Neurological Examination Dermatomes Each of the spinal nerves exits the spinal canal between two of the vertebra. Each then goes to a particular area of the body. The area of skin served by each of these nerves is called its dermatome. The nerves from the upper cervical spine serve the skin of the neck. The nerves from C5 to T1 the mid-cervical spine to the upper thoracic spine go to the arms.
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Neurological Examination Dermatomes Each of the spinal nerves exits the spinal canal between two of the vertebra. Each then goes to a particular area of the body. The area of skin served by each of these nerves is called its dermatome. The nerves from the upper cervical spine serve the skin of the neck. The nerves from C5 to T1 the mid-cervical spine to the upper thoracic spine go to the arms. The nerves from T2 to L2 thoracic to upper lumbar go to the chest and abdomen.
Those from L3 to S1 lumbar and the first sacral go to the skin of the legs. The remainder of the sacral nerves, and the coccygeal nerves, go to the groin.
For example, when the C6 nerve is pinched, there is pain and numbness in the thumb and index finger. C6 — The thumb and part of the forearm. C7 — The middle finger. C8 — The smallest fingers and part of the forearm. L5 — The medial part of the calf and foot, the big toe.
S1 — The lateral part of the calf and foot, the smaller toes. Myotomes Each of the spinal nerves controls certain muscles. The muscles or muscles controlled by a particular nerve root are called its myotome. Nerves from the neck levels control the muscles in the arms.
Those from the thoracic spine control the chest and abdominal muscles. The nerves from the low back control the muscles in the legs. For example, when the C6 nerve is pinched, there is weakness in the biceps muscle. When the biceps is weak, bending the arm at the elbow is difficult. When the L5 nerve is pinched, there is weakness in the tibialis anterior muscle in the shin.
With L5 weakness, extending the ankle to walk on the heels is difficult. C6 — The biceps flexion of the arm at the elbow. C7 — The triceps extension of the arm at the elbow. C8 — The small muscles of the hand. L4 — The quadriceps extension of the leg at the knee. L5 — The tibialis anterior upward flexion of the foot at the ankle.
S1 — The gastrocnemius muscle downward flexion of the foot at the ankle. Reflexes Some, but not all, of the nerve roots have a reflex. C5, C6 and C7 have reflexes. L4 and S1 have reflexes. For example, when the C6 nerve is pinched, there is loss of the pronator reflex in the forearm. When the L5 nerve is pinched, there is no reflex loss. Not all nerves have a reflex which can be tested.
C6 — Flexion at the elbow, brachioradialis. C7 — Extension at the elbow, triceps. C8 — Finger flexion. L4 — The knee reflex, quadriceps. L5 — No reflex. S1 — The ankle reflex, gastrocnemius.
The Neurological Examination The neurologic examination is a series of physical examination tests used to identify the exact location of a problem. He or she then checks the sensation, strength, and reflexes. By determining the location of a deficit, one can identify the probable location of an abnormality. For example, if there is numbness of the lateral part outside of the foot, weakness in plantar flexion at the ankle pushing the foot down and absence of the ankle reflex, the S1 nerve is likely damaged.
The problem is almost always between the L5 bone and the sacrum. It is almost always due to a ruptured disc. Similarly, many problems are identified by careful examination alone.
Spinal Conditions A myotome is a zone in the body that is served by one spinal nerve root. It is a zone where motor nerves travel as they fulfill their responsibilities of signaling your muscles to contract. Myotomes and dermatomes are a part of the somatic voluntary nervous system, which is part of the peripheral nervous system. The peripheral and central nervous systems communicate with one another regularly.
Dermatomes and Myotomes | Anatomy
The nerves of the brachial plexus are shown in figure 2. When an encroachment occurs to a spinal nerve, the corresponding dermatome may exhibit the symptoms. The list below details nerve roots and the approximate area of skin that they provide innervation to: Each of these nerves relays sensation including pain from a particular region of skin to the brain. As an example, the flexion of the elbow is innervated by the musculocutaneous nerve. The dermatomes of the thorax and abdomen are evenly spaced segments. The list below details nerve roots and the approximate area of skin that they provide innervation to:.
Myotomes, Spinal Nerve Roots, and Dermatomes
DERMATOMES AND MYOTOMES PDF