Carpal tunnel syndrome is a common nerve entrapment disorder characterized by pain, numbness, and
tingling in the hand and fi ngers. There are numerous patients who present to outpatient clinics with complaints
of pain, numbness, and stiffness in the wrist, and despite undergoing normal electroneuromyography and
cervical magnetic resonance imaging examinations, their clinical fi ndings are incongruent with the test results.

carpal tunnel syndrome, trigger points, tight fascia, myofascial pain, wrist pain

To the Editor,

            Carpal tunnel syndrome (CTS) is typically attributed to the compression of the median nerve as it passes through the carpal tunnel in the wrist. However, certain conditions can produce similar symptoms by different mechanisms [1]. There are numerous patients who present to outpatient clinics with complaints of pain, numbness, and stiffness in the wrist, and despite undergoing normal electroneuromyography and cervical magnetic resonance imaging examinations, their clinical findings are incongruent with the test results. Under such circumstances, it is necessary to expand our list of differential diagnoses and consider more commonly encountered overuse conditions, microtraumas, and repetitive injuries that occur in daily life, going beyond these two diagnoses. One such mechanism involves the presence of tight fascia and trigger points in the affected area. Tight fascia refers to the excessive tension and stiffness in the fascial tissues, while trigger points are hyperirritable nodules within skeletal muscles [2].

Fascia plays a significant role in compression symptoms. It acts as a supportive and protective tissue that surrounds muscles, tendons, and other structures. When fascia becomes tight or restricted, it can exert pressure on nerves, blood vessels, or other neighboring structures, leading to compression symptoms. Studies using shear wave elastography on human cadavers revealed that fascia might contribute to an increase in surrounding muscle stiffness through external compression [3]. The sliding mobility of fascial tissues could be evaluated by manual palpation and ultrasonography. Studies evaluating fascia generally focused on echogenicity and fascial thickness. As a general opinion, an increase in fascial thickness and echogenicity can be expected in fascial disorders, but the number of studies revealing this is low. The most advanced research in the literature has been conducted on thoracolumbar fascia. If there is chronic dysfunction in a muscle, it results in decreased water content and increased fi brous tissues such as perimysial and endomysial fascia, resulting in an appearance with higher echogenicity on ultrasound [4,5].

Fascial tension along the median nerve track, compressing the nerve, may cause CTS symptoms. For example, in the case of CTS, fascial tension along the median nerve track can become tight, compressing the nerve and causing symptoms such as pain, numbness, and tingling in the hand and fingers [6]. Similarly, in other conditions mimicking CTS including quadrilateral space syndrome, lateral antebrachial cutaneous nerve entrapment, thoracic outlet syndrome, radial tunnel syndrome and guyon’s canal syndrome can contribute to the compression of nerves, resulting in similar symptoms. Understanding the impact of fascia on compression symptoms is crucial for accurate diagnosis and appropriate management of such conditions. The increased tension in the fascial tissues may result from various factors, including repetitive motions, poor ergonomics, or trauma. The tightness of the fascia can restrict the gliding of the median nerve and compromise its blood supply, causing pain, numbness, and tingling sensations in the hand. Fascial anatomy of a muscle is given in Figure 1.

Figure 1. Understanding the Fascial Anatomy. Longitudinal Ultrasound Image of a Forearm Muscle

Magnifi ed area in white box showing two fascia layers between skin and muscle. Superfi cial fascia is a thin structure, located between the superfi cial and deep layers of the adipose tissue and is mainly composed of elastic fi bers. Deep fascia located over the adipose tissue whereby a transitional zone—made of loose connective tissue—separates it from the underlying muscle. The deep fascia is composed of multiple fi brous layers
and loose connective tissue—containing hyaluronic acid chains—that allows for regular gliding in between. The right image shows a picture of fascia layers and their interactions with each other.

Trigger points, particularly in the forearm, hand, and also shoulder muscles can refer to pain and sensory disturbances that mimic CTS. Pain originating from trigger points found particularly in the shoulder girdle, including the infraspinatus muscle, supraspinatus muscle, scalene muscles, subscapularis muscle, and subclavius muscle, as well as in the arm and forearm region, including the brachialis muscle, pronatorteres muscle, palmaris longus muscle, flexor carpi radialis muscle, and thenar muscles of the hand, can cause symptoms similar to CTS. These hyperirritable nodules can develop due to muscle overuse, chronic tension, or direct trauma. The referred pain patterns from trigger points may overlap with the distribution of the median nerve, leading to diagnostic confusion [7]. Additionally, trigger points can induce muscle stiffness and restricted range of motion, further contributing to the similarity of symptoms with CTS. The referred pain patterns of some of the relevant muscles are illustrated in Figure 2.

Figure 2. The Referred Pain Patterns of the Relevant Muscles
(A) infraspinatus muscle, (B) pronator teres muscle, (C) scalene muscles, (D) palmaris longus muscle.

In an article, Ricci et al. [8] discussed the relationship between trigger points and fascia as a cause of referred pain. They mentioned that trigger points are located near the muscle’s epimysium and there are connections between the epimysium and deep fascia. They emphasized the importance of this histological complex as a potential cause of referred pain.

The presence of tight fascia and trigger points in individuals with symptoms resembling CTS emphasizes the importance of a comprehensive differential diagnosis. Clinicians should consider evaluating the tension in fascial tissues and performing a thorough assessment of muscle trigger points. Before nerve conduction tests and imaging studies for differential diagnosis are requested, conducting a comprehensive musculoskeletal and fascial examination that includes manual palpation is crucial. This approach not only helps to minimize unnecessary investigations and reduce costs but also accelerates the return to work through prompt treatment, preventing loss of productivity. Furthermore, understanding the role of fascia and trigger points allows clinicians to develop targeted treatment approaches that may include manual therapy techniques, stretching exercises, or other interventions like ultrasound-guided dry needling and ultrasound-guided interfascial injections aimed at releasing the tension and restoring the normal function of the affected tissues.

In conclusion, tight fascia and active trigger points play a signifi cant role in producing symptoms resembling CTS. Understanding the mechanisms behind these conditions can help clinicians improve diagnostic accuracy and provide appropriate treatment strategies for patients presenting with similar symptoms.

None.