Symptoms vary depending on whether motor, sensory, or autonomic nerves are damaged. Motor nerves control voluntary movement of muscles such as those used for walking, grasping things, or talking. Sensory nerves transmit information such as the feeling of a light touch or the pain from a cut. Autonomic nerves control organ activities that are regulated automatically such as breathing, digesting food, and heart and gland functions. Some neuropathies may affect all three types of nerves; others primarily affect one or two types. Doctors may use terms such as predominantly motor neuropathy, predominantly sensory neuropathy, sensory-motor neuropathy, or autonomic neuropathy to describe the types of nerves involved in an individual’s condition.

Motor nerve damage is most commonly associated with muscle weakness. Other symptoms may include painful cramps and fasciculations (uncontrolled muscle twitching visible under the skin), muscle atrophy (severe shrinkage of muscle size), and decreased reflexes.

Sensory nerve damage causes a variety of symptoms because sensory nerves have a broad range of functions. Larger sensory fibers enclosed in myelin register vibration, light touch, and position sense. Damage to large sensory fibers impairs touch, resulting in a general decrease in sensation. Since this is felt most in the hands and feet, people may feel as if they are wearing gloves and stockings even when they are not. This damage to larger sensory fibers may contribute to the loss of reflexes. Loss of position sense often makes people unable to coordinate complex movements like walking or fastening buttons, or to maintain their balance when their eyes are shut.

Smaller sensory fibers without myelin sheaths transmit pain and temperature sensations. Damage to these fibers can interfere with the ability to feel pain or changes in temperature. People may fail to sense that they have been injured from a cut or that a wound is becoming infected. Others may not detect pain that warns of impending heart attack or other acute conditions. Loss of pain sensation is a particularly serious problem for people with diabetes, contributing to the high rate of lower limb amputations among this population.

Neuropathic pain is a common, often difficult to control symptom of sensory nerve damage and can seriously affect emotional well-being and overall quality of life. Often worse at night, neuropathic pain seriously disrupts sleep and adds to the emotional burden of sensory nerve damage. Neuropathic pain can often be associated with an oversensitization of pain receptors in the skin, so that people feel severe pain (allodynia) from stimuli that are normally painless. For example, some may experience pain from bed sheets draped lightly over the body. Over many years, sensory neuropathy may lead to changes in the skin, hair, as well as to joint and bone damage. Unrecognized injuries due to poor sensation contribute to these changes, so it is important for people with neuropathy to inspect numb areas for injury or damage.

Autonomic nerve damage symptoms are diverse since the parasympathetic and sympathetic nerves of the peripheral nervous system control nearly every organ in the body. Common symptoms of autonomic nerve damage include an inability to sweat normally, which may lead to heat intolerance; a loss of bladder control; and an inability to control muscles that expand or contract blood vessels to regulate blood pressure. A drop in blood pressure when a person moves suddenly from a seated to a standing position (a condition known as postural or orthostatic hypotension) may result in dizziness, lightheadedness, or fainting. Irregular heartbeats may also occur.