Clinical Neuroanatomy

Question 1

Describe the progression of CSF through the CNS.

Answer 1

Formed in the lateral ventricles, then it flows into the third ventricle, through the cerebral aqueduct and into the fourth ventricle. From there it enters the spinal meninges and then up and then the cortex

Question 2

Describe the development of the brain in a fetus.

Answer 2

Brain development starts with neural tube formation, and splits from then

• prosencephalon
  
  • > telencephalon (cerebral hemispheres and deep structures)
  • > diencephalon (thalamus, hypothalamus and subthalamus)
• mesencephalon
  
  • > becomes the midbrain
• rhombencephalon
  
  • > metencephalon (becomes the pons and cerebellum)
  • > myelencephalon (medulla)

Question 3

Roughly describe the function of each lobe of the brain.

Answer 3

Forebrain
- decision making and thinking
- motor function
Parietal
- sensation and processing sensation
Occipital
- processing shape, colour and movement 
- visual memory
Temporal 
- memory and hearing

Question 4

Describe the process of sight from light entering the eye, until the impulse reaches the brain.

Answer 4

1) The contralateral visual field projects onto the temporal/lateral portion of the retina. The ipsilateral field projects onto the nasal/medial portion of the retina
2) The optic nerve carries all the information from the ipsilateral eye
3) Nasal fibres cross in the optic chiasm, while the temporal fibres remain ipsilateral
4) The optic tract contains fibres from the contralateral visual field
5) The optic radiations are the projections from the lateral geniculate body to the primary visual cortex

Question 5

Describe the vision loss if there is damage to the optic nerve of one eye.

Answer 5

Monocular vision loss

• loss of a complete visual field of that eye
• the other eye will still perceive the entire visual field

Question 6

Describe the vision loss if there is damage to the optic chiasm.

Answer 6

Bitemporal hemianopia

• loss of the nasal retinal fibres from both eyes, which carry information about the temporal retinal fields
• temporal visual field loss in both eyes

Question 7

Describe the vision loss if there is damage to the optic tract on one side.

Answer 7

Contralateral homonymous hemianopia

• loss of nasal fibres from the contralateral eye and the temporal fibres from the ipsilateral eye
• these fibres carry information from the contralateral (to side of the lesion) visual field, so there will be contralateral visual field loss in both eyes

Question 8

Describe the vision loss if there is damage to the Meyer loop (part of the optic radiation that contains fibres from the inferior retina) on one side.

Answer 8

Contralateral superior quadrantanopia

- loss of fibres from the upper portion of the contralateral visual field in both eyes

Question 9

Describe the vision loss is there is a partial lesion of the optic radiations, before they are joined by fibres from the Meyer’s loop, one one side.

Answer 9

Contralateral inferior quadrantanopia

- affects fibres from the lower portion of the contralateral visual fields in both eyes

Question 10

Describe the vision loss if there is damage to the primary visual cortex on one side?

Answer 10

Contralateral homonymous hemianopia

• affects the processing of the image provided by the optic radiations on that side
• loss of the contralateral visual field from both eyes

Question 11

What is the arcuate fasciculus?

Answer 11

A bundle of axons that forms part of the longitudinal fasciculus
It connects Broca’s area in the inferior frontal gyrus and Wernicke’s area in the posterior superior temporal gyrus

Question 12

What is the function of Broca’s area of the brain?

Answer 12

Speech production

- deficit in this area is called expressive aphasia (language which is disjointed, but makes sense)

Question 13

What is the function of Wernicke’s area of the brain?

Answer 13

Comprehension of written and spoken language

- damage to this causes fluent aphasia (language which flows, but doesn’t make sense)

Question 14

What are the three main areas of the brainstem?

Answer 14

Midbrain - closest to the brain
Pons - between the midbrain and the medulla oblongata
Medulla oblongata

Question 15

What is found in the extra-dural space of the spine?

Answer 15

Filled with fat and a venous plexus

Question 16

What do the anterior and posterior roots of a spinal nerve do?

Answer 16

Anterior - motor information

Posterior - sensory information and cell bodies

Question 17

What are the denticulate ligaments?

Answer 17

Extensions of the pia that anchor the spinal cord to the dura.
The later denticulate liagments separate the postreior and anterior roots from each other

Question 18

List the tracts you would expect to find running through the spinal cord.

Answer 18

Fasciculus gracillus - sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
Fasciculus cuneatus - sensory (fine touch, vibration, proprioception) from ipsilateral upper limb
Spinocerebellar tract - proprioception from limbs
Lateral corticospinal tract - motor to ipsilateral anterior horn
Spinothalamic tract - pain and temperature from contralateral side of the body
Anterior corticospinal tract - motor function to the ipsi- and contralateral anterior horn

Question 19

Where do the corticospinal, dorsal column and spinothalamic tracts cross in the CNS?

Answer 19

Corticospinal
- lateral = medulla
- anterior = at the level of the spinal nerve
Dorsal column - brainstem
Spinothalamic - at the level of entry into the spinal cord

Question 20

Describe the pattern of sensory loss in a generalised peripheral neuropathy.

Answer 20

The most distal parts of the limbs

Question 21

Describe the pattern of sensory loss in a lesion of a sensory root.

Answer 21

Lack of sensation in the affected dermatome

Question 22

Describe the pattern of sensory loss in in a single dorsal column lesion.

Answer 22

Lack of sensation at and below the level of the lesion, on one side of the body

Question 23

Describe the pattern of sensory loss in a transverse thoracic spinal cord lesion.

Answer 23

Lack of sensation below the level of the lesion of the spinal cord

Question 24

Describe the pattern of sensory loss in a unilateral cord lesion (Brown-Sequard).

Answer 24

Loss of light touch and proprioception below the lesion on one side of the body
Loss of pain and temperature sensation below the lesion on the other side of the body

Question 25

Describe the pattern of sensory loss in a central cord lesion.

Answer 25

A pattern of sensory loss spreading down the arms and across the chest/over the ribs
- doesn include the neck or anything below the ribs

Question 26

Describe the pattern of sensory loss in a mid-brain stem lesion.

Answer 26

Loss of sensation on one side of the body, and the other side of the face.

Question 27

Describe the pattern of sensory loss in a hemisphere lesion.

Answer 27

Loss of sensation of one entire side of the persons body and face

Question 28

Briefly describe the spinal reflexes.

Answer 28

Ia fibre from the muscle spindle senses stretching of the muscle
Ia fibre synapses directly with an alpha-motor neuron in the anterior horn
- some Ia fibres also synapse with an inhibitory interneuron
- the inhibitory interneuron inhibits the alpha-motor neuron of the antagonist muscle
The alpha-motor neurons to the extensor muscle are excited, and the involuntary reflex occurs to counteract the strech
- alpha-motor neuron of the antagonist muscle is inhibited to allow stretching of this muscle when the other contracts