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|Year : 2012 | Volume
| Issue : 3 | Page : 321-324
Surgical treatment in startle epilepsy
Hong Tian1, Xiangen Shi2, Huancong Zuo3, Wenjing Zhou3
1 Department of Neurosurgery, Affiliated Fuxing Hospital, Capital Medical University; Affiliated Yuquan Hospital, School of Medicine, Tsinghua University, Beijing, China
2 Department of Neurosurgery, Affiliated Fuxing Hospital, Capital Medical University, Beijing, China
3 Department of Neurosurgery, Affiliated Yuquan Hospital, School of Medicine, Tsinghua University, Beijing, China
|Date of Submission||12-Feb-2012|
|Date of Decision||28-Feb-2012|
|Date of Acceptance||14-May-2012|
|Date of Web Publication||14-Jul-2012|
Department of Neurosurgery, Affiliated Fuxing Hospital, Capital Medical University, Beijing 100038
Source of Support: None, Conflict of Interest: None
This report presents a patient with medically intractable startle epilepsy who was treated with surgery. The ictal onset zone was further localized to a part of the premotor cortex on the basis of intracranial electroencephalography recording and surgical resection of the epileptogenic zone was done. The motor area close to the epileptogenic focus was localized using electrical cortical stimulation and thus preserved. Patient has been seizure-free postoperatively (Engel Class I) during the 18-month follow-up. The patient illustrates that surgery can be an option in patients with medically intractable startle epilepsy with well-defined unilateral epileptogenic zone.
Keywords: Electrical cortical stimulation, intracranial electroencephalography startle epilepsy
|How to cite this article:|
Tian H, Shi X, Zuo H, Zhou W. Surgical treatment in startle epilepsy. Neurol India 2012;60:321-4
| » Introduction|| |
Startle epilepsy is a type of reflex epilepsy and seizures are triggered by a sudden and unexpected stimulus from different sensory modalities.  Most patients are sensitive to auditory or somatosensory stimuli. Most patients with startle epilepsy have structural brain lesions, the common ones being birth-related injury. Often, in these patients, seizures are resistant to antiepileptic medication. Recently, surgical treatment in medically refractory startle epilepsy has been reported. , We report a patient with medically refractory startle epilepsy who underwent a surgical treatment with seizure remission (Engle Class I).
| » Case Report|| |
A right-handed nine-year-old boy was evaluated for seizures since the age of six years. Seizures were commonly evoked by sudden and unexpected auditory or somatosensory stimuli. Seizure semiology included deviation of head and angle of mouth to the right side with occasional generalized tonic-clonic seizures lasting for 1 to 2 min with no post-ictal deficits. He typically used to experience two to three seizures per week. There was history of perinatal hypoxic insult, but no family history of epilepsy. Neurological examination showed right hemiparesis with impaired hand grip and pincer grasp and no spasticity. He had an IQ of 93. Language lateralization was to the right hemisphere with Wada test. Motor examination revealed a right hemiparesis with impaired hand grip and pincer grasp but no obvious spasticity. Sensory and cerebellar examinations were within normal limits. Seizures were refractory to carbamazepine, topiramate, clobazam and levetiracetam. Interictal and ictal scalp epileptiform discharges were localized to the left central regions. Magnetic resonance imaging (MRI) scan showed no hemi-atrophy but a focal encephalomalacia over the left superior frontal gyrus and premotor cortex [Figure 1]. Functional MRI was not done as this facility is not available at our center.
|Figure 1: Pre-surgical MRI, malacia foci were seen in the left frontal lobe, near the central area (a) sagittal view (b) axial view|
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Based on the preoperative evaluations, clinical seizure semiology, MRI and scalp-EEG, an invasive EEG evaluation was performed. A 32 (4 × 8) contact subdural electrode grid and two 16 (2 × 8) contact grids were placed over the midline surface of the left frontal-parietal lobe [Figure 2]. In addition, five deep electrode strips (4-contact each) were placed over the mesial surface of the left frontal lobe, including the supplementary motor area (SMA). Interictal EEG (iEEG) recording performed for three days showed maximal spiking zone over the left SMA, primary motor cortex, and dorsolateral premotor cortex. Three seizures documented during video-EEG monitoring were triggered by unexpected acoustic stimuli (startle) such as hand clapping or sudden opening of the room entrance door resulting in clinical seizure onset within 60 sec. Ictal recording showed fast activity and rhythmic spikes from three channels, including one surface electrode and two depth electrodes [Figure 3]. These findings localized the ictal onset zone to the middle part of the left premotor area [Figure 3].
|Figure 2: CT (computed tomography)-reconstructed image showing the location of the subdural electrodes. All surface electrodes and depth electrodes were displayed|
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|Figure 3: (a) Before one seizure onset, fast oscillations were observed in 3 channels. In total, 5 electrodes were found to show epileptiform activities based on iEEG data from 3 seizures and were identified as the ictal onset zone. (b) An intraoperative photograph: the ictal onset zones are shown with blue circles and squares, corresponding to surface and depth channels respectively; the irritative zones are illustrated in yellow; the motor areas identified by ECS are marked by the red star; the planned brain area to be resected is shown by the dotted green lines|
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Protection of adjacent motor areas
Electrical cortical stimulation (ECS) was carried out over all intracranial electrodes in a pair-wise orientation to identify the functionally important brain areas. The electrode pairs with obvious behavior responses were recorded [Figure 3]. Moreover, electrical stimulation elicited seizures at the five electrode positions that were diagnosed to be in the ictal onset zone by intracranial EEG monitoring [Figure 3]. A single electrode contact revealed overlap of the eloquent cortex and ictal onset zones [Figure 3].
