17 Jan
Epilepsy is a common complex brain disease and refers to patients that have at least two or more seizures unprovoked 24 hours apart1.
Epileptic seizures can be broadly classified into two categories: generalised seizures and focal seizures. The differentiation of the two and further classification can be challenging.
This article aims to discuss new methods to detect seizures and manage epilepsy.
Epilepsy in canine and feline patients has conventionally been monitored using a home paper diary to log seizure activity, duration and timing of anti-epileptic drug medication. Many of these have been provided by anti-epileptic drug companies for owners’ use.
Veterinary surgeons and owners have used this method to evaluate the frequency and severity of their pet’s epilepsy, and change anti-epileptic medication as required. For full reliability, this type of monitoring requires owners to be present 24 hours a day with their pet due to the unpredictability of seizures.
This has the potential to have a detrimental impact on the quality of life of the patient with epilepsy if seizures are missed, as well as the owners’2.
A questionnaire-based study looked at quality of life aspects in dogs with idiopathic epilepsy; this showed a significant association with seizure frequency with carer-perceived dog’s quality of life. Higher seizure frequencies were associated with decreased carer-perceived dog’s quality of life3.
With ongoing advances in technology, more efficient and advanced technology has been developed to help monitor epilepsy in human patients – and emerging, veterinary patients – at all times of day and night without carers having to be present. These seizure detection monitors allow a more objective assessment of seizure frequency and treatment tailored to the individual patient4.
The Epilepsy Foundation found in its 2016 survey that unpredictability was selected as a top issue regardless of seizure frequency or severity in people with epilepsy.
In response to this, the Epilepsy Innovation Institute launched the My Seizure Gauge challenge in the hope of creating a personalised seizure advisory system device, to monitor the likelihood of a seizure on a daily basis to increase quality of life – again, highlighting the importance of seizure detection using non-invasive measures5.
A variety of technologies have been developed to detect seizure activity in people with epilepsy, with some recently adapted for the veterinary market, which will now be discussed.
A number of apps for smartphones and tablet devices have been developed for people with epilepsy and their carers, and since 2015, have been available for owners of pets with epilepsy.
Seizure diaries have become more beneficial to owners and their vets by becoming electronic.
The RVC Pet Epilepsy Tracker allows owners to track seizure activity and medication requirements on their mobile phone and tablet devices (Figure 1). The app additionally benefits veterinary surgeons, as owners can convert their dog’s up-to-date medical history, seizure diary and medication diary into a PDF, and send it directly to their vet prior to a consultation.
The option also exists for recording detailed information of an episode, including what happened during and after the seizure, how long it lasted and how severe the owner rated it to be.
An upgrade to the app allowed owners to view their pet’s frequency of seizures graphically. Additionally, owners could use the app to monitor their dog’s weight, as weight gain is a side effect of several epilepsy drugs.
As well as recording their dog’s weight, owners can also log their dog’s blood tests to monitor liver function, for example, another potential side effect of several epilepsy drugs.
Furthermore, a clinical trials tab has been created to feature up-to-date news and allow owners to sign up for potential new studies with their epileptic dogs. This will aid vets in better understanding their patients’ condition and whether treatment is effective.
The app is also set to revolutionise the understanding of how epilepsy progresses in individual dogs, and patterns of seizure activity, as owners can share their seizure and medication diaries directly with researchers at the RVC, to be stored on an anonymous database.
This will allow long-term studies of seizure activity that researchers have previously been unable to obtain data for a large number of dogs.
New collar devices for pets have been formulated to measure heart rate, respiratory rate, motion/gait and temperature (Figure 2).
At the time of writing, no published peer-reviewed papers exist on the efficacy of collar devices for the detection of seizures in animals with epilepsy. Consequently, the sensitivity and specificity of these products for seizure detection is unknown.
Some of these products may contain accelerometers, which are currently being used in human wrist and ankle devices to monitor seizure activity (Figure 3).
Accelerometry detects changes in velocity and direction6-8. These devices have been used to objectively measure gait in dogs using a collar/harness accelerometer and have shown promising results for research practice, as well as clinical9.
A study looking at gait showed no significant difference between two different sensor devices: one validated for use on a collar and the other providing un-filtered accelerometry data.
They also were shown to have low inter-site variability between placement on the ventral collar and dorsal harness locations10.
In addition, accelerometers are being used on sheep to detect lameness, in a study undertaken by the University of Nottingham, which could massively improve herd health and welfare11.
Some disadvantages of using accelerometry that have been highlighted in people is that it is mainly restricted to those patients with a motor component to their seizures, and free limb movement must be present8.
A variety of products have been developed using video detection systems for pets that can detect the motion of seizures and inform the owner via an alarm system linked to the owner’s mobile phone if a seizure is detected. This video software can be used to watch their pet when not in the household.
The video footage may be useful for veterinary surgeons to determine whether they think a seizure occurred and trying to localise the area of seizure activity.
Yet, an average agreement between veterinary surgeons as to whether a seizure occurred via observing videos has been shown to be only 29%, suggesting this may be an unreliable way to diagnose occurrence of a seizure12.
Further limitation to the video detection system is that the animal must be present in that area of the house to enable it to detect seizure motion activity. Some of these monitors commercially available also require use of markers to be placed on the animal, which could move from their intended position or cause discomfort.
However, the sensitivity of video monitoring systems has been shown to be between 75% to 100% when used for human epilepsy13. Such data is not yet available for canine epilepsy patients.
Mattress sensors have been created for use in human epilepsy for monitoring nocturnal seizure activity.
