Rubrospinal Tract

Introduction[edit | edit source]

Rubrospinal tract.jpg

The Rubrospinal tract is a descending pathway, beginning as axons of the neurons present in the red nucleus and terminates by synapsing with the interneurons in the spinal cord. [1]

It is part of the extrapyramidal system and is important for regulating the activity of the motor neurons. It plays an important role in a number of body reflexes[2].

Anatomy[edit | edit source]

Origin: The Red Nucleus of the midbrain tegmentum[1] The red nucleus is believed to be involved in movement along with a number of other functions, however it has a diminished role in humans due as other movement-related structures eg the corticospinal tract.[3]

Path: After leaving the red nucleus, the axons of the red nucleus cross to the opposite side. This crossing of nerve fibers occurs just in front of the red nuclei. After decussation, these axons descend downward as rubrospinal tract on the contralateral side of the spinal cord. These fibers of rubrospinal tract pass through the white matter of pons and medulla oblongata. After crossing the medulla oblongata, the rubrospinal tract enters the lateral white column of the spinal cord. Here the tract continues, descending and terminating and finishing by synapsing with the interneurons at different levels of the spinal cord. [1] The rubrospinal tract mainly terminates at the level of the cervical segments of the spinal cord[2].

Function[edit | edit source]

Rubrospinal tracts.png

The most important function of the rubrospinal tract is the control of muscle tone in flexor muscle groups (it is particularly important in the term newborn because of the flexor tone in the limbs).[4]Its functions are believed to be:

  1. Modulation of Flexor  Muscle Tone: has an important role in the modulation of motor tone, causing flexors to contract and extensors to relax and vice versa. This function is associated with the rubrospinal tract because the red nucleus receives input fibers from reticular formation (the archaic core of those pathways connecting the spinal cord and the brain)[5]. Due to these connections, the rubrospinal tract inhibits the activity of extensors and facilitates the activity of flexor muscles.
  2. Modulation of Reflex Activity: facilitates the reflex activity due to the connections of the red nucleus with reticular formation. Plays an important role in flexor reflex activity eg withdrawing hand after touching a hot object, flexion of limbs when something hits the flexor surface.
  3. Inhibition of Anti-gravity Muscles: inhibits the contraction of anti-gravity muscles. Important in the prevention of decerebrate posture (pathology in brainstem or cerebellum; abnormal breathing pattern, extension pattern in upper - and lower limbs)[2].

Pathology[edit | edit source]

Red Nucleus shown here in Green

No specific disease exists that targets the rubrospinal tract specifically, however other diseases of the spinal cord or red nucleus can compromise its functions. These diseases include:

  1. Red nucleus lesions due to vascular disease or tumor. Lesions within the region of the red nucleus can result in movement disorders and tremor, but these effects may be more associated with damage to fibers which are associated with the cerebellar and basal ganglia systems.[6]
  2. Complete cord transection due to fracture or stab wound
  3. Lower motor neuron lesions. These involve the extrapyramidal tracts, including the rubrospinal tracts. The clinical signs include severe paralysis, increased muscle tone, exaggerated deep muscle reflexes and rigidity.

Stroke/ Spinal Cord Injury significance: There is considerable functional redundancy between the corticospinal tract and the rubrospinal tract. In cases of corticospinal tract injury eg stroke or spinal cord injury, neurologic compensation and response take place in the acute setting, by which the red nuclei undergo remodeling, and increases activity. This upregulation may provide a small degree of compensation in motor function.[7]

In primate studies, it has been suggested that the rubrospinal tract is responsible for the separation process of movement, that is the ability to isolate movement to one joint independent of another. Therefore, it may be that the rubrospinal tract when affected could impact the fine tuning and fractionation of movement[8][9] .

References[edit | edit source]

  1. 1.0 1.1 1.2 Crossman AR, Neary D. Neuroanatomy: An Illustrated Colour Text. Third Edition. London: Elsevier, 2004
  2. 2.0 2.1 2.2 Brain made simple Rubrospinal tract Available: (accessed 25.4.2022)
  3. Neuroscientifically challenged Red Nucleus Available: (accessed 26.4.2022)
  4. JJ V. Volpe’s Neurology of the Newborn.2018 Available: 25.4.2022)
  5. Faraguna U, Ferrucci M, Giorgi FS, Fornai F. The functional anatomy of the reticular formation. Frontiers in Neuroanatomy. 2019 May 29;13:55. Available: 26.4.2022)
  6. What-When-How. The Upper Motor Neurons (Motor Systems) Part 3. (accessed on 1/4/2016)
  7. Vadhan J, Das JM. Neuroanatomy, Red Nucleus. InStatPearls [Internet] 2021 Jul 31. StatPearls Publishing. Available: (Accessed 26.4.2022)
  8. Belhaj-Saif A, Cheney PD. Plasticity in the distribution of the red nucleus output to forearm muscles after unilateral lesions of the pyramidal tract. J Neurophysiol 2000; 83: 3147–53
  9. Scheets PL, Sahrmann SA, Norton BJ. Use of movement system diagnoses in the management of patients with neuromuscular conditions: a multiple-patient case report. Physical therapy. 2007 May 15.