somatosensory pathways

Question 0

the posterior column medial lemniscal pathway decussates where?

Answer 0

lower medulla

Question 1

lateral corticospinal tract decussates where?

Answer 1

the medullary pyramids

Question 2

the spinothalamic tract decussates where?

Answer 2

anterior commisure of the spinal cord

Question 3

what are all the types of sensory fibres?

Answer 3

A alpha, A beta, A o and C fibres

prioprioception, touch, pain and temperature

muscle spindles and golgi tendon organ, receptors and free nerve endings

fibre diameter decreases, and so does conduction velocity

C fibres are unmyelinated, all the remainder are myelinated

Question 4

relay nuclei of the thalamus

Answer 4

send inputs to the cortex

for example the VPL, VPM relay information from the spinal cord and cranial nerves to the somatosensory cortex

Question 5

parasthesia

Answer 5

sensory loss or abnormal sensation

Question 6

transverse cord lesions are characterised by

Answer 6

loss of pain and temperature sensation, motor function and proprioception below the level of transection

causes - trauma, MS, tumours, and trasverse myelitis

Question 7

Brown Sequard lesions are….

Answer 7

hemicord (half of the cord has been severed) lesions that have:

• contralateral spinothalamic loss (pain and temperature)
• ipsilateral motor weakness (corticospinal) and loss of proprioception (PML)

to the lesion

common causes

• penetrating injuries
• lateral tumours
• multiple sclerosis

Question 8

central cord syndromes have

Answer 8

bilateral suspended sensory loss to pain and temperature with a classic cape distribution in a small lesion

larger lesions may produce complete sensory and motor loss with sacral sparing

causes - trauma or contusion of spinal cord, syringomyelia (cyst within spinal cord), intrinsic spinal cord tumours

Question 9

posterior cord syndrome

Answer 9

are characterised by a complete loss of proprioception and vibration

Question 10

anterior cord syndrome

Answer 10

have a complete loss of motor and pain and temperature sensation

Question 11

what is spinal shock?

Answer 11

this occurs soon after a spinal cord injury and is characterised by

1. hypo or areflexia (24 hours)
2. gradual reflex return (3 days) - neurotransmitter receptor upregulation
3. hyperreflexia (1 month) - new synapse growth by axons
4. hyperreflexia (1 year) - new synapse growth by cell bodies

Question 12

neurogenic shock is…

Answer 12

when a spinal cord injury has been sustained above or at the level of T6

it is a life threatening condition

sympathetic disruption with intact parasympathetic activity leading to profound hypotension and bradycardia

the end of neurogenic shock is confirmed when the bulbocarvernous reflex is elicited