SPINOTHALAMIC AND CORTICOSPINAL TRACTS.

The central grey matter of the spinal cord is distributed in a butterfly shaped pattern, surrounded by the white matter. The white matter of the spinal cord consists of ascending and descending nerve fibres.

the spinothalamic tract lies lateral and ventral to the ventral horn of the spinal grey matter. Carries information related to pain, temperature ,crude touch and pressure. The first order neurone enters the spinal cord through the dorsal root of a spinal nerve and terminates in synaptic contact with the second order neurone.

The second order neurons are widely distributed in the dorsal horn The second order neurons are widely distributed in the dorsal horn . The axons of the second order neurons decussate to the opposite side of the cord , enters the contralateral spinothalamic tract and runs closely with the medial lemniscus in the brainstem to form the spinal lemniscus and terminates upon the third order neurone. The third order neurone has its cell body in the thalamus and relays information to the somato - sensory area of the contralateral hemisphere.

Applied clinical neuroanatomy SYRINGOMYELIA: The central canal becomes enlarged to form a cavity compressing adjacent nerves( the second order neurones of the spinothalamic tract as they decussate in the ventral white commissure), causing selective loss of pain and temperature while joint position, light touch and vibration are preserved (dissociated sensory loss ). BROWN SEQUARD SYNDROME: Hemisection of the spinal cord, resulting in ipsilateral paralysis and loss of dorsal column sensations along with contralateral pain and temperature sensations (dissociated sensory loss).

CORTICOSPINAL TRACT Primarily concerned with control of voluntary, discreet, skilled movements. Originate in the cerebral cortex (primary motor cortex) The axons leave the cerebral hemisphere through the corona radiata and internal capsule to enter the crus cerebri of the midbrain. Decussate in the caudal medulla(75-90%) and enter the contralateral corticospinal tract to end in the anterior horn cells. The remaining 10-25% of the pyramidal fibres remain ipsilateral but ultimately decussate near to their termination.

Applied clinical neuroanatomy HERIDITARY SPASTIC PARAPARESIS. CEREBRO VASCULAR ACCIDENTS. MULTIPLE SCLEROSIS.

REFERENCES NEUROANATOMY , AR CROSSMAN AND D NEARY, 5th EDITION HARRISSON’S PRINCIPLES OF INTERNAL MEDICINE, 19th EDITION

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