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.

Researchers in the United State, using functional magnetic resonance imaging (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.

Reference:

Maeda Y et al., Acupuncture-Evoked Response in Somatosensory and Prefrontal Cortices Predicts Immediate Pain Reduction in Carpal Tunnel Syndrome. Evid Based Complement Alternat Med. 2013;2013:795906.   http://www.hindawi.com/journals/ecam/2013/795906

Acupuncture treatment for carpal tunnel syndrome

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.  The mechanisms underlying the effectiveness of acupuncture have been investigated 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.

Reference:

V Napadow (2007) Human Brain Mapping 28:159 –171.

http://www.ncbi.nlm.nih.gov/pubmed/16761270