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Australasian Journal of Neuroscience Volume 25 ● Number 2 ● October 2015
5
Vicki Evans
Editor
This edition brings together an array of
interesting topics for the neuroscience
nurse and related allied health personnel.
It begins with a review of the literature re-
garding the sampling of cerebrospinal fluid
from an external ventricular drain.
Then follows an article from Thailand that
describes the on-going disability & conse-
quences following TBI within the Thai con-
text. This is useful information for the world
neuroscience community as well.
There is a scarcity in the literature for man-
agement strategies relating to terminal ICH
in the palliative care setting — what to ex-
pect and how best to deal with the immi-
nent finality. Discussion in this manuscript
centres around these catastrophic events
and how best to deal with them from a
staff, patient and family perspective.
A Western Australia study looking at a
Neurological Integrated Care Pathway
(NICP) showed that once introduced, it
improved service efficiency for both the
hospital system and the community neuro-
logical support service. A useful introduc-
tion to patient care.
A literature review was conducted high-
lighting that the neurotrauma population
was at greatest risk for development of
venous thromboembolism. The neurosurgi-
cal nurse remains at the forefront of moni-
toring patients and implementing strategies
for treatment of VTE, DVT and PE. Throm-
boprophylaxis is discussed.
The journal begins with an interesting edi-
torial on the topic of surgical epilepsy from
Dr Mark Dexter relating to the use of
SEEG evaluations in drug resistant epilep-
sy patients. I thank Dr Dexter for his contri-
bution and support of the Australasian
Journal of Neuroscience.
Dr Mark Dexter
Surgical Epilepsy Program
Westmead Adult & Children’s Hospitals
Stereoelectroencephalography (SEEG)
Something Old Becomes Something New
– Invasive Electrode Recordings in the
Evaluation of Drug Resistant Epilepsy
Epilepsy is a common medical problem in
the Australian community with a prevalence
of 7.5 per 1000 Australian citizens. There
are approximately 52,000 people in New
South Wales who suffer from epilepsy. Ap-
proximately 30% will never achieve lasting
seizure control from medical therapy alone.
Patients with drug resistant epilepsy require
evaluation at a comprehensive epilepsy
surgery program similar to the one at the
Westmead Adult and Children’s Hospitals.
Drug resistant epilepsy is typically defined
as a failure of two anticonvulsant medica-
tions trialled at an adequate dosage. Pa-
tients would typically have at least a two
year period of uncontrolled seizures with an
average of one seizure per month for more
than 18 months and no seizure free period
lasting more than three months. The pre-
surgical evaluation involves referral to a
neurologist/epileptologist who would typical-
ly perform a detailed clinical evaluation,
EEG, video EEG telemetry, MR imaging,
PET imaging, SPECT studies and a neuro-
psychological evaluation.
This evaluation would define a group of pa-
tients who will benefit from epilepsy surgery.
The most common form of epilepsy referred
to surgical epilepsy programs involves tem-
poral lobe epilepsy. This is a well defined
electrical and clinical syndrome that has
been better defined in the PET and MR era.
The majority of these patients can proceed
to surgery without the need for an invasive
electrode evaluation. Seizure freedom rates
in the order of 70% would be standard in
high volume surgical epilepsy centres. There
has been a randomised clinical trial of sur-
gery for temporal lobe epilepsy published by
Wiebe et al (2001) in the New England Jour-
nal of Medicine. This demonstrated a signifi-
cant benefit of surgery over medical therapy
for temporal lobe epilepsy. Excellent out-
Australasian Journal of Neuroscience Volume 25 ● Number 2 ● October 2015
6
comes for surgery have been demonstrated
in a variety of other conditions, particularly
those where a lesion can be defined on ana-
tomical imaging.
There are however a group of patients with
drug resistant epilepsy where no lesion is
visible on MR imaging and the pre-surgical
evaluation suggests that the seizures begin
outside of the temporal lobe. These patients
are often referred for an invasive epilepsy
evaluation at the Westmead Hospitals. For
more than 20 years we have been implanting
subdural grid electrodes to evaluate patients
with non-lesional drug resistant epilepsy.
There remained a group of patients where
despite implanting multiple subdural grid
electrodes, we were unable to delineate the
site of seizure onset. In 2011 we began to
study the technique of stereoelectroenceph-
alography. The SEEG technique had been
common in France and Italy for more than 40
years, having originally been published by
Talairach and Bancaud in 1965 at the Sainte-
Anne Hospital in France. Initially this tech-
nique was performed with formal cerebral
angiography as the only imaging modality.
Over subsequent decades, complex three
dimensional MR, CT angiography as well as
formal digital subtraction angiography, has
been incorporated into the technique.
Over the last few years the technique has
become more common in Europe and also in
the United States. We performed our first
SEEG case at Westmead Hospital only three
years ago and have gone on to perform a
further 30 cases. Increasingly, it is replacing
the implantation of subdural grid electrodes
as our preferred technique for investigating
non lesional drug resistant epilepsy.
The SEEG technique involves implanting
multiple depth electrodes through twist drill
holes thereby avoiding the need for a craniot-
omy. We have found that the SEEG tech-
nique allows three dimensional definition of
the epileptogenic zone. The procedure is well
tolerated by patients and it is significantly
less invasive than the craniotomy required to
implant subdural grid electrodes. If an epilep-
togenic zone can be defined through the
SEEG technique, then patients would typical-
ly return for craniotomy and resection of the
epileptogenic tissue six weeks following the
SEEG procedure.
We use invasive monitoring in epilepsy sur-
gery to clarify discrepancies identified in the
pre-surgical epilepsy evaluation. It is very
important in patients with drug resistant epi-
lepsy who have a normal MRI scan. It allows
us to precisely localise multi-lobar discharges,
evaluate early involvement of functional corti-
cal areas and helps us define seizure onset
zones in patients with non lesional epilepsy
who have a normal MRI scan. We also occa-
sionally use invasive electrode monitoring in
patients with lesions that involve or are adja-
cent to functional areas of brain cortex or
where the lesion is likely to be surrounded by
a structurally normal epileptogenic region.
We have found that subdural grid electrodes
allow precise superficial two dimensional defi-
nition of the epileptogenic zone. The subdural
grid technique allows highly precise mapping
in eloquent cortex but provides very poor
mapping of deep foci of epilepsy, particularly
those involving the insular cortex. Similarly it
has a high potential for morbidity. The SEEG
technique which is a relatively new technique
on our campus allows more precise three di-
mensional definition of the epileptogenic
zone. Although we have only performed a
little over 30 cases at Westmead, the tech-
nique has been widely utilised in Europe for
50 years. It has some minor drawbacks in that
it allows less precise mapping of the eloquent
cortex. However it does allow us to perform
detailed electrical evaluations of deeply locat-
ed lesions, the insular cortex and the mesial
surface of the hemisphere. We have found
that it is certainly less invasive and patients
tolerate the procedure very well. Complication
rates are significantly lower than subdural grid
electrodes. This (old) technique has signifi-
cantly enhanced our ability to evaluate the
many patients in our community with drug
resistant non-lesional epilepsy.