Dr. Ahmed Fathalla Ibrahim

TRACTS REACHING TRACTS REACHING CONSCIOUS LEVELCONSCIOUS LEVEL

• DORSAL COLUMN (GRACILE & CUNEATE) TRACT: PROPRIOCEPTIVE SENSATION & DISCRIMINATIVE TOUCH

• LATERAL SPINOTHALAMIC TRACT: PAIN & TEMPERATURE

• VENTRAL SPINOTHALAMIC TRACT: CRUDE TOUCH

TRACTS REACHING TRACTS REACHING CONSCIOUS LEVELCONSCIOUS LEVEL

• ALL TRACTS HAVE 3 NEURONES TO REACH CEREBRAL CORTEX

FIRST ORDER NEURONECells of dorsal root ganglion

TRACTS REACHING TRACTS REACHING CONSCIOUS LEVELCONSCIOUS LEVEL

SECOND ORDER NEURONESECOND ORDER NEURONE• In the medulla: gracile & cuneate nucleusgracile & cuneate nucleus (for (for

dorsal column tract)dorsal column tract)• In the spinal cord: dorsal horn cellsdorsal horn cells1.1. Substantia gelatinosa of RolandiSubstantia gelatinosa of Rolandi (for lateral (for lateral

spinothalamic tract)spinothalamic tract)2.2. Nucleus propriusNucleus proprius (for ventral spinothalamic for ventral spinothalamic

tract)tract)• AXONS CROSS MIDLINE & DECUSSATE TO

FORM MEDIAL LEMINISCUS (FOR DORSAL COLUMN TRACT) OR SPINAL LEMINISCUS (FOR SPINOTHALAMIC TRACTS)

TRACTS REACHING TRACTS REACHING CONSCIOUS LEVELCONSCIOUS LEVEL

THIRD ORDER NEURONE

Cells of postero-ventral lateral nucleus of Cells of postero-ventral lateral nucleus of thalamusthalamus

• Its axons form the sensory radiationthe sensory radiation

• They ascend in the posterior limb of the posterior limb of internal capsuleinternal capsule

• They terminate in the postcentral gyrus the postcentral gyrus (somatosensory cortex)(somatosensory cortex)

DORSAL COLUMN TRACTDORSAL COLUMN TRACT

SPINOTHALAMIC TRACTSPINOTHALAMIC TRACT

TRACTS REACHING TRACTS REACHING SUBCONSCIOUS LEVELSUBCONSCIOUS LEVEL

SPINOCEREBELLAR TRACTS

• They carry proprioceptive fibers to the proprioceptive fibers to the cerebellumcerebellum for the control of posture & coordination of movement

• The fibers form 2 tracts:

1. Dorsal (uncrossed)(uncrossed) tract

2. Ventral (crossed)(crossed) tract

• Each tract is formed of 2 neurones2 neurones

SPINOCEREBELLAR TRACTSSPINOCEREBELLAR TRACTSFIRST ORDER NEURONECells of dorsal root ganglionSECOND ORDER NEURONEClarke’s nucleusClarke’s nucleus (in base of dorsal horn)• Dorsal tract: axons ascend in ipsilateral

laterallateral white column then enter the cerebellum through the inferior cerebellar peduncle

• Ventral tract: axons decusssate & ascend in contralateral laterallateral white column then enter the cerebellum through the superior cerebellar peduncle

SPINORETICULOTHALAMIC SPINORETICULOTHALAMIC SYSTEMSYSTEM

• The tract carries exteroceptive sensationexteroceptive sensation to the cerebral cortex for cortical activation

• The tract may be the route for dull aching slow the route for dull aching slow pain to be perceived by the cerebral cortexpain to be perceived by the cerebral cortex

FIRST ORDER NEURONEFIRST ORDER NEURONECells of dorsal root ganglionSECOND ORDER NEURONESECOND ORDER NEURONEDorsal horn cells of spinal cord. • Axons terminate in reticular formation (particularly Axons terminate in reticular formation (particularly

in medulla)in medulla)THIRD ORDER NEURONETHIRD ORDER NEURONECells of intralaminar nuclei of thalamusintralaminar nuclei of thalamus• Axons reach the cerebral cortex

LESION OF DORSAL COLUMN LESION OF DORSAL COLUMN TRACTTRACT

TABES DORSALIS

• Late stage of syphilitic infection of CNS

• Sensory ataxiaSensory ataxia

• Positive Romberg’s sign

SUBACUTE COMBINED DEGENERATION

• Due to deficiency of vitamin B12

• Lateral columns are also affected

LESION OF SPINOTHALAMIC LESION OF SPINOTHALAMIC TRACTSTRACTS

SYRINGOMYELIA

• Cavitation in the central canalCavitation in the central canal

• Usually in lower cervical & upper thoraciclower cervical & upper thoracic

• Fibers of lateral spinothalamic tractlateral spinothalamic tract crossing around central canal are affected

• Loss of pain & temperature on both sides with preserved touch sensation (dissociated sensory loss) taking a Jacket Jacket distributiondistribution