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Clinical Neuro > Forebrain Diseases > Flashcards

Forebrain Diseases Flashcards

1
Q

What are the 5 pairs of arteries that make up the blood supply to the brain?

A
  • 4 from the cerebral arterial circle (Circle of Willis)
    • Rostral cerebral
    • Middle cerebral
    • Caudal cerebral
    • Rostral cerebellar
  • 1 from the basilar artery
    • Caudal cerebellar
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2
Q

Blood is supplied to the rostral half of the brain in canines by what artery? Caudal half of the brain?

A
  • Rostral: internal cartoid a.
  • Caudal: vertebral a.
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3
Q

In cats, the entire brain is supplied by what artery? How is the basilar artery’s function different in cats?

A

Maxillary artery; Basilar artery actually carries arterial blood AWAY

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4
Q

In cows, their entire brain is supplied by a mixture of blood from which two arteries?

A

maxillary and vertebral a.

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5
Q

What are clinical signs and exam findings with forebrain diseases?

A
  • Seizures
  • Altered mentation
  • Behavioral change, dementia
  • Loss of training
  • Pacing, wandering
  • Wide circles (same side)
  • Head turn (same side)
  • Postural reaction deficits (opposite side)
  • Visual impairment, cortical blindness - (opposite side)
  • Head pressing, star-gazing, fly biting
  • +/- hemiparesis, hemi-neglect
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6
Q

With forebrain disease, typically animals will have a normal gait, but may have what?

A

proprioceptive ataxia

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7
Q

What are clinical signs NOT associated with forebrain disease?

A
  • Head tilt
  • Nystagmus
  • Stupor, coma
  • Ataxia
  • Abnormal spinal reflexes
  • Significant CN deficits
  • Intention tremors
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8
Q

Why are postural reaction deficits on the contralateral side with forebrain disease?

A

decussation of proprioceptive tracts occurs anatomically in the medulla oblongata

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9
Q

Why are visual defects on the contralateral side of a forebrain lesion?

A

because decussation occurs at the optic chiasm

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10
Q

What is your diagnostic work-up for forebrain disease?

A
  • thorough hx and neuro exam are key!
  • MDB, +/- Abdo/thoracic imaging
  • MRI (> CT for brain imaging)
  • CSF analysis
  • +/- infectious dz testing
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11
Q

What are some degenerative diseases of the forebrain?

A

lysosomal storage disease, leukodystrophy, and cognitive dysfunction

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12
Q

Describe lysosomal storage disease

A
  • accumulation of metabolic by-products due to defective enzyme
  • leads to cellular dysfunction
  • often autosomal recessive
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13
Q

Describe leukodystrophy

A
  • metabolic genetic dz
  • affects white matter
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14
Q

Describe cognitive dysfunction (CD)

A
  • mostly dogs >9yrs
  • +/- model for human Alzheimer’s
  • accumulations of beta-amyloi in brain
    • coalesce to form neuritic plaques
    • most prominent in frontal cerebral cortex and hippocampus
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15
Q

What are the clinical signs of CD?

A
  • progressive cognitive impairment
  • inactivity, abnormal sleep/wake cycle
  • wandering/pacing
  • dementia, urinary/fecal incontinence
  • anxiety
  • lost in familiar environments, failure to recognize familiar people/animals
  • decr interaction
  • hearing loss, vocalization
  • cats may show aggression
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16
Q

How do you diagnose and treat CD?

A
  • Dx: hx, CS, and excluding other causes
    • may or may not have abnormalities on MRI (e.g. cerebral atrophy, ventricular enlargement, microhemorrhages & infarcts)
  • Tx: no known cure
    • Selegiline (L-deprenyl) = MAO inhibitor
    • Holistic tx
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17
Q

What are considered anomalous forebrain disorders?

A

Congenital hydrocephalus and epilepsy

18
Q

Describe congenital hydrocephalus

A
  • Toy and brachycephalic breeds
  • Excessive CSF in ventricular system
    • flow obstruction vs. insufficient absorption
  • Destruction of ependymal lining of ventricles
  • Neuronal injury in cerebral cortex & compromise of cerebral vasculature
  • Damage periventricular white matter
  • often dogs are asymptomatic
    • can cause dysfunction from compression and stretching of brain parenchyma
19
Q

What are your general exam findings with congenital hydrocephalus?

A
  • dome shaped head
  • open fontanelle or larger calvarial defect
  • ventrolateral strabismus aka “sun set sign”
    • likely due to orbital malformation
  • Neuro exam findings:
    • typically apparent from 6 mo old
    • behavior change, obtundation, dementia, circling, pacing, restlessness, seizures (not common)
20
Q

What is the treatment for congenital hydrocephalus?

A
  • reduction of CSF production
    • Pred
    • Proton pump inhibitor (Omeprazole)
    • Furosemide
  • Surgical:
    • ventriculoperitoneal shunt

Can NOT address cerebrocortical damage

21
Q

Describe primary epilepsy

A
  • no identifiable brain abnormality
  • typically pure-bred dogs
    • genetic basis likely
  • Generally 1-5 yrs
  • seizures mostly generalized, can be partial
  • seizures often at rest/sleep
  • seizure frequency highly variable
  • documented in cats
22
Q

What is the primary treatment for epilepsy? What are a few examples of emergency anti-convulsants?

A

Primary tx:

  • Phenobarb
  • KBr
  • Levetiracetam (Keppra)
  • Zonisamide

Emergency anti-convulsants:

  • Phenobarb
  • Diazepam IV/per rectum
  • Levetiracetam
23
Q

What are two examples of forebrain metabolic diseases?

