GB2591581A

GB2591581A - Seizure logging

Info

Publication number: GB2591581A
Application number: GB2018664.9A
Authority: GB
Inventors: Mijovic Bogdan; Gligorijevic Ivan; Ristic Aleksandar
Original assignee: Mbrain Train LLC
Current assignee: Mbrain Train LLC
Priority date: 2019-11-29
Filing date: 2020-11-26
Publication date: 2021-08-04
Anticipated expiration: 2040-11-26
Also published as: GB2591581B; GB201917526D0; GB202018664D0

Abstract

A method of seizure logging comprising continuously detecting 35 electroencephalogram (EEG) waveforms of a patient using a portable EEG recording device. Video data is periodically recorded 37 using a camera and the recorded video and EEG data is synchronised 39 and logged 41 as a seizure event. Another aspect relates to seizure logging software which when run on a processor cause the processor to perform said method. Another aspect relates to a portable system including a mobile unit, a camera, and a portable EEG device comprising one or more electrodes and which streams data from the EEG waveforms to the mobile unit. The mobile unit synchronises the video and EEG data and logs it as a seizure event. The camera may initiate and terminate recording in response to a command from a patient, caregiver or the mobile unit. On detection of an EEG waveform event, the recording device may provide an indication that video recording should be initiated.

Description

SEIZURE LOGGING

Technical Field

The present invention relates to the recording of electroencephalography (EEG) signals, and particularly, but not exclusively, to portable systems and methods for recording EEG signals associated with one or more seizures of a patient.

Background

Epilepsy is a group of neurological disorders characterized by recurrent epileptic seizures. Seizures are bursts of electrical activity in the brain that temporarily affect how it works. Seizures can cause a wide range of symptoms depending on which part of the brain is affected.

Epilepsy is very difficult to diagnose, and many patients take up to several years to get to the correct diagnosis. Once diagnosed, in many cases seizures are controllable with medication or lifestyle changes. However, it is important for a physician to be able to monitor how a patient responds to a medication scheme in order to assess its effectiveness. Finding an appropriate medication scheme can be as difficult as making the initial diagnosis in some cases Electroencephalography (EEG) is an electrophysiological monitoring method that may be used to record electrical activity of the brain in the form of EEG waveforms. It is typically non-invasive, with electrodes being placed along the scalp in order to measure voltage fluctuations resulting from ionic current within the neurons of the brain.

EEG is often used to diagnose epilepsy, as the abnormal electrical activity that results in an epileptic seizure can be detected using EEG. Normal brain activity typically generates one of a number of well-known, recognisable EEG waveform patterns.

During a seizure a patient's EEG waveforms typically transition into epileptiform activity, which can be distinguished from regular EEG waveforms, for instance by visual inspection of the EEG output by a trained clinician or by analysis of the EEG output using an epileptiforrn detection algorithm. The EEG waveforms associated with both normal brain activity and epileptiform activity are well-documented and so will not be described further herein.

The gold standard for epilepsy diagnosis is EEG-Video monitoring. During such a monitoring procedure, a patient's EEG signals are recorded for a prolonged period, accompanied by continuous video observation. The digitized EEG signals and recorded behaviour are displayed simultaneously to a physician, allowing the physician to draw correlations between recorded events, such as patient seizures, and any accompanying electrographic changes.

EEG-Video monitoring is usually done in a dedicated hospital room, in which a patient may be held for up to seven days and constantly screened. Theoretically the patient can carry out normal activities during this time, although in reality this can be difficult given that the patient is away from his or her usual environment. Diagnosis using such a system can thus be inconvenient for the patient, especially if multiple screenings are needed. Furthermore, &though such systems can be effective at providing a successful initial diagnosis, such systems are not well-suited to ongoing day-to-day monitoring of the effectiveness of a patient's medication regime.

To combat the above difficulties sonic home EEG-monitoring systems are emerging, in which a camera is stationary and records for days, trying to capture seizure activity.

However, these systems are still rare (mostly because they are expensive). Furthermore, such systems still do not allow a patient to go about his or her normal life during the monitoring, as the patient must remain confined to the room of his or her home containing the recording equipment.

