Spinal Cord

  • anterior median fissure
  • posterior median sulcus
  • posterior median septum
  • anterolateral and posterolateral sulci
  • spinal segments (segments from which spinal nerves arise; 1 level above C, 2 levels above T, 3 levels above L)
  • cervical expansion (c5-t1/C3-7 > brachial plexus)
  • lumbar expansion (l2-s3/T9-L1 > lumbosacral plexus)
  • conus medullaris (L3 @ birth, L1/2 [or T12-L3] in adult)
  • filum terminale (pia > posterior Co1)
  • central canal of the cord (lined by ependyma; extends 5-6mm into filum terminale)
  • terminal/5th ventricle (fusiform dilatation in conus)
  • diastematomyelia = split cord (V, sagittal division in to 2 hemicords, each with central canal)

Internal Stucture

  • anterior/ventral horns (motor neurones)
  • posterior/dorsal horns (sensory neurones)
  • lateral horns (T and upper L; sympathetic)
  • anterior column (betw anterior horn and anterior median fissure)
  • lateral column (betw anterior and posterior horns)
  • posterior/dorsal column (betw posterior horn and posterior median septum)
  • grey and white commisures

Spinal_cord

Ascending/Afferent/Sensory Tracts/Pathways

  • post column (light touch, vibration, proprioception; large myelinated fibres, cell bodies in dorsal root ganglion)
    • gracile (medial, LLs) and cuneate (lateral, ULs) columns/tracts/fasciculi
    • gracile and cuneate nuclei > decussation > medial lemniscus > thalamus > anterior limb int cap > cortex
  • anterolateral tract (around anterior horn; anterior [crude touch] and lateral [pain, temp] spinothalamic tracts; sacral lat, cervical med)
    • pain > posterior nerve roots > posterolateral tract = tract of Lissauer > substantia gelatinosa > anterior to central canal > opposite anterolateral tract > spinal lemniscus (brainstem) > thalamus
    • substantia gelatinosa (of Rolando) (apex posterior horns)
  • spinocerebellar tract (peripheral lateral column, proprioception)

Descending/Efferent/Motor Tracts/Pathways

pyramidal system = direct corticospinal tract/pathway

  • UMN (cell bodies in cortex > pyramids [medulla] > white matter columns > anterior horn cells)
  • LMN (cell bodies in anterior horn cells > motor endplates)
  • lateral corticospinal tract (lat column dorsal to midline)
  • anterior corticospinal tract (ant column medially; terminate in upper thoracic region > decussate at their segmental level)

extrapyramidal system = indirect corticospinal tract

  • bypass pyramids, pass via subcortical nuclei to anterior horn cells
  • rubroreticulospinal/rubrospinal tract (ant to lateral corticospinal tract; <red nucleus; mediation of voluntary movement, facilitate flexion, inhibit extension)
  • vestibulospinal tracts (ant to anterior horns; vestibular nuclei [medulla]; facilitates extensor/antigravity mm, gaze, head and neck control)

Spinal Nerve Roots

  • segmental nerves (8c, 12t, 5l, 5s, 1co)
  • C1-7 above corresponding vertebra, the rest below
  • spinal nerve rootlets/filaments
  • ventral spinal roots (somatic motor fibres, sympathetics [T1-L2], parasympathetics [S2-4])
  • dorsal nerve roots (< 3-4 rootlets; somatic and visceral afferent sensory fibres)
  • dorsal root ganglion (in foramen and evagination of dura and arachnoid just before union of roots
  • (mixed) spinal nerve (in intervertebral canal) > ventral and dorsal rami (mixed motor and sensory)
  • cauda equina (l2-co1)
  • dermatomes (C2 head, C3-4 neck, C5 anterior arm, C6 thumb, C7 back arm/hand, C8 little finger, T1 anterior arm, T4 nipples, T10 umbilicus, L1 groin, L4 knees, L5 dosum/sole foot, S1 postlat leg, S2 postmed leg, S5 anus)
  • tendon reflexes (ankle S1-2, knee L3-4, biceps C5-6, supernator C5-6, triceps C7-8)
  • conjoined nerve roots (V1%, separate distal to neural foramen)
  • perineural cysts (of Tarlov) (V, junction dorsal nerve root and ganglion between perineurium [arachnoid] and endoneurium [pia])

