Transcript Depth electrodes

Electrical Stimulation and
Monitoring Devices of the CNS:
An Imaging Review
ASNR 2015 Electronic Educational Exhibit, #446
Sohil Patel MD1, Casey Halpern MD2, David
Mossa RT1, Vincent Timpone MD3
1. NYU-Langone Medical Center, Dept of Radiology
2. Stanford School of Medicine, Dept of Neurosurgery
3. San Antonio Military Medical Center, Dept of Radiology
Disclosures
• No financial disclosures.
• The opinions and views expressed in this
presentation are solely those of the authors
and do not represent an endorsement by or
the views of the Department of Defense, or
the United States Government.
Aims
• To familiarize the radiologist with various
implanted electrical neurological monitoring
and stimulator devices, including their:
– Clinical indications
– Normal components and function
– Expected imaging appearance
– Potential complications
– MRI compatibility
Content
•
•
•
•
•
•
•
•
•
•
Subdural and Depth electrodes
Foramen ovale electrodes
Deep brain stimulation
Motor cortex stimulator
Responsive neurostimulation
Middle ear implant
Auditory brainstem implant
Cochlear implant
Vagal nerve stimulator
Spinal stimulator
Subdural and depth electrodes
• Intracranial electrodes placed in epilepsy
patients to record brain electrical activity.
• Requires craniotomy or burr hole access.
• Subdural electrodes are arranged as a strip or
grid array along the surface of the brain.
• Depth electrodes are linear electrodes placed
directly into the brain parenchyma.
Subdural and depth electrodes
• Indications:
– Seizure localization:
• Indicated in patients with medically refractory seizures, whose
non-invasive tests (ie. scalp EEG with video monitoring, MRI) are
inconclusive or discordant with respect to seizure
localization/laterality.
– Minimization of surgical resection
• Intracranial EEG allows higher spatial and temporal resolution than
scalp EEG. This may allow minimization of the subsequent surgical
resection.
– Detection of eloquent cortex
• Electrodes can be stimulated to localize nearby eloquent cortex.
• MRI compatibility: Safe and conditional devices exist
for scanning at 1.5T
Subdural and depth electrodes
Intracranial EEG monitoring in an 18 year old with partial complex seizures.
Subdural and depth electrodes
Subdural grid electrodes (short solid arrows).
Subdural and depth electrodes
Depth electrodes (dashed arrows).
Subdural and depth electrodes
Wires connecting the intracranial leads to the external EEG recording device (long solid arrows).
Subdural and depth electrodes
Axial T2WI (right) and T1WI (left) show
subdural electrodes (solid arrows) and
depth electrodes (dashed arrows).
Changes from left temporal-occipital
craniectomy are noted.
Axial CT, maximum intensity
projection, shows bilateral depth
electrodes (dashed arrows).
Subdural and depth electrodes
Image from intraoperative neuronavigation shows
the planned trajectory of a depth electrode (solid
arrow) into a region of polymicrogyria (dashed
arrow).
Intraoperative image from
placement of a depth electrode
Foramen ovale electrodes
• Intracranial linear electrodes placed to record
medial temporal lobe electrical activity.
• The electrodes are inserted via a trans-facial
percutaneous approach with fluoroscopic
guidance.
• The electrodes are placed into the ambient
cisterns, adjacent to the medial temporal
lobes.
Foramen ovale electrodes
• Indicated in patients with suspected medial temporal
lobe epilepsy, but with unconfirmed
localization/laterality based on non-invasive testing.
• Foramen ovale electrodes provide higher spatial and
temporal resolution than scalp EEG.
• Compared to subdural/depth electrodes, foramen
ovale electrodes:
– Do not require craniotomy/burr hole.
– Are not placed into brain parenchyma.
– Evaluate only medial temporal lobes.
• MRI compatibility: Safe and conditional devices exist
for scanning at 1.5T
Intraoperative radiographs show the normal positioning of bilateral
foramen ovale electrodes (arrows). Both electrodes have 4 contact points.
