Page 868 - Problem-Based Feline Medicine

860 PART 10 CAT WITH SIGNS OF NEUROLOGICAL DISEASE

Neosporosis results in necrotizing encephalitis in cats Evaluation of titers for the infectious diseases often
experimentally inoculated with Neospora caninum. helps to rule in or out the diseases.
Only those cats that were concurrently immunosup-
Cerebrospinal fluid analysis (CSF) will usually show
pressed by administration of methylprednisolone had
evidence of increased nucleated cells and/or elevated
severe histological brain lesions.
protein content. Occasionally, CSF will be normal.
Of the fungal diseases of the brain in cats, cryptococcosis ● Evidence of inflammation on CSF evaluation alone,
caused by Cryptococcus neoformans is the most com- however, is not specific for primary encephalitis as
mon. The central nervous system is often affected through other CNS disease (e.g. neoplasia) may result in
direct extension of the infection from the nasal pas- a CSF pleocytosis and protein increases.
sages or from disseminated infection from other organs. ● With feline infectious peritonitis (FIP), cere-
brospinal fluid analysis may show a pleocytosis,
Involvement of the intracranial nervous can occur with
with either mononuclear or non-lytic neutrophils
parasites such as Cuterebra larvae, toxocara, and aber-
as the predominant cell type and elevated protein
rant heartworm migration.
concentration, often > 1 g /L (0.1 g/dl).
● With toxoplasmosis, cerebrospinal fluid frequently
Clinical signs contains a pleocytosis, usually with mononuclear
cells, and occasionally, eosinophils. Increasing IgG
Depression, inappetence or anorexia and weight loss
or a single positive IgM serum antibody titer is sug-
are common.
gestive of active infection. Animals with neuro-
Clinical signs often reflect multiple levels of neurolog- logic signs and positive IgM titers warrant
ical involvement. Neurological signs may indicate dif- treatment for the disease.
fuse or multifocal disease and often do not localize to
With cryptococcosis, identification of the organism
a single area within the nervous system.
from cytological evaluation of samples such as CSF,
Paresis, gait abnormalities, proprioceptive deficits, cra- nasal discharge and skin lesions supports the diagno-
nial nerve defects, and occasionally stupor or coma sis. A neutrophilic pleocytosis, and occasionally an
may occur. eosinophilic pleocytosis may be found on CSF
analysis. If positive, detection of the cryptococcal
Cerebellar signs such as intention tremor, ataxia, hyper-
capsular antigen in serum is usually diagnostic.
metria, head tilt and nystagmus may occur with
Tissue biopsy and fungal culture of CSF may be
involvement of the cerebellum.
more definitive in the diagnosis as occasionally the
Cervical pain can be present. serum titer is negative.
Fever is an inconsistent finding. With parasites such as Cuterebra larvae, toxocara, and
aberrant heartworm migration, CSF may show inflam-
Fundic examination is important to look for clues of sys-
mation with eosinophils is some instances.
temic inflammatory disease as chorioretinitis, which is
often present with diseases causing systematic infection. Imaging studies (CT and MR) are helpful for defining
structural lesions. Multifocal, contrast-enhancing
Other systemic signs such as vomiting, coughing, and
lesions are usually seen. Occasionally, non-contrast-
diarrhea may be seen concurrently.
enhancing lesions are present, especially with toxoplas-
mosis.
Diagnosis
Complete blood cell count may show evidence of sys-
Differential diagnosis
temic inflammation (e.g. leukocytosis).
Multifocal signs are more suggestive of encephalitis.
Serum biochemical analysis may show evidence of sys-
temic abnormalities if the disease diffusely affects the Cats with encephalitis may present with signs similar to
body (e.g. vasculitis) such as elevated globulin, CK, other intracranial diseases such as brain tumor, trauma,
liver enzymes or creatinine. hydrocephalus and cerebrovascular disease.