Nerve root

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A nerve root (Latin: radix nervi) is the initial segment of a nerve leaving the central nervous system. Types include:

  • Cranial nerve root: 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 root: 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 stem from a bundle of nerve rootlets (or root filaments).

Cranial Nerve Roots[edit]

Cranial nerves originate strait from the brains surface, two from the cerebrum and the ten others from the brain stem[2]. The nerve roots themselves are unique to that of the spinal roots in a few key ways. Some of these roots do not separate into individual sensory (dorsal) and a motor (ventral) roots, instead they can emerge from one fusion root. [3] Of the eleven cranial nerves, four express this concept of fusion. The remaining seven nerve roots are also unique as they 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[edit]

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, each forming sepperate sensory and motor root connections to the central nervous system. Sensory nerves all enter the column as dorsal nerve roots, while motor enter as ventral roots[5]. This is expressed in uniform fashion on both sides of each vertebrae along the spinal column.

Spinal nerve roots are classified by the specific vertebrae they originate from. These are separated into three sections as follows: Cervical, Thoracic, Lumbar and Sacral. Cervical is separated into eight vertebrae otherwise named C1-C8, if you were referring to a nerve root on the C3 vertebrae it would be referred to C3 nerve root. The Thoracic segment consists of T1-T12; Lumbar is L1-L5; and Sacral S1-S5.

Pain and pathologies[edit]

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 are lesions in the spine, such as prolapse of the nucleus pulposus, spinal tuberculosis, cancer, inflammation, spinal tabs. Root pain syndromes, known colloquially as radiculitis, sciatica are one of the most common symptoms caused by damage to the nerve root. Radiculopathy is commonly called the "root". In addition to pain, nerve damage may also bring about impaired muscle control. Typically, mechanical dysfunction is caused by pressure on the nerve root or shock, that can affect both the roots of the lower limbs and arms.

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


  • Forced, the reflexive position of the spine (the slope and a slight twist in the opposite direction has fallen Root)
  • Paraspinal muscle contracture
  • Reduction of cervical lordosis
  • Numerous painful points on the edges of the blade
  • Pain at the back of the head slope
  • Pain radiating to the upper chest and shoulder area
  • The positive sign of nerve root tension in the upper limbs (not always)

Upper limb radiculopathies[edit]

C5 radiculopathy[edit]

  • Pain is found along the lateral brachium of the affected side of the arm.
  • C5 innervated muscle weakness may be found (e.g., rhomboids, deltoid).

C6 radiculopathy[edit]

  • Pain is found along the lateral antebrachium of the affected arm
  • C6 innervated muscles are weak (e.g., forearm pronator and supinator, wrist extensors).

C7 radiculopathy[edit]

  • Pain is found along with the middle finger of the affected arm
  • C7 innervated muscle weakness is found (e.g., wrist flexors, finger extensors).


Treatment should be initiated as early as possible, before any increase in muscle tone, which further intensifies the pain. Traction is recommended to decompress compressed roots. Radiculopathy can be caused by herniated nucleus pulposus. Surgery is the last resort when conservative therapy is unsuccessful.

Lower limb radiculopathies[edit]

Often on a single nerve root, the cause is a herniated intervertebral disc. The first harbinger of roots is usually lumbago. The disease usually occurs with periods of remission. The first symptoms 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.


  • Scoliosis
  • Paraspinal muscle contracture
  • The reduction of lumbar lordosis

*Tingling or numbness

*Increased sensitivity

*Other Inflammatory disease

L4 radiculopathy[edit]

  • Pain located on the front of the thigh and shin further radiates towards the inner ankle, sometimes the medial toe
  • Occasionally, failure of the quadriceps muscle and reflex weakness

L5 radiculopathy[edit]

  • Pain radiates to the side of the thigh and lower leg towards the back of the foot and toes 1-3
  • All reflexes are preserved

S1 radiculopathy[edit]

  • Pain radiates to the posterior side of the thigh and lower leg to the ankle side, sometimes up to the fourth toe
  • Gluteal muscles are weakened
  • Difficulty standing on toes


Treatment can vary based on the nature and severity of the disease.

In the acute phase, to unlock the nerve root it is recommended to apply traction and isometric muscle relaxation. In cases where the manipulation is undesirable or impossible to carry out the infiltration may be root. In cases of severe pain, this procedure should be carried out first.

Anti-inflammatory medications may be used to alleviate symptoms. In the acute setting the main goal is to restore proper mobility by reducing pain. Surgery is used when other methods do not produce results.

The exception is when paralysis is observed; in those cases, surgery should be performed as soon as possible to avoid irreversible paralysis of muscles.

A new method of treating herniated discs is the direct cause of any root is thermonukleoplastic, the treatment consisting of introducing into the annulus fibrous of a special catheter tip heating. Warming up for a few minutes end to 65 °C results in the destruction of pain-sensitive nerve endings within the fibrous ring, reducing the volume of disk space and alleviate inflammation associated with chronic irritation.


  1. ^ Blumenfeld, Hal (2010). Neuroanatomy Through Clinical Cases (2nd ed.). Sunderland: Sinauer Associates. p. 321. ISBN 978-0-87893-058-6.
  2. ^ Sanders, K. (2019, March 30). Summary of the Cranial Nerves. Teach Me Anatomy.
  3. ^ Hagan, Catherine (2012). Comparative Anatomy and Histology. Academic Press: Piper M. Treuting, Suzanne M. Dintzis,. ISBN 9780123813619.CS1 maint: extra punctuation (link)
  4. ^ Biga, L., Dawson, S., Harwell, A., Hopkins, R., Kaufmann, J., LeMaster, M., . . . Runyeon, J. (unk). 13.3 Spinal and Cranial Nerves. Retrieved November 20, 2020, from
  5. ^ Biga, L., Dawson, S., Harwell, A., Hopkins, R., Kaufmann, J., LeMaster, M., . . . Runyeon, J. (unk). 13.3 Spinal and Cranial Nerves. Retrieved November 20, 2020, from