Case presentation:A four month old male German Shepherd puppy presented with a history of frequent generalised seizures for about 3 weeks, with some odd episodes of standing still and crouching, and some salivation. Neurological examination was unremarkable.
Question. What is your neurolocalistion?Question. What are your most likely differentials?
For investigations, imaging, and the answer to these questions, please scroll down the page.
InvestigationsRoutine haematology and biochemistry, faecal examination by Baermann's technique for lungworm, dynamic bile acids and serology for Toxoplasma/Neospora were all normal.
ImagingMRI showed a severe left sided brain malformation with the caudal left hemisphere replaced by CSF. See figs 1 and 2 below.
Fig 1. (above) T1 weighted parasagittal MRI of the brain, showing CSF in the region where the caudal cerebral hemisphere should be.
Fig 2. Transvese T1-weighted MRI showing CSF in place of cerebral tissue on the left.
TreatmentLevetiracetam was chosen as an initial treatment for its quick onset of activity. The prognosis was suspected to be poor.
OutcomeNo further seizure activity was observed for 7 days. The puppy was unfortunately found dead one morning, soon after this.
Post mortem examinationA small defect in the calvarium was noted, which was covered in meninges (fig 3). The gross post mortem findings were as expected from the MRIs, with the caudal third of the the left cerebral hemisphere missing, replaced with CSF (fig 4). Histology of the brain also showed evidence of acute meningitis.
Fig 3. Post mortem examination of the puppy. The scissors are pointing to a defect in the calvarium covered by meninges.
Fig 4. Post mortem examination showing the small left cerebral hemisphere (on the right of this picture)
Final diagnosisPorencephaly, with acute meningitis
DiscussionPorencephaly is a rare developmental condition in which a cavity is found in the skull in place of part of the cerebral hemispheres. In this case, the main signs were seizures, which are a common manifestation of forebrain lesions. Some behavioural abnormalities in this case could also be attributed to the forebrain disease. There is no specific treatment. Intracranial pressure is not elevated, so ventriculoperitoneal shunting is not indicated. Management of the condition is aimed at control of clinical signs. The prognosis is poor however. This case was further complicated by the surprising post-mortem discovery of acute meningitis. The cause and significance of this is not known. A CSF tap was not performed, because of initial fears regarding possible raised intracranial pressure making the procedure more dangerous. Whether treatment of the meningitis would have led to a better long term outcome in this case is debatable.
Question. What is your neurolocalistion?Answer. Seizures and behavioural changes suggest a forebrain localisation
Question. What are your most likely differentials?Answer. Major differentials in a young puppy include metabolic disease such as hepatic encephaopathy, infectious disease such as protozoal encephalitis, immune-mediated disease, and anomalous disease.
First published Thu, Mar 10 2011
I think this is an example of hydranencephalia and not porencephalia. What are the gross findings that made you suspect a porencephalia?
Have you considered the placement of a shunt? There are many board certified neurologists in this country that may place VP shunts with fairly good results. Let's see this statement: "Intracranial pressure is not elevated, so ventriculoperitoneal shunting is not indicated". How can you be sure that there was not raised ICP in this particular case? In addition: so you would place a shunt only if there is raised ICP?? It's interesting and goes against the current vet and human literature... Usually, you place a shunt to control the clinical signs associated with hydrocephalus (such as seizures...) in cases that do not respond to medical treatment.
Also you state that there is not raised ICP in cases of porencephaly but then you said that CSF tap was not performed because of possible underlying raised ICP??
Can we see the FLAIR pre- and postcontrast MR images? I am sure you have done it to try to rule out inflammatory periventricular brain disease...
(Comment first published Fri, Apr 29 2011)
Some good questions, Luca. The pathologist classified the lesion grossly as hydranencephaly/porencephaly. However, hydranencephaly is defined as complete or almost complete absence of the cerebral cortex (see for example Donaghy, Brain's Diseases of the Nervous System 12th edn 2009). You can clearly see from the gross pathology in this case as well as the MRIs that there is a substantial amount of cerebral cortex present, which fits to me more neatly with the diagnosis of porencephaly (a cyst or cavity in a cerebral hemisphere of the brain). This was also the opinion of the university neurology department that I discussed the case with. This particular department is also where I usually refer my cases for V-P shunts, and they have a good success rate, so i defer to them on decisions as to which cases to place shunts in. It was their opinion in this case that the pressure was not raised and so a shunt was unlikely to be helpful. Signs to look for on MRI that pressure is raised include coning of the cerebellum, which is absent in this case, and loss of CSF signal rostro-dorsal to the cerebellum, which in this case is harder to assess. The rare nature of the lesion did indeed make us uncertain initially as to whether there was raised intracranial pressure, and so CSF sampling was not performed immediately. As you say, FLAIR was performed to rule out inflammatory periventicular brain disease, and did not show evidence of inflammation.
(Comment first published Tue, May 3 2011)
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