The anterior (or ventral) white commissure, also known as the alba anterior medullae spinalis, is a bundle of nerve fibers which cross the midline of the spinal cord just anterior to the gray commissure (Rexed lamina X). A δ fibers and C fibers carrying pain sensation in the spinothalamic tract contribute to this commissure, as do fibers of the anterior corticospinal tract, which carry motor signals from the primary motor cortex.
Two of the five sensory modalities, pain and temperature, cross sides at the anterior white commissure. Therefore, a pre-medullary lesion will result in contralateral pain and temperature loss, whereas touch, pressure, and proprioception will be ipsilateral.
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Anatomy of torso (primarily): the spinal cord (TA 14.1.02, GA 9.749)
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| External, dorsal |
Posterior median sulcus · Posterolateral sulcus
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Grey matter/
Rexed laminae |
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I–VI: Posterior horn
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I: Marginal nucleus · II: Substantia gelatinosa of Rolando · III+IV: Nucleus proprius · Spinal lamina V · Spinal lamina VI
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VII: Lateral horn
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Intermediolateral nucleus · Posterior thoracic nucleus
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VIII–IX: Anterior horn
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Interneuron · Alpha motor neuron (Onuf's nucleus)
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X: Other
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Central gelatinous substance · Gray commissure
Central canal · Terminal ventricle
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| White matter |
somatic/
ascending
(blue)
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Posterior/PCML: touch: Gracile · Cuneate
Lateral: proprioception: Spinocerebellar (Dorsal, Ventral) · pain/temp: Spinothalamic (Lateral, Anterior) · Posterolateral (Lissauer) · Spinotectal
Spinoreticular tract · Spino-olivary tract
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motor/
descending
(red)
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Lateral: Corticospinal (Lateral) · Ep (Rubrospinal, Olivospinal)
Anterior: Corticospinal (Anterior) · Ep (Vestibulospinal, Reticulospinal, Tectospinal)
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both
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Anterior white commissure
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| External, ventral |
Anterior median fissure · Anterolateral sulcus
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| External, general |
Cervical enlargement · Lumbar enlargement · Conus medullaris · Filum terminale · Cauda equina
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M: CNS
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anat (n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp
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noco (m/d/e/h/v/s)/cong/tumr, sysi/epon, injr
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proc, drug (N1A/2AB/C/3/4/7A/B/C/D)
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Brain and spinal cord: neural tracts and fasciculi
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Sensory/
ascending |
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PCML
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1°: Pacinian corpuscle/Meissner's corpuscle → Gracile fasciculus/Cuneate fasciculus → Gracile nucleus/Cuneate nucleus
2°: → sensory decussation/arcuate fibers (Posterior external arcuate fibers, Internal arcuate fibers) → Medial lemniscus/Trigeminal lemniscus → Thalamus (VPL, VPM)
3°: → Posterior limb of internal capsule → Postcentral gyrus
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Anterolateral/
pain
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Fast/lateral
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1° (Free nerve ending → A delta fiber) → 2° (Anterior white commissure → Lateral and Anterior Spinothalamic tract → Spinal lemniscus → VPL of Thalamus) → 3° (Postcentral gyrus) → 4° (Posterior parietal cortex)
2° (Spinotectal tract → Superior colliculus of Midbrain tectum)
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Slow/medial
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1° (Group C nerve fiber → Spinoreticular tract → Reticular formation) → 2° (MD of Thalamus) → 3° (Cingulate cortex)
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Motor/
descending |
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Pyramidal
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flexion: Primary motor cortex → Posterior limb of internal capsule → Decussation of pyramids → Corticospinal tract (Lateral, Anterior) → Neuromuscular junction
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Extrapyramidal
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flexion: Primary motor cortex → Genu of internal capsule → Corticobulbar tract → Facial motor nucleus → Facial muscles
flexion: Red nucleus → Rubrospinal tract
extension: Vestibulocerebellum → Vestibular nuclei → Vestibulospinal tract
extension: Vestibulocerebellum → Reticular formation → Reticulospinal tract
Midbrain tectum → Tectospinal tract → muscles of neck
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Basal ganglia
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direct: 1° (Motor cortex → Striatum) → 2° (GPi) → 3° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 4° (Thalamocortical radiations → Supplementary motor area) → 5° (Motor cortex)
indirect: 1° (Motor cortex → Striatum) → 2° (GPe) → 3° (Subthalamic fasciculus → Subthalamic nucleus) → 4° (Subthalamic fasciculus → GPi) → 5° (Lenticular fasciculus/Ansa lenticularis → Thalamic fasciculus → VL of Thalamus) → 6° (Thalamocortical radiations → Supplementary motor area) → 7° (Motor cortex)
nigrostriatal pathway: Pars compacta → Striatum
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| Cerebellar |
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Afferent
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Vestibular nucleus → Vestibulocerebellar tract → ICP → Cerebellum → Granule cell
Pontine nuclei → Pontocerebellar fibers → MCP → Deep cerebellar nuclei → Granule cell
Inferior olivary nucleus → Olivocerebellar tract → ICP → Hemisphere → Purkinje cell → Deep cerebellar nuclei
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Efferent
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Dentate nucleus in Lateral hemisphere/pontocerebellum → SCP → Dentatothalamic tract → Thalamus (VL) → Motor cortex
Interposed nucleus in Intermediate hemisphere/spinocerebellum → SCP → Reticular formation, or → Cerebellothalamic tract → Red nucleus → Thalamus (VL) → Motor cortex
Fastigial nucleus in Flocculonodular lobe/vestibulocerebellum → Vestibulocerebellar tract → Vestibular nucleus
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Bidirectional:
Spinocerebellar
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Unc. prop.
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lower limb → 1° (muscle spindles → DRG) → 2° (Posterior thoracic nucleus → Dorsal/posterior spinocerebellar tract → ICP → Cerebellar vermis)
upper limb → 1° (muscle spindles → DRG) → 2° (Accessory cuneate nucleus → Cuneocerebellar tract → ICP → Anterior lobe of cerebellum)
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Reflex arc
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lower limb → 1° (Golgi tendon organ) → 2° (Ventral/anterior spinocerebellar tract→ SCP → Cerebellar vermis)
upper limb → 1° (Golgi tendon organ) → 2° (Rostral spinocerebellar tract → ICP → Cerebellum)
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M: CNS
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anat (n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp
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noco (m/d/e/h/v/s)/cong/tumr, sysi/epon, injr
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proc, drug (N1A/2AB/C/3/4/7A/B/C/D)
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M: PNS
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anat (h/r/t/c/b/l/s/a)/phys (r)/devp/prot/nttr/nttm/ntrp
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noco/auto/cong/tumr, sysi/epon, injr
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proc, drug (N1B)
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