Approaches to patients with CNS disorders

Question 1

Signs and symptoms of frontal lobe dementia

Answer 1

1. Disinhibited behaviour
2. Change in appetite – sweet tooth
3. Reduced sense of smell
4. Bladder dysfunction
5. Gait apraxia
6. Progressive motor (expressive) dysphasia

Question 2

A lesion in the right motor cortex will cause? (when decussation is in the medulla 90% and 10% in spinal cord)

Answer 2

Contralateral upper motor neurone weakness, since it has NOT decussated

Question 3

A lesion to the right cranial nerve nuclei in the brainstem will cause? (when decussation is in the medulla 90% and 10% in spinal cord)

Answer 3

Right sided (ipsilateral) lower motor neurone weakness to the areas supplied by those cranial nerves as it has decussated

Question 4

A lesion to the right side of the spinal cord will cause? (when decussation is in the medulla 90% and 10% in spinal cord)

Answer 4

Right sided (ipsilateral) UMN weakness below the level of the lesion

Question 5

Sensory pathway: dorsal column pathway decussates where? What does this normally control?

Answer 5

Decussates in the medulla

Normally controls fine touch, position and vibration

Question 6

Sensory pathway: spinothalamic pathway decussates where? What does this normally control?

Answer 6

1-2 segments above entry level

Normally controls crude touch, pain and temperature

Question 7

What is the clinical significance of pyramidal tracts crossing at the midline vs 1-2 segments above where they entered in the spinal cord?

Answer 7

A lesion in the brainstem = both pathways have decussated so you get CONTRALATERAL SENSORY LOSS

A lesion in the spinal cord = dissociated sensory loss. The spinothalamic pathway has decussated but the dorsal column has not. So if it occurs on the right side of the body, you get IPSILATERAL sensory loss for the dorsal column pathway (TOUCH, POSITION, VIBRATION) and CONTRALATERAL sensory loss for the spinothalamic pathway (PAIN, TEMP, CRUDE TOUCH)

Question 8

Give some different functions of the brainstem

Answer 8

1. Site of origin of cranial nerve nuclei III to XII
2. Substantia nigra - dopamine production (abnormalities lead to Parkinsonian ipsilateral conditions)
3. Red nucleus - abnormalities lead to contralateral tremor
4. Respiratory centre
5. Cardiac centre
6. Reticular activating system - system of wakefulness
7. Conduit for white matter tracts - eye movements, motor (corticopontine, corticobulbar, corticospinal), sensory (spinothalamic), co-ordination (spinocerebellar)

Question 9

Functions of the cerebellum?

Answer 9

1. Vermis = balance and equilibrium - alcohol causes degeneration of the vermis, even temporary freezes it which is why we fall when drunk
2. Paravermis = postural tone - keep us upright
3. Cerebellar hemispheres = fine co-ordination - ours is very developed which is why we are good at speaking and writing compared to other species

Question 10

Features of cerebellar dysfunction

Answer 10

VANISH’D

1. V - Vertigo
2. A - Ataxia (loss of muscle control in arms and legs = lack of balance, co-ordination etc)
3. N - Nystagmus
4. I - Intention tremor (finger to nose test)
5. S - Slowed, scanning, staccato speech
6. H - Hypotonia
7. D - Dysmetria, disdiadochokinesis (inability to do rapid, alternating hand movement)

Question 11

Do cerebellar lesions cause ipsilateral or contralateral limb signs?

Answer 11

IPSILATERAL

Question 12

Upper motor neurone facial weakness results in weakness of the muscles moving the ipsilateral or contralateral bottom half of the face?

Answer 12

CONTRALATERAL

This is because the bottom half of the face receives nerve supply from the contralateral side only

Question 13

Lower motor neurone facial nerve lesions result in weakness of the ipsilateral or contralateral upper and bottom muscles of the face?

Answer 13

IPSILATERAL
This is because the top half of the face receives nerve supply from both the ride and left sides of the cerebral hemisphere

Question 14

What are the features of a lower motor neurone facial nerve palsy?

Answer 14

1. Ipsilateral involvement of the facial nerve or its nucleus
2. Weakness of muscles of the top and bottom of the face
3. Incomplete closure of the eye
4. Abnormal taste sensation of anterior part of the tongue
5. Hyperacussis
6. Decreased lacrimation

Question 15

What are features of a LMN lesion of the hypoglossal nerve?

Answer 15

1. Wasting of the tongue
2. Fasciculations
3. Weakness of the tongue
4. Dysarthria

Question 16

Signs of a lumbar disc prolapse?

Answer 16

1. Positive straight leg raise sign
2. Ipsilateral weakness of L4/L5 supplied muscles
3. Ipsilateral loss of knee reflex
4. Ipsilateral L4/5 dermatomal loss