EMG, EEG, and Neurophysiology in Clinical Practice · • Review principles of Intracranial ... • Pathological HFOs may identify interictal EEG spikes that ... EEG, and Neurophysiology

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Mayo School of Continuous Professional Development

EMG, EEG, and Neurophysiology in Clinical Practice

Matthew T. Hoerth, M.D. Ritz-Carlton, Amelia Island, Florida

January 29-February 4, 2017

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Mayo School of Continuous Professional Development

Intracranial recordings and HFO’s

Matthew T. Hoerth, M.D. Ritz-Carlton, Amelia Island, Florida

January 29-February 4, 2017

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Disclosure Relevant financial relationships • None

Off-label/investigational uses • None

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Overview • Treatment of Intractable Focal Epilepsy

• Epilepsy Surgery • Review principles of Intracranial Recordings

• Electrocorticography • High Frequency Oscillations

• Neuromodulation for Epilepsy • VNS, DBS, RNS

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Refractory Epilepsy: What if medications do not work? • 2.5 million with epilepsy in the U.S. • >50% with partial epilepsy • 30% refractory to medical therapy • 2000 epilepsy surgeries/year • 60-70% of those evaluated for epilepsy surgery get a

resection

Refs: Epilepsy: A report to the nation. EFA 1999; Kwan &Brodie NEJM 2000, 342: 314; Engel et al., Surgical Treatment of the Epilepsies, 1993; Zimmerman & Sirven Mayo Clinic Proc 2003, 78:109

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Options for epilepsy surgery • Selective Amagydalohippocampectomy • Anterior temporal lobectomy • Lesionectomy • Focal cortical resection • Multiple subpial transection • Hemispherectomy • Corpus Callosotomy • NeuroModulation Devices

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Evaluation for Epilepsy Surgery • H&P • Ictal/interical video EEG • Structural imaging: MRI • Functional imaging: PET,

SPECT, fMRI • Neuropsychological

testing • Wada test

• Multidisciplinary conference • Epileptologists • Epilepsy surgeon • Neuropyschologist • Radiologist • EEG Technologists • Nursing Staff

(inpatient/outpatient) • Administrative support • Research support

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Epilepsy Surgery: Goals • Removal of the

“epileptogenic zone” • Seizure freedom • Working & Driving • Limit morbidity and

mortality

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Indications for Intracranial EEG Monitoring

• Localization of seizure onset when non-invasive testing is inadequate

• Tailoring of cortical resection • Mapping cortical function

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Temporal Depth Electrodes

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The Operating Room • You NEED to know where your electrodes are being placed

• Without knowledge of placement you cannot plug in electrodes appropriately

• All the tails have different colors • Each package is different

• Double-sided grids • Verify that electrodes are working properly

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Subdural Electrodes

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Safety for the Grid/Depth Patient • Increased level of risk • Risk related to surgery

• Bleeding • Infection • Swelling

• Pain related to surgery • Incision pain • Jaw pain

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Post-op day 1 4 days later

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Intracranial Monitoring • Advantages

• More localization value • Get the address not just the state

• Less artifact • Disadvantages

• Invasive • Narrow coverage

• If seizure does not occur adjacent to electrode then there is no localization value

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Intracranial Monitoring • Typically a bipolar montage is used

• Montaging by row • May need to make additional montages based on

recording • Usually a secondary referential montage is used

• Subdural ground/reference • Much lower sensitivities

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50 mcV/mm

7 mcV/mm

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High Frequency Oscillations (HFOs) • Some interictal EEG spikes correspond to the epileptogenic

zone, some do NOT • High sampling (>800 Hz) of scalp and depth electrodes can

show interictal local field potentials (HFOs). • HFOs occur spontaneously during slow wave sleep and can be

evoked during sensory information processing. • In the epileptic brain, interictal pathological HFOs are associated

with brain areas capable of generating spontaneous seizures • HFOs can occur either independently or coincident with some

EEG spikes.

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High Frequency Oscillations (HFOs) • Pathological HFOs may identify interictal EEG spikes that

reliably reflect the epileptogenic zone • Pathological HFOs can occur before or during the onset of

some epileptic seizures • Pathological HFOs could be an electrophysiologic biomarker of

brain areas that are capable of generating spontaneous seizures

• Capturing pathological HFOs, therefore, could provide important information to identify the epileptogenic zone and help plan surgical resection that may ultimately improve the prognosis of seizure freedom.

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High Frequency Oscillations (HFOs)

©2016 MFMER | 3554293-25 ©2016 MFMER | 3554293-25 Ren, et al. Neurology 2015

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Brain Mapping • fMRI

• Non-invasive • Looks at subtle blood flow changes while patients are

doing a specific task • Labor intensive • Biggest limitation is verbal/visuospacial memory

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Brain Mapping • Wada

• Intracranial sodium amytal • Most helpful for memory and language lateralization • Cannot localize as entire internal carotid vascular territory

effected • Invasive

• Very small risk of stroke

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Brain Mapping • Cortical stimulation

• Stimulation through intracranial grid • Typically done during Phase II monitoring

• Early vs. Late in admission • Risk of causing a seizure

• Seizures should not be considered helpful for localization of ictal onset

• Typically rescue medication is immediately avaliable • Patient must be awake and cooperative

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Brain Mapping • Cortical stimulation

• G1 and G2 are chosen • Typically will have patient read passage

• Repetitive • Gradually increase stimulation

• Monitor EEG for after discharges • Monitor patient for clinical changes

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Brain Mapping • Intraoperative

• Intracranial SEP • Localize primary somatosensory cortex

• Awake Mapping • Stimulation or Serial Testing • Motor • Speech • Sensory • Visual

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Surgical Outcomes • Can be up to 80% curative in the most ideal circumstances • Minimally invasive approaches are being attempted

• Laser Ablation • Ultrasound

• Must know neuroanatomy and neurophysiology to be successful