Foramen ovale electrodes
Axial CT scan image shows foramen
ovale electrodes in the ambient
cisterns, adjacent to the medial
temporal lobes (solid arrows).
Coronal CT scan images show the
electrodes traversing bilateral
foramen ovale (dashed arrows).
Deep brain stimulation (DBS)
• Intracranial electrodes that produce electrical stimulation
of functional targets in the brain parenchyma.
• DBS electrodes are placed via burr holes or craniotomy.
Guided to targets using image-guided neuronavigation
and neurophysiologic recording.
• FDA approval for treatment of essential tremor,
parkinson’s disease, primary dystonia, obsessive
compulsive disorder.
• Off-label use in the treatment of refractory depression,
chronic pain, epilepsy, and Tourette syndrome.
• MRI compatibility: Conditional devices exist for scanning
at 1.5T
Deep brain stimulation
• Targets
– Parkinson’s Disease
• Subthalamic nucleus
• Globus pallidus internus
– Essential Tremor
• Ventral intermediate nucleus of the thalamus
– Primary dystonia
• Globus pallidus internus
– Obsessive compulsive disorder
• Internal capsule anterior limb
• Subthalamic nucleus
Deep brain stimulation
Bilateral DBS in a 78 year old male with Parkinson’s disease.
Deep brain stimulation
The components of the DBS system include the intracranial leads (solid short arrows) which
contain 4 electrode contacts at their distal tips (arrowheads).
Deep brain stimulation
The intracranial electrodes are connected, via extension wires (long solid arrows), to the pulse
generators (dashed arrows) which are implanted subcutaneously in the chest wall.
Deep brain stimulation
Coronal T1WI shows bilateral DBS electrodes terminating in the subthalamic
nuclei (arrows) in this patient with Parkinson’s disease.
Deep brain stimulation
Axial and coronal T1WI show bilateral DBS electrodes (arrows) within the globus pallidus
internus in this 64 year old female with dystonia.
Deep brain stimulation
• Off-label use for the
treatment of epilepsy.
Targets include
hippocampus/amygdala and
the thalamus.
• In medial temporal lobe
epilepsy, DBS indicated if
patients are:
– Refractory to medical
treatment
– Unsuitable for surgical
therapy due to:
• Bilateral disease
• Surgical risk of major verbal
memory loss (assessed with
intraarterial amobarbital
testing).
Temporal lobe stimulators in a patient
with intractable epilepsy. Electrodes
(arrows) lie within the medial temporal lobes.
Motor cortex stimulator
• Used in patients with refractory pain syndromes.
• Strip electrodes are placed in the epidural space
overlying the motor cortex via craniotomy approach.
• The motor cortical representation of the painful site is
targeted (ie. contralateral to side of pain). The
electrodes are guided to the appropriate location using
image-guided neuronavigation and intraoperative
neurophysiologic testing.
• After appropriate positioning, the lead is sutured to the
dura, and connected via extension wiring to a pulse
generator that is implanted in the chest wall
subcutaneous tissues.
Motor cortex stimulator
• Variable success in the treatment of a variety
of pain syndromes, including
– Trigeminal neuralgia
– Post-stroke pain
– Phantom limb pain
– Herpetic neuralgia
– Multiple sclerosis.
• Usage is off-label.
• MRI compatibility: Unknown.
Motor cortex stimulator
Lateral scout radiograph shows a 4-contact
motor cortex electrode (solid arrow). The
intracranial lead is connected to a pulse
generator (not shown) via extension wiring
(arrowhead) that is tunneled through the
neck subcutaneous tissue.
Axial CT images from the same patient
show the intracranial lead (solid arrow)
within the epidural space overlying the
left motor strip (dashed arrow).
Responsive Neurostimulation
• FDA approved for the treatment of medication
refractory partial onset seizures in adults.
• The responsive neurostimulator device records and
processes EEG data from targeted brain regions. It
delivers electrical stimulation to these targets upon
detection of seizure activity. The electrical stimulation
disrupts the seizure activity.
