Lecture: Forebrain disease Flashcards
Lesion localization (test question)

- Intracranial
- C1-C5
- C6-T2
- T3-L3
- L4-S3
- Lower motor Neuron
Forebrain disease
Hallmark clinical signs
- Seizures (always come from forebrain)
- Altered mentation, behavoiral change, dementia, loss of training
- Pacing, wandering, wide circles towards lesion
- Head turn towards lesion
- Postural reaction deficits opposite side
- proprioceptive pathways cross over
- Blindness opposite side
- visual pathways cross over
- Head pressing, star gazing, fly biting
- Possible hemiparesis opposite side of lesion
- Proprioceptive deficits
Motor tracts in veterinary species
- midbrain
- brainstem
Other clinical signs forebrain dz
- Hemi-inattention/hemi-neglect
- thalamus damage inhibiting perception of pain
- Brain pain
- stretching of meninges
- OR brain perceives pain that is not there
- May look like neck pain, IS NOT NECK PAIN
Ataxia
- three types
- cerebellar
- proprioceptive/sensory
- vestibular
- NOT ASSOCIATED WITH FOREBRAIN DZ
- dogs with forebrain dz usually have NORMAL GAIT
Clinical signs NOT associate with forebrain dz
- Head tilt-vestibular
- Nystagmus-vestibular
- Stupor, coma-midbrain/brainstem involvement
- Ataxia
- Abnormal spinal reflexes
- Significant cranial nerve deficits
- Intention tremors
Cranial nerves associated with forebrain
CN I, II
Location of lesion if there is a visual deficit
Opposite from the eye with the visual deficit
DX workup for forebrain dz (7)
- GOOD HISTORY
- Neuro exam
- Minimum database (CBC, chem, UA)
- Abdominal and thoracic imaging
- MRI
- requires general anesthesia
- expensive
- CSF analysis
- Infectious dz testing if indicated
- short list of dz that cross BBB
Causes of forebrain dz
Degenerative
- Lysosomal storage dz
- genetic and breed specific, young animal
- untreatable
- Leukodystrophy
- white matter dz (abnormal myelinated tracts)
- rare
- untreatable
- Cognitive dysfunction
- model for human alzheimers, accumulation of beta amyloid
- dx of exclusion (MRI shrunken brain)
- seleginline, antianxiety meds
Cognitive dysfunction
CS
- progressive cognitive impairment
- inactivity, abnormal sleep/wake cycle
- wandering/pacing
- dementia, urinary/fecal incontinence
- anxiety
- decreased interaction
- hearing loss, vocalization
- cats may develop aggression
Cognitive dysfunction
Diagnosis
- HX, CS, exclusion of other causes
- +/- brain abnormalities on MRI
- atrophy
- ventricular enlargement
- microhemorrhages and infarcts
- small interthalamic adhesion
Cognitive dysfunction
Treatment
- No known cure
- MAOI therapy - selegeline
- SAM-e
- Holistic
- anti-anxiety meds
Causes of forebrain dz
Anomalous
- Congenital Hydrocephalus
- toy and brachycephalic breeds: chihuahua
- excessive CSF in ventricular system: white matter damage
- many animals can be asymptomatic
- If progressive, can cause dysfuntion from compression/stretching of brain parenchyma
- Primary epilepsy
- typically pure-breed dogs 1-5 years old
- documented in cats
Congenital Hydrocephalus
General exam findings
- dome-shaped head
- open fontanelle or calvarial defect: skull sutures don’t close
- sun-set sign (ventrolateral strabismus) from orbital malformation
Congenital Hydrocephalus
Neurologic exam findings
- typically apparent by 6 months old
- behavoir change, obtundation, dementia, circling
- innapropriate aggression
- blindness, seizures
Color of fluid on an MRI
WHITE
Congenital Hydrocephalus
TX
- Reduction of CSF production
- prednisone
- PPI (omeprazole) about 40% reduction
- Furosemide: loop diuretic - better in crisis than maintenance
- surgical
- ventriculoperitoneal shunt - last 7-10 years
Primary epilepsy
Treatment
Emergency treatment
- Treatment
- phenobarbital
- Potassium Bromide (KBr)
- Levetiracetam (Keppra)
