Brainstem and forebrain disease (1 and 2) Flashcards Preview

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Flashcards in Brainstem and forebrain disease (1 and 2) Deck (56):
1

What is the forebrain?

area of brain rostral to tentorium cerebelli:
- telencephalon or cerebrum
- thalamus (part of diencephalon)

2

Name 3 lobes of cerebrum

- olfactory bulbs/tracts
- frontal lobes
- parietal lobes
- temporal lobes
- occipital lobes

3

Function - olfactory bulb

* Perception of smell
- limbic system

4

Function - temporal lobe of cerebrum

* auditory area
- vestibular conscious perception
- pyriform lobe: olfactory and limbic systems

5

Function - frontal lobes

- mainly motor area - corticospinal and corticonuclear tracts (gives motor info to contralateral limbs)

6

Function - parietal lobes of cerebrum

- mainly sensory-motor areas (sensory info of contralateral limbs)

7

Function - occipital lobes of cerebrum

visual conscious perception

8

Outline the visual pathway

retina --> optic nerve --> optic chiasm --> optic tract --> lateral geniculate nucleus (LGN) --> optic radiation to occipital lobe (visual conscious perception)

9

What is a sign of optic neuritis when looking at an eye using ophthalmoscopy?

where the fundus looks like there is something pushing outwards from behind it

10

T/F: a cat with slow onset vision loss adapts to home very well and doesn't seem blind to owner until introduced into an unfamiliar environment.

True

11

Which tests can you use to assess vision?

- in dim and bright light
- observing the animal moving in an unfamiliar environment
- negotiating obstacle course
- visual placing
- menace response

12

Outline pathway of menace response

Visual pathway to occipital lobe --> association fibres --> motor cortex of frontal lobe --> projection fibres --> pontine nucleus --> transverse fibres of pons --> cerebellar cortex --> efferent cerebellar fibres --> facial nuclei --> increased firing in facial nn --> blinking

13

Describe how menace response is learned

- absent in first 10-12 weeks (dogs and cats)
- absent if stressed, lethargic or disorientated

14

CS - forebrain dysfunction

- altered mental status (depression, delerium, confusion, stupor, coma)
- behavioural changes (thalamic)
- seizures
- abnormal behaviour (hemi-neglect syndrome)
- gait - normal, head-pressing, pacing (to side of lesion), circling
- posture - head turn usually associated with body turn (pleurothotonus) and circling, postural reaction deficits (contralateral to lesion)
- decreased facial sensation (contralateral to lesion, all 3 branches of trigeminal are sensory, only mandibular is motor)
- spinal reflexes NORMAL unless multifocal

15

What is mesencephalon?

midbrain

16

What is metencephalon?

the pons, a part of rhombencephalon

17

What is the myelencephalon?

the MO, a part of the rhombencephalon

18

Which CNs have got parasympathetic components?

- occulomotor (3)
- facial (7)
- glossopharyngeal (9)
- vagus (10)

19

What is ARAS?

Ascending reticular activating system, part of the reticular formation. Found in brainstem. Reduced ARAS activity --> reduced sleep. It activates the cerebral cortex - keeps in an awake state with a certain level of consciousness.

20

What is the reticular formation?

a collection/ meshwork of neuronal cell bodies in the brainstem

21

Function - reticular formation meshwork

- respiration
- CV function
- voluntary excretion
- swallowing
- vomiting
- mm tone
- voluntary movement

22

What does the red nucleus in the midbrain/ mesencephalon control?

gait generation

23

What does a lesion in rostral midbrain cause?

contralateral postural deficits

24

What is decerebrate rigidity?

- extension of all limbs
- mentally v stuporous
- contrasts with decerebellate

25

What is decerebellate rigidity?

- increased mm tone
- mental status ok not stuporous (eyes open looking around) as brainstem not affected

26

What is the oculomotor nucleus?

- found in midbrain
- motor (to extraocular mm: dorsal, ventral, medial adn ventro-medial oblique) and parasympathetic parts (assess PLR for sphincter pupillary mm contraction)

27

Describe PLR pathway

optic nerve --> optic chiasm --> pretectal nucleus (thalamus) --> occulomotor nucleus (midbrain) --> occulomotor nn (CN3) --> ciliary ganglion --> short ciliary nerve
(remember an animal doesn't need to see to have a PLR, there is a double crossover of fibres to reach occulomotor nucleus)

28

How are the short ciliary nerves to the iridal sphincter mm different?

- DOGS: short ciliary fibres (5-8)
- CATS: nasal and malar fibres (2)

29

What is dyscoria?

abnormal pupil size

30

What causes a reverse D-shaped pupil dyscoria?

