Brain Diseases in the Dog and Cat Flashcards
What are the 3 main causes of intracranial dysfunction?
- Primary lesion in the cranium
- Secondary intracranial pathophysiological sequelae to a focal lesion: hemorrhage, obstruction of the ventricular system, edema formation, “cascade of cellular events” = progressive neuronal damage both locally and globally due to impaired oxygen. and glucose delivery, resulting in impaired ATP production and failure of neuronal membrane pumps and excitotoxicity
- Global CNS dysfunction as a consequence of extra-cranial systemic disease
Why does increased intracranial pressure lead to impaired neuronal function?
- Directly Impacts: ischemia/ trauma to the cerebral vessels/ hemorrhage +/- obstruction of CSF flow
- Indirectly Impacts: Will then get a systemic elevation of catecholamines to maintain cerebral blood flow –> hypertension
Sympathomimetics predispose to arrhythmia
Can lead to brain herniation out of the foramen magnum
What are the clinical signs associated with Brain Herniation out of the foramen magnum?
- Rapid deterioration in clinical signs
- Deterioration in mental status/ paresis
- Bradycardia + systemic hypertension
- Pupil changes + respiratory changes
What are the clinical signs associated with Cerebral Syndrome?
- Normal gait
- Altered mental status: apathy, depression, disorientation, lethargy, coma
- Change in behavior: loss of training, failure to recognize owner, aggression, hyperexcitability
- Abnormal movements/ postures: pacing, wandering, circling, head-pressing, twisted head + trunk
- Postural reaction deficits in contralateral limbs
- Visual impairment: a contralateral deficit in the menace, but normal palpebral reflex
- Seizures
What are some differentials for Cerebral Syndrome?
DAMNITV
D: Canine cognitive dysfunction, storage diseases
A: Hydrocephalus/ Lissencephaly
M: Hypoglycemia/ Hepatic Encephalopathy
N: Primary + Secondary neoplasia, Thiamine deficiency
I: Protozoal/ Bacterial/ Viral infection, Meningitis of Unknown Origin (GME/ NME), Epilepsy
T: Toxins (plants, ethylene glycol, lead, xanthines, RTA
V: Infarct/ hemorrhage
What is Canine Cognitive Dysfunction?
This is classified as a behavioral syndrome that affects older dogs (8+ years old), resulting in behavioral alterations: disorientation/ confusion, altered interactions with the owner or other pets, sleep-wake cycle disturbances, house-soiling and changes in activity
Vision impairment, smell disturbance, tremor, swaying or falling and head ptosis are physical signs of CCD, and may be useful in the early stages of CCD
“Analogous to human Alzheimer’s Disease”
What are the proposed causes of Canine Cognitive Dysfunction?
- Brain vascular damage
- Deposition of beta-amyloid protein
- Oxidative injury
- Neuronal mitochondrial dysfunction
- Excitotoxic neuronal damage
- Inflammation
Are there any treatments or supplements that can be given to a dog with Canine Cognitive Dysfunction?
- Balanced and fortified diet
- Antioxidants
- L-deprenyl (Selegiline)
- Cognitive Enrichment: interactive games such as puzzle toys
What are the possible Inflammatory diseases, and Infectious agents involved in forebrain inflammation?
Inflammatory Diseases:
- Meningitis of Unknown Origin (MUO)
- GME (granulomatous meningoencephalomyelitis), NME (necrotizing meningoencephalitis)
Infectious Agents:
- Viral: Distemper, FIP, Rabies
- Bacterial
- Protozoal: Toxoplasma/ Neospora
- Rickettsial: Ehrlichia, Rocky Mountain Spotted Fever (Anaplasma phagocytophylum)
- Fungal: Blastomycosis, Aspergillosis
- Unclassified: Protothecosis (type of algae)
How can Meningitis of Unknown Origin (e.g. GME and NME) be diagnosed?
- Biopsy + Histopathology of nervous tissue is required for definitive diagnosis
- CSF Fluid may help
- MRI + CT
What is the treatment for Meningitis of Unknown Origin (e.g. GME and NME)?
Immunosuppressive Therapy + Control of seizures if present
Prednisolone +
- Cytosine arabinoside
- Ciclosporine
- Procarbazine
What are the most common causes of cerebrovascular damage?