Because of the inconveniences associated with the systems described above, the most common method for epilepsy diagnosis is still that patients (or their caregivers) keep logs, in which they try to provide accurate description of any seizure-type event. These logs are very subjective however, and often contain misdescribed events. They arc therefore rarely of great value to neurologists.

An improved system and method for seizure monitoring is needed.

Summary of the invention

According to a first aspect of the invention we provide a portable system for logging seizures, the system comprising: a mobile unit; a portable EEG recording device comprising one or more EEG electrodes operable to continuously detect EEG waveforms from a patient and to stream data associated with the EEG waveforms to the mobile unit; and a camera operable to periodically record video data of the patient and stream the video data to the mobile unit, wherein the mobile unit is operable to: (a) receive the video data from the camera; (b) receive the data associated with the EEG waveforms from the portable EEG recording device; (c) synchronise the received video data with the received data associated with the EEG waveforms; (d) log the synchronised data as a potential seizure event.

Known EEG-Video monitoring systems create a continuous video recording and a continuous EEG recording. A user of the system (such as a physician) must scan through the video recording in order to identify events of interests (such as possible seizures). This manual partitioning of data is extremely lime consuming and can result in seizure events being missed (e.g. where a seizure has only moderate physical effects that re difficult to observe visually).

In contrast, a system of the type described in the first aspect of the invention does not record video data continuously. Rather, it records video data periodically. The system is therefore operable to produce one or more discrete seizure event logs, each log comprising EEG data relating to a potential seizure event that is synchronised with video data showing that same potential seizure event. A physician using the system thus has no need to comb through many hours of video footage in order to locate potential seizure events. Rather, irrelevant video data (i.e. data not related to a potential seizure event) is not recorded. The present system thus provides a tool for selectively recording video data by partitioning the recording of that data. a clinician can then subsequently review the logs of potential seizure events to arrive at a diagnosis in a much shorter time that when using a standard EEG-Video recording system.

The camera may be operable to initiate the recording of the video data in response to a command from the patient, a patient caregiver, or the mobile unit. For instance, the patient may become aware that a seizure event is beginning or is about to begin, and may instruct the camera to begin the recording. Similarly, a patient's caregiver may become aware that a seizure event is beginning or is about to begin, and may instruct the camera to begin the recording. Alternatively, the mobile unit may use the recorded EEG data to infer that a seizure event may be occurring or may be about to occur, and may instruct the camera to begin the recording.

The camera may be operable to terminate recording the video data in response to a command from one or more of the patient, a patient caregiver, and the mobile unit. In a similar manner to the above, the patient or a patient care giver may determine that a seizure event has ended, and may instruct the camera to terminate the recording. Alternatively, the mobile unit may use the recorded EEG data to infer that a seizure event may have finished occurring, and may instruct the camera to terminate the recording.

The portable EEG recording device may be operable to provide an indication that a recording of video data should be initiated on detection of potential epileptiform activity. The potential epileptifonn activity may be a defined initiation event (e.g. EEG signal amplitude rises above a defined threshold value; the energy of the EEG signal (measured by the energy operator or otherwise) rises above a threshold value; the detection of specific epileptiform signal patterns (such as one or more sharp waves, spike waves, sharp / spike and slow wave complexes or highly oscillatory signals); detection of enhanced EMG activity; EEG signal amplitude rises more than a defined amount above an average maximum signal amplitude).

The portable EEG recording device may be operable to provide an indication that a recording of video data should be terminated on detection of cessation of the potential epileptiform activity. The cessation of the potential epileptiform activity may be a defined termination event (e.g. EEG signal amplitude falls below a defined threshold value; EEG waveform has a recognisable normal pattern).

The indication that the video recording should be initiated / terminated may comprise a visible indication and/or an audible indication. This may permit a user of the system (e.g. the patient or a caregiver) to instruct the camera to initiate / terminate the video recording. Alternatively or additionally the indication may comprise an initiation signal to the mobile unit. In response to such an initiation signal the mobile unit may be operable to instruct the camera to initiate / terminate the video recording.

