Forebrain Diseases Flashcards
(40 cards)
What are the 5 pairs of arteries that make up the blood supply to the brain?
- 4 from the cerebral arterial circle (Circle of Willis)
- Rostral cerebral
- Middle cerebral
- Caudal cerebral
- Rostral cerebellar
- 1 from the basilar artery
- Caudal cerebellar
Blood is supplied to the rostral half of the brain in canines by what artery? Caudal half of the brain?
- Rostral: internal cartoid a.
- Caudal: vertebral a.
In cats, the entire brain is supplied by what artery? How is the basilar artery’s function different in cats?
Maxillary artery; Basilar artery actually carries arterial blood AWAY
In cows, their entire brain is supplied by a mixture of blood from which two arteries?
maxillary and vertebral a.
What are clinical signs and exam findings with forebrain diseases?
- 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
With forebrain disease, typically animals will have a normal gait, but may have what?
proprioceptive ataxia
What are clinical signs NOT associated with forebrain disease?
- Head tilt
- Nystagmus
- Stupor, coma
- Ataxia
- Abnormal spinal reflexes
- Significant CN deficits
- Intention tremors
Why are postural reaction deficits on the contralateral side with forebrain disease?
decussation of proprioceptive tracts occurs anatomically in the medulla oblongata
Why are visual defects on the contralateral side of a forebrain lesion?
because decussation occurs at the optic chiasm
What is your diagnostic work-up for forebrain disease?
- thorough hx and neuro exam are key!
- MDB, +/- Abdo/thoracic imaging
- MRI (> CT for brain imaging)
- CSF analysis
- +/- infectious dz testing
What are some degenerative diseases of the forebrain?
lysosomal storage disease, leukodystrophy, and cognitive dysfunction
Describe lysosomal storage disease
- accumulation of metabolic by-products due to defective enzyme
- leads to cellular dysfunction
- often autosomal recessive
Describe leukodystrophy
- metabolic genetic dz
- affects white matter
Describe cognitive dysfunction (CD)
- 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
What are the clinical signs of CD?
- 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
How do you diagnose and treat CD?
- 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
What are considered anomalous forebrain disorders?
Congenital hydrocephalus and epilepsy
Describe congenital hydrocephalus
- 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
What are your general exam findings with congenital hydrocephalus?
- 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)
What is the treatment for congenital hydrocephalus?
- reduction of CSF production
- Pred
- Proton pump inhibitor (Omeprazole)
- Furosemide
- Surgical:
- ventriculoperitoneal shunt
Can NOT address cerebrocortical damage
Describe primary epilepsy
- 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
What is the primary treatment for epilepsy? What are a few examples of emergency anti-convulsants?
Primary tx:
- Phenobarb
- KBr
- Levetiracetam (Keppra)
- Zonisamide
Emergency anti-convulsants:
- Phenobarb
- Diazepam IV/per rectum
- Levetiracetam
What are two examples of forebrain metabolic diseases?
Hepatic encephalopathy and hypoglycemia
Describe the causes and clinical signs of hepatic encephalopathy
Causes:
- Liver failure
- PSS
CS:
- obtundation
- pacing
- head pressing
- visual deficits
- seizures (infrequent)
*signs may be assoc. w/ feedings
