The changes of neuroactivity of Tui Na (Chinese massage) at Hegu acupoint on sensorimotor cortex in stroke patients with upper limb motor dysfunction: a fNIRS study

Stroke is a serious threat to the safety and quality of life in the world, and the rate of disability after stroke is relatively high. Most patients have motor dysfunction, especially upper limb (UL) motor dysfunction [1]. UL movement is delicate and complex, and its unsatisfactory recovery can reduce patients’ activities of daily life and affect the living quality of patients and their families [2]. Therefore, UL motor dysfunction is a key and difficult point in the process of rehabilitation after stroke.

Tui Na (Chinese massage) is a therapy that uses different manipulations to act on specific parts of the body to achieve the purpose of prevention and treatment of diseases. Skilled and appropriate manipulations can positively affect the nervous, circulatory, motor, and other systems of the body [3]. Tui Na is well received because of its simple operation, safety, and wide range of applications. However, the essence and structural basis of the meridian guiding Tui Na practice have not been scientifically clarified, which has become the "bottleneck" of Tui Na’s inheritance and innovation [4]. Researchers have found that there may be a relationship between neural circuits and the meridian system [5, 6]. The sensorimotor neural circuits are an important way All the stroke subjects were the first unilateral ischemic stroke patients for the human body to perceive external stimuli and result in a series of physiological and pathological changes. The normal function of the structure of the central nervous system depends to a large extent on the normal transmission of sensory information. The human body receives different stimuli through various receptors distributed in the skin, muscles, and joints to produce various types of sensation [7, 8].

Studies have shown that Tui Na can improve post-stroke motor dysfunction through sensory ascending stimulation [9, 10], but the related mechanism is unclear due to the lack of detection methods. fNIRS [11] (functional near-infrared spectroscopy) is an emerging neuroimaging technique, which indirectly reflects the intensity of neural activity by detecting the changes in blood oxygen activity in the cerebral cortex. fNIRS has a good temporal resolution (sampling rate up to dozens of Hz) and spatial positioning ability (centimeter scale), as well as portability, economy, and good ecological validity [12]. In recent years, it has been widely used in neuroscience [13, 14], clinical research [15, 16], brain-computer interface [17, 18] and other fields and made some progress.

In this research, fNIRS was used to reflect the changes of neuroactivity in the sensorimotor cortex during Tui Na Hegu (LI4, large intestine 4) acupoint in patients with UL motor dysfunction after stroke, and to explore the correlation between acupoints in traditional Chinese medicine and neural circuits. The Hegu point is commonly used in Tui Na therapy, located between the hand’s first and second metacarpal bones, with a relatively large corresponding position in the cerebral cortex, and was easily observed by fNIRS. Therefore, the Hegu point was chosen as a representative point for the study.

The results of this study indicate that patients with UL motor dysfunction after stroke do have the injury of sensorimotor neural circuits, and the combination of Tui Na and fNIRS has the potential to reflect the dysfunction of sensorimotor neural circuits. The changes in neural activity in the sensorimotor cortex during Hegu acupoint Tui Na indicate that there is a certain correlation between acupoints in traditional Chinese medicine and neural circuits.

The pattern of brain activation of the affected limb after stroke was mainly bilateral in the early stage, and gradually transferred to the ipsilesional cortex with the progress of rehabilitation [27]. Therefore, the detection of LI may help the physician to make an auxiliary judgment on the prognosis of patients. Previous studies are mainly based on patients’ active hands-on tasks for related testing, but for patients who are unable to take the initiative tasks, there is a lack of detection, this study makes up for this deficiency.

The analysis of the effect of Tui Na on neural circuits is of great significance in the clinic. The neural circuits are the basis of the coordination of sensory, motor, and balance functions, and it is also the structure and functional unit of nerve remodeling and rehabilitation. The repair of these neural circuits after injury requires the stimulation of a variety of senses, and then reconstructing the neural network connection [28, 29]. Similar to acupuncture [30], Tui Na on the hemiplegic UL can stimulate the peripheral nerves, and promote the activation and integration of the cortical sensorimotor network. Similar to physical therapy [31], Tui Na can coordinate the balance of muscle tension between muscle groups, inhibit and control spasms, and then establish a normal movement pattern. As a non-invasive brain functional neuroimaging technology, fNIRS has the advantages of simple operation, low cost, strong anti-interference, and good compatibility. It can realize the rapid examination of brain function in healthy subjects and patients with various brain dysfunction diseases [32]. The commonly used non-invasive brain function detection techniques include electroencephalogram (EEG), functional magnetic resonance imaging (fMRI), and fNIRS. Each detection technique has its characteristics in spatial and temporal resolution, coverage, application requirements of the instrument, etc [33]. fMRI, which is widely used in clinical research, has high spatial resolution and can detect the whole brain, but it has a high cost and is more used for brain functional activity examination in a static state, so it is difficult to evaluate brain function in motor state or magnetoelectric therapy state [34]. Rehabilitation of nervous system diseases is a dynamic and gradual process and is closely related to brain function. The activation and reconstruction of neural circuits are crucial to realize functional rehabilitation [35]. Clinically, rehabilitation needs the process of "evaluation--rehabilitation--re-evaluation--continuous rehabilitation--curative effect follow-up", and needs to optimize the rehabilitation program continuously through feedback mechanism and clinical evaluation [36]. Therefore, it still needs real-time dynamic, portable, and easy-to-operate cortical function detection equipment. With its gradual popularization, fNIRS technology will show important application value and significance in the field of clinical research.

The limitations of this study are that the sample size is relatively small, Which may affect the accuracy of the study results. This study focuses on whether a single Tui Na massage at one point can cause changes in the sensorimotor cortex. And such a short and single session of Tui Na maybe not be enough to induce clinical improvement in dysfunction. In the future, we will use a session of a massage program and other physical therapy as a controlled study to operate at multiple time points, and to evaluate the UL dysfunction before and after therapy.

The combination of Tui Na and fNIRS has the potential to reflect the functional status of sensorimotor neural circuits. The changes of neuroactivity in the sensorimotor cortex when Tui Na Hegu acupoint indicate that there is a certain correlation between acupoints in traditional Chinese medicine and neural circuits.