• The neurostimulator cassette (containing the pulse
generator) is implanted in the calvarium.
• The neurostimulator is connected to either cortical
strip leads (which are placed on the brain surface) or
depth leads (which are placed in the brain
parenchyma).
Responsive Neurostimulation
• Shown to lower seizures rates by 50% on average. The
therapeutic efficacy might increase over time via
neuromodulatory effects.
• Compared to surgical therapy:
– Different sites (up to two) can be targeted.
– Eloquent regions can be targeted without disruption
– Reversible (the device can be removed).
• Compared with DBS:
– Responsive neurostimulation does not provide continuous
stimulation. Rather, it is “triggered” by the detection of
seizure activity.
• MRI compatibility: Not MRI compatible.
Responsive Neurostimulation
Scout radiographs and axial CT images show an implanted Responsive Neurostimulator device
in a 24 year old female with medication resistant partial complex seizures.
Responsive Neurostimulation
The neurostimulator cassette (solid arrows) has been implanted within a parietotemporal
craniectomy bed. Neurostimulator cassette within a skull model (dashed arrow) for
comparison.
Responsive Neurostimulation
Four electrodes were implanted (arrows). Intraoperative electrocorticography was
performed from each electrode. The neurostimulator was connected to two of
the electrodes which recorded the greatest seizure activity. The remaining two
electrodes were left in place but were not connected to the neurostimulator.
Middle Ear Implant
• Electronic device that converts sound energy into
mechanical vibrations that directly stimulate middle
ear structures.
• Externally worn audioprocessor receives and
transmits signal to vibrating ossicular prosthesis
embedded subcutaneously overlying the temporal
bone.
• Vibrating ossicular prosthesis transmits signal to
middle ear transducer which is attached to incus or
round window and causes these structures to vibrate
and amplify acoustic input to cochlea.
Middle Ear Implant
• Indications: Moderate to severe sensorineural hearing loss
in patients with suboptimal response to traditional hearing
aid devices, or medical contraindication to such devices (ie
otitis externa).
• Compared to conventional external hearing aid devices:
– Similar hearing thresholds
– Improved sound quality, less feedback
– Improved comfort and patient satisfaction
• Potential complications: Bleeding, infections, facial nerve
injury.
• MR compatibility: No current MR compatible devices
available.
Middle Ear Implant
36 yo female with mixed hearing loss. Vibrating ossicular prosthesis implanted under the
skin (solid arrow) receives input from an externally worn audioprocessor (not shown) and
transfers signal to a vibrating middle ear transducer (dashed arrow).
Middle Ear Implant
CT images from same patient demonstrating subcutaneous vibrating ossicular prosthesis
(solid arrow), electrode (arrowhead), and transducer (dashed arrow) implanted adjacent
to the round window. In patients with normal ossicles, transducer may be attached to the
incus.
Cochlear Implant
• Implanted electronic hearing device converting sound
energey into electronic impulses that directly stimulate
the cochlea.
• Sound signal detected by an external microphone and
audioprocessor.
• Audioprocessor is magnetically attached to an implanted
receiver-stimulator seated within the temporal bone.
• Receiver-stimulator converts signal transmitted from
audioprocessor into electrical impulses that stimulate the
cochlea via a soft flexible electrode array.
Cochlear Implant
• Indications: Severe to profound sensorineural hearing loss.
• Majority of patients demonstrate significant improvement in
measurements of speech recognition though results vary based on
age at implantation and duration of hearing loss.
• Several studies suggest improved functional outcome with greater
insertion depth and when electrode located in the scala tympani.
• Cochlea coordinate system developed by consensus panel in 2010
and enables viewers to communicate implant array location with
less ambiguity.
• Potential complications: Facial nerve injury, CSF leak, loss of residual
hearing.
• MR compatibility: MR conditional devices available.
