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Flashcards in Brainstem Dz Deck (44):

What is the brainstem made up of? What are their alternative names and how can this be remembered?

- Midbrain = meSencephalon
- Pons = meTencaphalon
- Medulla Oblongata = mYelencephalon
(together pons and medulla = rhomboencephalon)


Where do the cranial nerves exit the brain?

- 1 and 2: forebrain
- 3 and 4: midbrain
- 5 : PONS
- 6-12: medulla oblongata


What is ARAS? What activities does it affect?

> ascending reticular activating system part of the reticular formation
- collection of neuronal cell bodies - meshwork
- activates cerebral cortex -> awake state and levle of conciousness
> affects many activities
- respiration
- CV function
- voluntary excretion
- swallowing
- vomiting
- muscle tone
- voluntary movement


What nuclei are present in the pons?

> pontine nucleus
- integrates visual inputs -> motor


What general functions (motor, sensory etc) do the cranial nerves have?

- motor, sesnory or mixed function
- any autonomic = PARASYMPATHETIC tone (occulomotor, facial, glossopharyngeal and vagus)
- no sympathetic


Which nucleus is responsible for gait generation and where is this found?

> red nucleus
- rostral midbrain (mesencephalon)
- responsibel for the CONTRALATERAL postural reactions


What type of lesion causes decerebrate rigidity?

- diffuse brainstem lesion affecting the mesencephalon (midbrain)


What does decerebrate rigidity look like?

- stuperous
- all 4 limbs stiff


How does decerebellate rigidity occour?

- concious
- flexion of pelvic limbs
- tense forelimbs


Where is the oculomotor nucleus and what is this responsible for?

> midbrain
> repsonsible for...
- motor and parasympathetic
- sphincter pupillary muscle constriction
- extraocular muscles (3 recti, not lateral, and the ventral oblique)
- levator palpebrae superioris muscle


Outline the path of the PLR

- optic nerve - chiasm -optic tract
- pretectal nucleus (thalamus)
- oculomotor nucleus (midbrain)
- oculomotor nerve (CN3)
- ciliary ganglion
- short ciliary nerve


How do the short ciliary nerves differ between species? Clinical implications?

(=iridal sphincter muscle)
- dogs: short ciliary fibres (5-8)
- cats: nasal and malar (lateral)
> in cats if one nerve is affected -> D shaped pupil (dyscoria)


What pathologies may affect the short ciliary nerves in cats?

- FeLV associated Lymphoma loves short ciliaries!


Localise the lesion: 5yo FS whippet, 2-3 week hx lethargy and acute onset blindness 4d ago, absent menace OU, fixed dilated pupils OU, normal fundus, depressed mental status

Bilateral optic nerves, optic chiasm


If PLR deficiits and vision loss both present where must the lesion be? potential causes

Where the pathways are shared ie. optic nerves and chiasm
- intramedullary or neoplastic most likely
- optic nerves can be compressed by severe meningitis


How does the eye appear if occulomotor is damaged?

Lateral stabismus and rotation medially d/t unopposed actions of lateral rectus and dorsal oblique


What does trochlear do?

- motor only to dorsal oblique (poor trochlear)
- only CN that crosses over (all others innervate ipsilateral side)
- Only CN that arises dorsally (all others arise medially)


How would the eye appear with a trochlear lesion?

- lateral rotaion of both eyes (only really seen in cats) d/t unoposed ventral oblique (dorsal oblique lost)
- may see BVs off centre looking at fundus
> BUT very rare to jsut have a trochlear lesion! Others probably present.


What is the tectotegmentalspinal tract? Where does it originate? What clinical signs are seen with dysfunction of this pathway?

- sympathetic innervation of the eye
- originates in midbrain, diencephalon has influence over this area
- 3 neuron pathway
- dysfunction = Horner's syndrome


What are the 1st, 2nd and 3rd order neurons in the tectotegmentalspinal tract?

1 - tectotegmental spinal tract from midbrain through spinal cord
2 - nerves from spine - cranial cervical ganglion [ not in brain]
3 - nerve innervating the eye via tympano occipital fissure and orbital fissure, past trigeminal ganglion


Where do sympathetic and parasympathetic fibres exit the spine?

