Neoplastic
Primary and Secondary (metastatic). Neurological signs are progressive. Tumors are usually found within the brainstem (gliomas,
ependymomas, metastatic tumors) or involving the cerebellomedullary angle or surface of the brainstem (meningiomas, neurofibromas,
choroid plexus tumours, lymphosarcoma). Diagnosis often requires advanced imaging and either surgical or CT guided needle
biopsy. Treatment is often palliative and may include corticosteroids to reduce peritumoral edema. Surgical excision or debulking
is generally more difficult in the brainstem compared to the superficial areas of the cerebrum, but is done regularly at UC
Davis with good outcomes. Radiotherapy and chemotherapy may also be done depending on tumor type and location. Prognosis is
generally guarded, but reasonable periods of remission/reduction of clinical signs can be achieved. It is VERY important to
include a good minimum data base including metastasis check thoracic radiographs and abdominal imaging to rule out metastatic
disease.
Nutritional
Thiamine deficiency. Generally seen in cats fed all fish diets (fish contains thiaminase). Thiamine deficiency causes spongy
necrosis and hemorrhage of grey matter. Vestibular signs may be present early in the disease with progression to seizures,
dilated pupils, cervical ventroflexion and death. Diagnosis is based on history, clinical signs, decreased blood thiamine
and transketolase activity and response to therapy. Treatment is supportive with thiamine supplementation and diet management.
Successful treatment is possible in the early stages.
Infectious
1. Bacterial: Uncommon. Extension of otitis media-interna. Treat with surgery and long term antibiotics, ideally based on
culture and sensitivity results.
2. Viral.
A. Canine distemper virus: Dogs, sealions, lions, tigers affected. May or may not exhibit systemic signs. Diagnosis antemortem
is difficult and is based on history, clinical signs, CSF analysis, serology and PCR. Treatment is supportive. Prognosis is
guarded.
B. Feline infectious peritonitis: Nervous system lesions often affecting ependymal surfaces and meninges. May be associated
with uveitis. Usually chronic progressive illness. A variety of CNS signs may be seen including vestibular disease. Diagnosis
antemortem is difficult. History, coronavirus titres, MRI, increased serum globulin and often markedly abnormal CSF (Markedly
raised protein with monocytic pleocytosis). Treatment supportive, may be transient response to corticosteroids. Prognosis
poor.
C. Rabies: Can manifest with almost any neurological syndrome, however behavioral signs and ataxia are most common. Diagnosis
is post mortem. There is no treatment. Suspect animals must be quarantined. Death normally occurs within 10-15 days.
D. d. West Nile Virus?
3.
Protozoa
A. Neospora/Toxoplasmosis: Relatively uncommon infection causing vestibular signs in cats (toxo) and dogs (neospora and toxo).
Respiratory and ocular signs may be more common. Myopathy may be seen in young dogs. Diagnosis antemortem may be difficult
as serology can be difficult to interpret. PCR may be helpful in diagnosis. Treatment is with potentiated sulphonamides or
clindamycin. Prognosis guarded once neurological signs are apparent.
4.
Mycotic
A. Several mycotic agents cause granulomatous disease of the CNS in cats and dogs.
B. The more common agents include:
•
Cryptococcus neoformans
•
Coccidiomycosis immitis
•
Blastomycosis
•
Histoplasmosis
C. Cryptococcus is the only common agent, particularly in California. Involvement of the respiratory tract is common. Diagnosis
is based on demonstration of the organism in CSF and serology. Treatment includes amphoteracin and the "azole" derivatives,
particularly fluconazole. Prognosis with CNS involvement is poor.
Parasitic
Aberant migration and growth of parasites within the CNS is rare in dogs and cats.
Rickettsia
Rarely involves the CNS.
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