Page 895 - Problem-Based Feline Medicine

40 – THE CAT WITH ANISOCORIA OR ABNORMALLY DILATED OR CONSTRICTED PUPILS 887

Cervical pain can be present. Imaging studies (CT and MR) are helpful for defin-
ing structural lesions. Multifocal, contrast-enhancing
Fever is an inconsistent finding.
lesions are usually seen. Occasionally, non-contrast-
Fundic examination is important to look for clues of enhancing lesions are present, especially with toxoplas-
systemic inflammatory diseases, as chorioretinitis is mosis.
often present.
TOXINS*
Diagnosis

Complete blood cell count may show evidence of sys- Classical signs
temic inflammation (e.g. leukocytosis).
● Cats with organophosphate intoxication
Serum biochemical analysis may show evidence of may have acute signs including miosis,
systemic abnormalities if the disease diffusely affects salivation, urination, defecation and muscle
the body (e.g. hyperglobulinemia). weakness.
● Envenomation from snakes may also cause
Cerebrospinal fluid (CSF) analysis will usually show
dilated pupils. Weakness, ataxia and
evidence of increased nucleated cells and/or elevated
coagulopathy may occur.
protein content. Occasionally, CSF will be normal.
● Sudden onset of unresponsive, bilaterally
● Evidence of inflammation on CSF evaluation alone,
dilated pupils occasionally occurs with
however, is not specific for primary encephalitis as
fluoroquinolone.
other CNS disease (e.g. neoplasia) may result in
CSF pleocytosis and protein increases.
See main reference on page 949 “The Cat With
Evaluation of titers for specific infectious diseases, is Generalized Weakness” and page 861 “The Cat With
often necessary to make a diagnosis. Tremor or Twitching”.
With feline infectious peritonitis (FIP), cerebrospinal
fluid analysis may show a pleocytosis, with either Clinical signs
mononuclear cells or neutrophils as the predominant
Cats with organophosphate intoxication may have
cell type.
acute signs including miosis, salivation, urination, defe-
With toxoplasmosis, cerebrospinal fluid frequently cation and muscle weakness or tremor.
contains a pleocytosis, usually with mononuclear cells, ● Occasionally the pupils have been reported to be
and occasionally, eosinophils. An increasing IgG titer or bilaterally dilated and poorly responsive to light
a single positive IgM serum antibody titer is suggestive stimulation.
of active infection. Animals with neurologic signs and
Snake envenomation may be associated with dilated
positive IgM titers warrant treatment for the disease.
pupils as well as ataxia, weakness or paralysis.
With cryptococcosis, identification of the organism
Sudden onset of bilaterally dilated pupils that are unre-
from cytological evaluation of samples such as CSF,
sponsive to light occasionally occurs following fluoro-
nasal discharge and skin lesions support the diagnosis.
quinolone use, especially when used at higher than
A neutrophilic pleocytosis and occasionally an
recommended doses. Retinas appear normal on fun-
eosinophilic pleocytosis may be found on CSF analy-
doscopy. Prognosis for return of vision is guarded
sis. Detection of the cryptococcal capsular antigen is
unless the toxicity is recognized early and the drug
possible in serum, or CSF. Tissue biopsy and fungal
stopped.
culture, or culture of CSF may be more definitive in the
diagnosis.
Diagnosis
With parasites such as Cuterebra larvae, toxocara,
and aberrant heartworm migration, CSF may show Serum cholinesterase activity may lend support to the
inflammation with eosinophils is some instances. diagnosis of organophosphate toxicity, but may be