The mobile unit and/or the portable EEG recording device may comprise a motion sensor, such as a gyroscope. The mobile unit / portable EEG device may be operable to provide an indication that a recording of video data should be initiated in response to a signal from the motion sensor. For example, the mobile unit may be operable to initiate the video recording (and/or instruct an operator to begin the video recording) in response to detection of a potential physical seizure symptom by the motion sensor (e.g. detection of a movement pattern indicative of muscles spasms). On detection of the cessation of the potential physical seizure symptom the video recording may be terminated.

The system may be operable to log a plurality of discrete potential seizure events.

Each seizure event log may comprise EEG data relating to a potential seizure event that is synchronised with video data showing that same potential seizure event.

The data associated with the recorded EEG waveforms that is transmitted by the portable EEG recording device to the mobile unit may comprise detected EEG waveform data (which may include detected potential cpileptiform activity) and timing data indicating a time elapsed since the continuous detection of the EEG waveform data began.

Alternatively, the portable EEG recording system may be operable to store recorded EEG waveform data (which may include detected potential epileptiform activity) in a memory, and the transmitted data associated with the EEG waveforms may comprise timing data indicating a time elapsed since the continuous detection and recording of the EEG waveform data began.

The mobile unit may be operable to synchronise the received video data with the received data associated with the EEG waveforms by: transmitting a time check signal to the portable EEG device at a first time; receiving a response signal from the portable EEG device at a second time measuring the latency between the first time and the second time; and determining that a transmission delay between the mobile unit and the portable EEG device is one half of the measured latency.

The step of synchronisation may be repeated periodically.

Alternatively, the mobile unit may be operable to estimate a difference in clock frequency between a clock of the portable EEG device and a clock of the mobile unit.

The mobile unit may be a mobile phone, and the camera may be a camera integrated into the mobile phone.

According to a second aspect of the invention we provide seizure logging software encoded on a computer readable medium, the software operable, when run on a processor of a mobile unit, to: (a) periodically receive video data of a patient from a camera (b) continuously receive data associated with EEG waveforms of the patient from a portable EEG recording device; (c) synchronise the received video data with the received data associated with the EEG waveforms; and (d) log the synchronised data as a seizure event.

According to a third aspect of the invention we provide a method of seizure logging, the method comprising: (a) continuously detecting EEG waveforms of a patient using a portable EEG recording device; (b) periodically recording video data of the patient using a camera; (c) synchronising the recorded video data with data associated with the EEG waveforms; and (d) logging the synchronised data as a seizure event.

Any of the features of the statements above may be used in combination with the first, second or third aspects of the invention. The skilled person will appreciate that, except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and/or combined with any other feature or parameter described herein.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which: Figure 1 schematically illustrates a seizure logging system; Figure 2 schematically illustrates an alternative seizure logging system Figure 3 illustrates an EEG waveform including a plurality of EEG waveform events; Figure 4 illustrates a plurality of seizure event logs corresponding to the waveform events shown in Figure 3; Figure 5 schematically illustrates a plurality of seizure event logs stored in memory; Figure 6 schematically illustrates an alternative seizure logging system; and Figure 7 illustrates a method of seizure logging.

Detailed description

Figure 1 shows a first seizure logging system 1 The system 1 includes a mobile unit 3, a portable EEG recording device 5, and a camera 7. Figure 2 shows a second seizure logging system 11. The system 11 also includes a mobile unit 3, a portable EEG recording device 5, and a camera 7, which in this case is housed within the mobile unit 5.

The portable EEG recording device 5 of the first system 1 is schematically shown being worn by a patient 9. For the patient's comfort the EEG recording device 5 is, in this example, housed within a pair of headphones 13 having a band shaped to extend around a patient's head and one or more car cups 17 shaped to cooperate with the patient's car(s).

The portable EEG recording device 5 includes one or more EEG electrodes 19. These are best shown in Figure 2, which shows the portable EEG recording device 5 when it is not being worn by a patient. The electrodes are operable to continuously detect EEG waveforms from a patient, and in particular from the brain of a patient.

