Electrical Stimulation and Monitoring Devices of the CNS: - PowerPoint Presentation

Slide1

Electrical Stimulation and Monitoring Devices of the CNS: An Imaging Review

Sohil Patel MD1, Casey Halpern MD2, David Mossa RT1, Vincent Timpone MD3

1. NYU-Langone Medical Center, Dept of Radiology2. Stanford School of Medicine, Dept of Neurosurgery3. San Antonio Military Medical Center, Dept of Radiology

ASNR 2015 Electronic Educational Exhibit, #446

Slide2

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.

Slide3

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

Slide4

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

Slide5

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

.

Slide6

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

Slide7

Subdural and depth electrodes

Intracranial EEG monitoring in an 18 year old with partial complex seizures.

Slide8

Subdural and depth electrodes

Subdural grid electrodes (short solid arrows).

Slide9

Subdural and depth electrodes

Depth electrodes (dashed arrows).

Slide10

Subdural and depth electrodes

Wires connecting the intracranial leads to the external EEG recording device (long solid arrows).

Slide11

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).

Slide12

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

Slide13

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.

Slide14

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

Slide15

Intraoperative radiographs show the normal positioning of bilateral foramen

ovale

electrodes (arrows). Both electrodes have 4 contact points.

Slide16

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).

Foramen

ovale

electrodes

Slide17

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

Slide18

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

Slide19

Deep brain stimulation

Bilateral DBS in a 78 year old male with Parkinson’s disease.

Slide20

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).

Slide21

Deep brain stimulation

The intracranial electrodes are connected, via extension wires (long solid arrows), to the pulse

g

enerators (dashed arrows) which are implanted subcutaneously in the chest wall.

Slide22

Deep brain stimulation

Coronal T1WI shows bilateral DBS electrodes terminating in the

subthalamic nuclei (arrows) in this patient with Parkinson’s disease.

Slide23

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.

Slide24

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 treatmentUnsuitable for surgical therapy due to:Bilateral diseaseSurgical 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.

Slide25

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

.

Slide26

Motor cortex stimulator

Variable success in the treatment of a variety

of

pain

syndromes,

including

Trigeminal neuralgia

Post-stroke pain

Phantom

limb

pain

H

erpetic neuralgia

Multiple sclerosis.

Usage is off-label

.

MRI compatibility

:

Unknown.

Slide27

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).

Slide28

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).

Slide29

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

.

Slide30

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.

Slide31

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.

Slide32

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.

Slide33

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.

Slide34

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.

Slide35

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).

Slide36

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.

Slide37

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.

Slide38

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.

Slide39

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.

Slide40

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.

Slide41

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 4

th

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.

Slide42

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.

Slide43

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 4

th

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

Slide44

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.

Slide45

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.

Slide46

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.

Slide47

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.

Slide48

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.

Slide49

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.

Slide50

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).

Slide51

Spinal Cord Stimulator

CT images from same patient demonstrate the desired posterior epidural placement of the electrodes (dashed arrows).

Slide52

Complications of implanting neurologic stimulators/monitoring devices

Infection

Hemorrhage

Infarction

Vascular

injury

Device

malpositioning

Lead fracture

Lead disconnection

Slide53

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.

Slide54

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.

Slide55

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