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Neurology > Principles of Forebrain and Brainstem Disease > Flashcards

Principles of Forebrain and Brainstem Disease Flashcards

1
Q

What is the mesencephalon?

A

Midbrain

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2
Q

What is the metencephalon?

A

Pons

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3
Q

What is the myeloencephalon?

A

Medulla oblongata

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4
Q

What is the rhomboencephalon?

A

Pons (metencephalon) and medulla oblongata (myeloencephalon)

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5
Q

Name the cranial nerves located in

  1. Midbrain
  2. Pons
  3. Medulla oblongata
A
  1. Occulomotor (III) and trochlear (IV)
  2. Trigeminal (V)
  3. Rest (except 1+2)
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6
Q

What are the roles of the olfactory bulbs/tracts?

A 
Perception of smell
Limbic system (instinct/mood)
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7
Q

Which CN are associated with the olfactory bulbs/tracts?

A

Olfactory (CNI)

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8
Q

Outline the pathway of the olfactory nerve…

A

Cell bodies in the nasal epithelium –> Cribriform plate of the ethmoid bone –> Olfactory bulbs –> Olfactory tracts

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9
Q

What are the roles of the temporal lobes of the telencephalon?

A

Auditory area

Vestibular conscious perception

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10
Q

What are the roles of the frontal lobes of the telencephalon?

A

Motor - corticospinal and corticonuclear tracts

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11
Q

What are the roles of the parietal lobes of the telencephalon?

A

Sensory-motor

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12
Q

What are the roles of the occipital lobes of the telencephalon?

A

Visual conscious perception

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13
Q

What proportion of the optic nerve fibres crossover in the optic chiasm in horses, dogs and cats?

A

Horse - 85%
Dog - 75%
Cat - 66%

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14
Q

What is the significance of the proportion of optic nerve fibres that crossover in the optic chiasm in different species?

A

An animal with fewer fibres crossing over e.g. human will show a much less prominent indirect PLR. This should be taken into account as a reduced PLR cannot always be assumed to be a lesion.

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15
Q

Outline the neural pathway of vision…

A

Retina –> optic nerve –> optic chiasm –> optic tract –> lateral geniculate nucleus –> optic radiation –> occipital lobe

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16
Q

How does the optic nerve differ from the other CN?

A

It is an extension of the CNS
Myelinated
Has retinal ganglion cells, glial cells and meninges

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17
Q

How can an animal’s vision be assessed?

A 
Dim vs bright light
Observing the animal moving in an unfamiliar env
Negotiating an obstacle course
Visual placing
Menace response
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18
Q

Outline the efferent neural pathway in the menace response…

A

Occipital lobe –> Associated fibres –> Motor cortex –> Projection fibres –> Pontine nucleus –> Transverse fibres of the pons –> Cerebellar cortex –> Efferent cerebellar fibres –> Facial nuclei –> Facial nerve –> Obicularis oculi muscle

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19
Q

Which muscle is responsible for closing the eyelid?

A

Obicularis oculi muscle

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20
Q

When can the menace response be absent without any pathology?

A

<10-12w old SA (haven’t learned it yet)
Stressed patients
Lethargic patients
Disorientated patients

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21
Q

What effects can forebrain dysfunction have on mental status?

A

Altered –> depression, delirium, confusion, stupor, coma
Behavioural changes e.g. hemi-neglect syndrome
Seizures

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22
Q

What is hemi-neglect syndrome?

A

One hemisphere of the brain is damaged which causes a deficit in attention to and awareness of one side of space e.g. only eating from one half of a food bowl

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23
Q

How can gait be affected by forebrain dysfunction?

A

No change
Head pressing, pacing, circling
Proprioceptive ataxia and tetraparesis

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24
Q

How can posture be affected by forebrain dysfunction?

