[Downloaded free from http://www.neurologyindia.com on Thursday, September 05, 2013, IP: 220.225.230.106] || Click here to download free Android application for this journal Editorial Intracranial arachnoid : Epileptic

Murthy J. M. K.

Department of Neurology, Continental Institute of Neuroscience and Rehabilitation, Continental Hospitals, Gachibowli, Hyderabad, Andhra Pradesh, India

Address for correspondence: Dr. Murthy JMK, Department of Neurology, Continental Institute of Neuroscience and Rehabilitation, Continental Hospitals, Gachibowli, Hyderabad-500 001, Andhra Pradesh, India. E-mail: [email protected] Received : 26-08-2013 Review completed : 26-08-2013 Accepted : 26-08-2013

Intracranial arachnoid cysts are benign developmental study by Yalcin and colleagues,[4] of the 20 patients with cysts containing (CSF) and are often and associated arachnoid cysts, eight patients incidental finding in magnetic resonance imaging (MRI) could be categorized under either idiopathic generalized done for other reasons. These cysts are slowly growing or localization related by clinical and EEG and often asymptomatic and when symptomatic the features. Of the remaining 12 patients, only one patient present features include focal neurologic deficits, raised had focal epileptiform abnormalities corresponding to , and/or epileptic seizures. There arachnoid location. In both the studies; the is a debate whether arachnoid cysts in patients with focus localization was mostly based on clinical and epilepsy reflect the location of the seizure focus.[1-5] In interictal EEG features, video-EEG was done in very few the retrospective epilepsy clinic-based study by Arroyo cases. Such an approach has significant limitations as [6] and Santamaria,[3] of the 867 with epilepsy, 17 (1.96%) shown in the study by Remi and colleagues. This study patients had associated arachnoid cysts. In six of them showed that the occurrence and localization of interictal other possible or predisposing factors for epilepsy could and ictal EEG findings differ vastly for lesions in different brain regions, more so with extratemporal epilepsies. be established. Of the remaining 12 patients, one had In the adult surgical series, preoperative video-EEG benign epilepsy with centrotemporal spikes and one recordings and intraoperative electrocorticography had bilateral frontal and parietal band heterotopia. In the (ECoG) findings showed good congruence with the rest of the patients, clinical and electroencephalography location of arachnoid cysts and these patients had good (EEG)/video-EEG features localized seizure focus seizure outcome following arachnoid cyst excision adjacent to the arachnoid cyst in only four patients. In the in adults with drug resistant arachnoid cyst-related epilepsy.[7] Similar were the findings in the pediatric Access this article online patients in the study by the same group published in this [7] Quick Response Code: Website: issue of the journal. Thus, the available data suggests www.neurologyindia.com that in patients with generalized and localization related idiopathic epilepsies[3,4] and some specific epilepsy PMID: [1,5] *** syndromes, the arachnoid cysts are more likely an incidental finding. In patients with identifiable possible DOI: or predisposing factors for epilepsy, arachnoid cysts may 10.4103/0028-3886.117580 be incidental and these patients require multimodality

Neurology India | Jul-Aug 2013 | Vol 61 | Issue 4 343 [Downloaded free from http://www.neurologyindia.com on Thursday, September 05, 2013, IP: 220.225.230.106] || Click here to download free Android application for this journal