Cochlear Implant
40 yo female with bilateral sensorineural hearing loss treated with bilateral cochlear
implants. Receiver-stimulators (solid arrows) are embedded to the temporal bone.
Flexible array electrodes (dashed arrows) are seen coiled within the cochlea,
approximately 360 degrees on the right, 180 degrees on the left.
Cochlear Implant
CT images from same patient demonstrating electrodes coiled within the cochlea, with
electrode tips visualized (solid arrow). Using standardized cochlear coordinate system,
electrode tips are positioned at approximately segment 5 on the right, segment 3 on the
left.
Auditory Brainstem Implant
• Electronic device which stimulates cochlear nucleus directly
and provides sound sensation to an otherwise deaf patient.
• Paddle array electrode placed in lateral recess of 4th ventricle
overlying dorsal-lateral surface of cochlear nucleus.
• Electrode connects to receiver-transmitter seated within the
temporal bone.
• Sound picked up by microphone at pinna, signal then sent to
pocket sized speech processor worn on the patient.
• Speech processor changes sound signal to an electronic
impulse sent to the receiver through a transmitter coil.
Auditory Brainstem Implant
• Indications: Patients without functioning cochlea or cochlear
nerve, but with intact auditory brainstem pathway:
– Bilateral vestibular schwannomas in Neurofibromatosis II
– Skull-base trauma with cochlea damage
– Congenitally absent cochlear nerve
• In clinical studies, >80% of patients able to detect familiar
sounds (ie doorbell, honking horn) and demonstrate improved
understanding of conversation with aid of lip-reading.
• Potential complications: Non-auditory stimulation of other
cranial nerves if electrode placed too far ventrally
• MR Compatibility: MR conditional devices available.
Auditory Brainstem Implant
A. Demonstrates the receiver-stimulator component that has a grounding
electrode embedded underneath temporalis muscle, and multichannel electrode
paddle inserted into the 4th ventricle lateral recess. B. External components
include microphone which sends sound to processor-digitizer which in turn sends
electrical impulses to the receiver via the transmitter coil.
Lekovic et al: Auditory Brainstem Implantation
Auditory Brainstem Implant
Auditory brainstem implant in 25 yo male with Neurofibromatosis type 2 and
bilateral sensorineural hearing loss. Receiver-stimulator embedded within the
temporal bone (solid arrow) connected to electrode paddle (dashed arrow)
located in the 4th ventricular lateral recess, abutting the dorsal lateral surface of
the cochlear nucleus.
Vagal Nerve Stimulator
• Stimulation of vagal cervical trunk to treat wide variety of
disorders, most commonly medically refractory epilepsy and
depression.
• Small electrode implanted around the left vagus nerve cervical
trunk, approximately 8cm above the clavicle and connected to a
programmable generator placed subcutaneously in the upper
thorax.
• Mechanism of action not fully understood, however afferent
vagal fiber activation appears to disrupt seizure-related circuitry.
• Vagal nerve stimulation may also alter neurotransmitter and
metabolite concentrations leading to antidepressant effects.
Vagal Nerve Stimulator
• Right sided vagus nerve stimulation thought to result in
increased cardiac side effects. Only left sided vagus nerve
stimulators currently FDA approved.
• In clinical studies:
– Greater than 50% reduction in seizure frequency, as
well as reduced seizure duration and post-ictal recovery
times.
– Greater than 50% reduction in depression scores after
12 months of therapy.
• Potential complications: vocal cord paresis, dysphagia.
• MR compatibility: MR conditional devices available.
Vagal Nerve Stimulator
53 yo with epilepsy treated with vagal nerve stimulation. Subcutaneous pulse generator
(solid arrow) is seen in the upper left thorax and is connected to a coiled electrode
(dashed arrow) attached to the left cervical vagus trunk.
Spinal Cord Stimulator
• Electronic device which stimulates posterior columns of spinal
cord in treatment of chronic pain.
• With stimulation patient will feel mild paresthesias in their area
of pain, which inhibits transmission of other nociceptive inputs,
reducing overall level of pain.
