Spinal cord

Question 1

1. What level does the spinal cord start at?
2. Where does it terminate?
3. What is the name of the band of pia that runs fromt he conus medullaris to the coccyx?
4. How many spinal nerves are there?
5. Where do they emerge?
6. What is different about the Lumbar, sacral and coccygeal nerves?

Answer 1

1. Starts superiorly to the foramen magnum
2. It terminates at the CONUS MEDULLARIS (L1/2 in adults and L4 in neonates)
3. FILUM TERMINAL
4. There are 31 pairs of spinal nerves: 8 cervical, 12 thorasic, 5 lumbar, 5 sacral, 1 coccygeal
5. The first cervical nerves emerges from between the occiput and the arch of the atlas.

C2-7 emerge above their respective vertebrae

C8 emerges between C7&T1

Below this each spinal nerve emerges below its corresponding vertebra

6. The L,S and C nerves descend from the bottom of the spinal cord as the CAUDA EQUINA. The spinal sac ends at S2

Question 2

1. Where do sensory neurones enter the spinal cord?
2. Where to Motor nerves emerge from the SC?
3. What makes up the REFLEX ARC?
4. What effect do prolapsed discs cause?

Answer 2

1. Dorsal horn where they synapse
2. Ventral horn
3. Sensory neurones synapse with interneurones and these synapse with motor neurones making a reflex arc
4. They willl impindge on spinal nerves and cause both sensory and motor symptoms

Question 3

Label the diagram

Answer 3

Red= Ascending pathways

Green= Descending pathways

1. Anterior corticospinal tract
2. Lateral corticospinal tract
3. Tectospinal tract
4. Rubrospinal tract
5. Anterior spinothalamic tract
6. Lateral spinothalamic tract
7. Anterior spinocerebellar tract
8. Posterior spinocerebellar tract
9. Dorsal columns
10. Fascicles cuneatus
11. Fascicles gracilis

Question 4

1. What is the major descending pathway?
2. What are the two major ascending pathways?
3. What information do the two ascending pathways transmit?
4. What is Brown-Séquard syndrome?

Answer 4

1. The major descending (motor) pathway is the LATERAL CORTICOSPINAL TRACT (pyramidal tract)
2. There are two major ascending (sensory) pathways the SPINOTHALAMIC TRACT and the DORSAL COLUMNS (posterior)
3. The SPINOTHALMIC TRACT is responsible for: PAIN, TEMP, HARD TOUCH

The DORSAL COLUMNS is responsible for: LIGHT TOUCH, VIBRATION, PROPIOCEPTION

4. Brown-Séquard syndrome: is where there is a hemisection of the cord.

It results in IPSILATERAL paralysis, loss of proprioception, pressure, light touch and vibration (motot and dorsal columns)

As well as CONTRALATERAL loss of pain, temp and hard touch (spinothalamic tract), due to the decasation of the STT at the spinal cord level

Question 5

Draw a diagram to describe the path of the 3 main tracts with in the spinal cord up to the brain

Answer 5

a) Marks the course of the corticospinal tract from motor cortex as it descends through the internal capsule (x). In the medulla (m) the tract decussates with the majority of its fibres descending as the lateral corticospinal tract. Infarction in the region of the internal capsule therefore results in contralateral paralysis
(b) Marks the course of the spinothalamic tract. First order neurones enter the spinal cord via the dorsal horn and synapse there. Second order neurones decussate within a few spinal levels and ascend to the ventroposterior nucleus (vp) of the thalamus where they synapse with the third order neurones which transmit to the somatosensory cortex
(c) Marks the course of the dorsal column. First order neurones again enter the spinal cord via the dorsal horn. They ascend in the ipsilateral fasciculus cuneatus and gracilis. They synapse in the medulla and the second order neurones decussate and ascend to the VP nucleus of the thalamus. Here they synapse with the third order neurones which pass to the somatosensory cortex

BOTH THE CST AND DC DECESATE AT THE MEDULLA!!!

Question 6

Describe the blood supply to the spinal cord. What can cause occlusion/infarct?

Answer 6

The Anterior spinal artery:

This artery arises from each vertebral artery at the level of the foramen magnum.

Infarction of the anterior spinal artery causes:

Paralysis

Reduced pain and temp sensation

It was be caused by the Adamkiewcz a being occluded

The Posterior spinal arteries:

These 2 arteries arise from the posterior inferior cerebellar artery at the same level.

The central area supplied only by the anterior spinal artery is predominantly a motor area.

Question 7

Describe how the spinal arteries are supplied and what a high take off is.

Answer 7

At each spinal level, radicular arteries arise from local vessels (e.g. intercostal, lumbar arteries) and feed the spinal arteries. The most important of these is the artery of Adamkiewicz which arises from lower thoracic/upper lumbar segmental arteries.

Generally the proportion of flow is greatest from the radicularis magna ‘feeder’ artery (artery of Adamkiewicz) to the thoracolumbar region.

In abnormal situations (e.g. high take-off) the iliac artery branch may supply the lower thoracolumbar region of the cord entering by way of the intervertebral foramen in the vicinity of L4-5.