Bilateral widespread mechanical pain sensitivity in carpal tunnel syndrome: evidence of central processing in unilateral neuropathy

Abstract

The aim of this study was to investigate whether bilateral widespread pressure hypersensitivity exists in patients with unilateral carpal tunnel syndrome. A total of 20 females with carpal tunnel syndrome (aged 22-60 years), and 20 healthy matched females (aged 21-60 years old) were recruited. Pressure pain thresholds were assessed bilaterally over median, ulnar, and radial nerve trunks, the C5-C6 zygapophyseal joint, the carpal tunnel and the tibialis anterior muscle in a blinded design. The results showed that pressure pain threshold levels were significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the carpal tunnel, the C5-C6 zygapophyseal joint, and the tibialis anterior muscle in patients with unilateral carpal tunnel syndrome as compared to healthy controls (all, P < 0.001). Pressure pain threshold was negatively correlated to both hand pain intensity and duration of symptoms (all, P < 0.001). Our findings revealed bilateral widespread pressure hypersensitivity in subjects with carpal tunnel syndrome, which suggest that widespread central sensitization is involved in patients with unilateral carpal tunnel syndrome. The generalized decrease in pressure pain thresholds associated with pain intensity and duration of symptoms supports a role of the peripheral drive to initiate and maintain central sensitization. Nevertheless, both central and peripheral sensitization mechanisms are probably involved at the same time in carpal tunnel syndrome.

Specific Mechanical Pain Hypersensitivity Over Peripheral Nerve Trunks in Women With Either Unilateral Epicondylalgia or Carpal Tunnel Syndrome

“…In fact, previous studies have also demonstrated that individuals with either CTS or LE also have lower PPT over the tibialis anterior muscle, supporting a central sensitization process in these pain conditions. 23,28 The results from the current study are clinically relevant, as they demonstrate that a musculoskeletal pain condition such as LE exhibits similar nerve sensitization as a neuropathic pain condition like CTS. A novel finding in the current study was that, generally, pressure nerve hypersensitivity was different between patients with CTS versus LE and was related to specific nerve trunks.…”

“…[ research report ] of previous studies conducted on individuals with LE or CTS. 23,28 However, PPT assessment in other areas unrelated to specific nerve trunks would have been helpful to clarify if current findings are neural tissue specific or just indicative of general hypersensitivity throughout the arm. In fact, previous studies have also demonstrated that individuals with either CTS or LE also have lower PPT over the tibialis anterior muscle, supporting a central sensitization process in these pain conditions.…”

“…Although central sensitization mechanisms appear to be present in individuals with either LE 23 or CTS, 19,28 it is known that hyperexcitability of the central nervous system is a dynamic condition influenced by multiple factors, particularly activity of peripheral nociceptors. 36 In such a scenario, central sensitization may be influenced by peripheral nociceptive activity from specific nerve trunks (the median nerve for CTS and radial and ulnar nerves for LE).…”

“…Additionally, it has been reported that the lower cervical spine (C5-C6 level) is sensitized in these conditions. 23,28 Therefore, the aim of our study was to investigate differences in pressure pain hypersensitivity over the 3 main nerve trunks of the arm and the cervical spine in women with unilateral LE or CTS. Our hypothesis was that women with LE would have greater hypersensitivity over the radial nerve and women with CTS would demonstrate greater hypersensitivity over the median nerve, without differences in neck sensitization between groups.…”

Widespread Pressure Pain Hypersensitivity in Elderly Subjects with Unilateral Thumb Carpometacarpal Osteoarthritis

“…This calculation generated a sample size of 16 individuals per group. This sample size calculation has been used in previous studies conducted in other pain disorders [13][14][15][16].…”