Tuesday, December 4, 2018

Seizure detection and SUDEP prevention

The seizures that cause the majority of SUDEP cases are often unattended. Most SUDEPs occur during unsupervised times, and most commonly, the decedent is found by family or caregivers in the morning. Persons with a history of seizures during unsupervised times may also be more vulnerable; a history of nocturnal seizures increases SUDEP risk.8 Increased nighttime supervision appears to be protective; having a roommate or use of a nocturnal listening device is associated with reduced SUDEP risk. This is likely because someone may be able to provide aid and resuscitation in the vulnerable postictal period when cardiopulmonary dysfunction may be reversible.4 Even tactile stimulation and repositioning can decrease postictal respiratory dysfunction.

There has been a growing interest in seizure detection and alerting devices for use in the home to notify caregivers of a seizure and turn unwitnessed seizures into attended seizures, as a method to reduce SUDEP risk. With the help of innovations in health technology, mobile sensors, and smartphones, many devices are in development and some have been commercialized. Recently 2 such devices were approved by the FDA for use as adjuncts to seizure monitoring…

Seizure activity can be detected using extracerebral (or nonEEG) devices. Video motion detectors, accelerometers, or surface EMG (sEMG) have been employed to detect the repetitive movements and muscle activity present during GTCS (Table 1). Audio recordings may be used to detect the unique sounds of GTCS such as ictal cry. Movement detection devices are noninvasive and more widely applicable than intracerebral devices. Sensors to detect seizure-related movements include wrist-worn accelerometers, computer vision analysis of video signals, and piezo-electric mattress sensors.

The movement signals recorded are not necessarily seizure specific; however, sophisticated algorithms are necessary to distinguish seizure-related motion from other forms of repetitive movements common in daily life (eg, running, chopping vegetables, or playing video games) to reduce false-detection rates. Some movement-detection sensors are location specific (ie, bed or mattress sensors), which can alleviate concerns for nighttime seizure detection but are not applicable to all forms of unattended seizures…

Several commercially available seizure monitoring devices are available or in development (Table 2). Many have been tested against the standard vEEG in patients admitted to epilepsy-monitoring units. Most target GTCS with reported sensitivities of 53% to 100% and false-positive rates between 0.1 and 2.52 per 24 hours in the epilepsy-monitoring unit.

Devices differ in how caregivers are alerted. Some pair with an application on the patient’s smartphone to issue text alerts or voice calls to prespecified responders, and others use a paired receiver that issues an audio alarm. At this time, no device links directly to first responders or centralized call centers, which is a concern for patients who live alone or are socially isolated without nearby friends or family to provide peri-ictal assistance.

Most data regarding the accuracy of seizure detection devices come from studies in the epilepsy-monitoring unit, but that is not an accurate representation of real-world use because of patients’ limited range of activity in the unit and the presence of study staff to apply and position devices. Little data exist for ambulatory patients and there are currently no standards for assessing accuracy. A set of outcome measures and standards for reporting have been proposed, but not all prior studies meet those standards. There is also the issue of patient adherence. Even if the device is readily available and applied correctly, there is no way of ensuring it is always used.

People with epilepsy are more likely to live alone after they become independent from their parents. For these people, seizure detection does not equate to timely intervention. A recent case report highlighted this for a patient who, despite using a device that detected a convulsive seizure and issued an alert, died before his parents (the prespecified responders) arrived 15 minutes later. 

There are no studies yet that demonstrate seizure detection and alerting devices reduce SUDEP risk and, because of the relatively infrequent occurrence of SUDEP even in the highest risk populations, these studies may be difficult to perform. Seizure detection may fail to prevent all SUDEP because although the majority of witnessed SUDEP occurred following GTCS, approximately 10% occurred following focal unaware seizures. Concurrent vEEG monitoring and ambulatory intracranial monitoring has shown that SUDEP can occur without antecedent seizures. In these cases, devices that detect only GTCS would not prevent SUDEP. It is also possible for SUDEP to occur despite immediate peri-ictal intervention by trained personnel, suggesting that simple resuscitative efforts may not always be enough to reverse the cascade of events leading to death. 

Noninvasive devices to detect GTCS and alert caregivers are becoming readily available. Although performance of some of these devices is uncertain, especially in the outpatient setting, there is sufficient information available to help choose between available options and determine which device may work best for a particular patient. Despite the lack of direct evidence that seizure detection devices prevent SUDEP, they may be a good tool to augment nocturnal supervision as a SUDEP-prevention strategy. The use of these seizure detection devices should be put in the context of SUDEP risk, seizure types, independence, and patient and family preferences.

The intersection of technology and health is constantly evolving, and there are a few things that we can expect to see going forward. The most common methods for detection discussed in this review may eventually play more of a role in a closed-loop warning system able to provide rapid treatment or prevention of seizures.57 As this technology is improved upon, seizure forecasting/prediction devices will emerge for the purpose of treatment and not just alerting. This will give the patient and family even more confidence and peace of mind, improving the quality of life of all parties involved. Although many patients can achieve seizure freedom, the population of people refractory to treatment remains and they are entitled to the same quality of life as their healthy counterparts.


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