Spinal Cord Anatomy of Ascending & Descending Pathways

Question 1

How many Spinal nerves are there?

Answer 1

31 Pairs

• 8 cervical
• 12 Thoracic
• 5 Lumbar
• 5 Sacral
• 1 Coccygeal

Question 2

Where are the two ‘enlargements’ of the spinal cord

Answer 2

Cervical -> Cervical & Brachial Plexi

Lumbar -> Lumbar Plexus

Question 3

What modalities are contained in which of the spinal roots?

Answer 3

Ventral Roots - Motor (Inc. Autonomics)

Dorsal Roots - Sensory

Question 4

Label Gross Sections of the spinal cord

Answer 4

Question 5

What Gross spinal cord structure is only visible at T1-L2, and what does it contain?

Answer 5

The Lateral Horn of the white Matter, which contains preganglionic sympathetic neurones

Question 6

Describe the main three sources of Arterial Supply to the Spinal Cord

Answer 6

A.Three major longitudinal arteries:

one anterior and two posterior that originate from the vertebral arteries. These run the length of the cord.

B.Segmental arteries

derived from vertebral, intercostal and lumbar arteries.

C.Radicular arteries

travel along the dorsal and ventral roots.

Question 7

Label diagram of Arterial and Venous supply to the spinal cord

Answer 7

Question 8

How is the primary somatosensory cortex (BA 3, 1, 2) organised?

Answer 8

Somatotopic organisation

The body is ‘mapped’ onto the cortex

Question 9

Name the main ascending spinal cord tracts

(5)

Answer 9

Gracile Fasiculus

Cuneate fasiculus

Dorsal Spinocerbellar tract

Ventral Spinocerebellar tract

Spinothalamic tract

Question 10

Name the main descending tracts of the spinal cord (8)

Answer 10

Lateral corticospinal tract

Ventral corticospinal tract

Rubrospinal tract

Medial longitudinal fasciculus

Medullary reticulospinal tract

Pontine reticulospinal tract

Lateral Vestibulospinal tract

Tectospinal tract

Question 11

What sensory information is carried by The Dorsal Column/Medial Lemniscus System?

Answer 11

Fine touch and conscious proprioception (particular from the upper limb). Fibres cross in medulla!

Question 12

Label the ascending and descending tracts

Answer 12

Question 13

Label the diagram of the dorsal column system

Answer 13

Question 14

What sensory information is carred by the spinothalamic tract?

Answer 14

Carries pain, temperature, deep pressure. Fibres cross segmentally!

Question 15

Describe the spinothalamic tract

Answer 15

Question 16

How is the primary motor cortex (BA 4) arranged?

Answer 16

Somatotopic mapping of the body onto the cortex

Question 17

Describe & Label the corticospinal tract

Answer 17

• Fine, precise movement, particularly of distal limb muscles (e.g. digits).
• Tract forms visible ridges referred to as the ‘pyramids’ on the anterior surface of the medulla, so also called the pyramidal tract. About 85% of fibres cross in the caudal medulla at the decussation of the pyramids.
• Crossed fibres form the

Lateral CST.

•Uncrossed fibres form the Ventral CST, which cross segmentally.

Question 18

What is the likely clinical effect of CVA to the internal capsule?

Answer 18

A CVA of the internal capsule can result in a lack of descending control of the corticospinal tract (as well as other effects – the CST is intermingled with other fibres here), which results in a spastic paralysis with hyperflexion of the upper limbs. This is sometimes referred to as decorticate posturing.

Question 19

Describe and detail the Tectospinal tract

Answer 19

• Input mostly to cervical segments.
• Thought to mediate reflex head and neck movement due to visual stimuli.

Question 20

Label the diagram of the reticulospinal tract

Answer 20

Question 21

Describe the function of the reticulospinal tract

Answer 21

• Reticular formation forms the central core of the brainstem. It has many nuclei and receives input from virtually all parts of the CNS. It has many functions, including the influencing of voluntary movement.
• Fibres originate in areas of the reticular formation in pons and medulla.
• In general: Fibres originating in pons facilitate extensor movements and inhibit flexor movements, while those originating in the medulla do the opposite.

Question 22

Describe the diagram of the Vestibulospinal tract

Answer 22

Question 23

Describe the function of the vestibulospinal tract

Answer 23

• Excitatory input to “antigravity” extensor muscles.
• Fibres originate in the vestibular nuclei of pons and medulla (these in turn receive input from vestibular apparatus and cerebellum).

The vestibulospinal tract is thought to play an important role in patients exhibiting decerebrate rigidity and paraplegia in extension.

Lesions of the brainstem at the level of the midbrain can result in a lack of descending cortical control of this tract (plus others). This leads to domination of extensor muscle tone and hyperextended spastic paralysis.

Question 24

Complete the diagram summary of spinal pathways

Answer 24

Question 25

What syndrome can present with hemisection of the spinal cord?

Answer 25

Brown-Séquard’s Syndrome

Question 26

Describe the consequences and origins of the Brown-sequard syndrome

Answer 26