The most complex system of the body is the brain (the central nervous system) and the spinal cord, its communication network with the rest of the body. All two-way traffic to and from the brain passes through this huge, major cable system.
The human body is segmented along the spine. The nerves from the most distant/distal body segments – the tail bone and then the legs – are layered into the spinal cord complex first. These nerve bundles are gradually pushed more centrally by nerve bundles from segments closer to the head/proximal layering in, joining segment by segment from the farthest out/distal to the ones closest/proximal to the brain. All these nerve bundles travel inside the spinal cord from the brain to the tail bone through a continuous passage through the back bones – the spinal canal – until they exit at their designated segmental levels.
The sensations of pain, touch, pressure, hot and cold, and the location of the body part in 3-D space – all these sensory abilities are transmitted to the brain through relatively smaller, sensory nerves, contained within the segmented nerve bundles as they join the spinal cord. The brain’s instructions to the muscles are transmitted from the brain through larger nerves contained within the same segmented bundles. Any pressure or damage to a bundle will affect both the sensory nerves carrying information to the brain and the muscular nerves carrying instructions from the brain.
A single nerve is the tubular extension arm of a single cell. The main body of the cell is in the spinal cord. The extension arm extends from the cell out to the body part that it serves. Nutrient food and fluid travel through the length, feeding the entire nerve. The electrical signals transmitted by the nerve travel over the surface and are modified by the protective coating on the nerve. Blood vessels are contained in this coating and in the segmented nerve channels to feed the nerves.
The bones of the spine (vertebrae) sit next to one another, with a cushion (intervertebral disc) between each pair to decrease the stress of standing, twisting, or bending. Also between each pair of vertebrae is a hole (foramen) formed by a notch in the first vertebra matched by a notch in the second vertebra. The nerve bundle at each segment level exits the spinal cord and passes through this hole. The nerve bundle is allowed to slide back and forth through this foramen to allow standing, twisting, or bending.
If the nerve bundle carrying the nerves gets caught or “pinched” (entrapment) in the foramen for any reason, the nerve is restricted from sliding – and this causes stretching of the nerves inside the nerve channel which is very painful. Bony overgrowth of the foramen, intervertebral disc intruding into the foraminal space, or swelling from repeated trauma to the nerve bundle within the foraminal space may cause entrapment of the nerves.
If the nerve bundles are still located inside the spinal canal before exiting, bony overgrowth or disc protrusion into the spinal canal will decrease the space within the canal, squeezing and entrapping the nerve bundles while still inside the spinal canal. Again, the nerve bundles can’t slide freely. The nerves are stretched, causing painful sensations in the nerve bundles entrapped.
As the entrapment gets worse, the fluid inside the individual nerves is restricted and the blood supply to the nerves is restricted. The decreased function of these life support systems causes the nerves to no longer function properly. The smaller sensory nerves – carrying pain, pressure, touch, etc. – being smaller, are affected first. Here pain is our friend, warning of a situation that can become very serious.
If the entrapment is relieved, either by steroid injections – in the case of swelling – or by surgical means, the smaller sensory nerves will recover quite quickly. If the situation continues, the nerves going to the muscles will become compromised. The signals they send to the muscles no longer get through to the special surface area of the muscle and this part of the muscle eventually ceases to exist. Even when the entrapment is relieved, the nerves going to the muscles no longer get a response and the muscle is permanently paralyzed.
DO NOT ignore the warning signal of shooting pains down the legs or “electric-like” shocks in the legs on assuming certain positions. These are the early warning signals that something is wrong. If ignored, the next warning will be decreased muscle reflexes followed by paralysis of the affected muscle groups – which will probably not be reversable.
Shooting pains down the legs and muscle weakness is an emergency and needs to be cared for immediately. Don’t ignore it.