Based on these findings, the area to be resected was decided, as shown in the right panel of [Figure 3]. The brain regions covered by the two electrodes with ECS-elicited motor responses (marked with red stars but within the dotted green line) were also resected since 1) these were part of the ictal onset zone by iEEG; and 2) they possibly belonged to the pre-motor area based on their anatomical locations.
A subpial resection of the cortex was done under an operating microscope. The gyri within the epileptogenic zone were resected to the bottom of the sulcus. The arteries and veins were conserved as much as possible, to avoid compromising perfusion of the adjacent cortex. We performed an extended resection including a part of the lesion, SMA, and dorsolateral premotor cortex. The surgical range was 3-4 cm on the medial surface, measured from the genu corporis callosi to the precentral region. On the lateral surface, we resected part of the superior frontal gyrus [Figure 4]. Pathological examination showed that the resected cortex had obvious degeneration of neurons and proliferation of glial cells.
|Figure 4: An intraoperative photograph showing the limited resection of the neocortex in the part of the premotor cortex|
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Postoperatively, the patient has been seizure-free for 18 months (Engel Class I). No deterioration in the neurological deficits was noted postoperatively. Surgery did not affect his IQ which was 100. The extent of surgical resection is shown in [Figure 5]. It is to be noted that not all the anatomically abnormal brain regions were resected.
|Figure 5: Comparison of the MRI before (a) and 2 weeks after the surgery (b)|
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| » Discussion|| |
Startle epilepsy is mainly triggered by unexpected auditory stimuli or sometimes somatosensory or visual stimuli. It typically exhibits uni-/bilateral tonic posturing of the limbs, occasionally leading to falls. , Startle epilepsy is an epilepsy syndrome associated with heterogeneous clinical and electrophysiological characteristics and often associated with poor seizure and developmental outcomes. Most patients with startle epilepsy have mental retardation, hemiplegia, or tetraparesis in association with uni-/bilateral hemispheric lesions due to congenital or acquired infantile brain damage with only rare asymptomatic or non-lesional cases reported in the literature. ,, Our patient had only mild neurological deficits and the decision for surgical treatment was made initially on the basis of MRI findings over the left fronto-parietal region.
Earlier studies support the hypothesis that activation of the cingulate cortex facilitates the preparation of the organism to execute rapid responses and is probably involved in the startle response.  As the cingulum and the SMA are involved in the neural circuitry for startles, an abnormal excitability in these structures could lead to an excessive startle response and thus activate neighboring motor areas, resulting in the typical motor semiology. Recent progress in medical imaging technologies such as diffusion tensor imaging may help to clarify the pathogenesis. ,
In our patient the seizures were commonly precipitated by sudden and unexpected auditory stimuli and the symptoms were mainly hypermotor seizures. iEEG recordings revealed abnormalities over the premotor and supplementary motor areas. Considering the fact that the primary sensory cortex (e.g. the auditory cortex) receives information through the direct projection of sensory afferents or by the proprioceptive input of the startle reaction to various sensory stimuli , the auditory sensory cortex may function normally but the sensory input is often back-projected from the abnormal motor cortex, forming a close-loop neural pathway, which is responsible for the observed epilepsy.
As startle epilepsy is usually medically intractable, it has been proposed that surgical treatment is a useful option.  Peri-insular hemispherotomy may be chosen if hemiplegia is identified before surgery. However, if the patient has intact sensori-motor functioning of the hemisphere with ictal onset zone, hemispherotomy can result in function deficits  with the associated post-surgery quality of life issues. Our patient had good function in the right upper and lower limbs and was not a suitable candidate for hemispherotomy. In our patient non-invasive EEG recordings could not provide localizing results for planning surgery. From the perspective of potential financial savings, multilobar resection with sparing of the motor cortex is a useful alternative. However, this is often planned without a clear hypothesis of epileptogenic zone with the added risks of removal of regions that are not involved in the epileptogenic network and incurring new deficits post surgery.
Surgical resection of the neocortex for startle epilepsy has rarely been reported. Preoperative evaluation in our patient showed moderately compromised limb function and MRI revealed gliosis extending to the pre- and post-central gyri. The epileptogenic zone was identified using intracranial electrode recording. Resection of the epileptogenic zone led to seizure freedom without increase in the preoperative deficits during follow-up (Engel Class I). Notably, part of the damaged brain areas was not resected [Figure 5] as these were part of the eloquent cortex. Surgical treatment of startle epilepsy has been reported before, without using intracranial electrode recordings.  We performed intracranial recordings for precise localization of the ictal onset zone, thus minimizing the brain regions to be resected. Therefore invasive EEG is a useful modality to plan surgical resection in startle epilepsies with major hemispheric pathologies in order to preserve pre-existing sensori-motor functions.
| » References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
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