The routine examination that the doctors do in the cervical spine usually includes an evaluation of the strength in the upper limbs. Exploring the strength of the arms has an explanation that I want to try to clarify today. We must take into account that it is a mere explanation, we should not stop going to our doctor who is the one who will evaluate us with the greatest guarantees.
In the neck there are 7 vertebrae. Between each vertebra comes a nerve root. We have a total of 8 cervical nerve roots. The roots that form the nerves that are going to move the muscles of the arms are basically the so-called C5, C6, C7, C8 and T1 (T1 refers to the first nerve root of the dorsal spine). The root C5 exits between the vertebrae C4 and C5 and so on except that between the vertebrae C7 and T1 the root is called C8.
Depending on the muscles we request during the exploration, we will be evaluating the health of different roots. Let’s detail the most frequent scans by ordering the nerve root being explored. In all of them, the doctor opposes resistance to the movement, that is, he requests a movement and tries to avoid it in order to see the force with which we do it.
– C5. The doctor will ask us to separate the arms from the body while resisting us by placing his hands on the side of our arms.
– C5 and C6. We will be asked to bend our elbow as if to biceps the resistance of the doctor’s hand.
– C6 and C7. Keep the fist back as if we accelerated a motorcycle.
– C7. Stretch the elbow by activating the triceps against resistance.
– C7 and C8. The doctor will shake hands and ask us to squeeze him hard to squeeze his hand.
– C8 and T1. Strongly separate all the fingers as if we opened them in fan form.
You have to understand that this is a simplification to make it more readable. Most of the muscles are actually innervated by more than one root and the movements we have explained are performed by more than one muscle. Despite this with the mentioned one can get a very approximate idea of the injury.
And how do we interpret it? This part becomes a little complex and very complicated to explain in a post but basically we want to know if the nerve roots are working well. If the nerve roots are healthy, we will be able to perform all these movements with good strength and the two arms being approximately symmetrical (right is always a little stronger in right hands).
When there is an injury to one of the nerve roots (usually due to a disc herniation) weakness occurs in the muscles moved by that root. The greater the injury, the less force. The evolution in the interpretation of the lesion is also very important. It is not the same a muscle that is getting less force than one that is improving.
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