It results from a complex sequence of events that leads to damage and destruction of the minute blood vessels that nourish nerves along their course to the region of the body they serve after leaving the spinal canal.
Each such nerve is a single cell. The longest nerves, much like long chains, are the most susceptible to damage.
If a peripheral nerve (i.e., a nerve cell not contained in the brain or spinal column) emerging from the spinal column and traveling to the toes were the thickness of a piece of string, it would be 3 miles in length!
At frequent intervals along its length, each peripheral nerve receives nourishment from tiny blood vessels. If any of these tiny blood vessels are irreversibly damaged, that part of the nerve dies and no signals are conducted in either direction along it, i.e., the chain fails at its weakest link.
Although there are a vast number of individual nerve fibers serving any one area of the body, when a sufficiently large number get damaged, symptoms will result.
Since the longest nerve fibers serve the parts of the body that are farthest from the spinal column, it is not surprising that they are the ones most frequently damaged.
Therefore, diabetic neuropathy is most frequently a problem in the feet, hands, and male genitals.
The symptoms represent a spectrum from those due to injury responses of the non-fatally injured nerves, such as pain, burning, and abnormal sensations such as bunched socks under the feet, to those due to loss of impulses, such as numbness and unperceived injury due to loss of protective sensation.
This includes inability to perceive heat and sharp pain, leading to burns and puncture wounds.
Although the typical form of diabetic neuropathy causes these symptoms, there are a number of other less common forms that can lead to sudden pain, weakness, and other unsuspected symptoms in almost every region of the body.