• 3 components:
– Generator: implanted under the skin and sends electrical
impulses to electrodes.
– Electrodes: inserted into the posterior epidural space and
threaded to the desired level under fluoroscopic guidance.
– Wireless programmable controller: regulates stimulation.
Spinal Cord Stimulator
• Indications:
– Treatment resistant chronic back/extremity pain.
– Failed back surgery syndrome
• In selected patients, spinal cord stimulation more
effective and less expensive than reoperation for
treatment of persistent post-operative radicular pain.
• Potential complications: CSF leak.
• MR compatibility: MR conditional devices available.
Spinal Cord Stimulator
64 yo female with chronic cervicalga. Subcutaneous pulse generator (solid arrow) is seen
in the left lower flank, connected to 2 leads each with 4 electrode contact points at their
distal tip in the cervical spine (dashed arrow).
Spinal Cord Stimulator
CT images from same patient demonstrate the desired posterior epidural placement of the
electrodes (dashed arrows).
Complications of implanting neurologic
stimulators/monitoring devices
•
•
•
•
•
•
•
Infection
Hemorrhage
Infarction
Vascular injury
Device malpositioning
Lead fracture
Lead disconnection
Complications - infection
21 year old female with complex partial seizures. Intracranial EEG recording with
subdural grid (solid arrows) and depth electrodes (dashed arrows) was undertaken.
Complications - infection
The patient returned to emergency department 2 months after the electrodes were
removed, complaining of swelling and discharge near the craniotomy site.
When compared to the axial CT image with intracranial electrodes in place (left image),
the axial CT image 2 months later (right image) shows new erosions (arrowheads) in the
bone flap. At surgical pathology, this proved to represent osteomyelitis of the bone flap.
References
1.Ben-Menachem E, Krauss GL: Epilepsy: responsive neurostimulation-modulating the epileptic brain. Nature
reviews Neurology 2014, 10(5):247-248.
2.Blount JP, Cormier J, Kim H, Kankirawatana P, Riley KO, Knowlton RC: Advances in intracranial monitoring.
Neurosurgical focus 2008, 25(3):E18.
3.Boex C, Seeck M, Vulliemoz S, Rossetti AO, Staedler C, Spinelli L, Pegna AJ, Pralong E, Villemure JG, Foletti G et
al: Chronic deep brain stimulation in mesial temporal lobe epilepsy. Seizure 2011, 20(6):485-490.
4.Carmichael DW, Thornton JS, Rodionov R, Thornton R, McEvoy A, Allen PJ, Lemieux L: Safety of localizing
epilepsy monitoring intracranial electroencephalograph electrodes using MRI: radiofrequency-induced heating.
Journal of magnetic resonance imaging : JMRI 2008, 28(5):1233-1244.
5.Chen XL, Xiong YY, Xu GL, Liu XF: Deep brain stimulation. Interventional neurology 2013, 1(3-4):200-212.
6.Cox JH, Seri S, Cavanna AE: Clinical utility of implantable neurostimulation devices as adjunctive treatment of
uncontrolled seizures. Neuropsychiatric disease and treatment 2014, 10:2191-2200.
7.Davis LM, Spencer DD, Spencer SS, Bronen RA: MR imaging of implanted depth and subdural electrodes: is it
safe? Epilepsy research 1999, 35(2):95-98.
8.Fisher RS, Velasco AL: Electrical brain stimulation for epilepsy. Nature reviews Neurology 2014, 10(5):261-270.
9.Heck CN, King-Stephens D, Massey AD, Nair DR, Jobst BC, Barkley GL, Salanova V, Cole AJ, Smith MC, Gwinn
RP et al: Two-year seizure reduction in adults with medically intractable partial onset epilepsy treated with
responsive neurostimulation: final results of the RNS System Pivotal trial. Epilepsia 2014, 55(3):432-441.
10.Henderson JM, Lad SP: Motor cortex stimulation and neuropathic facial pain. Neurosurgical focus 2006,
21(6):E6.
