Spinal cord function and dysfunction

Question 1

Where do the sensory nerves have their cell bodies?

Answer 1

Dorsal root ganglion.

Question 2

Where do the motor nerves have their cell bodies?

Answer 2

Within the grey matter of the spinal cord.

Question 3

What are the major tracts of the spinal cord?

Answer 3

Fasciculus gracilis
Fasciculus cuneatus
Anterior white commissure
Anterior corticospinal tract 
Spinocerebellar tract
Lateral corticospinal tract
Spinothalamic tract

Question 4

What is the role of the fasciculus gracilis?

Answer 4

Sensory (fine touch, vibration, proprioception) from ipsilateral lower limb.

Question 5

What is the role of the fasciculus cuneatus?

Answer 5

Sensory (fine touch, vibration, proprioception) from ipsilateral upper limb.

Question 6

What is the role of the anterior white commissure?

Answer 6

Pain and temperature fibres cross.

Anterior corticospinal tract fibres cross.

Question 7

What is the role of the spinothalamic tract?

Answer 7

Pain and temperature from contralateral side of body.

Question 8

What is the role of the lateral corticospinal tract?

Answer 8

Motor to ipsilateral anterior horn (mostly limb musculature).

Question 9

What is the role of the spinocerebellar tract?

Answer 9

Proprioception from limbs to cerebellum.

Question 10

What is the role of the anterior corticospinal tract?

Answer 10

Motor to ipsi- and contralateral anterior horn (mostly axial musculature).

Question 11

What is the corticospinal tract and its path?

Answer 11

Begins in cortex.
Decussates in medulla- opposite side in lateral tract, same side in anterior tract.
Main descending pathway for voluntary movement.

Question 12

What is the dorsal column pathway?

Answer 12

Discriminative touch, vibration and proprioception.
First order neuron enters spinal cord, travels up on ipsilateral side and synapses with second order neuron, decussates to contralateral side, travels through medial lemniscus then synapses with third order neuron in the thalamus (ventral posterolateral nucleus).

Question 13

What is the spinothalamic tract?

Answer 13

Pain and temperature.
First order neuron in dorsal root ganglion enters spinal cord, travels up and synapses with second order neuron which decussates to contralateral side in the anterolateral system of the spinothalamic tract, then synapses with third order neuron in the thalamus (ventral posterolateral nucleus).

Question 14

What is the knee reflex pathway?

Answer 14

Patellar tendon hit with hammer.
Fibre from muscle spindle senses stretching of muscle.
Fibre synapses directly with alpha-motor neuron in anterior horn.
Fibre synapses with inhibitory interneuron.
Alpha-motor neurons to the extensor muscle are excited.
Inhibitory interneuron inhibits the alpha-motor neuron of the antagonist muscle.
Alpha-motor neuron of antagonist muscle is inhibited.
Quadriceps muscles contract and leg kicks.

Question 15

What factors affect the severity of a spinal lesion?

Answer 15

Loss of neural tissue
Vertical level
Transverse plane

Question 16

How may loss of neural tissue vary the severity of a spinal lesion?

Answer 16

Usually small if due to trauma.

Can be more extensive, e.g. metastases, degenerative disease.

Question 17

How does the vertical level of a spinal lesion affect its severity?

Answer 17

Higher the lesion, greater the disability.

Question 18

What are the most common causes of spinal cord injury?

Answer 18

Broken neck or back.

Road traffic accidents, accidents during sports or recreation, falls in older people.

Question 19

How many people become paralysed in the UK every day and year as a result of spinal cord injury?

Answer 19

2-3 people per day.

Over 700 each year, adding to the 40,000 living in the UK that are already paralysed.

Question 20

What are the stages of injury to the lateral corticospinal tract?

Answer 20

Stage 1: Spinal shock- loss of reflex activity below the lesion, lasting for days or weeks = flaccid paralysis.
Stage 2: Return of reflexes- hyperreflexia and/or spasticity = rigid paralysis.