Principles of Forebrain and Brainstem Disease

Question 1

What structures compose the forebrain and are involved in forebrain disease?

Answer 1

Cerebrum and Thalamus

• Area of the brain rostral to the tentorium cerebelli
• does NOT include the brainstem and CN’s
• Thalamus (part of diencephalon)

Question 2

Anosmia

Answer 2

• the loss of the sense of smell, either total or partial. It may be caused by head injury, infection, or blockage of the nose
• can be in reference to loss of smell unilaterally due to a lesion on one olfactory bulb (ex: tumor growth) - would be rare to pick up on these clinical signs

Question 3

The Limbic System

Answer 3

• The structures and interacting areas of the limbic system are involved in motivation, emotion, learning, and memory.
• The limbic system is where the subcortical structures meet the cerebral cortex.
• The limbic system operates by influencing the endocrinesystem and the autonomic nervous system

Question 4

Optic Chiasm

Answer 4

• The optic chiasm is an X-shaped structure formed by the crossing of the optic nerves in the brain. The optic nerve connects the brain to the eye. To biologists, the optic chiasm is thought to be a turning point in evolution

Question 5

Main parts of the motor sensory cortex of the brain

(or sensory motor cortex)

Answer 5

• Frontal Lobe
• Parietal Lobe

Question 6

Pure sensory cortex of the brain

(cannot initiate any motor activity)

Answer 6

• OCCIPITAL LOBES
• only does visual conscious perception

Question 7

Pineal Gland

Answer 7

• located in the Thalamus
• important in circadian and seasonal reproductive activity
• The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles

Question 8

Tetraparesis

Answer 8

Tetraparesis, or quadraparesis, is a condition in which all four limbs are weak

Question 9

Ventriculoperitoneal shunting

Answer 9

Ventriculoperitoneal shunting is surgery to treat excess cerebrospinal fluid (CSF) in the cavities (ventricles) of the brain (hydrocephalus)

• -put in a valve and you have to make sure the direction of the valve is AWAY from the brain!!
• want that fluid to drain into the abdomen

Question 10

Dorsal Metencephalon becomes…

Answer 10

the cerebellum

Question 11

the mesencephalon becomes…

Answer 11

• the midbrain

Question 12

the ventral metencephalon becomes…

Answer 12

• the pons

Question 13

The myelencephalon becomes..

Answer 13

the medulla oblongata

Question 14

the rhomboencephalon is made up of which parts?

(2)

Answer 14

• pons (ventral metencephalon)
• medulla oblongata (myelencephalon)

Question 15

Autonomic fibers will always be….

Answer 15

PARASYMPATHETIC

Question 16

CN that is in charge of the lacrimal glands

Answer 16

• CN VII - Facial n.

Question 17

Which CN has parasympathetic fxn?

Answer 17

• CN X - Vagus n.

Question 18

which CN is in charge of making the pupil smaller? (contract)

Answer 18

• CN III - Oculomotor n.
• which is a parasympathetic fxn of this nerve

Question 19

the 4 Autonomic CN’s

Answer 19

1. Oculomotor n. (CN III)
2. Facial n. (CN VII)
3. Glossopharyngeal n. (CN IX)
4. Vagus n. (CN X)

• means they are always parasympathetic!

Question 20

The only CN coming from the pons

Answer 20

CN V - Trigeminal n.

Question 21

CN’s from the midbrain

(2)

Answer 21

CN III and IV

Question 22

CN’s coming from the medulla oblongata

Answer 22

• CN VI to XII

Question 23

Severe dysfunction in the Ascending Reticular Activating System will result in what presentation?

Answer 23

• Unconscious Mental Status

Question 24

Important in gait generation…

Answer 24

• red nucleus
• in the midbrain (most rostral part of the brainstem)

Question 25

proprioceptive pathways and postural reactions

Answer 25

* **contralateral forebrain** * **ipsilateral brainstem**

Question 26

What does it mean when a patient has **Decerebrate Rigidity** posture?

Answer 26

* means that there is a lesion in the midbrain (brainstem) * is so severe that they are always unconscious * different to other postures in that they will always be unconscious with this

Question 27

Opisthotonos

Question 28

recognize the 3 rigidity postural reactions

Answer 28

1. Schiff Sherrington 2. Decerebellate rigidity 3. Decerebrate rigidity

Question 29

Decerebellate Rigidity posture

Answer 29

Lesion in rostral part of the cerebellum **-they will be conscious!** - can be increased tone on all 4 - sometime the pelvic limbs will are flexed because you have increased tone on the iliopsoas muscle, but sometimes they cannot be flexed --\> don't rely on the pelvic limbs being flexed or not

Question 30

Oculomotor n - CN III is....

