HNN PBL2 Flashcards
What is spinal shock?
the loss of all neurological activity below the level of injury
What does the loss of neurological activity from spinal shock include?
motor, sensory, reflex and autonomic function
What are the clinical features of spinal shock?
- Loss of pain (nociception)
- Loss of proprioception
- Sympathetic dysfunction (bowel & bladder)
- Loss of thermoregulation
What are the 4 phases of spinal shock?
- Areflexia
- Initial reflex return
- hyperreflexia
- hyperreflexia- spacicity
What is the usual timescale for Phase 1 of spinal shock?
0-1d
What is the usual timescale for Phase 2 of spinal shock?
1-3d
What is the usual timescale for Phase 3 of spinal shock?
1-4w
What is the usual timescale for Phase 4 of spinal shock?
1-12m
What is the underlying physiology of Phase 1 of spinal shock?
Loss of descending facilitation - Neurones involved in various reflex arcs lose the basal level of excitatory stimulation they normally receive from the brain
What is the underlying physiology of Phase 2 of spinal shock?
Denervation super sensitivity - reflexes return due to the hypersensitivity of reflex muscles following denervation → more receptors for neurotransmitters are expressed and muscles therefore are easier to stimulate
What is the underlying physiology of Phase 3 of spinal shock?
Axon-supported synapse growth - Interneurones and lower motor neurons below the transection begin sprouting, attempting to reestablish synapses
first synapses to form are from shorter axons (usually from interneurones)
What is the underlying physiology of Phase 4 of spinal shock?
soma-supported synapse growth - Interneurones and lower motor neurons below the transection begin sprouting, attempting to reestablish synapses
takes longer since synapse formation is soma-mediated (takes longer for axonal transport to push growth factors and proteins from soma to the end of the axon)
Why do reflexes return a bit?
due to the hypersensitivity of reflex muscles following denervation → more receptors for neurotransmitters are expressed and muscles therefore are easier to stimulate
How can spinal shock be tested for?
Checking the bulbocavernosus reflex
What is the first reflex to return after spinal shock subsides?
Babinski (or plantar) reflex
What can spinal cord injury result from?
Trauma or compression
In somatic motor pathways where is the upper motor neurone?
Cell body lies in the primary motor cortex
In somatic motor pathways where is the lower motor neurone?
cell body lies in the nucleus of brain stem/ spinal cord
how do the upper and lower motor neurones interact?
The upper motor neurone synapses with the lower motor neurone, which in turn innervates a single motor unit in a skeletal muscle. Activity in the upper motor neurone may facilitate or inhibit the lower motor neurone.
What spinal nerves innervate the diaphragm?
C3,4 and 5
What nerves innervate the intercostal muscles?
C6 and 7
what does it mean if there is a lesion below C4 but above C6/7?
Breathing will occur but without the assistance of the respiratory/ accessory muscles
Do lesions below C6/7 affect breathing?
No
What does a lesion at C1-4 cause?
Quadriplegia (paralysis of all 4 limbs)
What does a lesion at C5 cause?
Control of the shoulder and biceps but no wrist/hand control
What does a lesion at C6 cause?
Wrist control but no hand control
What does a lesion at C7/T1 cause?
Most upper limb control, however fine dexterous control of hands/fingers affected
What does a lesion at T1-8 cause?
Paraplegia (both lower limbs), poor control of trunk/abdominal muscles.
What does a lesion in the Lumbar/sacral region cause?
Decreased control of hip flexors and legs
At what point of the spinal cord will a lesion cause issues with bladder control/
A spinal cord injury at almost every part of the cord will result in the loss of bladder control
Where is the micturition centre?
S2-4
If there is a lesion at S4/5 will there be bladder control?
There will be some control left
What type of motor neurone lesion causes muscle wasting?
Lower motor lesion
What type of motor neurone lesion causes vasiculations?
Lower motor lesion
What type of motor neurone lesion causes flaccid muscle tone?
Lower motor lesion
What type of motor neurone lesion causes spastic muscle tone?
Upper motor lesion
What type of motor neurone lesion causes reduced or absent tendon jerk reflexes?
Lower motor lesions
What type of motor neurone lesion causes exaggerated tendon jerk reflexes?
Upper motor lesion
