Carpal Tunnel Syndrome (CTS) is a common condition affecting the hand and wrist, causing symptoms like numbness, tingling, and pain. This compression neuropathy occurs when the median nerve, which runs through the wrist, is squeezed in the narrow passageway called the carpal tunnel. Symptoms frequently worsen at night for many sufferers. Understanding the anatomical and physiological factors that change during rest provides insight into why sleeping hours often bring the most intense discomfort.
The Anatomy of Median Nerve Compression
The carpal tunnel is a tight passageway located at the base of the hand. Its floor and sides are formed by the arched carpal bones of the wrist. The roof is the transverse carpal ligament, a thick band of connective tissue. Passing through this confined space are the median nerve and nine flexor tendons that control finger and thumb movement. CTS develops when inflammation or swelling of the tendons reduces the limited space inside the tunnel. This increased internal pressure compresses the median nerve, leading to symptoms in the hand and fingers.
Why Symptoms Intensify During Sleep
The nighttime aggravation of carpal tunnel symptoms is primarily due to fluid redistribution and unconscious wrist positioning.
When the body lies flat during sleep, the gravitational effect that pulls tissue fluids toward the lower extremities is lost. This allows fluids to redistribute more evenly, leading to an accumulation of fluid, or edema, in the hands and wrists. Because the carpal tunnel is a fixed space, even a minor increase in fluid volume raises the internal pressure, compressing the median nerve. Furthermore, the lack of muscle movement during rest inactivates the natural “muscle pump” that circulates fluids. This inactivity causes fluid to settle and stagnate within the wrist, intensifying the pressure.
Another major factor is the unconscious bending or positioning of the wrist during sleep. Many people sleep with their wrists sharply flexed (bent inward) or hyperextended (bent backward). Maintaining these non-neutral positions for hours significantly increases the pressure within the carpal tunnel. This increased pressure can trigger pain, numbness, and tingling. Studies suggest that even a change of 20 degrees in wrist position can alter nerve compression inside the tunnel.
Immediate Strategies for Nocturnal Relief
The most effective immediate strategy for nocturnal relief is maintaining a neutral wrist position throughout the night. Wearing a rigid wrist splint while sleeping is highly recommended. The splint mechanically prevents the unconscious flexion or extension that increases internal pressure by holding the wrist in a straight alignment. This maximizes the space available for the median nerve.
Elevating the hands above the level of the heart also helps reduce fluid pooling when lying flat. This can be accomplished by placing the hands and forearms on a pillow while sleeping on the back. Elevating the hands uses gravity to encourage fluid drainage from the wrist, reducing pressure on the nerve.
Before settling down, gentle pre-sleep routines can offer temporary relief. Mild stretching or nerve-gliding exercises help the median nerve move more smoothly within the tunnel. If symptoms wake you, shaking the hands vigorously, often called the “flick sign,” can quickly relieve symptoms by temporarily shifting fluid and pressure.