Peripheral neuropathies present as pain, numbness, tingling, and, sometimes, weakness. The initial symptoms generally depend on the nature of the underlying damage to the nerve.
Odd spontaneous sensations are often the initial symptom of a peripheral neuropathy. Patients with polyneuropathies often describe the sensation that a thin layer or film is surrounding their toes or the soles of their feet. It may also feel as though something is stuck between the toes. A pins-and-needles sensation may also occur in the feet.
Pain from a peripheral neuropathy is called neuropathic pain. Burning sensations are very common. Aching or stabbing pain may also occur. Electric shock sensations may go up or down the legs and feet.
Tactile sensations are often altered in body regions affected by peripheral neuropathy. Commonly, this manifests as increased sensitivity to pressure. For example, when a patient with polyneuropathy steps on a small pebble, it may feel like a sharp piece of glass is cutting into the sole of their foot. Also, the feet may feel swollen or bound up. Even very light sensations, like bedsheets being drawn across the feet, may cause severe discomfort.
Impaired sensation is a feature of almost all peripheral neuropathies. Patients may be unaware of these problems because pain in the affected body region overrides any appreciation of the numbness. Only when the physician applies light touches or a vibrating tuning fork or the sharp end of a pin to the skin does it become clear to everyone that sensation is impaired.
An unfortunate paradox of peripheral neuropathy is that the numbest areas of the body also tend to be the most painful.
In moderate-to-severe polyneuropathies, balance may be affected. In these cases, sensory fibers that carry information about joint position to the brain have degenerated. This type of sensory information normally allows us to do such things as touch the tip of the nose with a fingertip with closed eyes. We are unconscious of this type of sensation from our limbs.
If a neuropathy leads to impairment of joint position in the legs, the person becomes more dependent on vision for balance. It is for this reason that neuropathy patients have the toughest time with balance when their vision is limited—when, for example, they are shampooing their hair in the shower or walking in the dark.
Weakness may occur with any peripheral neuropathy. The region of weakness depends on the type of neuropathy. In polyneuropathies, weakness is usually worst at the ankles and toes.
Sometimes the nerves to blood vessels, gut, and bladder are diseased in a peripheral neuropathy. Autonomic neuropathy is a more specific name for this type of peripheral neuropathy.
When the nerve supply to blood vessels is diseased, the blood vessels cannot constrict in response to standing to maintain adequate blood pressure. Without this response, the blood pools in dependent body regions and the brain does not receive enough blood flow. This manifests as lightheadedness. The patient must sit or lie down for relief.
When the nerves to the bladder are affected, it may be difficult to fully empty the bladder.
When the nerves to the gut are affected, patients may have either constipation or, sometimes, diarrhea. Patients may feel full even after eating small food portions.
When the nerves to the sweat glands are affected, the pattern and frequency of sweating may be affected.