Neuropathic pain in an elderly population of an urban area of Iran with a special focus on carpal tunnel syndrome : epidemiological aspects, clinical characteristics, and non-surgical therapy

Abstract

Background: People are getting older, and aging problems and disorders are increasing fast. Knowing the rates, causes, symptomatology, treatment, relief, and prognosis of associated disorders can help and facilitate the elderly, their families, primary health care providers, and health policymakers. Chronic pain in the elderly is a common complaint and its prevalence differs in society and depends on many factors, including type, severity, and localization but also comorbidities, socio-economic factors, and genetics. Pain is in two main categories, nociceptive and neuropathic. Nociceptive pain usually occurs after end-organ damage or derangement such as musculoskeletal problems, osteoarthritis, or trauma. Neuropathic pain arises from central or peripheral nervous system injuries. One of the most common types of peripheral neuropathic pain is hand pain caused by the carpal tunnel syndrome (CTS). Hand pain and CTS are common among the elderly, especially in women. The etiology usually remains uncertain until the late stages of the disorder, when intrinsic hand muscles become weak or atrophy, when it is too late to manage the CTS adequately. Thus, it is important to be aware of its clinical symptoms, signs, and provocation maneuvers, but also to have a noninvasive diagnostic tool when CTS is suspected. Also, it is important to have a solution for mild and moderate types of CTS to prevent surgery in older adults, especially in those with frailer constitutions.

Objectives: We evaluated the prevalence of pain, with special focus on neuropathic pain and CTS, in a large population-based study in Tehran, the capital of Iran. We chose CTS as being the most common symptom of focal neuropathy and evaluated the median nerve by noninvasive, high-resolution ultrasonography. We investigated and diagnosed CTS and determined its severity. Following the results of our diagnostic study, we performed interventional treatment studies on patients diagnosed with CTS. To find the optimum steroid dose site, we examined three different doses of steroid in a mixture injected in the tunnel near the affected nerve medianus with an adhesion removal technique called hydro dissection. Finally, we compared different methods of injection in our last study to examine a hypothesis about nonsurgical flexor retinaculum release.

Methods and material: More than 5,000 patients were investigated randomly by a multistage cluster sample. Participants were then interviewed using a sociodemographic checklist, a standard pain questionnaire, and general health through GHQ-28. In the 2nd study, demographics were noted along with the clinical presentation of CTS, and the median nerve anatomy was assessed by ultrasound and electrodiagnostic tests. The median nerve cross-sectional area (CSA) at the tunnel inlet and four different areas over the median nerve were measured and analyzed. In the 3rd paper with an intervention, we designed a prospective three group, randomized, double-blind trial to evaluate 40, 80, and 0 mg triamcinolone in a mixture of 3 mL containing 1 cc of lidocaine 2%. Outcome measures included the Boston Carpal Tunnel Questionnaire, VAS (visual analog scale), median nerve conduction criteria, and the ultrasound median CSA. All data were recorded at the baseline, 14 days, 1 month, and 6 months after the injection. In the 4th study, the design was similar to the 3rd one, though we had only two groups and the injecting mixture was 40 mg of triamcinolone and 1 cc of lidocaine 2%. The location of the injection was different with one group injected in the flexor retinaculum and the other near the nerve. All data were recorded as in the 3rd study but only at baseline, and 6 weeks after injection.

Results: We found a 13.7% prevalence of chronic neuropathic pain and 30% of chronic nociceptive pain, overall chronic of 31.7% and overall acute of 39.1% which, in combination, add up to 70.8%. The major comorbidities were osteoporosis, diabetes, disability, and stroke. In the 2nd study with 203 CTS and 103 control subjects, CSA at the tunnel inlet with a threshold of 8.5 mm2 had a sensitivity and specificity of 96.9% and 93.6% respectively. In the 3rd study with 161 patients, we did not find any statistically significant differences between groups, i.e., all groups with a steroid dose had similar results. In the last study with 50 eligible subjects randomized into two groups, there was a significant improvement in Boston scores (p-value 0.023), VAS (p-value 0.026), and ultrasonographic measure (p-value 0.004), in favor of intra-flexor retinaculum steroid injection compared to near the nerve.

Conclusions: Neuropathic pain prevalence is relatively high; 13.7% among Iranian elderly people, and the overall pain is very high around 70 %. It should be addressed by health policymakers, primary care physicians, and caregivers. High-resolution ultrasonography is a noninvasive diagnostic tool with about 95% sensitivity and specificity in detecting CTS in the elderly and should be introduced as a screening tool by primary physicians engaged in elderly care. The use of plain lidocaine was beneficial in managing CTS in elderly patients, and we did not find any superiority for the steroids. Finally, in case of no contraindication for steroids, we prefer the intra-flexor retinaculum injection. Larger studies should be performed in future studies in this field to confirm our results.