A

Head turn (+body turn, circling) towards side of lesion

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25
Are postural reaction deficits lateral or contralateral?
Contralateral
26
What are the 3 branches of the trigeminal nerve?
Ophthalmic Maxillary Mandibular
27
Which branch of the trigeminal nerve has motor components?
Mandibular
28
In forebrain dysfunction, would decreased facial sensation be ipsilateral or contralateral to the side of the lesion?
Contralateral
29
How are spinal reflexes affected by forebrain dysfunction?
Unaffected unless multifocal
30
Where is the neurological lesion in a dog with these clinical signs? Depressed Decreased facial sensation on the left Right sided head turn Decreased menace response and vision on left Decreased postural reactions on left
Right forebrain
31
``` Where is the neurological lesion in a cat with these clinical signs? Depressed, v lethargic Decreased facial sensation on right Absent menace response bilaterally Left sided head turn Decreased postural reactions on right ```
Left forebrain
32
What are the parts that make up the brainstem?
Midbrain - mesencephalon Pons - metencephalon Medulla oblongata - myelencephalon
33
What are the cranial nerves?
``` I. Olfactory II. Optic III. Oculomotor IV. Trochlear V. Trigeminal VI. Abducens VII. Facial VIII. Vestibulocochlear IX. Glossopharyngeal X. Vagus XI. Accessory XII. Hypoglossal ```
34
Are the autonomic fibres of the CN symp, parasymp or a mixture?
Parasympathetic only
35
Outline the mnemonic for CN functions...
Some say marry money but my brother says big brains matter more
36
Where in the brainstem do the CN come from?
I, II - forebrain III, IV - midbrain V - pons VI-XII - medulla oblongata
37
What is the ARAS? What is its function?
Ascending reticulation activating system Activates the cerebral cortex --> awake state, level of consciousness
38
What happens when the ascending reticulation activating system is depressed?
Sleep
39
What is the reticular formation? What functions is the reticular formation involved in?
``` A meshwork of neuronal cell bodies: resp CV voluntary excretion swallowing vomiting muscle tone voluntary movement ```
40
What is the function of the red nucleus and where is it found?
Gait generation. | Midbrain - contralateral
41
Where does a dysfunction occur that results in decerebrate/decerebellate rigidity?
Decerebrate - midbrain | Decerebellate - cerebellum
42
What are the roles of the oculomotor n?
Motor and parasymp to extraocular m Sphincter pupillary muscle contraction Levator palpebrae superioris m
43
Outline the innervation of the extraocular m...
Oculomotor - superior rectus, inferior rectus, medial rectus, inferior oblique Trochlear - superior oblique Abducens - lateral rectus, retractor bulbi
44
Where are parasymp nerve cell bodies found?
Near to the efferent muscle
45
What kind of innervation causes the PLR?
Parasympathetic
46
Outline the neural pathway of the PLR...
Retina --> optic nerve --> optic chiasm --> pretectal nucleus --> oculomotor nucleus --> oculomotor n --> ciliary ganglion --> short ciliary nerve --> iridal sphincter muscle
47
Define dyscoria. How does this appear in cats? What is it assoc with in cats?
Abnormal pupil shape. Cats - D-shaped pupil FeLV-assoc lymphosarcoma infiltration.
48
``` Where is the lesion in a dog with the following clinical signs? Absent menace response OU Fixed dilated pupils OU Normal fundus Depressed ```
Bilateral optic nerves, optic chiasm
49
Where is the lesion in a dog with the following clinical signs? Right dilated pupil Absent direct PLR Ventrolateral strabismus
Oculomotor nevre
50
Which m does the trochlear nerve innervate?
Dorsal oblique extraocular muscle
51
How does a dysfunctional trochlear nerve appear in cats and dogs?
Cats - tilted pupil | Dogs - cannot tell due to round pupil
52
What is the role of the tectotegmentalspinal tract? Where does it originate?
Sympathetic innervation to eye which regulates pupil response to emotional factors arising from the midbrain
53
Which muscles does the mandibular branch of V provide motor and sensory innervation to?
Temporalis Masseter Pterygoid (lateral and medial) Digastricus rostral
54
What causes dropped jaw? What are the clinical signs?
Dysfunction of the motor component of the trigeminal nerve (mandibular branch) --> inability to close the mouth Hypersalivation Difficulty drinking and eating Abnormal facial sensation Horner's (sometimes)
55
What are non-neuro DDx for dropped jaw?
Bilateral luxation of the temporomandibular joint Mandibular fracture Oral FB --> can't close mouth
56
What diagnostic tests can be used to find the cause of dropped jaw?
``` Haem and biochem Radiographs of thorax Abdom US MRI of brain CSF ```
57
How is dropped jaw treated?
Elastic band/strap around muzzle when eating/drinking
58
What muscle does the abducens n supply motor innervation to?
Retractor bulbi extraocular muscle
59
What is a clin sign of abducens n dysfunction?
Pupil of eye pointing medially
60
What can cause facial neuropathy?
``` Infection of middle/inner ear Trauma Neoplasia Polyneuropathy Idiopathic ```
61
What is the most common cause of facial neuropathy in dogs?
Idiopathic
62
What is a clinical sign of vestibulocochlear dysfunction?
Hearing loss
63
What structures does the glossopharyngeal nerve provide motor, sensory and parasymp innervation to?
M - pharynx, palatine structures S - caudal 1/3 tongue and pharyngeal mucosa P - parotid and zygomatic glands
64
What structures does the vagus nerve provide motor, sensory and parasymp innervation to?
M - larynx, pharynx, oesophagus S - larynx, pharynx, thoracic and abdom viscera P - thoracic and abdom viscera
65
What innervation does the hypoglossal nerve supply?
Motor to the muscle of the tongue
66
Why does a lesion to the brainstem result in a stuporous or comatose mental state?
Loss of activation of the ascending reticulation activating system - - > loss of consciousness

Neurology (12 decks)

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