Damage to the nerves outside the brain and spinal cord, known as peripheral neuropathy, can lead to a variety of symptoms, including weakness, numbness, and burning pain. The nervous system is a complex network responsible for all communication between the body and the brain. When this system is compromised, motor function can be affected. A tremor, an involuntary, rhythmic movement, is one motor symptom sometimes linked to nerve damage. Understanding the specific types of nerves affected and the resulting disruption helps determine if neuropathy can directly cause these shaking movements.
Defining Neuropathy and Tremors
Peripheral neuropathy describes a condition where the peripheral nerves are damaged, disrupting the signals that travel between the central nervous system and the rest of the body. This damage is categorized based on the type of nerve fiber involved. Sensory neuropathy affects nerves that relay feelings like pain and temperature, while motor neuropathy involves the nerves controlling muscle movement and strength. Autonomic neuropathy affects involuntary functions such as heart rate and digestion.
A tremor is characterized as an involuntary, rhythmic muscle contraction that causes a part of the body to shake. These movements are often classified based on when they occur. A resting tremor is visible when the muscle is relaxed and fully supported, such as when the hands are resting in the lap. An action tremor occurs during voluntary muscle contraction, divided into postural tremors and kinetic tremors.
The Mechanism Linking Nerve Damage to Tremor
The physiological link between nerve damage and tremor centers on the disruption of the body’s internal sensing and feedback system, known as proprioception. Proprioception is the unconscious sense of where one’s body parts are located in space, a function largely relayed by large-diameter sensory nerve fibers originating from muscle spindles. When these large sensory nerves are damaged, the brain receives inaccurate or delayed information about the position and movement of a limb.
This faulty signaling disrupts the reflex arc, a rapid, automatic feedback loop between the muscle, spinal cord, and brain that constantly works to maintain muscle stability. The brain attempts to correct for this instability by sending out motor commands. However, because the sensory feedback is unreliable, the motor system overshoots or repeatedly miscalculates the force needed to hold a position. This continuous cycle of miscommunication and over-correction results in a rhythmic, involuntary oscillation in the limb, which is the neuropathic tremor. This type of tremor is typically classified as an action or postural tremor because it is most evident when the patient attempts to hold a limb steady against gravity.
Specific Neuropathy Conditions Associated with Tremor
Tremor is a known feature in a subset of demyelinating neuropathies, where the protective myelin sheath around the nerve axon is damaged. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is an acquired autoimmune disorder that commonly presents with this particular type of tremor. The demyelination in CIDP severely slows the speed of nerve signal transmission, which exacerbates the proprioceptive feedback delay. This delay means the muscle spindle signals informing the brain of a muscle’s position are consistently late, amplifying the instability that causes the rhythmic shaking.
Another condition is Charcot-Marie-Tooth Disease (CMT), the most common inherited peripheral neuropathy. Certain types of CMT, particularly those involving significant demyelination, frequently include tremor as a feature. The progressive nature of the nerve damage in these inherited neuropathies leads to chronic sensory loss and muscle weakness, which further contributes to the difficulty in maintaining steady posture. The presence of tremor in these specific conditions underscores the severity of the feedback disruption.
Ruling Out Other Causes of Involuntary Movement
While neuropathy can cause tremor, it is important to recognize that the majority of tremors have a different origin. The diagnosis of a neuropathic tremor requires careful evaluation to distinguish it from more common movement disorders. Essential Tremor (ET) is the most prevalent cause of involuntary movement, typically a bilateral action or postural tremor often affecting the hands, head, and voice. Unlike neuropathic tremor, ET is a disorder of the central nervous system and does not involve primary damage to the peripheral nerves.
Parkinsonian Tremor (PT), a symptom of Parkinson’s disease, is another common cause. It is classically a resting tremor that diminishes with intentional movement. Since the characteristics and underlying causes of tremors vary widely, a professional diagnosis is necessary to determine the true source of the involuntary movement. Evaluation typically includes a detailed history, neurological examination, and sometimes nerve conduction studies or electromyography to confirm the presence and nature of peripheral nerve damage.