References
11.Jenkins HA, Uhler K: Otologics Active Middle Ear Implants. Otolaryngologic clinics of North America 2014, 47(6):967978.
12.Lefaucheur JP, Drouot X, Cunin P, Bruckert R, Lepetit H, Creange A, Wolkenstein P, Maison P, Keravel Y, Nguyen JP:
Motor cortex stimulation for the treatment of refractory peripheral neuropathic pain. Brain : a journal of neurology
2009, 132(Pt 6):1463-1471.
13.Merkus P, Di Lella F, Di Trapani G, Pasanisi E, Beltrame MA, Zanetti D, Negri M, Sanna M: Indications and
contraindications of auditory brainstem implants: systematic review and illustrative cases. European archives of otorhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies 2014, 271(1):3-13.
14.Morrell MJ, Group RNSSiES: Responsive cortical stimulation for the treatment of medically intractable partial
epilepsy. Neurology 2011, 77(13):1295-1304.
15.Rushton DN: Electrical stimulation in the treatment of pain. Disability and rehabilitation 2002, 24(8):407-415.
16.Sheth SA, Aronson JP, Shafi MM, Phillips HW, Velez-Ruiz N, Walcott BP, Kwon CS, Mian MK, Dykstra AR, Cole A et al:
Utility of foramen ovale electrodes in mesial temporal lobe epilepsy. Epilepsia 2014, 55(5):713-724.
17.Yang AI, Wang X, Doyle WK, Halgren E, Carlson C, Belcher TL, Cash SS, Devinsky O, Thesen T: Localization of dense
intracranial electrode arrays using magnetic resonance imaging. NeuroImage 2012, 63(1):157-165.
18.Yuan J, Chen Y, Hirsch E: Intracranial electrodes in the presurgical evaluation of epilepsy. Neurological sciences :
official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology 2012, 33(4):723729.
19. Verbist BM, Skinner MW, Cohen LT, et al. Consensus panel on a cochlear coordinate system applicable in histologic,
physiologic, and radiologic studies of the human cochlea. Otol Neurotol 2010;31:722–30
20.Beltrame AM, Martini A, Prosser S, Giarbini N, Streitberger C. Coupling the Vibrant Soundbridge to cochlea round
window: auditory results in patients with mixed hearing loss. Otol Neurotol. 2009 Feb;30(2):194-201.
References
21. Kahue CN, Carlson ML, Daugherty JA, Haynes DS, Glasscock ME 3rd. Middle ear implants for
rehabilitation of sensorineural hearing loss: a systematic review of FDA approved devices. Otol
Neurotol. 2014 Aug;35(7):1228-37
22. Finley CC, Holden TA, Holden LK, et al. Role of electrode placement as a contributor to variability in
cochlear implant outcomes. Otol Neurotol 2008;29:920–28
23. Colby CC, Todd NW, Harnsberger HR, Hudgins PA. Standardization of CT Depiction of Cochlear
Implant Insertion Depth. AJNR. 2015 Feb;36(2):368-71
24. Manchikanti, L, Boswell MV, et al. Comprehensive review of therapeutic interventions in managing
chronic spinal pain. Pain Physician. 2009 Jul-Aug;12(4):E123-98.
25. Kumar K, Taylor RS, Jacques L et al. Spinal cord stimulation versus conventional medical
management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back
surgery syndrome. Pain 2007;132:179-188.
26. Lekovic G, Gonzalez F, Syms M, Daspit C, Porter R. Auditory Braintstem Implantation. Barrow
quarterly vol (20) no 4 2004.
27. Ghaemi K, Elsharkawy AE, Schulz R et al. Vagus nerve stimulation: outcome and predictors of
seizure freedom in long-term follow-up. Seizure 2010; 19:264–268.
28. Beekwilder JP, Beems T. Overview of the clinical applications of vagus nerve stimulation. J Clin
Neurophysiol. 2010 Apr;27(2):130-8.
29. www.fda.gov