What appears strikingly abnormal to a vet does not always ring warning bells for the general public. In fact, one owner presented his ‘rottweiler puppy’ for first vaccination only to be told it was a guinea pig. Always comment on the abnormal, even if it is not the reason for the animal’s presentation.
Frequent generalized seizures commenced 4 days prior to referral. Since then the pup had not been able to find treats thrown to her, she had lost interest in her toys and had begun urinating and defecating in the house. The pup had previously been house-trained successfully. She had always bumped into things while walking and this was thought to be normal behaviour for a puppy. The owners had noticed the pup’s domed head (Fig. 20.1) at 8 weeks of age when they had bought her from the breeder.
The alert ambulatory puppy walked normally but occasionally bumped into table legs. The menace response was absent bilaterally. Both pupils were small but possessed normal pupillary light reflexes. Proprioception and hopping responses were normal in all limbs. The head was enlarged. No open fontanelles were palpated. Slight bilateral ventrolateral strabismus was present but eye movement was normal.
Cerebrum. The menace response is present from 10–12 weeks of age in puppies. The absent menace response may reflect the age of the dog or bilateral cerebral involvement. Seizures, loss of learnt behaviour and miotic pupils are all signs of cerebral disease. Bumping into objects suggests altered vision in this puppy with an otherwise normal gait. Ventrolateral strabismus with normal eye movements is a characteristic finding of congenital hydrocephalus.
Enormously enlarged lateral ventricles, an enlarged third ventricle and a narrowed aqueduct through the midbrain were found on MRI of the head (Fig. 20.2). The 4th ventricle appeared to be a normal size.