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SURGICAL
MANAGEMENT OF INTRACTABLE EPILEPSY |
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Epilepsy is one of the commonest
neurological disorders. Approximately 70% of people with newly diagnosed
epilepsy can expect to achieve seizure freedom within a 10-year
period following diagnosis. Factors that predict favourable outcome
include idiopathic or cryptogenic epilepsy and childhood epilepsy.
Though the prevalence data from India is not available, it is estimated
that the incidence of intractable epilepsy is around 6-7/1,00,000.
Out of this more than 50% are suffering from secondarily generalized
epilepsy that can benefit from surgery. By this estimate approximately
2.4 to 3.2 lac people suffering from intractable epilepsy can benefit
from surgery.
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Surgical treatment of epilepsy is a treatment option
in patients whose seizures are not responsive to medications or
for patients who are unable to tolerate medication side effects.
Medication may not also be the preferred treatment for patients
whose seizures are caused by structural abnormalities in the brain.
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Patients with poorly controlled seizures of any
age who are otherwise in good health are candidates for epilepsy
surgery. Epilepsy surgery candidates are typically young adults.
However, the current trend is toward early intervention in children
to avoid many of the psychosocial consequences of growing up with
epilepsy.
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The Epilepsy Surgery Program at the Jaslok Hospital
and research centre is managed by a group of specialist dedicated
to the field of epilepsy. They include Epileptologist; Dr. Joy Desai,
Neurophysiologists Dr. Firuza Wadia and Dr. Margi Desai, Neuroradiologist
Dr. Srinivas Desai, Neuropsychologist and Neurosurgeon Dr. Paresh
Doshi. It is a major referral centre of India that offers complete
evaluation and surgical treatment for epilepsy.
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The presurgical evaluation involves a detailed
workup comprising of history, EEG, MRI video telemetry and neuropsychological
assessment. In certain cases single photon emission computerized
tomography and MRI spectroscopy are also utilized. The data collected
from all these investigation is than utilized to pinpoint the epileptic
focus. Once the focus is identified a strategy for surgical resection
is planned. The various surgical procedures that can be undertaken
for treatment of epilepsy are:
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- Temporal
lobectomy - removal of the anterior temporal lobe including
the medial temporal structures. This is the most common and rewarding
of all the surgeries for epilepsy.
(Fig. 1 & 2).
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Fig.
1 Temporal lobe being exposed during surgery for temporal
lobectomy |
Fig.
2 Picture after the resection of temporal lobe
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- Extratemporal
resection - removal of epileptogenic cerebral cortex or
lesions (tumors, hamartomas, vascular malformations etc.) outside
the anterior temporal lobe
- Hemispherotomy
- a recent modification of hemispherectomy in which the damaged,
epileptogenic hemisphere is disconnected rather than removed.
It is a much shorter operation than hemispherectomy, and is
ideally suited for patients with significant atrophy of the
damaged hemisphere. The common seizure disorder that respond
to this procedure include Rasmussen’s encephalitis, Sturge-Weber
syndrome, HHE syndrome and hemimegaencephaly.
- Corpus
callosotomy - Corpus callosum connects the right and the
left cerebral hemisphere. Sectioning of the corpus callosum
disconnects the two hemispheres and prevents the spread of seizures
from one hemisphere to the other. The common seizure disorders
that respond to this form of surgery include tonic and atonic
attacks that are frequently seen in Lennox-Gastaut syndrome,
multi centric complex partial seizures with secondary generalization,
etc.(Fig. 3).
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Fig.
3 T1 weighted Coronal MRI showing a corpus callosotomy.
The corpus callosum between the roofs of the lateral ventricles
has been sectioned and the body of the left later ventricle
is seen herniating through the section. |
- Multiple
subpial transection - When the eplileptogenic lesion is
located in a functionally important area like speech or motor
power centre of the brain, it is not advisable to resect the
same due to high risk of neurological deficit. In such cases
transection of the cortex without removal of the epileptogenic
zone by specially designed instruments can decrease the seizure
frequency and intensity.
- Vagal
nerve stimulation - involves implantation of a stimulating
electrode around the left vagal nerve and attaching it to a
pulse generator which is implanted under the skin just below
the collar bone. The pulse generator is programmed so that it
may be turned on or off at specified times and so that the amplitude
and frequency of stimulation can be modified as indicated.
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Results
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Surgical
success depends on the type of surgery, but most patients are substantially
improved. |
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- Approximately
80 percent of patients who have an anterior temporal lobectomy
are seizure-free one year following surgery, and 90 percent
show marked improvement.
- 70-80%
of the patients having lesion excision have significant control
of their seizures with 50% of them being seizure free.
- More
than 50 percent of patients who have a corpus callosotomy are
substantially improved where in others the frequency and the
intensity of the seizures is decreased.
- Seventy-five
percent of patients who undergo functional hemisphotomy are
seizure-free postoperatively, and 100 percent are improved.
- Preliminary
data suggest multiple subpial transection maybe effective in
decreasing seizures without causing a neurological deficit.
- Preliminary
data suggest that certain patients with generalized seizure
disorders may benefit significantly from vagal nerve stimulation.
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EPILEPSY
SURGICAL PROTOCOL, JHRC |
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Phase
I
History
and evaluation by Epileptologist
MRI and MR spectroscopy
EEG
Neuropsychology
Video telemetry
SPECT scan
Phase
II
Wada
test
Invasive EEG recordings (Subdural and Depth electrodes) Corticography
Cortical stimulation and mapping |
