Neurology 2 - Spinal cord function & dysfunction Flashcards
Describe the structure of the spinal cord meninges
- Epidural space containing fat and venous plexus between dura and bone - not present in the skull. Allows needle insertion
- Pia mater has lateral projections called dentate ligaments which extend to the dura and stabilize the spinal cord
- Arachnoid mater is ballooned against the dura mater. Still a subarachnoid space.
- Dura mater is the outermost layer
List the three factors that affect the degree of damage following a spinal cord lesion
- Loss of neural tissue (usually small if due to trauma)
- Vertical level
- Transverse plane
How does vertical level affect damage caused by a spinal cord lesion?
- The higher the vertical level, the more severe the disability
How does the transverse plane affect damage caused by a spinal cord lesion?
- Complete/ partial section
- Damage to white matter is more important as ascending/descending tracts are affected
- If posterior sensory affects
- If anterior motor effects
What is the result of damage to the ascending and descending spinal tracts?
- Motor and/or sensory loss
- Paralysis
- Anaesthesia
- Hyperreflexia/ spacsticity may develop due to raised sensitivity of spinal motoneurones
- CNS may not regenerate, but there may be some improvement if tracts are only compressed
List the pairs of spinal nerves
31 pairs
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
What is the result of injury to the lateral corticospinal tract?
- Stage 1: loss of reflex activity below the lesion, lasting for days or weeks (flaccid paralysis)
- Stage 2: return of reflexes, hyperreflexia (rigid paralysis)
What are the enlargements in the spinal cord for innervation of the limbs?
- Cervical (C3-T1) - upper limb
- Lumbar (L1-S3) - lower limb
Where does the pattern of emergence of the spinal nerves change?
- Between cervical nerves and thoracic nerves
- This is because there are 8 cervical nerves and 7 cervical vertebrae
- C1-C7 come above their vertebrae
- Every other nerve below
What is the difference between spinal levels and vertebral levels?
- Vertebral level is the level of the vertebra
- Spinal level is the level of emergence of the nerve from the spinal cord (Coccygeal nerve emerges at level of L1)
Where are the transverse vertebral foramina present?
Cervical vertebra
Where is the spinal cord located?
In the subarachnoid space, therefore needles can safely be inserted into the epidural space
Define dermatome
An area of skin innervated by a single spinal nerve or spinal segment
Define myotome
Muscles innervated by a single spinal nerve or spinal segment
Define rostral and caudal
- Rostral towards the head
- Caudal towards the feet
Describe the structure of the spinal cord
- Gray matter has dorsal horns and ventral horns
- Ventral horn has motor rootlets which form the anterior root
- Anterior and posterior roots join to form the spinal nerve
- The spinal nerve splits to the posterior ramus (supplies back) and anterior ramus (much thicker)
What is the difference between a root and ramus?
- Roots contain one of motor or sensory nerves
- Ramus contains mixed motor and sensory nerves
What are the fasciculus gracilis and cuneatus?
- Contain sensory neurons from lower limb (gracilus) and upper limb (cuneatus)
- In the posterior column, gracilis is the most medial
What is the function of the spinocerebellar tract?
- Proprioception from the limbs to cerebellum
- In the lateral column
What is the function of the lateral corticospinal tract?
- Motor to ipsilateral anterior horn
- Swaps sides in the brainstem
What is the function of the spinothalamic tract?
Sensory for pain and temperature to the contralateral side of the body
Describe the main sensory pathways
- Primary neurone from stimulus to synapse in the spine
- Secondary crosses over to the other side of the body in the spinal cord (anteriolateral - pain and temperature) or at the medulla (posterior column medial lemniscus - discriminative touch/vibration). Synapses in the thalamus
- Tertiary begins in the thalamus and ends in the cortex
What are the dorsal column pathways?
- Pathways that cross over in the medulla
- Discriminative touch, vibration and proprioception
- Passes through fascilulus fracilis and fasciculus cuneatus
What is the pathway of the spinothalamic tract?
- Crosses over at the vertebra where it comes in at the spinothalamic tract
- Pain and temperature
What are the main tracts affected by spinal injury
- Lateral corticospinal
- Spinothalamic
- Dorsal columns
Describe the main voluntary movement motor pathway
- 85% changes side in the medulla (lateral corticospinal tract)
- 15% anterior corticospinal tract
