Transcript Brain Computer Interface

EPILEPTIC SEIZURE:
PREDICTION AND PREVENTION
Dan Coughlin
Kevin McCabe
Bob McCarthy
Steve Moffett
Background
•Epilepsy is a brain disease
that triggers seizures
•Electroencephalograms
(EEGs) read electrical
impulses from the brain
PREDICTION
Methods
• Artificial Neural
Networks (ANNs)
• Support Vector
Machines (SVM)
• Fuzzy Logic
ANNs – Lyapunov’s Constant
• Impending epileptic epoch will lower chaos of
brain waves
• Lyapunov’s exponent can model the amount
of chaos.
• Exponent (normally positive) will decrease
when seizure is coming
ANNs
• Zandi - correlation between the time intervals
between positive zero crossings in the signal
and an oncoming seizure
• Use the probability density function, p(x), to
model entropy and predict seizure
SVMs
• Represent the examples as
points in space, mapped so
the examples of the
categories are as wide as
possible
• Use Cao’s method to classify
each data series
Fuzzy Logic
• Creates states in
between 0 and 1.
• Eg. “very low”, “low”,
“medium”, “high”, “very
high”.
• This creates a better
way to classify the risk
of an epileptic seizure
Ex. Cold = 0, 1; Hot = 0, 1;
Warm can be interpreted as
Cold = 0, Hot = 0.
Fuzzy Logic
• Basic Structure
• A fuzzifier, which converts crisp
values (real time values) into fuzzy
values.
• An interference engine, that applies
a fuzzy reasoning mechanism to
obtain a fuzzy output
• A defuzzifier, which translates this
new output into crisp values
• A knowledge base which contains
both an ensemble of fuzzy rules
known as rule base and an
ensemble of membership functions
know as database
Fuzzy Logic with HDT
• Hierarchical Decision
•
•
•
•
Trees
Greatly reduce missclassification
Removes unnecessary
computations from the
system
Rectangles: weighted
average aggregations
Circles: MAX/MIN
decisions
Wave Packet Transform (WPT)
• Wavelet-based algorithm for real-time detection of
•
•
•
•
seizures using scalp EEG
Patient specific
Algorithm uses index based on rhythmicity and relative
energy of EEG
From these, a combined seizure index (CSI) is formed
from every channel/frequency of the EEG
One-sided cumulative sum tests of the CSI generate the
seizure warnings
Accuracy
Method
Best Accuracy
Artificial Neural
Networks (ANNs)
84.7%
Support Vector
Machines (SVMs)
100%
Fuzzy Logic
97.5%
Wavelet Packet
Transform
90.5%
PREVENTION
PREVENTION
• Prevention of epileptic seizures through medications
• Prevention of epileptic seizures through surgery and
common practices
• Preventing a seizure with the use of Biosensors
• Vagus Nerve Stimulation
• Purdue University – Nanotech Sensor
• Glutamine-Glutamate Transfer
• Electrical Pulses on Rats
• Most Viable Method
PREVENTION
•
Prevention using medications
• Most Common Medications
•Tegretol or Carbatrol (carbamazepine)
•Zarontin (ethosuximide)
•Valium and similar tranquilizers such as Klonopin or Tranxene
•Anti-convulsion – Phenytoin also known as Dilantin
• Common Side Effects
•Slurred Speech
•Nausea and Vomiting
•Rash
•Depression
•Headache
•Light Headed
PREVENTION
• Surgery
• Not 100% effective
• Can be effective if taken with medication
• Common Practices
• Ketogenic Diet
• Low carbohydrate, high-fat diet
• Get plenty of sleep
• Avoid bright, flashing lights and other visual stimuli
• Avoid video games, watching TV, drugs and alcohol
PREVENTION
•VNS – Vagus Nerve Stimulation (passes thru neck to brain)
• Designed to prevent seizures by sending regular, mild pulses of electrical
energy to the brain via the vagus nerve
• Pulses supplied by a device similar to a pacemaker
• Works for 30 seconds of stimulation followed by 5 minutes of no stimulation
•Holding magnetic near devices activates it outside of its programmed interval
•Stimulation Parameters
•Stimulation amplitude, frequency, pulse width
• Relieves side effects (pain) and controls seizure
PREVENTION
• VNS
• Side Effects
• Paresis of the vocal fold
• Hoarseness
• Cough
• Symptoms were reported as very low and mild and were weakened with
decreasing current
• Tingling in the neck
• Problems s
• Most common times these side effects occur is when the nerve is being
stimulated
PREVENTION
• VNS
• Risks – Functional/Placement
• Injury to the Vagus nerve
• Blood vessels nearby, including the carotid artery and jugular vein
• Risks – Surgery
• Infection
• Bleeding
• Allergic reaction to the anesthesia
PREVENTION
• Purdue University – Nanotech Sensor
• Transmitter and battery implanted in the brain
• Detects the signs of an epileptic seizure before it occurs
• Data will be picked up by an external receiver not implanted under the
scalp
• Collect data specifically related to epileptic seizures from one
thousand channels or locations in the brain
• The more channels, the more parts of the brain to look at simultaneously
• The electrodes that will get the data are inserted in the brain through
holes made in the skull and are connected directly to the transmitter by
the use of wires
• Prevents an epileptic focal seizure
• Researchers are creating a neuroprosthesis that dispenses a
neurotransmitter called GABA that calms the brain once a seizure is
detected
• Electrode is coated with engineered neurons and once they are
stimulated, will release the neurotransmitter to inhibit the seizure
PREVENTION
• Molecular Imaging Biosensor
• Identifies excess amounts of neurotransmitter glutamate build up in brain tissue
• Excess levels thought to be produced by dysfunctional “glutamate-glutamine
shuttle”
• Biological sensors being developed to detect glutamate levels from shuttle
process
• Using FRET (fluorescence resonance energy transfer) imaging and electrical
signals to detect evidence of alterations
• If technology is feasible and shows that epileptic seizures occur from this
imbalance, this will be a potential new therapeutic way to control epilepsy
PREVENTION
• Electric pulses used on rats
• Supported by the Canadian Institutes of Health Research
(CIHR) and The Natural Sciences and Engineering
Council of Canada
• Electrical stimuli are applied to the neurons and in the
Mossy Fibers of the rat
• Early results show that this technique can prevent the
upcoming electrical event
• Successful suppression of these events is achieved
using an extra cellular field stimulating electrode
PREVENTION
• Most Viable Method
• VNS – Vagus Nerve Stimulation
• Most reviews from patients say it has stopped their seizures all together
• Those that have not stopped have experienced seizures less frequent
and are mild compared to before implantation of the device
• Some patients experience side effects such as a hoarse voice or
speech impediments
• In little cases, the device has not worked at all
MARKET AND PRODUCTS
Overview of Market/Products
• Most epilepsy detection/prevention devices are not yet
products, and lack marketable features such as mobility,
and battery life.
