Presenter: Pip Boydell CertVOphthal MRCVS, co-founder and Senior Clinician (Neurology and ophthalmology) at Animal Medical Centre Referral Services (AMCRS)
Having previously listened to webinars led by Pip Boydell, I knew I would enjoy and appreciate the straight forward no-nonsense advice delivered by Pip and last week’s webinar, did not disappoint. Pip initiated the webinar by explaining that although a number of intracranial emergencies would require some form of brain scan to make a diagnosis, in most cases a diagnosis is not necessary to treat these emergencies in first opinion practice. For example, an animal presenting with seizures is a classic intracranial emergency and the initial treatment for this patient is likely to be the same regardless of the underlying diagnosis.
Pip also stated that in his opinion, the seizuring animal is probably totally unaware of what is happening and for this reason the continual seizuring of a patient is not necessarily a welfare issue. Hence treatment should be attempted wherever possible and owners should be encouraged to allow the management of their seizuring pet rather than opting for euthanasia. Pip advised diazepam either rectally or intravenously should be the first drug of choice in the treatment of seizures, but if diazepam is not effective, the use of injectable levetiracetum which has a rapid onset of action should be considered. Propofol can also be administered as a continuous rate infusion (CRI) but Pip warned that propofol products must be checked to ensure they can be administered in this way. We were also reminded that many seizuring patients develop hyperthermia which must be addressed by using treatments such as the placement of ice packs over major arteries.
Although a diagnosis is not always necessary to provide treatment, intracranial emergencies develop as a result of an increase in intracranial pressure (ICP) and Pip advised that a simple in-practice neurological assessment can often indicate whether a patient has an elevated ICP and whether there is any brain involvement. Pupil and ocular examination is a crucial part of the work up with the optic nerve being an excellent ‘window to the brain’. For example swelling of the optic nerve could indicate swelling of the brain, and this can be observed on retinal examination where the optic nerve is seen to be in focus when the rest of the retina is out of focus. An increase in intracranial pressure can also lead to herniation of the brain either through the tentorial opening or the foremen magnum. If herniation occurs through the tentorial opening, the oculomotor nerve will become affected causing initially miosis of the pupil, and in severe cases, pupil mydriasis. If herniation occurs through the foremen magnum, signs include respiratory depression and eventually death.
Emergency treatment for an elevated ICP includes oxygen therapy which can be delivered via an oxygen cage, intranasally or ideally through ventilation. Diuretics can be administered using drugs such as mannitol and furosemide, but Pip advises that these drugs are only effective for a short period of time and repeated treatments are likely to be necessary every few hours. Other drugs such as barbiturates can be used to induce a coma which is thought to help decrease cerebral metabolism, decrease cerebral blood flow, decrease oxygen consumption and also play a role in free radical scavenging. The use of steroids in these patients is an area of controversy and although they decrease cerebral oedema they can also exacerbate ischaemic neuronal damage. In humans the use of steroids in ICU patients has shown to decrease a person’s chance of survival by 2% per day due to the development of secondary problems such as pneumonia, and because of this increased risk, Pip usually only considers the use of steroids as a last resort where all treatment and diagnostic options have been exhausted or where the owner has financial restraints.
Pip as always delivered common sense advice on the treatment of intracranial emergencies but had one final tip to offer prior to finishing this webinar. He advised that we should all be trying to differentiate between central and peripheral vestibular syndrome (sometimes wrongly called a stroke) before making a decision on the treatment options for patients presenting with classic vestibular signs. Dogs presenting with peripheral vestibular syndrome should not have proprioceptor deficits, and in Pip’s experience, do well given some time which is why it is so important to differentiate these cases. This tip is just one of several others and useful pieces of information delivered within this webinar and exactly the reason why it is worth spending an hour of your time listening to Pip.
The Stethoscope (MRCVS)