Spinal Meninges

  • outer layer dura = periostium of vertebrae
  • extradural/epidural space (venous plexus, fat)
  • spinal dura = theca (< inner layer cerebral dura)
  • spinal dural sac = thecal sac (>tectorial membrane, PLL and body axis; to S2 where it blends with filum terminale)
  • subdural (potential) space (lubricating serous fluid)
  • arachnoid mater (avascular)
  • posterior median septum = cribriform septum (incomplete, arachnoid mater)
  • subarachnoid space (~75mL CSF)
  • denticulate ligament (foramen magnum > conus; pia > dura; between nerve roots; 21 pairs)
  • ant and posterior compartments (separated by dent lig)
  • pia mater (vascular, >epineurium)
  • filum terminale (pia and glia┬▒ fat; perforate theca at S2 > periosteum of Co1; internum > dural sac at S2; externum > Co1)
  • dural sheath/sleeve (covering nerve roots; meninges fuse distal end)
  • endoneurium, perineurium, epineurium (peripheral nn)

Arterial Supply

  • ant spinal artery (ant median fissure; <ant spinal branches of vertebral aa; > all cord apart from posterior horns and dorsal columns)
  • posterolateral spinal arteries (2; amongst plexus < PICAs; dorsal to posterior nerve roots; >doral horns, posterior columns)
  • posterior anastomotic a (betw post-lat spinal aa)
  • lateral anastomotic a (betw post-lat and anterior spinal aa)

segmental radicular arteries

  • run in neural foramina along nerve root
  • radiculomedullary junction with spinal a (hairpin at thoracolumbar, Y-shaped at cervical)
  • anterior radiculomedullary aa (radicular aa that > anterior spinal a; 6-10)
  • post radiculomedullary aa (radicular aa that > posterolateral spinal aa)
  • superior territory (c1-t2 < 3 radiculomedullary aa with c3 c6 and c8 nerve roots)
  • < artery of the cervical enlargement (c6)
  • < ascending cervical a < thyrocervical trunk
  • < deep cervical a < costocervical trunk
  • < supreme intercostal a < costocervical trunk
  • < cervical vertebral a
  • intermediate territory (t3-8)
  • < posterior intercostal arteries
  • < bronchial aa (sometimes)
  • inferior territory (t9>filum terminale)
  • < artery of the lumbar enlargement = arteria radicularis magna (of Adamkiewicz) = major anterior radiculomedullary a (betw t9-l1, L in 80%; passes superior to have small ascending and large descending branches to anterior spinal a)
  • < 1st lumbar arteries
  • < (ascending) cauda equina aa <iliolumbar, median and lateral sacral aa
  • anastomotic loop around conus medullaris (ant and posterior spinal aa, cauda equina aa)

internal branches to the cord

  • sulcal branches < anterior spinal a (>ant cord)
  • sulcocommisural aa = central sulcus aa (ant spinal > anterior median fissure supply alternate sides of cord; several per spinal seg)
  • arterial vasa corona = lateral pial network (plexus in pia between posterolateral and anterior spinal aa)
  • posterior pial network (>post cord)
  • radial perforating aa < pial network (>periphery cord)
  • glomus-like structures where dorsal nerve roots penetrate dura (<post radicular and radiculomedullary aa shunt blood> perimedullary venous plexus)

variants

  • anterior spinal aa < from one vertebral a
  • anterior spinal aa < anastamotic comm between vertebral aa
  • posterior spinal aa < PICA or vertebral aa
  • anterior spinal a segmentally duplicated or absent
  • 2nd major a of L enlargment (when 1st major a <t8 or >l2)
  • artery of Adamkiewicz from branchial trunk

Venous Drainage

  • posterior spinal vein
  • anterior spinal vein (1 L, 2C/T)
  • perimedullary/coronal venous plexus
  • anterior and posterior segmental medullary/radicular vv > intervertebral vv
  • epidural plexus> intervertebral v > paraspinal veins
  • communication with medulla oblongata vv, vertebral vv, azygos vv, lumbar vv