Spinal cord function and dysfunction Flashcards
How many spinal cord segments are there?
31
Spinal nerve pairs (31)
- Cervical-> 8 pairs
- Thoracic-> 12 pairs
- Lumbar-> 5 pairs
- Sacral-> 5 pairs
- Coccygeal-> 1 pair
Enlargements of the spinal cord for innervation of the limbs
- Cervical enlargement (C3-T1)-> upper limb innervation
- Lumbar enlargement (L1-S3)-> lower limb innervation
Enlargements contain more neurons in that region-> responsible for limb innervation
Epidural anaesthesia
- Anaesthetic delivered into epidural space (access to space within vertebral column)
- dura mater not pierced
- performed below L2 (epidural space no longer filled with spinal cord which could be damaged by needle=low risk of spinal cord injury)
- used if not safe to put under anaesthetic= allows sedation(labour, hip replacements in elderly)
Dermatomes and myotomes
Dermatome=area of skin innervated by one single spinal nerve or spinal segment
Myotome=muscle innervated by one single spinal nerve or spinal segment
Major tracts of the spinal cord
- Fasciculus (posteromedial location)->divided into 2 tracts (fasciculus gracilis from ipsilateral lower limb and fasciculus cuneatus from ipsilateral upper limb) at the posterior column of the spinal cord carrying fine touch, vibration and proprioception information
- Spinocerebellar (posterolateral location)->proprioception from limbs to cerebellum
- Lateral corticospinal (lateral location)->motor to ipsilateral anterior horn
- Spinothalamic (anterolateral location)->pain and temperature from contralateral side of the body
- Anterior corticospinal tract (anterior location)->motor to ipsilateral and contralateral anterior horn
Factors affecting spinal lesion severity
- Loss of neural tissue
- Vertical level
- Transverse plane
Loss of neural tissue
- Small if due to trauma
- more extensive in degenerative disease/metastases
Vertical level
-Higher the spinal cord lesion, the greater the disability (closer to head->more of body is affected)
Transverse plane
-most lesions are not complete
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Brown-Sequard syndrome
-Spinal cord lesion results in weakness/paralysis on one side of body and sensation loss on opposite side
Main tracts affected by spinal injuries
- Lateral corticospinal (major movement loss->paralysis)
- Dorsal columns (loss of touch sensation)
- Spinothalamic (loss of ability to feel pain/temp)
Stages of lateral corticospinal tract injury
Stage 1: SPINAL SHOCK
-lots of inflammation with complete loss of reflex activity below lesion (flaccid paralysis)
-lasts for days/weeks
Stage 2: RETURN OF REFLEXES
-reflex pathway between sensory neuron and motor neuron is more excitable
-reflexes return more intense and more rapid
-hyperrflexia and/or spasticity (rigid paralysis)
Nerve emergence
- Pattern of nerve emergence changes between cervical and thoracic nerves
- C1-C7=nerves emerge above vertebrae
- C8=nerve emerges below vertebrae
- Onwards=nerves emerge below corresponding vertebrae
Spinal levels vs vertebral levels
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