L02: Forebrain Disease in the Vet Patient (Seneca) Flashcards
What does forebrain include?
Cerebrum (telencephalon)
Thalamus, Hypothalamus (diencephalon)
5 lobes of cerebrum and functions
1) frontal - motor cortex
2) parietal - somatosensory cortex
3) temporal - auditory complex
4) occipital - visual cortex
5) piriform - olfactory complex
blood supply to brain (5 arteries)
From Circle of Willis: -Rostral cerebral -Middle cerebral -Caudal cerebral -Rostral cerebellar From basilar artery: -Caudal cerebellar
Species variation in blood supply to brain: DOG
- blood to rostral half (FOREBRAIN) supplied by internal carotid a.
- caudal half supplied by vertebral a.
Species variation in blood supply to brain: CAT/SHEEP
entire brain supplied by maxillary a.
cats: basilar a. carries arterial blood AWAY
Species variation in blood supply to brain: BOVINE
entire brain supplied by a mixture of maxillary and vertebral blood.
6 categories of lesions**
1) intracranial
2) C1-C5
3) C6-T2
4) C6-T2
5) L4-S3
6) Lower motor neuron (diffuse)
where do seizures come from?**
forebrain ONLY
CS of forebrain disease
- Seizure
- altered mentation/behavior change/dementia/loss of training
- pacing, wandering, wide circles (typically to SAME side as lesion)
- head turn to SAME side as lesion
- postural reaction deficits (OPPOSITE side as lesion)
- visual impairment, cortical blindness (OPPOSITE side)
- head pressing, star-gazing, fly-biting
- hemiparesis (OPPOSITE side)
- NORMAL gait (but may have proprioceptive ataxia)
- hemi-inattention, hemi-neglect
- brain pain (flinches when clamp on head or neck)
CS NOT assoc. with forebrain disease
- head tilt
- nystagmus
- stupor, coma (typically comes from brainstem)
- ataxia
- abnormal spinal reflexes
- significant cranial n. deficits
- intention tremors (come from cerebellum)
where does coma come from?
brainstem
where do intention tremors come from?
cerebellum
why are postural reaction deficits on the CONTRALATERAL side in forebrain disease?
crossing over occurs in the medulla oblongata
where does crossing over (decussation) of proprioceptive tracts occur?
medulla oblongata
proprioceptive information remains ipsilateral to level of:____
midbrain
diagnostic work-up for forebrain disease
- Hx, neuro exam
- minimum database
- MRI (superior to CT)
- CSF analysis
- infectious disease testing if indicated
DAMNITV
acronym for common forebrain diseases and their clinical presentations. Stands for: Degenerative Anomalous Metabolic Neoplasia/Nutritional Inflammatory/Infectious Toxin/Trauma Vascular
why are visual deficits on contralateral side in forebrain disease?
because of crossover at optic chiasm
DEGENERATIVE includes:
Lysosomal storage diseases
Leukodystrophy
Cognitive Dysfunction
chars. of lysosomal storage diseases
- rare
- usually autosomal recessive
- accumulation of metabolic by-products usually due to a defective enzyme
- leads to cellular dysfunction
- usually develop progressive encephalopathy soon after birth
chars. of cognitive dysfunction
- mostly older dogs
- similar to human Alzheimer’s
- accumulation of beta-amyloid in the brain, which coalesce to form neuritic plaques
CS of cognitive dysfunction
- progressive cognitive impairment
- inactivity, abnormal sleep/wake cycle
- wandering/pacing
- dementia, incontinence
- anxiety
- failure to recognize people
- dec. interaction
- hearing loss, vocalization
- cats can develop aggression
Dx of cognitive dysfunction
-Hx, CS
+/- abnormal MRI (cerebral atrophy, ventricular enlargement, microhemorrhage, infarct, interthalamic adhesion)
Tx of cognitive dysfunction
- no known cure
- Optional: Selegiline, SAM-e, acupuncture
ANOMALOUS includes:
Congenital Hydrocephalus
Primary Epilepsy
chars. of Congenital Hydrocephalus
- toy/brachiocephalics
- excess CSF
- destruction of ependymal lining of ventricles
- neuronal injury in the cerebral cortex and compromise of cerebral vasculature
- damage to periventricular white matter
- can be asymptomatic
- can cause dysfunction from compression and stretching of brain parenchyma
General Exam findings of Congenital Hydrocephalus
- dome-shaped head
- open fontanelle or larger calvarial defect
- ventrolateral strabismus (due to orbital malform.)