Answer 30

* motor and parasympathetic * motor to the majority of the extraocular muscles - does everything _except_ for the dorsal oblique and lateral rectus m.'s * does the **dorsal, the ventral, medial rectus and the ventral oblique** * also the motor to the **levator palpebrae superioris muscle** * also responsible for constricting hte iris muscle when we conduct the PLR - **sphincter pupillary muscle constriction**

Question 31

what happens when there is a dysfunction of the oculomotor n. ?

Answer 31

* pupil is dilated * may have ptosis of the upper eyelid

Question 32

Is the forebrain involved in the PLR?

Answer 32

**NO.** - PLR is a **REFLEX** and therefore the forebrain is not involved

Question 33

Dyscoria

Answer 33

An abnormality in the shape of the pupil of the eye

Question 34

If you see this presentation, what should you immediately test for? (2)

Answer 34

* Lymphoma * FeLV attack the short ciliary nerves

Question 35

What does the Trochlear Nerve do?

Answer 35

* **Innervates the Dorsal Oblique** -extraocular muscle * motor fibers * if it is not working, then you don't really see anything in terms of clinical signs * BUT, it is the only cranial nerve that arises from the dorsal part of the brainstem and is the only cranial nerve that **crosses over and does the contralateral muscle**

Question 36

Which Branch of the trigeminal nerve is Motor?

Answer 36

**MANDIBULAR BRANCH** Only one of these branches is MOTOR --\> Mandibular! **Innervates the muscles of mastication** 1. Masseter 2. Rostral digastricus 3. Temporalis 4. Pterygoids (medial and lateral) 5. Very tiny tympanic muscle (ex: for popping ears under pressure)

Question 37

Functions of the Abducens nerve (CV VI)

Answer 37

* Motor * Extraocular muscle: **lateral rectus** * **retractor bulbi m.** * job is to abduct the eye

Question 38

What presentation could you get if you had an issue with the inner ear? (2 together)

Answer 38

* vestibular signs * facial drooping (issues with the facial n. CN VII) ## Footnote **both run closely together by the inner ear**

Question 39

xeromycteria

Answer 39

* pathological dryness of the nose * would see if parasympathetic fibers of the facial nerve are affected along with dry eye (KCS) * if you see this all together with a normal mental status, this can only happen in the inner ear

Question 40

Keratoconjunctivitis Sicca

Answer 40

* **Keratoconjunctivitis sicca (KCS)**, commonly referred to as "Dry Eye", is one of the most common dog eye problems.Dry Eye affects 1 in 22 of all dogs in the UK. Dry Eye is caused by destruction of the tear glands by your dog's own immune system. This means that too few natural tears are produced

Question 41

Vestibulocochlear Reflex

Answer 41

* way of testing CN VIII - **vestibulocochlear n.** * -move head side to side -gives bilateral and symmetrical connections to the CN 6,3, 4 to control the extraocular muscles

Question 42

Nucleus Ambiguus | (3 components)

Answer 42

1. **Glossopharyngeal (CN IX)** 2. **Vagus (CN X) -** all parasympathetic remember! 3. **Accessory n (CN XI)** * extremely important in the gag reflex! - gag reflex could be affected if there is a lesion here and then there is a risk of aspiration pneumonia for these patients - so check this!! - especially is you expect a lesion on the caudal part of the medulla oblongata

Question 43

Most commonly encountered brain tumor in cats? other honorable mentions - 5

Answer 43

* **_meningioma_** * other common ones:* 1. **CNS lymphoma** 2. **gliomas** (astrocytomas and oligodendrogliomas) 3. **Choroid plexus tumors** 4. **Ependymomas** 5. **Pituitary Tumors**

Question 44

stroke

Answer 44

* result of an infarction of the CNS * generally a vascular disorder

Question 45

Predominating clinical sign in cats with a Thiamine Deficiency

Answer 45

* **signs of brainstem dysfunction (particularly vestibular dysfunction) usually predominate** * Thiamine deficiency will cause an encephalopathy and is occassionally encountered even in cats that are fed a commercial diet

Question 46

Exception to toxins regarding symmetrical neuropathies

Answer 46

**anticoagulant rodenticide toxicity** * may cause focal hemorrhage into the CNS and therefore deficits referable to a focal lesion

Question 47

Bacteria commonly found in abscesses formed by cat bite trauma

Answer 47

* *Actinomyces viscosus* * generally sensitive to Amoxycillin/Clavulanate

Question 48

the 8 parts of a neurological examination

Answer 48

1. Mentation 2. Posture 3. Gait 4. Postural Reactions 5. Spinal Reflexes 6. Cranial Nerves 7. Palpation 8. Nociception