A simplified example of an EEG waveform 21 as detected by an EEG electrode is shown in Figure 3. The EEG waveform 21 includes regions of epileptiform activity 20a. Epileptiforms in a recorded EEG waveform suggest that the patient may have been experiencing a seizure at the time the epileptiform activity was recorded (although this is not always the case). The regions of epileptiform activity 20a occur between regions of normal brain activity 20b. A seizure is extremely unlikely to occur when such normal brain activity is recorded It will be appreciated that each electrode 19 will detect a separate (different) EEG waveform depending on its placement with respect to the brain of the patient.

Therefore the EEG recording device 5 may be operable to continuously detect a plurality of EEG waveforms simultaneously. The functioning of such EEG electrodes is known in the art, and thus will not be described in more detail herein.

As discussed in more detail below, the portable EEG recording device 5 comprises an internal processor 23 that is operable to stream data associated with the EEG waveforms to the mobile unit 3. The data may be descriptive of the EEG waveforms 21 themselves (e.g. digitised waveforms), or may be timing data associated with the EEG waveforms 21 (e.g. counter data from an internal clock of the EEG device). The waveforms (together with associated counter data) may alternatively or additionally be recorded in a memory 25 of the portable EEG recording device 5 (see Figure 2). Although the EEG waveforms arc continually detected, and data associated with the EEG waveforms is continually streamed, the EEG waveforms need not be stored continually by the system.

The camera 7 is operable to periodically record video data 27 of the patient. The camera 7 is configured to stream the video data to the mobile unit 3. When the camera is a separate component from the mobile imit the video data may be streamed wirelessly from a transmitter in the camera to a receiver in the mobile unit.

Alternatively, when the camera is comprised within the mobile unit the data may be "streamed" via a wired connection within the mobile unit. The video data may be one or more video files including a video recording of the patient, or may be timing data associated with the video recording. The video recording may alternatively or additionally be recorded in a memory 29 (see Figure 1) of the camera 7.

The mobile unit 3 is operable to receive the video data 27 from the camera and receive the data associated with the EEG waveforms 21 from the portable EEG recording device. The mobile unit is further operable to synchronise the received video data with the received data associated with the EEG waveforms, and to log the synchronised data as a seizure event. The mobile unit shown in Figures 1 and 2 includes a processor 22 having loaded thereon software (such as an app) operable to receive and process data, and a memory 24 in which data, such as received data, may be stored.

As discussed briefly above, it is known to record both video and EEG data of a patient over an extended time period during which one or more seizures occur. Such known systems generate many hours of recorded data, through which a clinician must sort to find data useful for diagnosis. We have found that clinicians do not actually need all of this data in order to be able to diagnose and classify a seizure. In most cases, a portion of this data is sufficient; in particular, any epoch of a synchronously recorded Video-EEG seizure recording may be sufficient to allow a clinician to provide a diagnosis.

The systems shown in Figures I and 2 provide an alternative to known Video-EEG recording systems, in which video data is not continuously recorded; rather, video data is recorded periodically. The systems 1, 11 use a portable EEG recording device 5 in combination with a mobile unit 3, which could be a mobile phone belonging to a patient (or the patient's caregiver). Software, for example in the form of an application running on the mobile unit 3, receives EEG data continuously from the portable EEG recording device 5. When a seizure occurs, or is about to occur (e.g. when the patient has an aura, or when seizure symptoms begin) then a video recording may be initiated using the camera 7. The recorded video is synchronised with the received EEG data by the software of the mobile unit 3 and the two synchronised data sels are stored as a seizure event log 31.

With such a system only data relevant to a seizure need be stored. Although all EEG data may be stored if required, this is not necessary. EEG data that is not synchronised with corresponding video data (i.e. EEG waveforms that did not occur during a video recording) may be discarded. Video data that is not relevant to a potential seizure event is simply never recorded.

