SCI-Fit Spinal Cord Injuries Overview

What causes spinal cord injury? How is it defined

spinal cord bruised, torn, crushed or stretched; trauma to the vertebral column

defined by vertebral level, neurological level and severity

Name the vertebrae

cervical: C1-C7

thoracic: T1-T12

lumbar: L1-L5

sacrum: S1-S5

coccyx: Co1-Co5

Where does the spinal cord originate and end?

C1→L1

L1-S5 is termed as what?

Spinal roots (Conus)

S5 and below is referred to as…

cuada equine

what is the foramina?

foramina is an opening in the vertebral column; this is where spinal roots leave from

what role do posterior roots play vs anterior roots?

Posterior roots receive sensations while anterior roots send motor signals to muscles

How many cervical spinal roots are there?

8, not 7 because they originate above C1

where do upper motor neurons originate?

motor region of cerebral cortex/ brainstem

what do upper motor neurons do?

carry motor information down the final common pathway

what is the final common pathway?

consists of motor neurons by which nerve impulses from cerebral cortex pass by muscle or gland in the periphery; not directly responsible for stimulating target muscle

Upper motor neuron tract does what

connects brain to the appropriate level in the spinal cord, nerve signal then continues to the muscles by lower motor neuron tract

an UMN injury presents as:

• muscle disuse atrophy

• increased tone and spasticity

• increased reflexes

• extensor plantar response (Babinski Sign)

spinal motor neurons remain intact and muscles continue to be stimulated irregularly by spinal reflex activity

how does acute UMN present:

flaccid paralysis, decreased tone, and decreased reflexes

• hours/weeks after —> increased tone and hyperreflexia

where is disuse atrophy typically more pronounced?

weight bearing muscles, esp those that cross single joints, large portion type I muscle fibers

• mainly muscles maintaining posture and bearing weight

most severe disuse atrophy occurs in unloaded muscles immobilized at a shortened length (ex: hamstrings)

Lower motor neurons

connect brainstem and spinal cord (UMNs) to muscle fibers (bring nerve impulses from UMNs out to muscles)

Describe how the innervation for LMN manifest

each muscle fiber is innervated by single LMN, but each LMN may innervate more than one muscle fiber

how does a LMN injury usually manifest

• pronounced denervation atrophy

• reduced tone

• fasciculations (muscles twitches)

• reduced reflexes

Describe denervation atrophy with LMN injury

muscles that lose their innervation go through drastic and rapid wasting (usually only a few muscles have complete denervation)

• partial denervation usually occurs due to irreversible motor neuron damage

With what injury is denervation common?

• T-10 and below; injures LMN in cauda equina (denervation of major leg muscle groups)

• C-level; injures LMNs at level of injury

  • results in denervation at that level

    • ex: C6 injury —> bicep denervation

What is the reversal of atrophy dependent on?

• number of how many LMNs survive + effectiveness of sprouting

what is sprouting?

sprouting increases number of muscle fibers that LMNs supply