Electrical Stimulation and Monitoring Devices of the CNS:
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 noninvasive 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, parkinsons 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 Parkinsons 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 Parkinsons 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 Parkinsons 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.
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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;29:92028 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; 19:264268. 28. Beekwilder JP, Beems T. Overview of the clinical applications of vagus nerve stimulation. J Clin Neurophysiol. 2010 Apr;27(2):130-8.
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