These devices consist of a sensor placed under the patient’s mattress and are connected to a monitor. They detect movement and can alert a family member, nurse or carer via phone, particularly during nocturnal hours if seizure activity is detected.
These sensors could have the potential to be used in dogs to monitor nocturnal seizure activity. However, it would require the animal to sleep in the same place to be directly over the sensor, the animal would need to be over a certain weight for the product to detect movement and it would only allow for those patients with generalised seizures associated with sufficient motor activity14, 15. One of the mattress alarms available primarily detects abnormal bed motion in patients weighing more than 6.4kg14. This, therefore, is not able to be used in some smaller breeds of dog, and would need to be scientifically tested to ensure it is also reliable in detecting nocturnal seizures in companion animals.
Some mattress sensors also have additional features such as a microphone to detect seizure-associated sounds, heart rate and breathing monitors.
The Epilepsy Research UK seizure alarm report in 201516 found that people with epilepsy reported a high proportion of missed seizures with mattress devices in addition to a high number of false alarms.
Users were additionally disappointed with the cost of the sensor and the frequency new batteries needed to be added.
More investigation is required in the use of mattress sensors in the management of canine and feline epilepsy.
Seizure-alert dogs are reported to detect an impending seizure in people. It is thought they alert to subtle human behavioural changes prior to a seizure occurring17-19.
Seizure-alert dogs have been reported to detect a range of seizure types including atonic, focal and generalised seizures17, 20, 21. To date, no investigations have been undertaken with the use or efficacy of seizure-alert dogs for dogs with epilepsy.
In people with epilepsy, a study reported a sensitivity estimate of 80% and specificity of 100%18.
If dogs are also able to be trained to detect seizures in other dogs, this could be great in improving quality of life of the patient and the owners with epileptic pets.
A key disadvantage of using an assistance dog as a monitoring tool is they are unable to monitor during their own sleep and the owner may need to be present to detect the change in clinical signs in their non-epileptic dog.
Electroencephalography (EEG) remains the “gold standard” for diagnosis of seizures22.
EEG is widely used in human epilepsy patients, but is rarely used in veterinary patients. A recent study looked at the diagnostic utility of wireless video EEG in 81 un-sedated dogs and found EEG achieved/excluded diagnosis of epilepsy in 58 dogs (72%)23.
Where used, ambulatory EEG is often only kept in place for up to 24 hours, as it requires semi-permanent attachment to the scalp (for example, with bandaging), which can be removed by the patient. In addition, reliable and validated EEG-analysis software for longer-term recordings of veterinary patients are not yet available.
Intracranial EEG has been used in a research setting with dogs with epilepsy; however, this method is highly invasive, requiring implantation of an intracranial device, accurate localisation of the seizure-onset zone and definition of the EEG dynamics of seizure onset24.
Studies have been performed on the accuracy of seizure detection in canine patients using EEG, which have proved successful. One study used a seizure alert system (SAS) to alert a veterinarian if an impending seizure was going to occur and, on each occasion, the SAS successfully alerted and emergency medication was administered25.
Currently, EEG is largely being used in a research setting in veterinary patients due to its cost and limited expertise in the profession. A few groups are using EEG clinically as a diagnostic method to detect seizures – particularly in Europe, Japan and the US; however, it is not being used as a standard diagnostic tool yet in most practices, but is likely to in the near future.
It is likely that with more widespread expertise, reduced costs of recording equipment and advances in EEG detection software, this technology will become more widespread within veterinary neurology.
Diagnosis of idiopathic epilepsy is described in a three-tier system (Table 1), with tier three giving the most confidence that idiopathic epilepsy is the diagnosis. Tier three involves both factors listed in tier one and tier two, as well as EEG abnormalities characteristic for a seizure disorder26.
| Table 1. Criteria for the diagnosis of idiopathic epilepsy in a three-tier system as outlined by the International Veterinary Epilepsy Task Force26 | |
|---|---|
| Tier | Criteria |
| I | • History of two or more unprovoked epileptic seizures occurring at least 24 hours apart. • Age at epileptic seizure onset between six months and six years old. • Unremarkable inter-ictal physical examination and neurological examination. • And no significant abnormalities on minimum database blood tests and urinalysis. |
| II | • All factors listed in tier I. • Unremarkable fasting and post-prandial bile acids. • MRI. • And CSF analysis. |
| III | • All factors listed in tier I. • All factors listed in tier II. • And electroencephalographic abnormalities characteristic for seizure disorders. |
A variety of other detection devices are available for human epilepsy patients, and include surface electromyography (analysis of muscle activity)27, electrodermal activity (reflects the sympathetic branch of the autonomic system using sweat)28, cerebral oxygen saturation sensors4 and near-infrared spectroscopy (wavelengths used to measure cerebral oxygen saturation)29.
None of these products have been developed for the veterinary market, but may also prove useful in combination with the technologies described previously. Most recently, two A-level students developed a vest that is able to measure body temperature and heart rate readings to forecast a seizure in people up to eight minutes in advance30.
To summarise, a variety of products are becoming available for owners to buy for the management of their dog’s epilepsy; however, each one has its own advantages and disadvantages, and none have peer-reviewed evidence documenting their reliability in this role as yet. At the time of writing, no standardised equipment exists that owners can commercially purchase and is non-invasive, low-cost and has high specificity and sensitivity for detection of seizures.
More research is needed to develop such products and bring epilepsy management of our canine patients into the 21st century, improving the quality of life for the patient and their owners.
Much inspiration can be sought from human neurology, with many promising devices available that may be adaptable to veterinary patients.
