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|LETTERS TO EDITOR
|Year : 2018 | Volume
| Issue : 5 | Page : 1503-1505
Gelastic seizures due to inferior frontal gyrus cavernoma
Sita Jayalakshmi1, Rajesh Reddy2, Rammohan Vadapalli3, Sudhindra Vooturi1, Manas Panigrahi2
1 Department of Neurology, Krishna Institute of Medical Sciences, Secunderabad, Telangana, India
2 Department of Neurosurgery, Krishna Institute of Medical Sciences, Secunderabad, Telangana, India
3 Department of Radiology, Krishna Institute of Medical Sciences, Secunderabad, Telangana, India
|Date of Web Publication||17-Sep-2018|
Dr. Sita Jayalakshmi
Department of Neurology, Krishna Institute of Medical Sciences, 1.-8.-31/1, Ministers Road, Secunderabad, Telangana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jayalakshmi S, Reddy R, Vadapalli R, Vooturi S, Panigrahi M. Gelastic seizures due to inferior frontal gyrus cavernoma. Neurol India 2018;66:1503-5
Gelastic seizures are defined as epileptic fits where laughter is the only or predominant symptom. Gelastic seizures are an uncommon seizure type which in most cases has an underlying structural cerebral pathology and particularly a hypothalamic hamartoma. Neocortical origin of gelastic seizures is rare and has been reported to originate from a dysplastic cortex in the temporal, parietal, or frontal lobes.,,,, In the cases with a frontal focus, the anterior cingulate and orbital structures have been implicated in the genesis of laughter. This occurs due to the disconnection within the premotor mesial system, by an imbalance between the premotor mesial and the premotor lateral systems or by activation of a previously conditioned orbital region.
A 43-year old man, a mechanic by occupation, presented with seizures for the previous 2 years. Seizures were characterized by a sudden loud laughter lasting for nearly 30s, followed by a state of confusion, bimanual automatisms with loss of awareness of the surroundings for 40–60s. He never had secondary generalized seizures. The patient recovered immediately after the event. Initially, the seizure frequency was 5–6 per week, which increased to 3–4 per day in the subsequent 6 months. The patient was not aware of his laughter and there was no mirth associated with the episode. There were no autonomic or motor phenomena, myoclonic jerks, or drop attacks. He had neither a past history of seizures, nor febrile convulsions or status epilepticus. There was no family history of epilepsy. Seizures were resistant to multiple antiepileptic drugs (AEDs) [carbamazepine, clobazam, topiramate, and sodium valproate] at an optimum dosage. Frequent seizures caused social embarrassment and injuries, which forced him to quit his job.
On evaluation, magnetic resonance imaging (MRI) of the brain showed a lesion in the left inferior frontal gyrus with findings consistent with a cavernoma [Figure 1]. A blood oxygen level dependent (BOLD) functional MRI with verbal fluency paradigm localized the language area to the parts adjoining the anteroinferior, medial, and anterosuperior aspects of the lesion. He had an above-average intelligence, significant deficits on visual memory testing, and mild deficits on verbal memory testing.
|Figure 1: Magnetic resonance imaging of the brain – axial (a) and coronal (b) T2--weighted images and proton density image (c) suggestive of a cavernoma|
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The patient underwent a long-term video electroencephalogram (EEG) recording. The interictal EEG showed intermittent bilateral frontal slowing. No lateralized spikes were noted. Four events were recorded. The seizure semiology was suggestive of gelastic and auto-motor seizures. The ictal EEG showed a 6–7 Hz left frontal and temporal rhythmic theta activity for 14–20s, evolving into bifrontal rhythmic theta activity, followed by bi-hemispherical rhythmic theta activity intermixed with spike and wave activity [Figure 2].
|Figure 2: Ictal EEG showing the left frontal and temporal rhythmic activity suggestive of ictal onset|
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The patient underwent an awake craniotomy with cortical stimulation for language mapping. The patient had speech arrest during cortical stimulation very close to the medial, lateral, and inferior margins of the lesion signifying that the lesion was on the Broca's area. The lesion was partially resected and disconnected from rest of the cortex, guided by an intra-operative eletrocorticography (ECoG). Postoperatively, the patient had no language deficits. Histo-pathological examination was suggestive of a cavernoma. A follow-up MRI brain including diffusion tensor imaging (DTI) showed disconnection of the fibers of pars opercularis from the inferior frontal gyrus [Figure 3]. The patient was seizure free on AEDs for 18 months post-surgery. However, he reported two episodes of laughter after progressive withdrawal of the last AED, and hence was restarted on a single AED. At the last follow-up, >10 years post-surgery, the patient has been totally seizure free and on one AED.