A patient using such a system can go about his or her normal daily life while the system is in operation Whenever a seizure-type event occurs video footage may be recorded, and a corresponding potential seizure event log created (including synchronised EEG data). The system thus permits multiple separate logs to be created, each of a discrete potential seizure event, over an extended period without excessively disrupting the patient's daily life. These logs can then be presented to the patient's clinician for review in the form of a segmented data series, as opposed to one extended data sequence, dramatically reducing the time needed to review the data, and diagnose the patient.

Figure 4 shows an example of two logged se zure events 31. A first seizure event log 31a comprises video data 27a relating to a video recording of the patient made using the camera 7. The first seizure event log 3 la also comprises EEG data 21a relating to one or more EEG recordings of the patient's EEG waveforms at the time the video recording of the patient was made. The recorded EEG waveforms include recorded epileptiform activity 20a (as shown in Figure 3). The EEG data 21a relating to the recorded EEG waveforms is, in the example shown, a digitised version of the recorded epileptiform activity 20a.

In the example shown, the first seizure event log 31a includes video data 27a in the form of a video file starting at a first time t1 and ending at a second time t2, later than ti. In addition to the video data 27a, the first seizure event log also includes EEG data 21a having the same starting and end times as the video file (i.e. EEG data starting at the first time ti and ending at the second time t4, later than ti).

Similarly, a second seizure event log 31b comprises second video data 27b relating to a second video recording of the patient made using the camera 7. The second seizure event log 31b also comprises second EEG data 21b relating to one or more EEG recordings of the patient's EEG waveforms at the time the second video recording of the patient was made. The second EEG data 2 lb is synchronised with the second video data 27b, such that both data sets start at a first time t3 and end at a second time t4, later than t3.

Figure 5 shows an example of a plurality of discrete seizure event logs 31 stored within a memory 35, such as the memory 24 of the mobile device 3 shown in Figure 1 or Figure 2. It will be appreciated that the EEG data 21a, 2 lb, need not have the same respective start and end times as the video data 27a, 27b in order to be synchronised.

Rather, what is needed for synchronisation is knowledge of which instance (e.g. frame) of video data relates to which instance (e.g. signal sample) of an associated EEG waveform. The two data sets (video and EEG) are preferably synchronised to better than 20ms disparity at any given point in time, for example a frame of video should be synchronised to within 20ms of a corresponding EEG waveform sample, and preferably to within 5ms, or 1ms.

Correct synchronisation of the two data sets is not a simple matter. Each device (EEG detector, mobile unit and camera, if separate) comprises a separate internal processor having a separate internal clock. Under normal circumstances these clocks will not be synchronised with one another. This means that a recording made on one device (e.g. the video recording made by the camera) cannot be synchronised with a recording made on another device (e.g. the portable EEG recording device) simply by comparing the times at which the two recordings were made. Even if the internal clocks of both devices were at one time synchronised, over time the clocks of those two devices will drift apart, such that two files having the same timestamp but made on different devices cannot be guaranteed to have been made at the same time. This is particularly problematic for EEG recordings, as EEG waveforms typically have a high frequency, meaning that even small deviations between the clocks can result in significant potential for error.

In an exemplary synchronisation scheme, when it is desired to initiate synchronisation (e.g. on initiation of the monitoring period, or on initiation of a video recording) a first signal >TIMECHECK< is transmitted from the mobile unit 3 to the portable EEG recording device 5 at a first time Ti. On receipt of the >TIMECHECK< signal the portable EEG recording device immediately responds with a second signal >OK<. A latency between the first time TI (of transmission of >TIMECHECK< from the mobile unit) and a second time T2 of receipt of >OK< at the mobile unit is measured. The time needed to go from the mobile unit to the EEG recording device is assumed to be the same as the time back. The time at which the EEG recording device received the >TIMECHECK< signal is thus assumed to be the time at which the >TIMECHECK< was transmitted plus half of the latency, i.e. Ti + (T2-T1)/2.

