The explanation for the symptoms of sciatica is found in the anatomy of the nerves coming out of the back to go to the legs. Nerves are wires that carry information from the brain to the different areas of the body and collect signals from the body to send them to the brain. I will give some more details later. If you find it complicated do not worry because I clarify it in the video that you can see in the post.
In the case of the legs, the nerves leave the brain and go down the spinal cord until they reach the lower back. Here the nerve roots that are going to leave the spinal canal are separated through small holes between the vertebrae. Once outside, they come together to form the biggest nerves that run through our leg. The nerves carry the signal to the muscles so that they contract and we can move the leg. On the other hand, the legs have receptors that detect pain, sensitivity, temperature and position of the joints among others. These signals are sent to the brain through the sensory nerves.
The nerves in the back and legs The nerve roots that come out of the marrow are called according to the place through which they exit. Thus, the root that emerges through the conjunction hole between the L5 vertebra and the sacrum bone, we call it root L5. The most common hernias that occur in the lower back are hernias L4-L5 and especially L5-S1. These hernias will compress the nerves L5 and S1 respectively. It is not always exactly like this, this is the most frequent thing. The hernia usually occurs in the posterolateral area and therefore does not compress the nerve root of that level but damages the lower level (it is traveling through this area to exit through the hole of the inferior vertebra). There is the exception, less frequent, that are the hernias that we call foraminal, that being very lateral hernias compress the nerve that leaves by the hole that is next to the disc.
From the above, we must keep in mind that the most frequent hernias of the lumbar region (L4-L5 and L5-S1) will compress the L5 and S1 roots. Well, the roots L5 and S1 will form part of the sciatic nerve. As we have said, the roots leave the spine and then come together to form the nerves. In the case of the sciatic nerve, it is formed by nerve fibers of the roots from L4 to S2.
To understand the symptoms of sciatica, it is necessary to know the function of this nerve. This nerve carries the signal to some muscles of the pelvis and thigh such as the buttocks and hamstrings as well as the muscles that move the ankle and foot (the leg muscles). As for the sensitive part, pick up the sensitivity of the leg and the back of the thigh and glutes.
Herniated discs can sometimes contact the nerve root and compress it. Keep in mind that what damages the herniated disc is a nerve root that will form part of the sciatic nerve, which is the set of many roots. Each nerve root participates differently in each muscle and in the collection of sensory signals. Thus:
– When the L5 root is injured, we may notice a pain in the side of the thigh that descends through the anterolateral aspect of the leg to the dorsum of the foot. In severe cases there will be paralysis of the muscles that move the foot and the fingers upwards (there is what we call fallen foot).
– When the S1 root is injured we may notice a pain in the gluteus that descends through the back of the thigh and leg and reaches the sole of the foot. In severe cases there will be a paralysis of the muscles that carry the foot and the fingers downwards, that is to say that they impel the foot (like to jump, for example).
This is an explanation of why the symptoms of sciatica are trying to make it simple and understandable. Of course each injury is different and produces different symptoms and not everything that is described necessarily must suffer. What’s more, most hernias will never squeeze any nerve roots and possibly give no more symptoms than mild back pain.
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