|Figure 3: Postoperative magnetic resonance imaging (a) and diffuse tensor imaging (b) TI weighted image showing the disconnection of fibers of pars opercularis from the rest of the lesion located in the inferior frontal gyrus|
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Hypothalamic hamartoma is the most common cause of gelastic epilepsy. Among gelastic seizures originating from the neocortex, the temporal lobe epilepsies are more frequently associated with gelastic seizures than the frontal lobe epilepsies. The characteristic features of gelastic epilepsy described by Gascon and Lombroso  include stereotyped recurrence, absence of external precipitants, concomitance of other manifestations generally accepted as epileptic such as spasms, simple partial seizures, complex partial seizures or generalized tonic clonic seizures, interictal and ictal EEG showing epileptiform discharges, and absence of conditions in which pathological laughter may occur.
The characteristic laughter in gelastic seizures is inappropriate, sudden, violent, paroxysmal, and uncontrolled, possibly followed by facial contractions in the form of a smile or grimace (the latter is referred to as “dacrystic” seizures). Sometimes there is giggling, smiling, laughing, and crying. Mirth, the emotional component may be present during the laughter, especially with a temporal lobe focus. The duration of laughter is usually short (<30 s) but can be prolonged if it occurs with complex partial seizures. Autonomic features such as flushing, tachycardia, and changes in respiration can occur with the seizure. The severity of epilepsy is variable but most of the cases evolve as intractable epilepsy.,
The pathophysiology of epilepsy due to a cavernoma is often because of repeated micro-hemorrhages and deposition of hemosiderin in the surrounding cortical tissue. The cortex is hyper-excitable probably due to iron ions that generate free radicals and lipid peroxides. The seizure control observed in the current patients may be attributed to the extended excision of the surrounding area of hemosiderin deposition (as evident on the follow-up MRI) [Figure 3]. Frontal, temporal, limbic, and parietal locations of the brain lesions produce abnormal laughter.[3-8, 10, 12, 13] Among the neocortical epilepsies, the frontal lobe is more frequently associated with gelastic epilepsy, especially the mesial frontal and orbitofrontal lobe lesions., Sartori et al., reported 10 cases of gelastic seizures originating in the frontal lobe in their literature search . Unlike seizures with a temporal or hypothalamic focus, laughter from gelastic seizures with a frontal focus presents a homogeneous clinical pattern: it appears always forced and with no emotional component. They proposed that there may be a “critical” functional disconnection between the motor loop and the limbic loop within the mesial premotor system. The laughter is considered as a behavioral “output” arising in a motor program detached from all motivation. Alternately, there could also be an imbalance between the mesial and lateral premotor systems. The laughter in this case was a consequence of hyper- reactivity to the environmental stimuli that was detached from the motivational aspects.
In the current report, we report a case of gelastic epilepsy due to a cavernoma involving the left inferior frontal gyrus. Fernández-Baca Vaca et al., reported a patient with intractable epilepsy in whom mirth and laughter were consistently produced during stimulation of the opercular part of left inferior frontal gyrus using stereotactically placed depth electrodes. Cortical sites that produce mirth when stimulated are located in the dominant hemisphere close to language areas; or, cortical negative motor gelastic seizures may evolve as pharmacoresistant epilepsy. Surgical resection or disconnection of the epileptogenic focus from the surrounding cortex results in a good outcome in terms of seizure of control. Our patient had seizure freedom after disconnection of the lesion from the inferior frontal gyrus.
Gelastic seizures are not always due to hypothalamic hamartomas. Structural lesions in the temporal, parietal, or frontal lobes can also be the epileptogenic foci for gelastic seizures. Mesial frontal, orbitofrontal, and dominant inferior frontal gyrus lesions can cause gelastic seizures. Resection or even a simple “disconnection” of the lesion from the surrounding cortex can result in excellent seizure control.
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[Figure 1], [Figure 2], [Figure 3]