The main symptoms of neuropathy are expressed in the parts of the body supplied by the affected nerve: Functional impairment of muscles up to paralysis, sensory disturbances, regulatory disorders of the skin, and nerve pain; in addition, reflexes may also be altered. The type, location, and extent of symptoms depend primarily on the affected nerves and the trigger.
Signs of polyneuropathy
Polyneuropathy typically begins with skin sensations (especially formication) and sensory disturbances that are symmetrical and tend to be localized – sock-like – to the legs. Paralysis and muscle atrophy appear later.
Sciatica syndrome, on the other hand, is often manifested mainly by the nerve pain moving into the leg, and a herniated disc often shows muscle paralysis and numbness of the skin at an early stage.
What is typical of neuralgia?
Nerve pain shoots in suddenly, rises and falls in waves, or exists as constant pain. Some occur spontaneously, i.e., without an identifiable trigger; others are “triggered” by certain factors (for example: cold, touch). Nerve pain does not occur at the point where the nerve is damaged, but in its course.
This is because the brain assigns nerve pain to the regions of the body where the sensing elements of the nerve fibers are located to register pain. So, for example, if an intervertebral disc presses on the sciatic nerve at its passage through the vertebral holes, it does not hurt there (the back pain is caused by the muscle cramps), but mainly at the back of the thigh, where the pain receptors of the sciatic nerve are located. Incidentally, this is also how phantom limb pain occurs after amputations.
Trigeminal neuralgia and Morton’s neuralgia.
In the head, nerve pain often takes the form of trigeminal neuralgia. This flashing stabbing or burning pain, usually confined to one side of the face, is extremely severe and is often triggered by activities such as talking, chewing, or brushing teeth. Presumably, trigeminal neuralgia is caused in most cases by pressure damage from a nearby blood vessel.
Similar pain in the metatarsal region (usually between the third and fourth toes), triggered by touch, for example, is called Morton’s neuralgia. It is caused by nerve damage probably as a result of chronic pressure in a splayfoot.