Spinal Nerves and Tracts - Benifla

Question 1

In what order on the inside of the spinal cord do the axons for the different spinal areas run?

Answer 1

Motor:

Cervical - Thoracic - Lumbar - Sacral
Injury from the outside of the spinal cord hits the cervical branch first on ipsilateral side.

Sensory:

Sacral - Lumbar - Thoracic - Cervical
Injury on inside of spinal cord would cause injury to cervical branch first on contralateral side.

Question 2

Where on the ventral horn are extensory versus flexor muscle nerves?

Distal versus Proximal muscles?

Answer 2

Flexor muscles are in the posterior part of the ventral horn.

Extensory muscles form the anterior part.

Distal muscles from the lateral aspect of ventral horn.

Proximal muscles from medial aspect of ventral horn.

Grey matter thus has 4 quadrants:

I: FP, II: EP, III: ED, IV: FD

Question 3

Where are the fibers for pain and temperature in the lateral spinothalamic tract?

Tactile?

Answer 3

Pain fibers in anterior part of tract

Temperature in the posterior part of tract

Tactile in anterior tract, originating in Tactile receptors (Meissner’s corpsucles), enter from dorsal root.

Question 4

What are the components of gray matter?

Answer 4

1. Afferent fibers (posterior roots from reflex arcs)
2. Posterior horns
   - Lamina I (thermal stimuli to contralateral spinothalamic tract)
   - Posterior marginal Nucleus (Pain fibers, to thalamus)
   - Lamina II and III: Gelatinous substance for interconnection within spinal cord.
   - Lamine IV: tactile to lateral cervical nucleis, gracilis and cuneatus nuclei, spino reticular lateral basiallry, etc. Receive proprioceptive.
3. Anterior horns:
   -Lamina IX-m (ventral horn, motor neurons)
   -Lamina IX
   Laminal VII, VIII

Question 5

Blood supply to spinal cord

Answer 5

Anterior spinal artery:
Supplies anterior 2/3 of spinal cord.
Originates from vertebral artery.
Extends entire length of spinal cord
Supplies pyramids, hypoglossal nerve and medial lemniscus.

Posterior spinal arteries (2):
From vertebral arteries.
Supply posterior 1/3 of the spinal cord.
Injury causes loss of motor and sensory below injury level but spares prprioception.
Each receives 10-23 posterior radicular arteries off the aorta.

Segmental arteries:
Give rise to meduallary arteries that anastermose with the ASA to provide the anterior 2/3 of spinal cord.
Direct branch from aorta (Artery of Adamkiewicz)
Usually from left side of T8-12.
Injury causes paraplegia/paraparesis

Question 6

What are the results of injuries to the spinal cord?

Answer 6

Transection causes spinal shock:
Flaccid paralysis and loss of spinal reflexes and cutaneous and proprioception, etc. for 4-6 weeks. After: spastic paresis-hyperreactive tendon reflexes, upper motor neuron disease.
Loss of function below the level of injury.
Below T2 will spare arms. Below mid-thorax will drop blood pressure and cause bradycardia (neurogenic shock).
T1 or above will cause bilateral Horner’s syndrome.

Loss of reflex:
Flaccid paresis.
Lower motor neuron disease
From cut of peripheral nerve

Brown- Sequard Syndrome
A Transverse cut through half of the spinal cord from medial to lateral or lateral to medial (not anterior/ posterior)
Ipsilateral paralysis or paresthesia (upper motor neuron disease)
– ipsilateral vasomotor paralysis
– ipsilateral loss of the sensation of vibration and
proprioception.
– Contralateral loss of the sensation of pain and
temperature, beneath the height of the injury and 2 levels below. Ex: injury of C5: loss of sensation below contralateral C6/7 and ipsilateral of C6/7.
– The degree of loss for pain and temperature are not
indicative of the stage of the pathology.

Intromedullary tumor:
Upper level fibers first. Lower limbs may be OK but upper limbs paralyzed.

Syringomyomelia:
enlargement of central canal for a few levels. Pain and temperature first impaired on bilateral sides (because it is at the area of decussation).
Loss of sensation in upper limbs. Compression of anterior commissure an issue. Weakness of upper limbs and sparing of lower limbs. Burning of hands without noticing.

Tumor from outside: sacral loss first.