spinal cord function after injury
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Spinal Cord Function After Injury
• spinal cord structure in relation to vertebrae
• types of lesions• fibre tracts in spinal cord• sensory loss• motor loss• reflexes and spinal shock• neuropathic pain
Orientation of spinal cord and spinal roots with respect to
vertebrae
Posterior
Collapse of disc space
Disc prolapse
Slippage of vertebra over disc
Collapsed vertebra in patient with
severe osteoporosis
Arrows indicate S3-S4 disc prolapse
Arrow indicates L4-L5 disc prolapse
Arrow indicates compression fracture at C5
Arrow indicates fracture-dislocation at C6/C7
Head and neckDiaphragmDeltiods, BicepsWrist extendersTricepsHand
Chest muscles (T1-T7)
Abdominal muscles (T7-T12)
Leg muscles
Bowel, bladderSexual function
Paralysis of the lower half of the body is called paraplegia.
Paralysis of both arms and legs is called quadriplegia (or tetraplegia).
Dorsal root ganglion
Posterior
Anterior
Dorsal columnsCuneate funiculusGracile funiculus
Leg,Lowertrunk
Uppertrunk,arm,neck,head
Touch, vibration, pressure,ProprioceptionAα, Aβ
Ventrolateralspinothalamic
Pain, temperature, crude touchAδ, C
Sensory fiber tracts
Aα motor neuron
Motor fiber tracts Posterior
Anterior
Lateralcorticospinal
Medialcorticospinal
Anteriorhorn cells
anteriorhorn cellsfor limbs anterior
horn cellsfor trunk
dorsal and ventralhorns
motor
pain, temperature
vibration,proprioception,touch
Dorsal columns
Ventrolateralspinothalamic
LateralCorticospinal,Anteriorhorn cells
lower limbs
upper limbs
medulla
Aα, Aβ (touch, vib,propriocep)
Aδ, C (pain, temp.)
Aα motor
ExamplesThe diagrams that follow indicate the motor and
sensory loss as a consequence of one of the following lesions. Identify the lesion in each case and indicate on the spinal cord and spinal cord section the site, level and side of the lesion.
Lesions:Anterior cord syndromePosterior cord syndromeCentral cord syndromeTransverse cordHemicord (Brown-Sequard)
Central cord syndrome(small lesion) – cape distributionEg. Spinal cord contusion (bruisecausing bleeding in spinal column),spinal cord tumors
Anterior cord syndromeEg. Trauma, multiple sclerosis,anterior spinal artery infarct
cervical
T8/T9Damage to spinothalamicfibers as cross anteriorcommissure
C D ETransverse cord lesionEg. Trauma, tumors,multiple sclerosis (demyelination)
T8/T9
Hemicord lesionBrown-SequardEg. Penetrating injuries,lateral compression from tumors,multiple sclerosis
T8/T9
Posterior cordSyndromeEg. Trauma,extrinsic compression fromposterior tumors,multiple sclerosis
T8/T9
Signs and symptoms of UMN versus LMN lesions
UMN lesion LMN lesionYes Weakness YesNo (yes, disuse) Atrophy YesNo Fasciculations YesIncreased* Reflexes DecreasedIncreased* Muscle tone Decreased
*except decreased during spinal shock
Spinal Shock
• Initially hyporeflexia (spinal shock) (24hrs up to ~2months)
Loss of descending excitation (bleeding, oedema, inflammation, cell hypoxia, cell death, demyelination)
• Followed by return of reflexesDenervation hypersensitivity (increased
neurotransmitter release, increased responsiveness to neurotransmitter)
• Followed by hyperreflexiaAxonal and soma regrowth (neural
plasticity) with denervation hypersensitivty
Neuropathic pain
AAδδ, C, C
Descending inhibition
Inhibitoryinterneuron
++Serotonin
NA
--Enkephalin
Opioids
SCI SCI →→ Wind-up Wind-upDenervation hypersensitivity,
increased neurotansmitter release, increased responsiveness to neurotransmitter,
neural plasticity
++Glutamate
Treat early to prevent wind-up (hyperalgesia)
Drugs: opioids, antiepileptics (block Na+ channels),Tricyclic antidepressants (serotonin and NA reuptake inhibitors)
Surgery: nerve root ablation
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