Clinical Use of the RNS
®
System
29
RNS
®
System User Manual
C
LINICAL
U
SE OF THE
RNS
®
S
YSTEM
I
DENTIFYING
C
ANDIDATES FOR THE
RNS
®
S
YSTEM
T
HERAPY
Clinical trials have shown that the RNS
®
System is safe and effective in patients who are 18 years of
age or older with disabling partial onset seizures from no more than two foci and have medically
intractable epilepsy, defined by the International League Against Epilepsy (ILAE) as a failure to
control seizures after 2 seizure medications that have been appropriately chosen and used.
Patients benefiting from the RNS
®
System have partial onset epilepsy with one or more of the
following seizure types:
•
Simple partial motor: seizures characterized by alteration in motor function without change in
awareness
•
Complex partial: seizure includes impairment in awareness
•
Generalized tonic, clonic or tonic-clonic seizures
The RNS
®
System is appropriate only in patients whose seizures begin in one or two foci that can be
implanted with NeuroPace
®
Depth Leads and/or NeuroPace
®
Cortical Strip Leads. Only 2 leads can
be connected to the neurostimulator and therefore detection and stimulation can occur in no more
than 2 locations.
The RNS
®
System should not be considered in patients who are likely to require MRIs of the brain in
the future because an MRI is contraindicated in patients implanted with the RNS
®
System. The RNS
®
System is also contraindicated in patients who have implanted medical devices that deliver electrical
energy to the head. Patients who have medical or neurological conditions that place them at high risk
for surgical complications are not good candidates for the RNS
®
System. For a complete list see the
L
OCALIZING
T
HE
S
EIZURE
F
OCUS AND
P
LANNING
L
EAD
L
OCATION
The RNS
®
System delivers responsive stimulation to one or two seizure foci. In order to accomplish
this, a precise detection of the electrocorticographic activity of interest must be achieved to provide
stimulation to the seizure focus. If electrocortiocographic activity of interest is not detected as
intended, and / or stimulation cannot be delivered to the focus, it is possible that the seizure focus will
not be adequately treated. Therefore, it is essential that the seizure focus be sufficiently well localized
to guide placement of the lead or leads.
Localization of the seizure focus is accomplished using standard localization tests available at
qualified Comprehensive Epilepsy Centers. This will always include in-patient video-EEG monitoring
with scalp electrodes with or without supplemental electrodes such as sphenoidal electrodes, as well
as MRI with appropriate magnet strength and sequences for the detection of mesial temporal
sclerosis and other common epileptogenic lesions.
Non-invasive EEG and MRI imaging may be adequate to determine the number and location of
seizure foci. However, some patients may require additional testing with video-EEG monitoring with
intracranial electrodes to identify or refine the localization of the seizure focus. This may also include
intraoperative or extraoperative stimulation with subdural electrodes for functional cortical mapping.
Additional imaging studies may include Positron Emission Tomography (PET), ictal single photon
emission computed tomography (SPECT), functional MRI (fMRI) or magnetoencephalography (MEG).
Neuropsychological testing and intracarotid amytal (Wada) testing is included in many
Comprehensive Epilepsy Centers’ localization evaluation.
Patients with medically refractory partial epilepsy following resective surgery should have had
appropriate studies following the surgery to adequately localize the seizure focus or foci prior to
implantation of the RNS
®
System.