Parasympathetic fibres (nsasl and molar fibres in cats). In cats, FeLV-associated lymphosarcoma infiltration can cause this (lymphoma likes short ciliary nn)

31

What is idiopathic hypertrophic pachymeningitis?

an immune-mediated type of meningitis

32

How can you differentiate an infectious and immune-mediated meningitis?

CSF sample -> no bacteria/ neutrophils etc suggests immune-mediated and vice versa

33

Function - trochlear nn (CN4)

Motor (from trochlear nucleus) to extraocular mm (dorsal oblique only). This is the only CN to arise in dorsal midbrain. It is also the only CN to innvervate the contralateral mm (all other CNs innervate the ipsilateral mm)

34

What is the tectotegmental spinal tract?

- tract originates in midbrain
- SNS innervation to eye
- diencephalon has influence over this part of midbrain
- 3-neuron pathway
- dysfunction --> Horner's syndrome

35

What are the 3 parts of sympathetic innervation to the eye?

1. 1st order neuron: tectotegmental spinal tract
2. 2nd order neuron: cranial cervical ganglion
3. 3rd order neuron: tympano-occipital fissure
* lesion in any part of this pathway --> Horner's

36

CS - 1st order Horner's syndrome

- intracranial signs
- spinal cord dysfunction

37

Causes - 2nd order Horner's syndrome

- brachial plexus problem --> lame
- cervical trauma

38

Causes and CS - 3rd order Horner's syndrome

- CAUSES: middle/inner ear disease
CS: facial paralysis, vestibular dysfunction

39

What does the pons (metencephalon) contain?

- trigeminal nucleus (trigeminal nerve)
- UMN (ipsilateral)

40

Classic CS of lesions to ophthalmic branch of trigeminal nn

- no corneal sensation
- no sensation inside ipsilateral nare

41

Which mm does the trigeminal nn (CN5 innervate)?

- temporalis
- masseter
- pterygoid (lateral and medial)
- digastricus rostral

42

What is a dropped jaw? Cause? Other CS?

inability to close mouth
- dysfunction of motor part of trigeminal nn (mandibular branch)
- hypersalivation with difficulty drinking and eating
- some dogs can also have abnormal facial sensation
- some dogs present with Horner's syndrome

43

Ddx - dropped jaw - 2 main categories and examples

NON-NEURO CASES:
- bilateral luxation of TMJ
- mandibular fracture
- oral FB inability to close mouth (due to overstretching)
NEURO CASES:
- inflammatory/ infectious
- trauma (carrying large heavy objects with mouth)
- toxic (botulism)
- idiopathic (trigeminal neuropathy or cranial polyneuropathy_
- neoplasia (lymphoma)

44

Diagnostic tests - dropped jaw

- CBC and comprehensvie biochem
- radiograph thorax
- abdominal ultrasound
- MRI brain
- CSF

45

What is found in MO?

- CN nuclei (6-12)
- UMN (ipsilateral)
- respiratory centre (thus may need ventilator if dysfunction with this)

46

Function - abducent nn (CN 6)

- motor (abducent nucleus)
- extraocular mm (retractor bulbi mm and lateral rectus mm. Thus dysfunction --> strabismus (medial) and won't be able to retract eyeball.

47

Function - facial nn

- motor
- parasympathetic (lacrimal and salivary glands)

48

Function - vestibulocranial nn

Unique sensory CN for balance
Dysfunction --> imbalance and heariing loss

49

Which CNs control eye movement?

- occulomotor
- abducens
- trochlear from vestibulocochlear?

50

What is the nucleus ambiguus?

contains motor, sensory and P/S nn all at the same level in the MO

51

What controls the gag reflex?

Stems from nucleus ambiguus - the important CNs are 9 and 10

52

Function - glossopharyngeal nn (CN9)

- motor to pharynx and palatine structures
- sensory (caudal 1/3 tongue and pharyngeal mucosa)
- P/S (parotid and zygomatic glands)

53

Function - vagus nn (CN10)

- motor larynx (recurrent laryngeal nn), pharynx and oesophagus
- sensory (larynx, pharynx, thoracic and abdominal viscera)
- P/S (thoracic and abdominal viscera)

54

Describe hypoglossal nn (CN12)

- exits from hypoglossal canal
- motor (mm of tongue)
- cranial cervical lesions
- dalmation, hemiparesis, mild cervical dysfunction

55

ddx- facial neuropathy

- infxn middle/inner ear
- trauma
- neoplasia
- polyneuropathy (canine hypothyroid)
- idiopathic (--> 75% dogs, --> 25% cats)

56

Facial P/S neuropathy - CS

- KCS
- dry nose
- head tilt