Dr Miroslav Todorov
Veterinary Clinic Blue Cross
Case presentation: a 3 and a half year old female pug dog was presented at the Bluecross Veterinary Clinic in Sofia for additional diagnostics in view of resently started seizure events.
A month ago the dog started having problems with its hind left limb and another vet started him on prednisolone. The limping improved but 20 days later the dog started having seizures.
The patient was examined at the Bluecross Veterinary Clinic in Blagoevgrad within two hours after one of the seizures. At that stage the dog wasn‘t able to see properly and showed a tendency to circle to the left. Blood was taken for Cbc and biochemistry analysis and the results were normal. The patient was started on an antiepileptics drug – Phenobarbital and the steroids were continued (because of the high possibility of an inflammatory process). An examination at the clinic in Sofia and additional advance imaging were scheduled.
good general condition, slight difficulties in breathing (because of the brachiocephalic syndrome), normal heart and lung sounds, normal temperature.
Neurological examination: a little overexcited behaviour (but it was impossible to tell if this behaviour was abnormal for the dog or not). Normal cranial nerve reflexes, no nysgmus or circling, normal pupillary light reflexes. There was slight spinal ataxia in all four limbs. The proprioceptive tests were normal on all four. On the hind left limb the dog has pattelar luxation second degree (this explains the limping epizode a month ago). From the video provided by the owner it could be observed that the dog was demonstrating clonic- tonic seizure.
The owner was questioned for possible toxins, drugs and plants that could be the reason for the seizures but he said that the dog couldn’t have eaten anything abnormal.
A forebrain lesion was localised but the possibility of a multifocal process was very high.
The blood results were normal; therefore, possible extracranial reasons for the seizures were excluded. Toxin exposure was excluded by the anamnesis.
The list of differential diagnoses was:
- Inflammatory process – Necrotizing Meningoencephalitis (NME or Pug encephalitis)
- Idiopathic epilepsy
- Brain neoplasia
- Congenital lesion- hydrocephalus, cysts
To exclude most of the diagnoses from the list, advance imaging was performed – MRI 1,5tesla was used. The test was done with and without contrast material.
On the MRI we discovered a bilateral enlargement at the cranial part of both lateral ventricles within the frontal lobe of the brain. There was a visible communication between the ventricles and the subarachnoid space at the level of the eyes. They looked like cystic lesions filled with CSF. Bilateral loss of brain tissue was observed in both hemispheres. Around the cavities the cerebral cortex was reduced. These bilateral lesions could explain all the clinical signs that this dog was showing – seizures and the ataxia of all four limbs. There are motor cortex within the frontal lobe of the brain. There was no contrast enchantment after injection of contrast material within the brain tissue.
Therapeutic plan: the dog antiepileptic treatment was continued and regular measurements of the level of phenobarbital were scheduled. I added proton pump inhibitor –Esomeprazole (S enantiomer of omeprazole) because the drug has the effect of reducing the cerebrospinal fluid production. The steroids are slowly taped and they will be discontinued after two weeks.
The dog’s condition will be monitored by the owner and the vets at the BlueCross Veterinary Clinic in Blagoevgrad. In case of progression, especially after we stop the steroids, the necessity to take a CSF sample in order to finally exclude an inflammatory process is being discussed with the owner.
Porencephaly is a rare congenital cerebral defect and it is described in several reports in the field of veterinary medicine. It is more commonly seen in ruminants but there are few reports about dogs and cats.
There are few cystic congenital lesions of the brain, including focal lesions (porencephaly), extensive lesions (hydranencephaly) and very rarely schizencephaly (more commonly seen in humans). In porencephaly the defect creates a communication between the lateral ventricles and the subarachoid space. In schizencephaly the defect may be surrounded by a ring of polymicroglia. The schizencephalic defects are lined by gray matter.
The most frequent classification of these lesions based on their pathogenesis divides these defects into two major categories: developmental and encephaloclastic. Developmental porencephaly is due to a focal neuronal migration disorder, leaving a gap in the developing cerebral hemisphere. Encephaliclastic porencephaly includes cerebral cavities that result from tissue breakdown of various etiologies (cerebral ischemia, infection, trauma). In utero infection is the most common reason, especially in ruminants.
The interesting thing is that this type of lesions are congenital in nature but the clinical signs can start after the birth of the animal (which should be expected from the age) or sometimes later in life (after a few years).
According to the few reports about this type of pathology, the progression of the disease is different in every case. Some of those are completely asymptomatic, other cases are well controlled with drugs (antiepileptic drugs) third – their condition worsened, with poor control on drugs and some of those were euthanized. There was one report on a case of hydranencephaly where a ventriculoperitoneal shunt was placed and the dog’s condition slightly improved. Therefore, this is also a therapeutic option in some of those severe cases.
- Porencephaly and cortical dysplasia as cause of seizures in a dog: Gisele Fabrino, Maria-Gisela Laranjeira, Augusto Schweigert and Guilherme Dias de Melo BMC Veterinary Research 2012
- Porencephaly and hydranencephaly in six dogs: Davies ES1, Volk HA, Behr S, Summers B, de Lahunta A, Syme H, Jull P, Garosi L. Vet Rec. 2012 Feb
- Porencephaly in dogs and cats: Magnetic resonance imaging findings and clinical signs: Schmidt MJ1, Klumpp S, Amort K, Jawinski S, Kramer M. Vet Radiol Ultrasound. 2012
- Porencephaly in dogs and cats: relationships between magnetic resonance imaging (MRI) features and hippocampal atrophy: Ai HORI, Kiwamu HANAZONO, Kenjirou MIYOSHI and Tetsuya NAKADE, J Vet Med Sci. 2015