTS compared to steroid (as an anti-inflammatory agents) hydrodissection of MN as regards BCTQ (SSS, FSS), electrophysiological studies (SNCV, DML), and sonographic data (CSA, echogenicity score, mobility score, and vascularity score) not only at 1 week, 1 month and 3 months follow up post-injection times but these parameters were also significantly improved at 6 months post-injection time in bupivacaine- hyaluronidase hydrodissection group compared to bupivacaine-steroid hydrodissection group.