1) Infarct: due to a hyper-coagulable state or hypertension
2) Hemorrhage: due to trauma, coagulopathy or angiostrongylus
Both infarct and hemorrhage will lead to a disruption of blood flow to the brain tissue, causing cell death + stroke
What common toxins cause CNS stimulation?
Strychnine Metaldehyde Xanthines Organochlorines Cocaine
What common toxins can cause a mixed clinical effect? (either CNS stimulation and/or CNS depression)
Lead
Pyrethrins
Ethylene glycol
Mushrooms
What common toxins can cause CNS depression?
Opiates
Marijuana
Ivermectin
What are Lysosomal Storage Diseases?
These are inherited disorders resulting from a lack of specific enzymes that break down certain fats, proteins and CHOs in the body cells
What are the clinical signs associated with Lysosomal Storage Diseases?
- Cerebellovestibular signs: ataxia, incoordination, changes in attitude, seizures, tetraparesis, intention tremor and blindness
- Signs usually appear within the first few months of life and progressively worsen over the first year (but some do occur later in life)
How can Lysosomal Storage Diseases be diagnosed?
- Signalment: young animal, of a susceptible breed that progressively worsens with a symmetrical neurologic disorder
- Genetic tests are available: PennGen/ Laboklin
- Definitive test: biopsy + histopathology
What is the diagnostic approach to animals with suspected Intracranial Disease?
1) Complete history, physical exam + neurologic assessment: a focal or asymmetric deficit suggests intracranial disease
2) Rule out Metabolic encephalopathies: Hematology + Biochem, Urinalysis, Blood glucose, liver function test
3) Evaluate for systemic inflammatory or neoplastic disease: complete ophthalmic exam, thoracic + abdominal rads, abdominal U/S, aspirates of lymph nodes
4) Intracranial exam: CT + MRI, CSF collection and analysis
Why does Thiamine deficiency cause neurological disease?
Thiamine (B1) is important in normal CHO metabolism and synthesis of neurotransmitters
Why might a dog or cat be Thiamine deficient?
Dogs: regular ingestion of thiaminase in raw fish
Cats: ingestion of thiaminase in raw fish, prolonged anorexia, maldigestion/ malabsorption disorders, or inadequate dietary intake
What are the clinical signs associated with Thiamine deficiency in dogs and cats?
- Impaired vision
- Mydriasis
- Ataxia
- Ventroflexion of the head + neck
- Vestibular signs
- Seizures
- Coma + Death
What is the treatment for suspected Thiamine deficiency?
IM or SC Thiamine: should lead to a rapid recovery and resolution of neurological signs
Oral supplementation after this
Are Primary or Secondary neoplasias of the brain more common?
Secondary
What breeds are most commonly affected by primary brain neoplasias?
- Boxers
- Goldens
- Lab Retrievers
- Mixed breed dogs
What are the most common metastatic neoplasias, which end up in the brain
- Mammary
- Prostatic
- Hemangiosarcoma
- Lymphoma
What are the most common signs associated with a brain neoplasia?
- Depends on the site and growth rate of the neoplasia, but the following are most commonly reported:
Seizures
Changes in mentation: dull, depressed and acting “old”
Forebrain lesion: Compulsive circling towards the side of the lesion, abnormal postural reactions, vision and facial sensation on the side opposite the lesion
Brainstem lesion: positional nystagmus + subtle cranial nerve deficits
How can an intracranial neoplasia be diagnosed?
- CBC + Biochem + Urinalysis: look for evidence of neoplasia or paraneoplastic syndrome
- Rads + U/S: look for primary tumor, since secondary neoplasia is the most common
- MRI > CT
- Biopsy for definitive diagnosis
Note: CSF analysis is not usually helpful
What are the most common Primary intracranial tumors in the dog and cat?
1) Meningiomas
2) Glial tumors in dogs, Lymphoma in Cats
What are the treatment options for primary intracranial tumors?
Depends on tumor type, location, growth history, neurological signs and results on CT/MRI
- Surgical removal
- Radiotherapy
- Supportive chemotherapy: prednisone
- Anti-convulsant therapy for seizures
What is the definition of Delirious?
Reduced ability to pay attention to external stimuli- agitation, hyperactivity, excessive vocalization
What is the definition of Obtunded?
Dull, tends to fall asleep if left but aroused by non-noxious stimuli
What is the definition of Stuporous?
Unresponsive to environmental stimuli but responsive to noxious stimuli
What is the definition of Comatose?
