ElectricZebra

medtech in everyday life

catching a temporal lobe seizure on the Empatica E4?

I sometimes put the Empatica E4 on as I am going to bed. It is a medical-grade research device which measures BVP, skin conductance (EDA), temperature and movement (accelerometer).

This image shows the real-time output. You can see the level of detail we are talking about by looking at the time stamps.

But unless I am in a lot of pain, I fall asleep *really* fast. It is rare for me to have a seizure as I am sliding into sleep.

But this time, the seizure woke me up.

Just as I was drifting off to sleep, I woke up with that uneasy, not very nice feeling that comes before a focal seizure. The TLE seizures have a similar, deeply-famliar middle, that I can never remember once I am out if it. By the end the feeling is not pleasant. Near the end I swallow, run into a corner (???), run (or hobble) away, swallow a lot and sometimes throw up. Last week, after we watched a video (‘I don’t do that’, I said) my mum said that actually, she had seen me smack my lips a long time ago. This really surprised me. I’ve told every neurologist I have ever had that I don’t do that, I just swallow, retch and maybe throw up. Apparently I do smack my lips after all.

This time I ran into the lounge, petrified.

Here’s the ‘wide’ view of the data as stored in the cloud. (You can keep zooming in to see more detail). The seizure happened at 11.58 on the 9th of Feb 2017. I am writing this post some days later. (Click for larger image).

I’ve written about the MIT research on EDA and seizures before.  Focal seizures have smaller magnitude EDA changes than grand mal seizures [Poh 2011;p115]. You can see some EDA peaks and troughs in this data before the seizure – not terribly big in amplitude, but as I said, the MIT research says that focal seizure EDA changes are smaller. I’m not convinced my data are significant, but I decide to look deeper in at the time around the seizure. Luckily with the E4, you can magnify right down to individual beats.

So, looking in a bit closer (below), I see the BVP pulsing every 7 seconds or so in the period leading up (23.50, 23.53), to the seizure (red line pressed shortly after but before I ran into the lounge) and this BVP pulsing is accompanied by EDA changes. I dont know enough about BVP yet to say whether this just happens all the time….  I think about my hunch that the artery squeezed between my medulla oblongata and low-lying cerebellar tonsils is causing seizures (see scans and research paper below). I wonder if this pulsing BVP is related? But then again, maybe this pulsing is just a normal pattern.

The phenomenon of herniated cerebellar tonsils associated with both scoliosis and epilepsy has been described in the literature by Narasimhan et al (10.13070/rs.en.1.818) and others. In the case study described, the authors say: “It is debatable that if left untreated, the natural history of scoliosis would have inevitably lead to curve progression, disability from back pain, cardiopulmonary problems and psychosocial concerns.’

The two scans above, taken 4 years apart, [as I went from doing active voluntary work (despite being in pain) to struggling to function with completely disabling pain], appear to show the cerebellar tonsils descending lower into/through the foramen magnum. (The herniations are so thin, they don’t show up on the McRae line, but US doctors don’t use this any more anyway). The thin herniations can be seen this on the 3D image here:

2015 brain dark fluid slower

[More recently I’ve been wondering, in the case of hypermobile people with Chiari/herniated tonsils all closely packed around the medulla, what happens when a person is afraid and crouches/hunches up their shoulders into their neck (as many of us do when we are afraid)? If a hypermobile cervical spine moves so much more? Are cerebellar seizures more sensitive to loud noises or stress?]

Although the EEG report from 2011 says ‘Epilepsy proven on telemetry’ [Right at the very end!! In the postscript after the signature! No wonder I missed it for years!], the fact that my symptoms were judged to be ‘MRI negative’ has caused a lot of umming and ahhing over the years. However I dont think the radiologist looked at my MRI very carefully. Herniated tonsils are not the only sign. The hippocampus appears in just two slices (I think?) but to me, the second slice  appears to show one of the signs of mesial temporal sclerosis: a relatively hyperintense signal on one of the hippocampi in the FLAIR image (click image to make it larger):

and possible asymmetry, both of which can be indicators of MTS /temporal lobe epilepsy. (10.1007/s00234-014-1397-0)

(doi.org/10.3988/jcn.2008.4.1.1) See also International League Against Epilepsy Classification.

[See also research paper by Urbach et al (014): “Is the type and extent of mesial temporal sclerosis measureable?”]

I look back into the E4 data. I wonder if there is anything more to see in the data, where movement artefacts are at a minimum?

This snapshot of the data at the same time, taken much closer in, shows a great deal of artefact at first, but something odd happening at the time I pressed the E4 button.

I look closer in.

Um, is that my BVP amplitude dropping to zero for 2 or 3 seconds? I look closer in again.

Next stop: I’ll be reading ‘Identify Blood Volume Pulse (BVP) Artifacts Before Analyzing and Interpreting BVP, Blood Volume Pulse Amplitude, and Heart Rate/Respiratory Sinus Arrhythmia Data‘ by Peper et al (2010)  (10.5298/1081-5937-38.1.19)

The link to the data in the cloud is here. If you’re in a hospital/research unit somewhere, I can share the data with you if you like. E4 worn on left arm.

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