Neuro Exam findings of Congenital Hydrocephalus
- typically apparent by 6mo
- behavior change, obtundation, dementia, circling, pacing, restlessness (uncommonly seizures)
Tx of Congenital Hydrocephalus
Reduce CSF production with: -Prednisone -Omeprazole (proton pump inhibitor) -Furosemide Surgery: ventriculoperitoneal shunt (shunts extra fluid to abdomen) *Can NOT address cerebrocortical damage*
chars. of Primary Epilepsy***
- no identifiable brain abnormality
- usually younger pure-bred dogs
- usually generalized seizures during rest/sleep
- highly variable seizure frequency
- more common in dogs
most commonly used drugs to tx primary epilepsy***
Phenobarbital Potassium Bromide (KBr) Levetiraceta Zonisamide Emergency: Diazepam IV
METABOLIC includes:
Hepatic encephalopathy
Hypoglycemia
2 causes of hepatic encephalopathy
liver failure
portosystemic shunt
CS of hepatic encephalopathy
obtundation (altered consciousness) pacing head pressing visual deficits head pressing seizures (infrequent) *may be assoc. with feeding* copper colored eyes in cats
Dx of hepatic encephalopathy
Hx Pre and post-prandial bile acids*** inc. ALT/ALP, NH3 ammonium biurate crystals in urine scintigraphy
Tx of hepatic encephalopathy
Sx shunt attenuation
low protein diet
lactulose (binds NH3)
abx
causes of hypoglycemia
- glycogen depletion in very young, small puppies/kittens
- excess insulin secretion (insulinoma)
- insulin overdose in diabetic animals
- Addison’s disease
- Liver failure
- Toxin (ie. xylitol)
CS of hypoglycemia
- tremor
- vocalization
- altered mental status
- seizure
- visual dysfunction
etc. ..
Most common primary forebrain neoplasms
Meningioma (most common in dogs and cats!) Glioma Choroid plexus tumors Lymphosarcoma Histiocytic sarcoma
what produces CSF?
choroid plexus
most common secondary forebrain neoplasms
hemangiosarcoma adenocarcinoma lymphoma melanoma nasal/frontal sinus carcinoma calvarial tumor pituitary tumor peripheral nerve sheath tumor
CS of neoplasm effecting forebrain
(highly variable)
- behavior change, circling, head press, visual deficits, hemi-inattention
- proprioceptive deficits
- gradual development
- endocrine signs w/ pituitary tumors
Tx of neoplasm effecting forebrain
sx, radiation, chemo
NUTRITIONAL causes of forebrain dz
thiamine deficiency (all fish diet in cats)
hypoglycemia
hypocalcemia
INFLAMMATORY causes of forebrain dz
Immune-mediated:
- Necrotizing Leukoencephalitis (NLE)
- Necrotizing Meningoencephalitis (NME)
- Granulomatous Meningoencephalitis (GME)
- Meningoencephalitis of unknown cause
INFECTIOUS causes of forebrain dz
More common in cats, pigs
- Bacterial
- Protozoal
- Viral (ie. West Nile Virus Encephalomyelitis, Equine Herpes virus myeloencephalopathy, Rabies)
- Fungal
- Rickettsia
- Parasitic
- Equine infectious encephalitidies (including EEE, WEE, VEE)
Ex. of protozoal cause of infectious forebrain dz
Equine Protozoal Myeloencephalitis (EPM)
-Apicomplexan protozoa (Sarcocystis neurona**)
Dx of infectious forebrain dz
CSF analysis: inc. WBCs, elevated protein lvls
Serology
Tx of infectious forebrain dz
Drugs that cross BBB:
- Abx: doxy, clindamycin, sulfas
- Immune suppression: pred, cyclosporine, etc.
TOXIN-related causes of forebrain dz
- xylitol
- narcotics
- ivermectin
- rodenticide
- methylxanthines
- lead
- strychnine
- organophosphates
- pyrethrins
- ethylene glycol
TRAUMA-related causes of forebrain disease in NEONATES
narrow birth canal
oversized cranium
forced whelping/fetal extraction
TRAUMA-related causes of forebrain disease in SMALL BREEDS
- mishandling
- Hit by car
- blunt or penetrating trauma
TRAUMA-related causes of forebrain disease in LARGE BREEDS
HBC
blunt or penetrating trauma
TRAUMA-related causes of forebrain disease in FELINES
High rise fall
HBC
blunt or penetrating trauma
Why are felines more at rick for penetrating skull injury compared to dogs?
thinner calvarium, reduced muscle mass
VASCULAR-related causes of forebrain dz
Brain infarct (stroke) (non-hemorrhagic or hemorrhagic) Hypercoagulability Hyperviscosity IV neoplasia Atherosclerosis
causes of brain infarct
Hypertension (1ary or 2ary to hyperadrenocorticism, renal dz, pheochromocytoma)
Cardiac dz
Atherosclerosis most common in what breed?**
Schnauzer