Murthy: Arachinoid cyst-related epilepsy

workup to establish the causal relationship between temporal lobectomy or thermocoagulation of the adjacent the two. In patients with no other identifiable factor for cortex. The extent of surgical resection was based on the epilepsy, the association between epilepsy and arachnoid intraoperative ECoG findings. The variable results in the cysts is more likely and these patients need detailed earlier studies may be related to imprecise localization preoperative surgical evaluation before considering for and inadequate resection of the epileptogenic zone.[2,10,11] epilepsy to establish the causal relation. In patients with arachnoid cyst-related epilepsy, the choice of the most appropriate surgical approach is The exact pathogenic mechanism of epileptogenesis still debated. The two recent studies both in adults in arachnoid cyst-related epilepsy is not unknown. and children with arachnoid cyst-related epilepsy, the Compression of the surrounding brain structures has surgical approach was microsurgical . Full been proposed as the possible mechanism. Okada and space microsurgical craniotomy ensures the ability to colleagues[8] studied the relationships among seizures, perform to another operation for cyst-related epilepsy the volume of arachnoids cysts, and regional cerebral and also intraoperative ECoG monitoring.[7] blood perfusion around arachnoid cysts. The volume of arachnoid cysts in patients without epilepsy was To establish the causal relationship between arachnoid significantly larger than in patients with epilepsy. cysts and epilepsy in patients with epilepsy and Single photon emission computed tomography (SPECT) arachnoid cysts, probably a multimodality workup is demonstrated hyperperfusion around arachnoid cysts essential. There is an urgent need for systematic studies in patients with no epilepsy, whereas in patients with to determine the ideal surgical approach and also the epilepsy SPECT demonstrated hypoperfusion. Lesional extent of resection to get a good seizure outcome in side to normal side ratio of region of interests in the patients with arachnoid cyst-related drug resistant posterior temporal area and irregular region of interests epilepsy with a large sample size. in the temporal area were significantly lower in patients with epilepsy than in patients without. These results References suggest that the epileptogenic focus probably lies in compressed cerebral cortex surrounding the arachnoid 1. Pascual-Castroviejo I, Pascual-Castroviejo SI. Bilateral archnoid seizures and severe : Case report. Neuropediatrics cyst is probably the epileptogenic focus. These authors 1994;25:42-3. had also proposed that the associated parenchymal 2. Koch CA, Voth D, Kraemer G, Schwarz M. Arachnoid cysts: Does lesions in the surrounding brain may also participate surgery improve epileptic seizures and ? Neurosurg Rev in the epileptogenesis. This needs confirmation by 1995;18:173-81. 3. Arroyo S, Santamaria J. What is the relationship between archnoid histological studies of the excised surrounding brain cysts and seizure foci? Epilepsia 1997;38:1098-102. tissue. 4. Yalcin AD, Oncel C, Kaymaz A, Kuloglu N, Forta H. Evidence against association between arachnoid cysts and epilepsy. Epilpsy Res The surgical indication in patients with arachnoid 2002;49:255-60. 5. Mainali NR, Jalota L, Aryal MR, Schmidt TR, Badal M, Alweis R. cyst-related drug resistant epilepsy is localizing Laugh-induced seizure: A case report. J Med Case Rep 2013;7:123. electroencephalographic interictal, ictal, and ECoG 6. Remi J, Vollmar C, de Marinis A, Heinlin J, Peraud A, Noachtar S. abnormalities.[7,9] In pediatric[7] and adult[8] patients with Congruence and discrepancy of interictal and ictal EEG with MRI arachnoid cyst-related epilepsy, pre-surgical video- lesions in focal epilepsies. Neurology 2011;77:1383-90. 7. Wang C, Liu C, Xiong Y, Han G, Yang H, Yin H, et al. Surgical EEG studies revealed epileptiform discharges strongly treatment of intracranial archnoid cysts in adults patients. Neurol correlating to location of the cyst. Intraoperative ECoG India 2013;61:60-4. in both adults and children demonstrated epileptiform 8. Okada Y, Hamano K, Iwasaki N, Horigome Y, Enomoto T, Sato M, discharges correlating to the cyst location.[7] et al. Epilepsy accompanied by intracranial arachnoid cysts: Studies on volume and regional cerebral blood perfusion using MRI and SPECT. J Epilepsy 1998;11:195-201. The place of surgery in arachnoid cyst-related epilepsy 9. Tambumini G, Dal Fabbro M, Di Rocoo C. Sylvian fissure arachnoid has not been systematically studied and the data is cysts: A survey on their diagnostic workout and practical management. limited to a few case series. In these studies no details Childs Nerv Syst 2008;24:593-604. 10. Pradilla G, Jallo G. Archnoid cysts: Case series and review of the of presurgical evaluation in regard to localization of literature. Neurosurg Focus 2007;22:E7. epileptogenic zone were given. In a recent surgical 11. Holst AV, Danielsen PL, Juhler M. Treatment options for intracranial series in adults, good seizure outcome was observed archnoid cysts: A retrospective study of 69 patients. Acta Neurochir in 87.5% of patients.[7] The same group reported good Suppl 2012;114:267-70. seizure outcome in 77.7% of pediatric patients.[7] These encouraging results in both the series may be related to How to cite this article: Murthy J. Intracranial arachnoid cysts: Epileptic seizures. Neurol India 2013;61:343-4. the surgical techniques, cyst excision, and either anterior

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