A

Hepatic encephalopathy and hypoglycemia

24
Q

Describe the causes and clinical signs of hepatic encephalopathy

A

Causes:

  • Liver failure
  • PSS

CS:

  • obtundation
  • pacing
  • head pressing
  • visual deficits
  • seizures (infrequent)

*signs may be assoc. w/ feedings

25
Q

How might you diagnose and treat hepatic encephalopathy?

A

Dx:

  • Hx
  • pre & post-prandial bile acids
  • Elevated ALT, ALP, NH3
  • Ammonium biurate crystals in urine
  • visualization of PSS on U/S or CT
  • Mesenteric portography
  • per-rectal scintigraphy

Tx:

  • surgical shunt attenuation
  • low protein diet
  • lactulose (binds NH3)
  • abx
26
Q

Describe the causes and clinical signs of hypoglycemia?

A

Brain is COMPLETELY dependent on glucose for metabolism

Causes:

  • glycogen depletion in very young/small puppies and kittens
  • excess insulin secretion (insulinoma)
  • insulin overdose in diabetics
  • Addison’s
  • liver failure
  • toxins (xylitol)

CS: tremors, vocalization, altered mental status, seizures, visual dysfunction

27
Q

What are the most common primary forebrain neoplasms?

A

Primary tumors

  • Meningioma (both dogs and cats)
  • Glioma (oligodendoglioma, astrocytoma)
  • Choroid plexus tumors
  • LSA
  • Histiocytic sarcoma
28
Q

What are the most common secondary forebrain neoplasms?

A
  • Hemangiosarcoma
  • Mammary, pulm, prostatic adenocarcinoma
  • LSA
  • Melanoma
  • Nasal & frontal sinus carcinoma
  • Calvarial tumors
  • Pituitary tumors
  • Peripheral Nerve Sheath Tumors (CN V)
29
Q

T or F: a defiinitive diagnosis for any brain tumor can be made just by imaging it

A

F; cannot be made without histopath

30
Q

What are the signalment, clinical signs, and treatment options for forebrain neoplasms?

A

Signalment: typically older dogs (>5yrs), any breed

CS:

  • variable - often seizures
  • behavior change, circling, head pressing, visual deficits, hemi-attention
  • CP deficits
  • Often gradual development
  • Endocrine signs w/ pituitary tumors

Tx: surgery, radiation, chemo

31
Q

What are 3 nutritional forebrain diseases?

A
  • Thiamine deficiency (cats on all-coldwater fish diets)
  • Hypoglycemia
  • Hypocalcemia
32
Q

What are a few immune-mediated/inflammatory diagnoses for forebrain disease?

A
  • Necrotizing Leukoencephalitis (NLE) - Yorkies
  • Necrotizing meningoencephalitis (NME) - Pugs
  • Granulomatous meningoencephalitis (GME)

*All of these can ONLY be made with histopath!

Catch-all term: meningoencephalitis of unknown etiology (MUE)

33
Q

What are examples of infectious causes of forebrain disease?

A
  • Bacterial (Staph, Strep, E.coli, Klebsiella)
  • Protozoal (Toxo, Neospora)
  • Viral (Rabies, Distemper, Coronavirus - FIP)
  • Fungal (Crypto)
  • Rickettsia (Erlichia canis, Rickettsia rickettsii)
  • Parasitic (aberrant migration - Dirofilaria, Baylisacaris, Cuterebra, Taenia)
34
Q

What are 5 horse-specific infectious conditions that cause forebrain disease?

A
  • Equine infectious encephalitidies - horses do not become contagious
    • Mosquito-borne Alphavirus
      • EEE (Eastern Equine Enchephalitis)
      • WEE (Western)
      • VEE (Venezuelan)
  • Equine protozoal myeloencephalitis (EPM): Sarcocystis neurona - typically localize to SC
  • West nile virus encephalomyelitis - Flavivirus
  • EHV myeloencephalopathy
  • Rabies
35
Q

How do you diagnose and treat infectious forebrain diseases?

A

Dx:

  • CSF analysis: sig. pleocytosis, elevated protein levels
  • serology

Tx: drugs must cross BBB

  • Abx: potentiated sulfas, doxy, clindamycin
  • immune suppression: pred, cytosin arabinoside, procarbazine, cyclosporine
36
Q

What are some toxins that can cause forebrain disease?

A
  • Xylitol
  • Narcotic and “recreational” drugs
  • Ivermectin
  • Bromethalin (rodenticide)
  • Metaldehyde (snail bait)
  • Caffiene/methylxanthines
  • Lead
  • Strychnine
  • OPs
  • Pyrethrins (cats)
37
Q

What are some examples of traumatic causes of forebrain disease?

A
  • Neonates - narrow birth canal, oversized cranium, forced whelping/fetal extraction
  • small breeds - fall/dropped, mishandling/stepped on, HBC, blunt trauma, penetrating trauma
  • large breeds - HBC, blunt trauma, penetrating trauma
  • felines - high rise fall, HBC, blunt trauma, penetrating trauma (more at risk b/c thinner calvarium and reduced muscle mass)
38
Q

What are the causes of brain infarcts (strokes)?

A
  • non-hemorrhagic vs. hemorrhagic (less common)
  • Hypertension
    • primary (rare)
    • secondary (Cushings, renal dz, pheochromocytoma)
  • Cardiac dz
39
Q

What are the causes and clinical signs of brain infarcts, and how would you treat them?

A

Causes:

  • hypercoagulability
  • hyperviscosity (polycythemia vera, mult myeloma)
  • intravascular neoplasia (LSA, hemangiosarc)
  • Atherosclerosis (hypothyroid, hyperlipidemia, diabetes) - Schnauzers

CS: typically per-acute to acute, may be transient

Tx: treat underlying cause!, supportive care if no cause found

40
Q
A

Clinical Neuro (7 decks)

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