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Ascending and descending tracts of spinal cord

detailed pathways of spinal tracts and spinal cord syndromes

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Ascending and descending tracts of spinal cord

  1. 1. Ascending and Descending Tracts of Spinal Cord & Spinal cord syndromes
  2. 2. CENTRAL NERVOUS SYSTEM integration / processing / modulating stimulus receptor neurone motor / descending tracts effector organ / response PNS transmission lower motor neurone sensory / ascending tracts
  3. 3. Ascending Sensory Pathway are organized in three neuronal chain - First order neuron - Second order neuron - Third order neuron
  4. 4. First order neuron • cell body in posterior root ganglion • peripheral process connects with sensory receptor ending • central process enter the spinal cord through the posterior root • synapse with second order neuron in spinal gray matter dorsal root ganglion
  5. 5. Second order neuron • cell body in posterior gray column of spinal cord • axon crosses the midline ( decussate ) • ascend & synapse with third order neuron in VPL nucleus of thalamus
  6. 6. Third order neuron • cell body in the thalamus • give rise to projection fibres to the cerebral cortex, postcentral gyrus ( sensory area )
  7. 7. ascending tracts in spinal cord
  8. 8. Lateral spinothalamic tract  pain and thermal impulses ( input from free nerve endings, thermal receptors )  transmitted to spinal cord in delta A and C fibres  central process enters the spinal cord through posterior nerve root, proceed to the tip of the dorsal gray column • Second order neuron – in the dorsal horn, cross to the opposite side (decussate) – ascend in the contralateral ventral column – end in VPL nucleus of thalamus • Third order neuron – in the VPL nucleus of thalamus – project to cerebral cortex ( area 3, 1 and 2 )
  9. 9. Anterior spinothalamic tract light touch and pressure impulses ( input from free nerve endings, Merkel’s tactile disks ) • First order neuron – dorsal root ganglion( all level ) • Second order neuron – in the dorsal horn, cross to the opposite side (decussate) – ascend in the contralateral ventral column – end in VPL nucleus of thalamus • Third order neuron – in the VPL nucleus of thalamus – project to cerebral cortex ( area 3, 1 and 2 )
  10. 10. Posterior & anterior spinocerebellar tract  Transmit unconscious proprioceptive information to the cerebellum  receive input from muscle spindles, and pressure receptors  involved in coordination of posture and movement of individual muscles of the lower limb
  11. 11. • Spinotectal tract  passes pain, thermal, tactile information to superior colliculus for spinovisual reflexes • cross the median plane • synapse in the superior colliculus • integrate visual and somatic sensory information ( it brings about the movement of eye and head towards the source of information )  Spinoreticular tract – uncrossed fibres, synapse with neurones of reticular formation (important role in influencing level of consciousness)  Spino-olivary tract
  12. 12. • Descending tracts
  13. 13. motor homunculus cerebral cortex
  14. 14. Corticospinal tract • arises from the pyramidal cells of cerebral cortex – fibres travel through • corona radiata • posterior limb of the internal capsule • cerebral peduncle ( middle 3/ 5th ) • pons • medulla oblongata ( passed through the pyramids ) – eventually fibres cross the mid line and terminate on LMN of anterior gray column of respective spinal cord segments
  15. 15. Rubrospinal tract • nerve cells in red nucleus ( tegmentum of midbrain at the level of superior colliculus ) • nerve fibres / axons – cross the mid line – descend as rubrospinal tract • through pons and medulla oblongata • terminate anterior gray column of spinal cord ( facilitate the activity of flexor muscles )
  16. 16. Tectospinal tract • nerve cells in superior colliculus of the midbrain • nerve fibres/ axons – cross the mid line – descend close to medial longitudinal fasciculus • terminate in the anterior gray column of upper cervical segments of spinal cord ( responsible for reflex movement of head & neck in response to visual stimuli )
