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