AN57.1-5 | Spinal Cord — Glossary

Widening of the spinal cord at C4-T1 where the large anterior horns contain motor neurons for the upper limb via the brachial plexus

Widening of the spinal cord at L1-S3 where the motor neurons supply the lower limb via the lumbar and sacral plexuses

Cone-shaped terminal end of the spinal cord at L1-L2 in adults and L2-L3 in neonates

Bundle of lumbar and sacral nerve roots below the conus medullaris resembling a horse's tail; freely floating in CSF

Fasciculus gracilis and fasciculus cuneatus carrying fine touch, vibration, and proprioception ipsilaterally to the medulla where they cross

Ascending tract carrying pain and temperature; crosses 1-2 segments above entry in the anterior commissure; ascends contralaterally

Major descending motor tract; 85% of fibres cross at the pyramidal decussation; controls voluntary skilled movements contralaterally

Hemisection of the cord causing ipsilateral motor loss and proprioception loss with contralateral pain/temperature loss

Fluid-filled cavity (syrinx) in the central canal destroying crossing spinothalamic fibres; causes bilateral cape-like loss of pain/temperature

Demyelination of posterior columns and lateral corticospinal tracts from vitamin B12 deficiency; loss of proprioception plus spastic paraplegia

Ten layers (I-X) of grey matter in the spinal cord; I-IV sensory, VII intermediate with Clarke's column, VIII-IX motor, X pericentral

Nucleus dorsalis in lamina VII at T1-L2/L3; origin of the posterior spinocerebellar tract carrying unconscious proprioception

Alpha motor neuron in lamina IX; the lower motor neuron that directly innervates skeletal muscle via the ventral root

Upper motor neuron lesion features: spastic paralysis, hyperreflexia, positive Babinski, clonus, no significant wasting

Lower motor neuron lesion features: flaccid paralysis, areflexia, fasciculations, significant muscle wasting, negative Babinski

Extensor plantar response (great toe dorsiflexion with fanning of other toes) on stroking the lateral sole; indicates UMN lesion in adults

Crossing of 85% of corticospinal fibres at the caudal medulla; explains why brain lesions cause contralateral motor deficits

Posterior column tract medially carrying fine touch and proprioception from the lower limb (below T6); synapses in nucleus gracilis in the medulla

Posterior column tract laterally carrying fine touch and proprioception from the upper limb (above T6); synapses in nucleus cuneatus

Transient loss of all spinal reflexes below the level of acute spinal cord injury; lasts days to weeks before reflexes return

Loss of sympathetic vasomotor tone from high spinal cord injury (above T6); causes hypotension and bradycardia with warm peripheries

Dense small neurons at the tip of the posterior horn (lamina II); modulates pain transmission; site of action of enkephalins and endorphins

Standardised classification of spinal cord injury severity from A (complete) to E (normal motor and sensory function)