extra pyramidal tracts

1. Extrapyramidal tracts
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
NRIIMS
Email: dr.goothy@gmail.com

2. Reticulospinal tracts
Throughout the midbrain, pons and medulla, groups of scattered
nerve cells and nerve fibers exist that are collectively known as
the reticular formation
From the pons, these neurons send axons
Mostly uncrossed
Down into the spinal cord – pontine reticular tract

3. Reticulospinal tracts
 From medulla, similar neurons send axons
 Crossed and uncrossed
 Medullary reticulospinal tract
 Reticulospinal fibers from pons descend through the anterior white column
 Medullary reticulospinal tract descends through the lateral white column

4. Reticulospinal tracts
Both sets of fibers enter anterior gray column of spinal cord
and may facilitate or inhibit the activity of alpha and gamma
motor neurons
Reticulospinal tract influence voluntary movements and
reflex activity.

6. Tectospinal tracts
Fibers from this tract arise from nerve cells in the superior
colliculus of the mid brain
Most of the fibers cross the midline soon after their origin and
descend through the brainstem close to the medial
longitudinal fasciculus

7. Tectospinal tracts
Descends through the anterior white column of the spinal
cord close to the anterior median fissure
Majority of fibers terminates in the anterior gray column by
synapsing with inter neurons
Concerned with reflex postural movements in response to
visual stimuli

9. Rubrospinal tract
The red nucleus is situated in the tegmentum of the midbrain
The axons of the neurons in this nucleus cross midline at the
level of the nucleus and
descend as rubrospinal tract through pons and medulla
to enter the lateral white column of spinal cord
Terminates on interneurons at anterior gray column

10. Rubrospinal tract
Considered as important indirect pathway by which the
cerebral cortex and the cerebellum can influence the
activity of alpha and gamma motor neurons of the spinal
cord.

12. Vestibulospinal tract
The vestibular nucleus is situated in the pons and medulla
The vestibular nuclei receive afferents from inner ear and
cerebellum
The neurons of lateral vestibular nucleus give rise to the axons
that form the vestibulospinal tract
The tract descends uncrossed

13. Vestibulospinal tract
Descends through medulla
Enter spinal cord in the anterior white column
Terminates by synapsing with inter neurons of anterior gray
column
This tract facilitates the activity of extensor muscles and inhibits
the activity of flexor muscles- maintenance of balance

15. Olivospinal tract
Arise from the inferior olivary nucleus
Descends in the lateral white column of the spinal cord
Influence activity of the motor neurons in the anterior gray
column
There is now considerable doubt that this tract exists..

17. Upper Motor Neuron lesion
Lesions of corticospinal tract (pyramidal tract)
Lesions restricted to corticospinal tracts produce the following
clinical signs
Babinski sign is present – great toe is dorsi flexed and
fanning of other toes – Plantar extensor response

18. Upper Motor Neuron lesion
Superficial abdominal reflexes are absent
Cremasteric reflex is absent
Loss of performance of fine skilled voluntary movements

19. Upper Motor Neuron lesion
Lesions of descending tracts other than pyramidal tract (
extrapyramidal tract lesion)
Severe paralysis- with little or no muscle atrophy
Spasticity or hypertonicity of muscles – lower limb is
maintained extension. Upper limb is maintained in flexion

20. Upper Motor Neuron lesion
Exaggerated deep muscle reflexes
Clasp knife reaction

21. Upper Motor Neuron lesion
In clinical practice it is rare to have organic lesion that is
restricted only to pyramidal tracts or only extra pyramidal
tracts
Usually both sets of tracts are affected to variable extent
producing both group of clinical signs

22. Lower Motor Neuron lesion
Trauma, infection (poliomyelitis), vascular disorders, and
degeneration may produce lesion of lower motor neuron by
destroying the cell body of anterior gray column

23. Lower Motor Neuron lesion
Flaccid paralysis of muscles supplied
Atrophy
Loss of reflexes
Muscle contracture
Reaction of degeneration

24. Types of paralysis
Hemiplegia – paralysis of one side of body and includes the
upper limb , one side trunk and lower limb
Monoplegia –paralysis of one limb only
Paraplegia – paralysis of the two lower limbs
Diplegia – paralysis of two corresponding limbs
Quadriplegia – paralysis of all four limbs

25. THANK YOU