An EEG is a recording of the brain activity. Multiple small electrodes attached to the skull pick up electrical signals that are produced by neurons in the brain. We have good success with non-invasive surface electrodes. The information is then recorded in a continuous pattern and reviewed by comparing normal and abnormal brain waves.
The EEG machine is a brand new, highly specialised electrodiagnostic piece of equipment which complements our already well quipped neurology department. The machine is capable of multiple functions, including:
- Brainstem auditory evoked response (BAER)
- Hearing test Electroretinography (ERG)
- Electromyography (EMG)
- Nerve conduction velocity (NCV) studies
- Electroencephalography (EEG)
We’re now also able to record long term EEG’s alongside our video-recording suite, which allows for real time recording. This is really important as there is a naturally a lot of signal interference with this technique so differentiating between something like an eye blink and a seizure is of great importance.
If the pet is calm, we can often do an EEG without sedation. And as mentioned previously, long-term EEG with video recording can be performed to catch seizures at night in hospitalised patients.
The Types Of Cases An EEG Machine Is Useful For
An EEG can be used on a variety of cases. Firstly, we can use it to aid in the diagnosis of epilepsy. The erroneous electrical activity can be detected and used to help to identify the location of the seizure focus. An EEG is also useful when differentiating diseases from epilepsy such as movement disorders or syncope.
It can help to identify if the seizures are controlled in a patient, even if they are currently sedated to control the seizures. In some cases the patient appears not to be seizuring anymore, but EEG can look and see if they are still happening sub clinically.
Recently we used the EEG on a seemingly well controlled, epileptic feline patient. However, the EEG revealed seizure activity was still present and as a result the anti-epileptic medication was increased.
Likewise, the EEG can therefore detect absence or vacant seizures, whereby the animal has seizure activity with no movement. It can also provide information if the patient is in between seizure episodes and detect abnormal electrical activity in the interictal period.
One of the interesting things for us neurologists is that it is helping us to challenge traditional thinking such as head bobbing in dogs. In the past it was thought that it was due to a movement disorder. However, when an EEG was done on a group of these dogs, electrical activity was found in the brain, which suggests it was a form of seizure. So now the question is… Is head bobbing a movement disorder or a seizure or both!
We are also able to assess presence of brain activity and look at the brain waves in patients that are compromised, such as head trauma patients. Consequently, severely ill patients can be checked to see if they are brain-dead. This can help with the decision process for turning off life support, which can benefit the patient, their family and the vets themselves.
Services That Use The Machine
We can use the same machine for three different services due to its multi-functionality:
- Neurology/Neurosurgery
- Ophthalmology
- The Hearing Clinic
The BAER Hearing test measures the external hearing ability via the pathways within the brain stem. Typically, the hearing test is used to find congenital problems in the ear that leads to hearing loss.
We can also use this machine to perform an ERG, which is typically used in ophthalmology cases. It can differentiate between retinal and central blindness and this can be particularly useful in the diagnosis of Sudden Acquired Retinal Degeneration (SARD). If the eye and retina are normal, then the blindness is likely due to brain disease and we can follow up with a MRI scan.
The machine is also useful for looking at muscle diseases. For example, a dog presenting with weakness of unknown origin, the EMG can be used as an ancillary test and may negate the need for a MRI scan.
Another useful aspect of the machine is to perform nerve conduction velocity (NCV) tests which can be a useful diagnostic tool for conditions such as polyneuropathy or myasthenia gravis.
Having the machine enables us here at Pride Veterinary Centre to expand our services and expertise. The machine is very accurate and helps us to individualise the therapy to each patient.
Looking Forward
The EEG is still fairly new in the veterinary field. There are cases now coming out looking at different seizures and their causes. This may help us in the future to be able to identify areas for epilepsy surgery (as it can be done in humans).
We are delighted to have this equipment at the practice so we can be at the forefront of these developments.