Clinical neuroanatomy

Question 1

Explain the visual system

Answer 1

• The contralateral visual field projects onto the temporal or lateral portion of the retina, the ipsilateral visual field projects onto the nasal or medial portion of the retina
• The optic nerve carriers all information from the ipsilateral eye
• Nasal retinal fibres cross in the optic chiasm
• The optic tract contains fibres from the contralateral visual field
• Optic radiations are the projections from the lateral geniculate body to the primary visual cortex

Question 2

What leads to monocular vision loss?

Answer 2

A lesion to the optic nerve of one eye

Question 3

what leads to a bitemporal hemianopia?

Answer 3

•A lesion to the optic chiasm leads to the loss of the nasal fibres from each side

Question 4

What leads to a contralateral homonymous hemianopia?

Answer 4

• A lesion to the optic tract

* A lesion of the entire primary visual cortex

Question 5

What leads to a contralateral superior quadrantanopia?

Answer 5

•A lesion to the Meyer loop

Question 6

What leads to a contralateral inferior quadrantanopia?

Answer 6

A lesion to the optic radiations

Question 7

Where is Broca’s area

Answer 7

Frontal lobe

Question 8

What does a lesion to Broca’s area result in?

Answer 8

Expressive dysphasia - speech may be non fluent, can’t say what they want to but they understand what is being said

Question 9

What does a lesion to Wernickes area result in?

Answer 9

• Receptive aphasia

* Cannot understand what is being said

Question 10

Describe the structure of the brainstem

Answer 10

• Midbrain most superior
• Pons is kind of a bulge anteriorly
• Medulla is most inferior and in posterior to the pons, anterior to the cerebellum

Question 11

When does the spinal cord end?

Answer 11

L1-2

Question 12

What is the order of the meninges?

Answer 12

Pia around spinal cord then arachnoid then dura

Question 13

What is the denticulate ligament?

Answer 13

• Extensions of the Pia mater the anchor the spinal cord to the dura
• The lateral denticulate ligaments separate the anterior and posterior roots

Question 14

What does the anterior root carry?

Answer 14

Motor information

Question 15

How does the anterior root exit the spinal cord?

Answer 15

Through the anterolateral sulcus

Question 16

What does the posterior root carry?

Answer 16

Sensory information

Question 17

How does the posterior root enter the spinal cord

Answer 17

Postero-lateral sulcus

Question 18

Where does the dura extend to?

Answer 18

S2

Question 19

What is the epidural space?

Answer 19

• True space between the dura and the vertebral periosteum

* Filled with fat and venous plexus

Question 20

Fasciculus gracilis

Answer 20

• Sensory - fine touch, vibration, proprioception

* Ipsilateral lower limb

Question 21

Fasciculus cuneatus

Answer 21

• Sensory fine touch, vibration, proprioception

* ipsilateral upper limb

Question 22

Spinocerebellar tract

Answer 22

Proprioception from the limbs to the cerebellum

Question 23

Lateral corticospinal tract

Answer 23

•Motor to ipsilateral anterior horn

Question 24

Spinothalamic tract

Answer 24

•Pain and temperature from the contralateral side of the body

Question 25

Anterior corticospinal tract

Answer 25

• Motor to ipsilateral and contralateral anterior horn

Question 26

At what level of the spine do the fibres enter the fasciculus gracilis vs fasciculus cuneate

Answer 26

T6

Question 27

Where do the fibres that have travelled in the fasciculus gracilis/cuneate terminate?

Answer 27

Nucleus gracilis and nucleus cuneatus in brainstem

Question 28

Where do the fibres carrying sensory information (fine touch, birbaiton and proprioception) cross?

Answer 28

After they have terminated in the nucleus cuneatus and gracilis, secondary fibres cross the midline as internal arcuate fibres and form the medial lemniscus

Question 29

Where does the medial lemniscus terminate?

Answer 29

In the VPL of the thalamus

Question 30

What happens after the medial lemniscus terminates in the VPL?

Answer 30

Fibres project through the internal capsule and corona radiata to terminate in the primary somatosensory cortex

Question 31

Explain the route of the sensory tract carrying light touch, vibration and proprioception

Answer 31

*  Axons enter the spinal cord from the spinal ganglion and pass directly to the ipsilateral posterior column. (Caudal fibres below T6 = gracilis, rostral = cuneatus) *  Ascend then terminate in culceus gracilis and nucleus cuneatus *  From these nuclei, axons of secondary neurones cross the midline as internal arcuate fibres and form medial lemniscus *  in the rostral medulla, the fibres travel as the medial lemniscus adjacent to the midline *  In the caudal pons, the medial lemniscus flattens horizontally *  As the medial lemniscus continues to ascend through the rostral pons and midbrain it moves horizontally and laterally

Question 32

Explain the route of the sensory tract carrying pain and temperature

Answer 32

*  Axons enter the spinal cord from the spinal ganglion, travel up or down 1-2 segments in the lissauer tract then synapse in the posterior horn *  Axons of secondary neurones cross the midline in the anterior commissure and ascend as the anterolateral tract in the spinal cord *  Anterolateral tract ascends through the caudal medulla * In the rostral medulla, the anterolateral tract lies between the inferior olivary nucleus and the nucleus of the spinal tract of the trigeminal nerve *  in the pons and midbrain, the anterolateral tract lies lateral to the medial lemniscus *  The anterolateral tract terminates in the VPL of the thalamus *  From the thalamus the fibres project through the internal capsule and corona radiate to terminate in the primary somatosensory cortex (post central gyrus)

Question 33

Explain the route of the motor corticospinal tract

Answer 33

*  Originates from the primary motor cortex *  Descending fibres form the corona radiata and converge to pass through the posterior limb of the internal capsule *  Corticospinal fibres descend through the middle three fifths of the crus cerebra in the anterior part of the midbrain *  In the pons, the fibres are broken up into many bundles *  The corticospinal tract descends as the pyramids in the anterior part of the medulla *  At the junction of the medulla and the spinal cord, most of the fibres cross the midline in the decussation fo the pyramids *  Crossed fibres = lateral corticospinal tract, uncrossed = anterior corticospinal tract

Question 34

What fibres cross in the anterior white commissure?

Answer 34

* Pain and temperature fibres | *  Anterior corticospinal tract fibres

Question 35

Explain the spinal reflex of the hamstring

Answer 35

*  Ia fibre from the muscle spindle senses stretching of the muscle *  Ia fibre synapses directly with an alpha motor neurone in the anterior horn and an inhibitory interneurone *  The alpha motor neurone to the extensor muscles are excited and the inhibitory interneurone inhibits the alpha motor neurone of the antagonist muscle