2A - Spinal Cord Tracts (copy)

Tract info from main SC PPT in here as well

Dorsal Column (medial lemniscus)

Ascending - posterior white matter

• Decussation: Medulla

• Function: 2-point discrimination, vibration, conscious proprioception to primary sensory cortex

• Damage: Ipsilateral

*Information regarding the LE travels in the gracile fasciculus

Information regarding the UE travels in the cuneate fasciculus

What happens if the dorsal columns are injured?

• If unilateral lesion below the decussation → ipsilateral loss

• If superior to decussation → contralateral loss

Lateral Spinothalamic

Ascending - anterior white matter

• Decussation: After ascend 1-2 levels

• Function: Pain and temperature to somatosensory cortex

• Damage: Contralateral

What occurs if the lateral spinothalamic tract is injured?

Contralateral loss of pain and temperature sensation

Anterior Spinothalamic

Ascending - anterior white matter

• Decussation: After ascend 1-2 levels

• Function: Pressure and touch, texture, and light touch to somatosensory cortex 

• Damage: Contralateral

What occurs if the anterior spinothalamic tract is injured?

Contralateral loss of pressure and touch sensation 

Spinocerebellar

Ascending - lateral white matter, anterior and posterior input from mm spindle and GTO

• Decussation: Partially crossed

• Function: Unconscious proprioception to cerebellum

• Damage: Partial loss

What occurs if the spinocerebellar tract is injured?

Partial loss of unconscious proprioception, lack of coordinated movement

How is the spinocerebellar tract often injured?

Demyelinating diseases such as MS

Spino-olivary

Ascending 

• Decussation: Yes (maybe medulla)

• Function: Info from cutaneous and proprioceptive organs (tendons and muscles) to cerebellum

Spinoreticular

Ascending

• Decussation: Yes at spinal level

• Function: Afferent pathway to the reticular formation that influences levels of consciousness. Assists in immediate reaction to painful stimuli 

Spinotectal

Ascending 

• Decussation: Yes (at spinal)

• Function: Info for spinovisual reflexes and assists with movement of eyes towards a stimulus

Lateral corticospinal 

Descending - lateral white matter originating in cerebral cortex

• Decussation: Begins in medulla (at the pyramids)

• Function: Voluntary motor mvmt

• Damage: Ipsilateral 

What occurs if the lateral corticospinal tract is injured?

Unilateral lesion of the spinal cord below decussation → Ipsilateral spastic paralysis

Anterior corticospinal

Descending - anterior white matter originating in cerebral cortex

• Decussation: Debatable (most sources say no)

• Function: Voluntary motor, neck and shoulder mms

• Damage: Ipsilateral?? (Dr. Mel put this), spastic paresis

What occurs if the anterior corticospinal tract is injured?

Spastic paresis (but less than the lateral)

Reticulospinal

Descending - anterior white matter originating in the brainstem 

• Decussation: Most do not cross

• Function: mms used for gait and posture, provide a pathway by which the hypothalamus can control sympathetic thoracolumbar outflow and parasympathetic sacral outflow 

• Damage: Loss of control, limb flexors, hypertonicity and mm spasms 

What occurs if the reticulospinal tract is injured?

Impair autonomic function; impair posture and walking due to loss of control of limb flexors; hypertonicity and muscle spasms. Hyperactive tendon reflexes and + Babinski.

Vestibulospinal

Descending - anterior white matter

• Decussation: Bilateral tracts so cross in brainstem (vestibular nuclei) , others remain ipsilateral (or do not cross)

• Function: Control proximal limb mms (extensors); also for balance, posture, and gait

• Damage: Loss of control 

What occurs if the vestibulospinal tract is injured?

Loss of control of postural muscles, impaired balance (ataxia)

Rubrospinal 

Descending 

• Decussation: In midbrain

• Function: Motor input of gross postural tone, facilitating flexor mms and inhibiting extensor mms

Tectospinal 

Descending 

• Decussation: In brainstem

• Function: Contralateral postural tone associated with auditory/visual stimuli

Which tracts decussate in/at the medulla?

Dorsal columns, spino-olivary, lateral corticospinal 

What tracts decussate in/at the midbrain?

Rubrospinal

What tracts decussate after ascending 1-2 spinal levels?

Lateral and anterior spinothalamic 

What tracts decussate in the brainstem?

Vestibulospinal (partially), tectospinal

What is the only spinal tract that mostly does NOT decussate?

Reticulospinal

What tracts are associated with ipsilateral losses?

dorsal columns (below decussation), lateral corticospinal, anterior corticospinal

What tracts are associated with contralateral losses?

Lateral and anterior spinothalamic, dorsal columns (above decussation)

What does “spino-” and “-spinal” in the names of spinal tracts?

Spino = ascending tract (except dorsal columns), spinal = descending tract