Denervation supersensitivity refers to an increased sensitivity of nerve cells that occurs as a result of trauma or disease processes (such as diabetes, sickle cell, or viruses) or exposure to toxic chemicals. This supersensitivity (or hypersensitivity) is the dramatic increase in sensitivity of postsynaptic muscles, glands, or neurons to chemical neurotransmitters (like acetylcholine) after their nerve supply is cut or damaged. This compensatory mechanism occurs as cells become “starved” of neural signals, typically peaking 48–72 hours after injury, with receptors spreading across the entire membrane.

Cannon’s Law of Denervation (1939) states that when an efferent nerve is destroyed, the isolated structure (muscle, gland, or neuron) develops an increased irritability to chemical agents. This “supersensitivity” means denervated tissue reacts excessively to substances like acetylcholine or norepinephrine. It is a fundamental concept in neurology and pain medicine.

Mechanism

When nerves are damaged or cut (denervated), the target cells (e.g., muscles) lose their trophic, regulatory input and become more sensitive to chemical signals as a compensatory mechanism. Following denervation, muscles increase synthesis and expression of extrajunctional acetylcholine receptors across the entire muscle fiber membrane, rather than just at the synapse. As a result, skeletal and smooth muscle become highly sensitive to cholinergic agonists.

This serves as a compensatory reaction to the loss of nerve impulses and trophic factors, making the structure more responsive to any neurotransmitter present. Structures become supersensitive or hyperreactive to neurotransmitters or chemical excitants. Increased sensitivity can start within 1–2 days and can persist until innervation is restored. In striated muscle, sensitivity to acetylcholine can increase 10- to 100,000-fold.

It often leads to pain syndromes, including myofascial pain, causalgia, and neuropathies resulting from trauma or nerve compression (e.g., in spondylosis). In chronic pain syndromes, the “current of injury” (referring to the abnormal electrical potential produced by damaged nerve tissue) causes this hypersensitivity, leading to chronic pain and sensitivity to stimuli.

Reversibility

Denervation supersensitivity is generally considered a reversible phenomenon. The primary mechanism for reversing this state is reinnervation, which restores normal synaptic input and reverses the structural and biochemical changes induced by denervation.

Evidence suggests this supersensitivity can be reversed by providing new stimulation to the denervated tissue, such as through electric impulses. Directly stimulating denervated muscle electrically to cause contraction can prevent or reduce this supersensitivity.

Reversibility declines over time, particularly after long-term denervation (beyond 2–7 months) due to muscle fiber degeneration and replacement with fibrous tissue and also depends on whether the neuron can regenerate. If the nerve damage is permanent, the supersensitivity generally persists.

Electrical stimulation

Because a major cause of supersensitivity is the lack of muscle activity, chronic direct electrical stimulation can mimic nerve-driven activity. Studies on animal models (e.g., rat diaphragm) show that direct stimulation reduces or completely prevents the spread of ACh sensitivity. It is most effective if started before severe degeneration of the muscle tissue has occurred.

Pharmacological reversal

In cases of central dopaminergic denervation (e.g., in Parkinson’s models), high-dose administration of L-dopa/carbidopa can reduce the receptor supersensitivity. This reversal is typically partial and temporary. The supersensitivity returns when the medication is discontinued.

Desensitization massage

Desensitization massage is a therapeutic technique used to reduce nerve hypersensitivity, pain, or discomfort following injuries, surgeries, or chronic conditions by repeatedly exposing the area to different textures, pressures, and temperatures. It involves daily, short, and consistent stimulation — such as soft brushing, towel rubbing, tapping, or vibration — to retrain the brain’s pain response.

Rub the affected area with various materials, starting with soft items (cotton balls, silk) and gradually moving to rougher materials (towels, felt). Apply gentle, then gradually firmer pressure using lotions or creams. Gently tap the sensitive area, increasing pressure over time. Use a handheld massager for 3 to 5 minutes over the area. Perform these techniques for 3-5 minutes, 4-5 times a day.

Start with the least irritating texture and move toward more uncomfortable ones. Daily, consistent, short-duration sessions are more effective than infrequent, long ones. Ensure that the area (especially for scars) is fully closed, with no open wounds or infection before starting. While the goal is to reduce sensitivity, the process may cause mild, temporary discomfort.

This type of therapy is often recommended for conditions like complex regional pain syndrome (CRPS), nerve injuries, and post-surgical recovery. For structured, step-by-step guidance, this home desensitization program from the Michigan Occupational Therapy Association is a helpful resource.