Page 806 - Clinical Small Animal Internal Medicine

Table 71.1 Clinical signs of forebrain disease
Clinical sign Notes

Seizures Can occur with lesions in the cerebral hemispheres, thalamus or hypothalamus
VetBooks.ir Propulsive walking Patients with forebrain disease circle towards the side of the lesion, but without signs of vestibular disease
Circling
(no head tilt or nystagmus present)
Head pressing
Obtundation Obtundation describes decreased responsiveness to normal stimuli. This is often a sign of bilaterally
symmetric, global cerebral hemisphere disturbance. Further disturbance of level of consciousness (i.e., stupor
or coma) is more likely to signify the presence of a brainstem lesion
Contralateral cortical Absent menace response (as a result of absent vision) with normal consensual and indirect pupillary light reflex
blindness occurs as a result of lesions in the occipital cortex or affecting the internal capsule, caudal to the level of the
lateral geniculate nucleus, on the side opposite the affected eye
Proprioceptive Patients with forebrain disease often have a relatively normal gait but significant proprioceptive deficits that are
deficits only evident on testing or on negotiating stairs or other difficult terrain
Decerebrate rigidity Decerebrate rigidity (increased extensor tone in all four limbs with opisthotonus) indicates severe, bilateral
forebrain disease and is a reflection of functional disconnection of the cerebral peduncles from the brainstem
Hemi‐inattention This occurs rarely as a result of lesions affecting the sensory cortex and is most commonly evident while eating.
syndrome Patients with hemi‐inattention syndrome will eat one half of a bowl of food, apparently ignoring the other half unless
it is rotated 180°. The lesion is situated within the cerebral hemisphere contralateral to the “ignored” side of the body
Behavioral/memory The most commonly noted behavioral and memory changes seen in patients with forebrain disease include loss
changes of toilet training, loss of recognition of family members or toys, and changes in personality
Vestibular signs Lesions in the thalamus will rarely produce vestibular signs. This is most commonly reported in patients with
cerebrovascular accidents

Box 71.1 Differential diagnoses for forebrain disease according to underlying etiology
Degenerative Lysosomal storage diseases
L2‐hydroxyglutaric aciduria in Staffordshire terriers
Anomalous Hydrocephalus
Lissencephaly
Porencephaly
Hydranencephaly
Meningoencephalocele (Dandy‐Walker syndrome)
Metabolic Hepatic encephalopathy
Renal (uremic) encephalopathy
Hypoglycemia
Electrolyte abnormalities: hypo/hypernatremia
Hypothyroid myxedema coma
Neoplastic Meningiomas
Glial tumors:
Oligodendrogliomas
Astrocytomas
Ependymomas
Choroid plexus tumors
Pituitary tumors
Metastatic disease
Lymphosarcoma
Nutritional Thiamine deficiency
Infectious/inflammatory Viral: distemper, feline infectious peritonitis, rabies, Borna disease virus
Protozoal: Toxoplasma, Neospora
Fungal: Cryptococcus, Aspergillus, blastomycosis, others (pheohyphomycotic encephalitis)
Rickettsial: Rocky Mountain spotted fever, Ehrlichia
Bacterial: abscess; meningitis
Parasitic: Cuterebra, verminous encephalitis
Inflammatory (noninfectious) Granulomatous meningomyeloencephalitis
Necrotizing encephalitides
Idiopathic Idiopathic epilepsy
Toxins Lead
Organophosphate
Metronidazole
Cyanide, sodium fluoroacetate, hydrocarbons, other heavy metals
Vascular Hemorrhagic and ischemic infarcts
Feline ischemic encephalopathy