  17. 17. Vestibulospinal tract • nerve cells in vestibular nucleus (in the pons and medulla oblongata – received afferents from inner ear and cerebellum • axons descend uncrossed – through medulla and through the length of spinal cord • synapse with neuron in the anterior gray column of the spinal cord ( balance by facilitate the activity of the extensor muscles )
  18. 18. Reticulospinal tract • nerve cells in reticular formation • fibres pass through – midbrain, pons, and medulla oblongata • end at the anterior gray column of spinal cord – control activity of motor neurons (influence voluntary movement and reflex activity )
  19. 19. Spinal cord syndromes • Complete • Incomplete
  20. 20. COMPLETE CORD TRANSECTION
  21. 21. Sensory all sensations are affected. Pin prick test is very valuable. Sensory level is usually 2 segments below the level of lesion. Segmental paresthesia occur at the level of lesion. Motor -paraplegia due to corticospinal tract. First spinal shock-followed by hypertonic hyperreflexic paraplegia. Loss of abdominal and cremastric reflexes. At the level of lesion LMN signs occur. Autonomic Urinary retention and constipation. Anhidrosis ,trophic skin changes, vasomotor instability below the level of lesion. Sexual dysfunction can occur.
  22. 22. CENTRAL CORD SYNDROME
  23. 23. CENTRAL CORD SYNDROME
  24. 24. • CAUSES 1. Most common cause is syringomyelia. • others 1. hyperextension injuries of neck, 2. intramedullary tumours, 3. trauma. 4. Associated with chiari type 1 and 2.and dandy walker malformation. • SENSORY  Pain and temperature are affected.  Touch and proprioception are preserved.  Dissociative anaesthesia.  Shawl like distribution of sensory loss. • MOTOR.  Upper limb weakness >lowerlimb
  25. 25. • Other features; Horners syndrome Kyphoscoliosis . Sacral sparing Neuropathic arthropathy of shoulder and elbow joint Prognosis is fair.
  26. 26. ANTERIOR CORD SYNDROME • Usually caused by hyperflexion injuries. • Paralysis below the level of lesion. • Pain and temperature loss. • Dorsal column is preserved. .
  27. 27. POSTERIOR COLUMN SYNDROME • Occurs due to neurosyphilis,diabetes mellitus • Usually occurs 10 to 20 yrs after infection • SENSORY • Impaired position and vibration sense in LL • Tactile and postural hallucinations can occur. • Numbness or paresthesia are frequent complaints.. • Sensory ataxia. • Positive rhomberg sign. • Positive sink sign • Positive lhermittes sign.
  28. 28. • Abadie’s sign positive. • Urinary incontinence. • Absent knee and ankle jerk.(areflexia,hypotonia) • Abdominal and laryngeal crisis can occur. • Charcots joint. • miotic and irregular pupil not reacting to light. • Argyl robertson pupil
  29. 29. POSTERO LATERAL COLUMN DISEASE – CAUSES; • VITB12 DEFICIENCY • AIDS • HTLV ASSOCIATED MYELOPATHY. • CERVICAL SPONDYLOSIS • Sensory • Paresthesia in feet • Loss of proprioception and vibration in legs • Sensory ataxia • positive rhomberg sign • Bladder atony • Corticospinal tract involvement • spasticity,hyperreflexia ,bilateral Babinski sign.
  30. 30. ANTERIOR HORN CELL SYNDROMES • CAUSED BY SPINAL MUSCULAR ATROPHY • MOTOR  weakness ,atrophy and fasciculations.  Hypotonia,depressed reflexes.  Muscles of trunk and extremities are affected.  Sensory system is not affected.
  31. 31. Ant horn cell and pyramidal tract syndrome • Occurs in amytrophic lateral sclerosis. • Affects the ant horn cells and corticospinal tract. • Both lmn and umn sign occur. • MOTOR • Ant horn cell-paresis , • Atrophy and fasciculations. • Corticospinal tract – • paresis ,spasticity and extensor plantar response. •
  32. 32. SPINAL ARTERY
  33. 33. • MOTOR • Flaccid and areflexic paraplegia • SENSORY • Loss of pain and temperature. • Preservation of positon and vibration. • AUTONOMIC • urinary incontinence. • Spinal cord infarction usually occurs in T1 to T4 segment.and L1 • Occurs due to • syphilitic arteritis , • aortic dissection, • atherosclerosis of aorta, • SLE ,AIDS • ,AV malformation ANTERIOR SPINAL ARTERY SYNDROME.
  34. 34. • POST SPINAL ARTERY SYNDROME • UNCOMMON • Loss of proprioception and vibratory sense. • Pain and temperature is preserved. • Absence of motor deficit.

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