Once the >TIMECHECK< signal is received, the portable EEG device starts streaming and EEG data. The time T3 at which the streaming began (according to the clock of the EEG device) can thus be assumed to be the same as the time Ti + (T2-T1)/2 (according to the clock of the mobile unit) at which the >TIMECHECK< signal is thought to have been received. This assumption can be used to synchronise the two data sets. l0

As noted above however, the clocks of the two devices work at slightly different frequencies, so that the data streams misalign over time. In order to combat this, as the data is continuously streamed, the mobile unit may perform a linear regression of the time stamps of the samples, assuming that they arrive linearly. Based on this regression, the difference between the frequencies of the two clocks is estimated.

This frequency difference can be used to ensure the two data streams remain synchronised. The frequency difference may be estimated using the equation v=xp+s, where you try to estimate 13. Y are the timestamps when the data samples are received on the receiving device (e.g. mobile unit). X are the sample numbers as recorded on the EEG device. 13 is 1/f, where f is the frequency of the transmitting device observed on the receiving device.

If required, the time difference between the clocks of the two devices can be checked occasionally by sending the >TTMECHECK< and >OK< signals repeatedly.

The above synchronisation schemes are useful because, if required, it is possible to continuously stream only the counter of the sampled data, rather than the detected EEG waveforms themselves. Using this method the EEG waveforms do not have to be sent to the mobile unit at all but can be stored in the internal memory of the EEG device. In this way, as the waveforms are not sent, the connection is not overloaded, so the EEG timing data arrives more regularly, and the frequency estimation works better.

In some cases EEG waveform data may be stored continuously in the EEG device, or may be stored for a period of time (e.g. 10 minutes, or 5 minutes, or 1 minute) before being overwritten, in such an arrangement the two devices can be "synced backwards-after a seizure occurs. In particular, once the seizure occurs, a >TIMECHECK< signal can be sent to synchronise the clocks at a time T4 after the seizure starts. The starting time of the EEG data relevant to the seizure according the clock of the EEG device can then be estimated backwards from the >TIMECHECK< signal using the (known) starting time of the video recording. Using such a synchronisation scheme the devices do not have to be continuously connected.

The systems described herein are operable to record synchronised EEG and video data for a (potentially) indefinite period of time, because only video data that is potentially relevant to a seizure event is recorded (EEG data corresponding to the time periods between video recordings may be retained if required, or discarded). There is a simple practical benefit to the present system: if you continuously record EEG-Video data for an extended period, such as 7 days, as with known systems, it can be exhaustive to go through all of that data and locate the seizures. On the other hand, if, as with the present system, only data relevant (or potentially relevant) to epileptic event are presented to a clinician, the time that clinician needs to devote to determining a diagnosis is drastically shortened.

The current state-of-the-art is that the doctors screen through all of the recorded EEG data to try to locate the seizure and then do a deeper analysis on the extracted events.

The present system removes the need to screen the recorded data, because that data is automatically already segmented by partitioning it into potentially relevant events.

The video recordings may be started by the patient or a caregiver at will, perhaps in response to an indication from the patient that a seizure is about to begin, or in response to an aura of the patient.

Alternatively (or additionally) the system can have an epileptiform detection algorithm and can alert the caregiver to start the video recording based on detection of a potential seizure event in the monitored EEG waveforms. The alert may be in the form of an alarm, which could be visible or audible or both, in some alternatives the system may be configured to automatically start the video recording based on detection of a potential seizure event in the monitored EEG waveforms. In such a case the patient or caregiver may be alerted to point the camera towards the patient such that useful video footage can be obtained. A similar alert may be provided when the system requires the patient/caregiver to terminate the recording. Alternatively, the recording may be terminated automatically.

The system may also make use of a motion sensor, either in the EEG device or in the mobile unit, to determine whether the patient is making abnormal movements, such as spasms or sudden motions indicative of falling. A detection of such an abnormal movement may be used to trigger initiation of a video recording The portable EEG device may communicate with the mobile unit via any suitable wireless communication protocol, such as Bluetooth, wifi or mobile data.

