Page 1132 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1107

VetBooks.ir 10.59 Diagnosis
Ante-mortem diagnosis can be difficult. A his-
tory of recent bacterial infection, particularly
severe purulent disease with S. equi infection,
should prompt further investigation of cerebral
abscessation, although other causes of asym-
metrical cerebral disease should be ruled out.
Hyperfibrinogenaemia, hyperglobulinaemia and
leucocytosis may be present, but are not consis-
tent. Changes in the CSF depend on the degree of
meningeal or ependymal involvement. Most cases
exhibit xanthochromia and a moderate elevation of
CSF protein levels reflective of cerebral damage
and compression. CT and MRI can be very use-
ful for diagnosis but may be of limited availability.
Fig. 10.59 Evidence of necrosis and haemorrhage The horse should be evaluated for the presence of
in the cerebrum section on the left associated with an a septic focus elsewhere in the body. Appropriate
abscess caused by Streptococcus equi subsp. equi. diagnostic specimens, including blood, should be
submitted for bacterial culture in an attempt to
identify the causative organism.
to colonise skin or respiratory mucosal surfaces,
such as Streptococcus equi subsp. equi, S. zooepidemicus, Management
Actinobacillus equuli, Klebsiella spp. and Pasteurella spp. If the signs are acute, severe and rapidly progres-
Bacterial meningitis may be present concurrently. sive, it is likely that brain oedema is also present.
Corticosteroids (dexamethasone, 0.1–0.5 mg/kg i/v
Clinical presentation q24 h) are controversial, but used by some clinicians.
Neurological examination will usually localise the Osmotic agents (mannitol or hypertonic saline) and
lesion to the cerebrum, with behavioural changes diuretics (furosemide, 0.75–1.0 mg/kg i/v q12–24 h;
such as depression, wandering or unprovoked excite- DMSO, 1 g/kg as a 10–20% solution q12–24 h) are
ment the most obvious. Signs may be insidious or often used to try to counteract life-threatening
acute in onset, and pyrexia is not usually present. increases in intracranial pressure (ICP). In addi-
Characteristically, the signs may vary in severity tion to the treatment of increased ICP, prolonged
over a period of days. Contralateral impaired vision, antimicrobial administration is required. Based
deficient menace response and decreased facial sen- on pathogen(s) isolated from cerebral abscesses in
sation are consistent early findings. Affected horses horses, the use of potassium or sodium penicillin
frequently circle or stand with the head and neck (20,000 IU/kg i/v q6 h) and gentamicin (6.6 mg/kg
turned towards the side of the lesion. Progression i/v q24 h) would seem to be a good initial choice.
leads to recumbency, unconsciousness, seizures and Surgical evacuation of the lesion is another approach
signs of brainstem compression such as asymmetri- that has been used successfully in a limited number
cal pupils, ataxia and weakness. of cases.

Differential diagnosis Prognosis
EPM; trauma; arboviral encephalitis; leucoenceph- The prognosis is poor. Medical therapy alone is
alomalacia; verminous myeloencephalomyelitis; unlikely to treat a cerebral abscess successfully.
hepatoencephalopathy; cholesterol granuloma of Horses that recover may have residual deficits such
the choroid plexus of the lateral ventricle; uraemic as impaired vision.
encephalopathy; rabies.