emg, eeg, and neurophysiology in clinical practice · • review principles of intracranial ... •...
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©2016 MFMER | 3554293-1 ©2016 MFMER | 3554293-1
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