If required, the seizure event logs may be automatically transmitted to a computer 33 accessible by the clinician, as shown in the system I I I of Figure 6. it is not needed that the seizure event logs are stored on the mobile unit in such a system -instead the EEG data could be sent directly to the clinician's computer (or to an associated server) Figure 7 schematically illustrates a method of seizure logging that can be implemented using the systems of Figures 1, 2 and 6. In step 35, EEG waveforms of a patient are continuously detected using a portable EEG recording device, in step 37, video data of the patient is periodically recorded using a camera. The recorded video data is synchronised with data associated with the EEG waveforms in step 39 Finally, the synchronised data is logged as a seizure event in step 41.

The skilled person will appreciate that the invention is not limited to the specific systems and methods described herein; rather, the scope of the invention is defined by the appended claims.

Claims

CLAIMSA portable system for logging seizures, the system comprising: a mobile unit; a portable EEG recording device comprising one or more EEG electrodes operable to continuously detect EEG waveforms from a patient and to stream data associated with the EEG waveforms to the mobile unit; and a camera operable to periodically record video data of the patient and stream the video data to the mobile unit, wherein the mobile unit is operable to (a) receive the video data from the camera; (b) receive the data associated with the EEG waveforms from the portable EEG recording device; (c) synchronise the received video data with the received data associated with the EEG waveforms; (d) log the synchronised data as a seizure event.
2. The portable system for logging seizures of claim 1, wherein the camera is operable to initiate recording the video data in response to a command from one or more of: (i) the patient, (ii) a patient caregiver. and (iii) the mobile unit.
3. The portable system for logging seizures of claim 1 or claim 2, wherein the camera is operable to terminate recording the video data in response to a command from one or more of: (i) the patient, (ii) a patient caregiver, and (iii) the mobile unit.
4. The portable system for logging seizures of any preceding claim, wherein, on detection of an EEG waveform event, the portable EEG recording device is operable to provide an indication that a recording of video data should be initiated.
The portable system for logging seizures of claim 4, wherein the indication comprises one or more of: a visible indication, an audible indication and an initiation signal to the mobile unit.
6. The portable system for logging seizures of any preceding claim, wherein the system is operable to log a plurality of discrete seizure events.
7. The portable system for logging seizures of any preceding claim, wherein the transmitted data associated with the EEG waveforms comprises detected EEG waveform data and timing data indicating a time elapsed since the continuous detection of the EEG waveform data began.
S. The portable system for logging seizures of any one of claims 1 to 7, wherein the portable EEG recording system is operable to store recorded EEG waveform data in a memory, and wherein the transmitted data associated with the EEG waveforms comprises timing data indicating a time elapsed since the continuous detection and recording of the EEG waveform data began.
9. The portable system for logging seizures of any preceding claim, wherein the mobile unit is operable to synchronise the received video data with the received data associated with the EEG waveforms by: transmitting a time check signal to the portable EEG device at a first time; receiving a response signal from the portable EEG device at a second time; measuring the latency between the first time and the second time; and determining that a transmission delay between the mobile unit and the portable EEG device is one half of the measured latency.
10. The portable system for logging seizures of claim 9, wherein the step of synchronisation is repeated periodically.
11. The portable system for logging seizures of claim 9, wherein the mobile unit is operable to estimate a difference in clock frequency between a clock of the portable EEG device and a clock of the mobile unit.
12. The portable system for logging seizures of any preceding claim, wherein the mobile unit is a mobile phone, and the camera is a camera integrated into the mobile phone.
13. Seizure logging software encoded on a computer readable medium the software operable, when run on a processor of a mobile unit, to: (a) periodically receive video data of a patient from a camera, (b) continuously receive data associated with EEG waveforms of the patient from a portable EEG recording device; I 0 (c) synchronise the received video data with the received data associated with the EEG waveforms; and (d) log the synchronised data as a seizure event.
14. A method of seizure logging, the method comprising: (a) continuously detecting EEG waveforms of a patient using a portable EEG recording device; (b) periodically recording video data of the patient using a camera; (c) synchronising the recorded video data with data associated with the EEG waveforms; and (d) logging the synchronised data as a seizure event.