- Zonisamide
- Emergency
- Phenobarbital
- Diazepam
- Levetiracetam
Causes of forebrain dz
Metabolic
- Hepatic encephalopathy
- liver failure
- looks like a sick animal
- Portosystemic shunt (extra vs intra-hepatic)
- runty puppy
- liver failure
- Hypoglycemia
Hepatic encephalopathy
CS
- Obtundation
- Pacing
- Head pressing
- Visual deficits
- Head pressing
- Seizures
- CS may be associated with feedings
Hepatic encephalopathy
DX
TX
- DX
- Blood work
- pre and post prandial biles acids
- TX
- surgical shunt attenuation
- low protein diet
- lactulose
- antibiotics
Hypoglycemia
Causes
- glycogen depletion in very young, small puppies/kittens
- excell insulin (insulinoma)
- insulin OD
- Addison’s
- Liver failure
- Toxins (xylitol)
Hypoglycemia
CS
- Tremors
- vocalization
- altered mental status
- seizures
- visual dysfunction
Brain is completely dependant on _______ for metabolism
glucose
Causes of forebrain dz
Neoplasia
Primary tumors
- Primary tumors
- meningioma: most common lesion in dogs and cats
- Glioma
- often aggressive/not surgical
- Choroid plexus tumors
- Lymphosarcoma: can do whatever they want
- Histiocytic sarcoma
Dont see many brain tumors in
horses and cows
Definitive DX for tumors
- Can’t be made without histopath
- often diagnosis is presumptive
Tumors
Signalment
CS
TX
- Signalment
- typically older than 5, any breed
- CS
- variable
- behavoir change
- endocrine disruption
- TX
- palliative vs definitive
- sx, radiation, chemo
Causes of forebrain dz
Nutritional
- Thiamine deficiency
- cats on all coldwater fish diet
- hypoglycemia
- hypocalcemia
Causes of forebrain dz
Inflammatory
- Immune-mediated (require histopath for def dx)
- necrotizing leukoencephalitis (NLE)
- Yorkies
- Necrotizing meningoencephalitis (NME)
- pugs
- Granulomatous meningoencephalitis (GME)
- necrotizing leukoencephalitis (NLE)
Causes of forebrain dz
Infectious
- Bacterial
- staph
- strep
- e. coli
- klebsiella
- Protozoal
- toxoplasma
- neospora
- EPM
- Viral
- rabies
- distemper
- coronavirus (FIP)
- Fungal
- Cryptococcus
- Rickettsia
- ehrlichia canis
- rickettsia rickettsii
- Parasitic
- dirofilaria
- baylisacaris
- cuterebra
- taenia
Equine infectious encephalitidies
- Mosquito-borne alphavirus
- EEE (Eastern Equine Encephalitis)
- WEE (Western Equine Encephalitis)
- VEE (Venezuelan Equine Encephalitis)
- Horses don’t become contagious
- People also susceptible to dz from mosquitos
Other equine neurologic diseases
- Equine protozoal myeloencephalitis
- apicomplexan protozoa (sarcocystis neurona)
- forebrain or spinal cord localization
- apicomplexan protozoa (sarcocystis neurona)
- West Nile virus encephalomyelitis (WNE)
- Flavivirus
- Equine Herpes virus myeloencephalopathy
- Rabies
Equine infectious neuropathy
DX
TX
- DX
- CSF
- look for significant pleocytosis
- TX
- must cross BBB
- Antibiotics
- potentiated sulfas
- doxy
- clindamycin
- Immune suppression
- pred
- cytosine arabinoside
- procarbazine
- leflunomide
- cyclosporine
- Antibiotics
- must cross BBB
Causes of forebrain dz
Toxin
- Xylitol
- drugs
- ivermectin
- bromethalin (rodenticide)
- metaldehyde (snail bait)
- caffeine/methylxanthines
- lead
- strychnine
- organophosphates
- pyrethrins
- ethylene glycol
Causes of forebrain dz
Trauma
- Neonates
- birthing/extraction
- Small breeds
- fall, mishandling
- Large
- HBC
- blunt trauma, penetrating trauma
- Felines
- penetrating trauma
Causes of forebrain dz
Vascular
- Brain infarcts (stroke)
- non hemorrhagic vs hemorrhagic
- causes
- hypertension
- cardiac disease
Vascular dz
Causes
- Hypercoagulability
- Hyperviscosity
- Intravascular neoplasia
- Atherosclerosis
Vascular dz
CS
TX
- CS
- typically per-acute to acute
- signs may be transient
- TX
- treat underlying cause
- supportive care