Non-responsive to environmental and noxious stimuli
To be alert and normally orientated to the environment requires a normal level of consciousness + behaviour
Consciousness in a patient requires what parts of the brain to be functioning?
- Cerebral hemispheres
- Thalamus
- Brainstem: specifically the reticular activating system (ARAS), which determines the level of arousal
Abnormalities of consciousness in a patient can be attributed to?
- Focal lesions of the ARAS
- Diffuse cerebral lesion
- Extra-cranial diseases: e.g. hypoglycemia, hypocalcemia, intoxication etc.
What is a tremor?
An involuntary rhythmic, oscillating movement of a fixed frequency, occurring constantly when the animal is awake but disappearing during sleep
- Can affect head and/or limbs
What are the potential causes of Tremors?
Lesions at multifocal sites, or diffusely throughout the CNS
- Extra-cranial diseases: e.g. hypoglycemia, hypocalcemia, intoxication etc.
- Non-suppurative meningoencephalomyelitis
- Cerebellar disease: leading to an intention tremor
- Idiopathic tremor
- Episodic, idiopathic head bobbing
- Hypomyelination/ dysmyelination
Describe idiopathic Cerebellitis or “Little White Shakers”, and its treatment
Defined as an acute onset of whole body tremors +/ ataxia, which will worsen with goal orientated movements, and disappear at rest
- Seen in young terrier and small breeds: Yorkie, WHWT, Cairn, Maltese
Tx: Prednisolone + diazepam
Good prognosis: improve in 7-10 days
What are the clinical signs associated with Cerebellar syndrome?
- Symmetrical ataxia with preservation of strength
- Dysmetric gait: changes in rate, range or force
- Hypermetria in all limbs, especially the thoracic
- Intention tremor of the head and eyes
- Broad-based stance
- Postural reactions delayed with exaggerated responses
What is the most common cause of Feline Cerebellar Hypoplasia?
- In-utero infection with panleukopenia virus (feline parvovirus) OR when a pregnant queen is vaccinated with a modified-live panleukopenia virus vaccine
When is Feline Cerebellar Hypoplasia usually noticed in the cat?
Kitten stages, when the kitten first begins to walk
May see hypermetria, ataxia, truncal sway and tremor
What are some causes of Peripheral Vestibular Disease?
- Idiopathic vestibular syndrome: sudden onset head tilt, dysequilibrium, nystagmus. Most common in old dogs and young cats. Occasionally bilateral. Suspected to be due to an osmolality disturbance of fluid in the vestibular labyrinth
- Otitis media/ interna: very common, CN 7 involvement is common + Horner’s syndrome
- Neoplasia
- Head trauma
- Iatrogenic
- Ototoxicity: aminoglycosides/ topical iodophors, chlorhexidine
What are some causes of Central Vestibular Disease?
- Meningoencephalitis
- Head trauma
- Neoplasia
- Cerebrovascular injury
- Metronidazole toxicity
A dropped/ weak jaw that is unable to close is suggestive of a lesion in what location?
Bilateral, peripheral CN 5
note: if it was bilateral central, this lesion would have to be very large and in the brainstem, which would make it fatal
What are the possible underlying causes of Dropped Jaw?
- Idiopathic
- Neuritis of bilateral CN 5
- Trauma
- Masticatory myositis: this is a very painful condition! Dog will be head shy
Define Horner’s Syndrome
This is a syndrome characterized by dysfunction of the sympathetic trunk leading to the head, resulting in miosis (pupil constriction), ptosis (drooping of upper eyelid), 3rd eyelid protrusion and Enophthalmos (posterior displacement of eye- sunken eye)
Define Feline Dysautonomia, and the common clinical signs
This is a polyneuropathy affecting the sympathetic and parasympathetic nerves of the autonomic NS, resulting in vomiting/ regurgitation, straining to urinate, dribbling urine, depression, anorexia, constipation
Physical exam results: bradycardia, decreased or absent anal tone, dilated pupils wont respond to light, dry nose + eyes + mucous membranes and 3rd eye lid prolapse
What are the causes of Feline Dysautonomia?
Unknown etiology, suspected to be toxic or autoimmune causes
How can Dysautonomia be diagnosed?
- Clinical signs are helpful
- Rads or US: help identify megaesophagus, megacolon/ constipation, and a full bladder, general ileus
- Definitive diagnosis: histopathology at PM
