Carpal tunnel syndrome (CTS) is the most common median entrapment neuropathy and occurs when the median nerve, which runs from forearm into the palm of hand, becomes pressed or squeezed at the wrist. The median nerve controls sensation to the palm side of the thumb and fingers (not the little finger), and impulses to some small muscles in the hand that allow the finger and thumb to move. The carpal tunnel – a narrow, rigid passageway of ligament and bones at the base of hand – houses median nerve and tendons. Sometimes, thickening from irritated tendons or other swellings narrows the tunnel and causes the median nerve to be compressed. The results may be pain, numbness and weakness in the hand and wrist. Symptoms usually start gradually, with frequent burning, itching, and numbness in the palm of hand and fingers, especially the thumb, the index finger and middle finger. The symptoms often first appear in one or both hands during the night, since many people sleep with flexed wrist. In chronic and/or untreated cases, some CTS suffers may not tell between hot and cold by touch. Conventional treatment for CTS includes non-surgical treatment such as nonsteroidal anti-inflammatory drugs, oral steroidal and injection of corticosteroids into neural wrist splinting. These medications normally provide temporal pain relief. However, symptoms generally reoccur within one year. Surgery is considered as a definitive treatment. Although symptoms may be relieved immediately after surgery, full recovery can take months. Some patients may have infection, nerve damage, stiffness and scare at the wrist. In addition, surgery drives up costs. 

Acupuncture is used to treatment CTS for many years. Clinical studies reported that acupuncture treatment produced a significant improvement in symptoms, with effects similar to steroids treatment and night splinting. During past decades there is an increasing interesting in studying the mechanisms underlying the effectiveness of acupuncture in treating CTS and many clinical studies were reported. Here, a brief review of recent development of acupuncture research in CTS was reported.  

 

Is acupuncture treatment effective in treating CTS – fMRI study 

Approximately ten years ago Dr. Napadow and colleagues (2007) investigated the effectiveness of acupuncture on CTS using functional magnetic resonance imaging (fMRI), a non-invasive technique looking neuronal activity in the brain. fMRI imaging studies showed pain of CTS patients coincided with sensorimotor hyperactivation and an overlapping representation of adjacent fingers within the primary somatosensory cortex and changes in subcortical limbic regions. Following a 5 week course of acupuncture treatment, there is a significant reduction in pain and paresthesia in CTS patients and partial release from hyperactivation, and more focused somatosensory cortex finger representation. CTS patients demonstrated a more closely separated somatotopic representations for 2nd and 3rd fingers (both are innervated by median nerve) compared to healthy adults. After acupuncture treatment, the 2nd and 3rd fingers representation moved further apart, similar to the separation found in healthy adults. Further changes in limbic regions are restored following acupuncture. The findings of study demonstrate that effectiveness of acupuncture to CTS is mediated by modulating cortical and subcortical brain activity. 

 

How does acupuncture alleviate symptoms in carpal tunnel syndrome? 

Through its modulating brain activity acupuncture treatment is effective in alleviating pain and paresthesia in patients with carpal tunnel syndrome. However which brain areas are responsive to specific stimulation and pain reduction are not clear. Maeda et al (2013), using fMRI technique, assessed brain response to acupuncture and correlated changes in clinical symptoms in patients with carpal tunnel syndrome.  

Patients with carpal tunnel syndrome were allocated to three groups. Group one was given acupuncture at local acupoints (PC7 and TW5) on the affected wrist. Group two was given acupuncture at distal acupoints (SP6 and LV4) on contralateral ankle, based on mirror point methods common in acupuncture practice. Group three was given sham acupuncture at non-acupoints. Symptom ratings were measured prior to and after fMRI scan. It was found that both local and distal acupoints significantly alleviated symptoms. Brain response to local acupoints in the somatosensory cortex and supplementary motor cortex and brain response to distal acupoints in the prefrontal cortex were associated with greater pain relief following acupuncture. The study suggests that both acupoints either close to or distal to affected area are able to elicit therapeutic effect but induced responses in different brain areas.  

 

Acupuncture is more effective than anti-inflammatory drug ibuprofen in relieving symptoms in carpal tunnel syndrome 

Recently Dr. Momeninejad and colleagues (2015) conducted a clinical study to assess the effectiveness of acupuncture treatment in mild to moderate carpal tunnel syndrome. Fifty patients with mild to moderate carpal tunnel syndrome were divided into acupuncture group and ibuprofen group. Patients in the former group were given acupuncture at acupoints PC-7 (Daling), PC-4 (Ximen), PC-6 (Neiguan), PC-8 (Laogong), HT-2 (Qingling), HT-7 (Shengmen), HT-8 (Shaofu), LU-9 (Taiyuan), and LI-11 (Quchi), for 20 min twice a week for 4 weeks. Patients in the latter group were given ibuprofen 400mg, three-time a day for 10 days. The outcome measures include the visual analog scale (VAS) score, the score on the Boston Carpal Tunnel Questionnaire for Functional Status and Symptom Severity (BCTQ FUNCT and SYMPT), and the electrodiagnostic findings at the baseline and end of 4-week treatment.  

At the end of treatment, patients with acupuncture had greater improvement in pain, numbness, tingling and performing daily activities e.g. doing house work compared with those treated with ibuprofen. The VAS score, BCTQ FUNCT and SYMPT and electrodiagnostic findings were significantly improved in patients with acupuncture compared with their baseline and drug control group. The study showed that acupuncture is a very effective and alternative treatment to mild and moderate carpal tunnel syndrome.  

 

Acupuncture treatment was able to rewire the primary somatosensory cortex in the brain of patients with carpal tunnel syndrome 

It have been shown that both verum and sham acupuncture reduced CTS symptom severity, only verum acupuncture improves physiological outcomes and such changes predict long term clinical outcomes. However, the physiological mechanism of acupuncture treatment, in particular how activity reconnection was re-established in the brain is less well understood. 

Very recently Meada et al., (2017) conducted a clinical study to assess the brain activity connection, using fMRI in patients with CTS. Eighty patients with CTS were recruited and were divided into three groups. 1). Verum acupuncture ‘local’ to the more affected Hand (stimulation on LI5, LI10, TW5, SI4, PC7, PC3, HT3 and LU5); 2). Verum acupuncture at ‘distal’ body sites, contralesional to the more affected hand (stimulation on GB34, LV4, SP5, KD3 and SP6); and 3). Sham acupuncture (stimulation on SH1, SH2, SH3, SH4 and SH5). Acupuncture stimulation was performed on above acupoints 30 mins each session, twice a week for 8 weeks. fMRI scanning was performed before and after acupuncture treatment. The results showed while both verum and sham acupuncture reduced CTS symptoms, verum acupuncture was superior to sham in producing improvements in both peripheral and brain neurophysiological outcomes. Furthermore, improvement in functional primary somatosensory cortex plasticity immediately following acupuncture predicted long-term symptom relief. Interestingly, Diffusion sensor imaging analysis of white matter microstructure found that acupuncture at local versus distal acupuncture sites may improve median nerve function at the wrist by somatotopically distinct primary somatosensory cortex-mediated neuroplasticity following therapy. The study suggests that acupuncture may improve CTS pathophysiology by both local and brain-based mechanisms involving primary somatosensory cortex neuroplasticity 

 

 

Reference: 

Grateful acknowledgements are due to Drs Napadow V, Maeda Y, Hadianfard M and colleagues (This paper was based on their articles cited in above Reference section), as well as to Dr. Bai-Yun Zeng for his work in preparing this briefing paper.