• Most effective devices are for stationary patients hooked
up while in a bed or a lab
• Tradeoff in available products, processing power versus
battery life.
• Prevention devices require implantable sensors, whereas
detection devices can be found out of body.
Types of Products
• Open Loop Implantable devices
• Closed Loop Implantable devices
• Seizure Detection while sleeping
• Electrodermal Activity Sensor
• Audio sensors
Open Loop vs Closed Loop Devices
• Open Loop constantly provides electrical stimulus (usually
to a particular nerve or brain region) to stave off seizures.
• Open Loop are more mobile with less hardware required,
less power requirements.
• Closed Loop read in data from the body, and react with
appropriate feedback response.
• Closed Loop require more processing power/hardware, so
primarily used at stationary locations.
Available Prevention/Detection Products
• Emfit detects shaking movements/hyperventilation
typical of seizures while sleeping
• Placed on bed underneath sleeper, triggers alarm
http://www.tunstall.co.uk/assets/Literature/477-Epilepsy_product_datasheet.pdf
Available Prevention/Detection Products
• Bed Sensor with Microphone to detect audible
sounds sometimes associated with seizures
http://www.medpage-ltd.com/MEDPAGE%20MANUAL%20MP2%20REV-01-01.04-09.pdf
Available Prevention/Detection Products
• Electrodermal Activity Sensor measures skin
conductance.
• Electrodes sense change when seizure occurs .
http://affect.media.mit.edu/pdfs/10.Poh-etal-EMBC2010.pdf
Available Prevention/Detection Products
• SHIMMER uses kinematic sensors placed on the
body, transmits shaking movements to a Nokia
device.
Conclusion
• Prediction: All methods are viable still; SVM have proven
to be 100% accurate
• Prevention: VNS is the most effective way to control
epilepsy when medication won’t
• Overall: The VNS could be combined with the SVM to
more accurately stop seizures;
• Improvements needed to provide a prevention system
• Still looking for a non-invasive prevention method
• Market is there
Bibliography
• Bezobrazova, S.; Golovko, V.; , "Comparative Analysis of
Forecasting Neural Networks in the Application for
Epilepsy Detection," Intelligent Data Acquisition and
Advanced Computing Systems: Technology and
Applications, 2007. IDAACS 2007. 4th IEEE Workshop on
, vol., no., pp.202-206, 6-8 Sept. 2007
• Zandi, A.S.; Dumont, G.A.; Javidan, M.; Tafreshi, R.; , "An
entropy-based approach to
predict seizures in
temporal lobe epilepsy using scalp EEG," Engineering in
Medicine and Biology Society, 2009. EMBC 2009.
Annual International Conference of the IEEE , vol., no.,
pp.228-231, 3-6 Sept. 2009
Bibliography
• Ye Yuan; , "Detection of epileptic seizure based on EEG
signals," Image and Signal Processing (CISP), 2010 3rd
International Congress on , vol.9, no., pp.4209-4211, 1618 Oct. 2010
• Sukanesh, R.; Harikumar, R.; , "Fuzzy techniques and
hierarchical aggregation functions decision trees for the
classification of epilepsy risk levels from EEG
signals," TENCON 2008 - 2008 IEEE Region 10
Conference , vol., no., pp.1-6, 19-21 Nov. 2008
Bibliography
• "Vagus Nerve Stimulation | Epilepsy.com." Epilepsy and
Seizure Information for Patients and Health Professionals
| Epilepsy.com. Ed. Steven C. Schachter. 15 Dec. 2006.
Web. 03 Apr. 2011.
<http://www.epilepsy.com/epilepsy/vns>.
• Reimer, Richard J. "Real-time Imaging of the GlutamineGlutamate Shuttle in Epilepsy - Dana Foundation." Brain
and Brain Research Information - Dana Foundation. Dec.
2006. Web. 03 Apr. 2011.
<http://www.dana.org/grants/imaging/detail.aspx?id=1118
2>.
Bibliography
Dalton, Anthony; "Detecting Epileptic Seizure Using
Wearable Sensor Technologies"
http://ama-ieee.embs.org/wpcontent/themes/ieee/papers/March%2023%20%20PM/Dalton%20Abstract%2085.pdf
Hively, L.M.,Kruse, K.L., Munro, N.B., Protopopescu, V.A.;
"Epilepsy Forewarning Using a Hand Held Device" Febrary
2005,
http://www.ornl.gov/~webworks/cppr/y2005/rpt/122819.pdf