- craniosacral: parasymp
- thoracolumbar: symp


What are the 3 forms of Horner's syndrome? Clinical signs associated with each?

> 1st order
- intracranial signs
- spinal cord dysfunction
> 2nd order
- brachial plexus
- cervical trauma
> 3rd order
- middle/inner ear dz
- facial paralysis
- vestibular dysfunction


What nucleus is in the pons? Functions?

- 3 braches (opthalmic, maxillary, mandibular)
- all 3 sensory
- mandibular only mm. of mastication


Where are the regions innervatedby each branch of trigem?

- opthalmic does around the orbit, globe (cornea) AND THE NARES
- maxillary dorsal face
- mandibular obvs mandible


Ddx for a specific nerve branch targetted pathology?

- granulomatous neuritis
- neoplasia


What are the muscles of mastication innervated by trigem?

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


How would a unilateral trigem neuropathy manifest?

- severe masticatory muscle atrophy
- no sensation to one side of face
- may have ulcer in affected eye d/t lack of sensation


What sings wouldb e expected if midbrain affected?

- altered mental status
- ipsilateral posture deficits


What is dropped jaw and what signs may be seen alongside it?

-in ability to close mouth d/t dysfunction of mandibular trigem branch
- hypersalivation
- difficulty eating and drinking
- abnormal facial sensation
- some presetn with Horner's 2* as nerves pass next to each other


Ddx dropped jaw?

> non neuro
- bilateral luxation of TMJ
- mandibular fx
- oral FB with inability to cloe the mouth
> neuro
- inflam/infectious
- trauma (carrying heavy objects)
- toxic (botulism)
- idiopathic (trigem neuropathy or cranial polyneuropathy)
- neoplasia (lymphoma)


Diagnostics for dropped jaw?

- haem and biochem
- rads of thorax
- abdo ultrasound
- MRI brain
r/o other causes > idiopathic trigeminal neuritis and Horner's syndrome


Tx dropped jaw? ( idiopathic trigeminal neuritis and Horner's syndrome )

- put elastic band around face to allow them to close mouth and eat
- physioltherapy


Which CN nuclei are found in the medulla oblongata (myelencephalon?) What else is present here?

6-12 and respiratory centres


What does CN 6 innervate?

> abducent
- motor to extraocular mm. lateral rectus only
- motor to retractor bulbi m.


What would a CN6 lesion cause the eyes to do?

Medial strabismus d/t unopposed medial rectus and no globe retraction


Causes of facial n. paralysis

- otitis media/interna (as leaves medulla oblongata v. close to base of the ear)
- trauma
- neoplasia
- polyneuropathy (hypothyroid dogs)
- 75% idiopathic dgos, 25% cats


What does the facial n. innervate?

- motor to the face
- parasympathetic to salivary and lacrimal glands


So what would a facial n. lesion likely cause?

- facial paralysis


Which nerve is very closely assocaited with the facial n?

vestibulocochlear nerve exits via same foramina (so head tilt may also be seen with facial n. problems)


Is vision necessary for vestibulocochlear pathway?



What would vestibulocochlear lesions cause?

See vestibular lecture
- head tilt
- hearing loss


What makes up the nucleus ambiguous?

- motor, sensory and parasympathetic


What are CN IX and X responsible for?

- Gag reflex
- Motor, sensory and autonomic
> IX
- motor pharynx and palatine structures
- sensory (caudal 1/3 tongue and pharyngeal mucosa)
- parasympathetic (parotid and zygomatic glands)
- gag and swallow
> X
- motor larynx (RLN) pharynx and oesophagus
- sensory (larynx, pharynx, thoracic and abdominal viscera)
- parasympathetic (thoracic and abdo viscera)


What is CN XII responsible for? When may theis be damaged?

- hypoglossal canal
- motor mm. of tongue
> damage w/ very cranial cervical lesions
- dalmation, hemiparesis, mild cervical discomfort