Nerve root

A nerve root (Latin: radix nervi) is the initial segment of a nerve leaving the central nervous system. Nerve roots can be classified as:

• Cranial nerve roots: the initial or proximal segment of one of the twelve pairs of cranial nerves leaving the central nervous system from the brain stem or the highest levels of the spinal cord.
• Spinal nerve roots: the initial or proximal segment of one of the thirty-one pairs of spinal nerves leaving the central nervous system from the spinal cord. Each spinal nerve is formed by the union of a sensory dorsal root and a motor ventral root,^[1] meaning that there are sixty-two dorsal/ventral root pairs, and therefore one hundred and twenty-four nerve roots in total, each of which stems from a bundle of nerve rootlets (or root filaments).

Cranial nerve roots

Cranial nerves originate directly from the brain's surface: two from the cerebrum and the ten others from the brain stem.^[2] Cranial roots differ from spinal roots: some of these roots do not separate into individual sensory (dorsal) and motor (ventral) roots, but can emerge from one fusion root instead;^[3] of the eleven cranial nerves, four express this concept of fusion. The remaining eight nerve roots only express one of the two types of connections. Five of these are exclusive motor roots, and the remaining three are all sensory.^[4]

Spinal nerve roots

Spinal nerve roots are much more uniform than cranial nerves, one emerging from each level of the spinal column. These roots look extremely similar to one another, and form separate sensory and motor root connections to the central nervous system. Sensory nerves all enter the column as dorsal nerve roots, while motor nerves enter as ventral roots.^[4] They are expressed uniformly on both sides of each vertebra along the spinal column.

The specific vertebrae classify spinal nerve roots they originate from. These are separated into three sections: cervical, thoracic, lumbar, and sacral. The cervical is separated into eight vertebrae named C1-C8. The thoracic segment consists of T1-T12; the lumbar is L1-L5; and sacral S1-S5.^[5]

Pain and pathologies

Damage to nerve roots can cause paresis and paralysis of the muscle innervated by the affected spinal nerve. It may also cause pain and numbness in the corresponding dermatome. A common cause of damage to the nerve roots is spine lesions, such as prolapse of the nucleus pulposus, spinal tuberculosis, cancer, inflammation, spinal tabs. Root pain syndromes, known colloquially as radiculitis and sciatica, are among the most common symptoms caused by damage to the nerve root. Radiculopathy is commonly called the "root". In addition to pain, nerve damage may lead to impaired muscle control. Typically, mechanical dysfunction is caused by pressure on the nerve root or shock, affecting both the lower limbs and arms' roots.

The first sign of disease (sometimes preceding the occurrence of the radicular syndrome by up to a few years) is a sensation of pain in the neck and shoulder area. This pain often manifests due to hypothermia, poor posture or ergonomics during work or sleep, or sudden head movement. Team roots are localized mostly within the three lower cervical roots, namely C5, C6, and C7.

Lower limb radiculopathies

The cause is a herniated intervertebral disc, often on a single nerve root. The first sign of the nerve root sickness is usually lumbago, which usually occurs with periods of remission. The time to develop a full radicular syndrome may take several months or several years. Pain generally increases gradually, but it can also be sudden. Cold causes muscle contraction, which leads to increased previously hidden symptoms.

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