What is the Relationship Between Arachnoid Cysts and Seizure Foci?

Abstract

Summary:Purpose: Arachnoid cysts are sometimes encountered in MRIs performed for a variety of reasons. In patients with epilepsy, particularly those with refractory epilepsy, arachnoid cysts are often assumed to be related to their seizure focus. We conducted a study to investigate this putative relationship.Methods: A retrospective study on the incidence of arachnoid cysts was performed in patients seen in our Epilepsy Clinic who had CT or MRI scans, interictal EEGs or ictal EEGS. Locations of seizure foci in these patients were defined from clinical and electrophysiologic data.Results: Seventeen of 867 patients had arachnoid cysts.Twelve patients had temporal lobe cysts and only 3 of them had temporal lobe seizures. Four patients had frontal lobe cysts and only 1 had frontal lobe seizures ipsilateral to the cyst. One patient had a cerebello-pontine angle cyst and frontal lobe seizures. Thus, clinical manifestations of seizures and EEG findings (interictal and/or ictal) indicated that the seizure focus was adjacent to the cysts in only 4 patients (23.5%).Conclusions: Our findings suggest that arachnoid cysts are often an incidental finding in patients with epilepsy and do not necessarily reflect the location of the seizure focus. Key Words: Arachnoid cysts-Frontal lobe seizures-Temporal lobe seizures-Complex partial seizures-Epilepsy surgery.Arachnoid cysts are frequently encountered in association with various neurological disorders, including epilepsy (1-3). In a recent study of 27 patients with arachnoid cysts in the middle cranial fossa, 10 had neurologic symptoms not referable to the cyst, 17 had neurologic symptoms which were possibly related to the cyst, and 7 of these 17 patients had epilepsy (3).Arachnoid cysts are congenital lesions of unknown causes and consist of a reduplication of the arachnoid membrane within which fluid collects as a cyst (4). The etiology of the cysts is controversial, but it has been ascribed to congenital malformation, infection, trauma, or increased intracranial pressure. Their most common locations in the sylvian or choroidal fissure (3). In most cases, cysts are not associated with progressive symptoms related to raised intracranial pressure, and frequently are detected incidentally, or following hemorrhagic complications due to minor trauma.A number of anecdotal reports have yielded inconsistent conclusions about the relationship of arachnoid cysts and epilepsy. A patient with Landau-Kleffner syndrome was reported to have an area of hypometabolism around an arachnoid cyst. Shunting of the cyst led to seizure Accepted May 7, 1997. Address correspondence and reprint requests to Dr. S. Arroyo at Servicio de Neurologia, Hospital Clinic i Provincial de Barcelona, cNillarroel 170, Barcelona 08036, Spain. improvement and reduction of the hypometabolism (5).However, bilateral temporal lobe cysts were described in a patient with multifocal epilepsy and Lennox-Gastaut syndrome, suggesting that arachnoid cysts in themselves are not necessarily related to a specific epileptogenic regi...

Surgery for intracranial arachnoid cysts in children—a prospective long-term study

“…In our series, the cognitive impairment persisted despite surgery. The causative relationship between ACs and epileptic seizures is controversial [22]. Similar to our results, some studies find a complete resolution of seizures in some patients, while other patients experience either a reduced or an unchanged frequency of seizures [23].…”

Amino acid composition of brain cysts: levels of excitatory amino acids in cyst fluid fail to predict seizures

“…In clinical practice, however, more often brain cysts without signs of compression are observed in epileptic patients, raising the question whether the cyst content may be relevant for epileptogenesis. In a retrospective analysis of 867 patients of whom 17 had arachnoid cysts, only in 4 patients the seizure focus was adjacent to the cyst, suggesting that arachnoid cysts are often incidental findings in epileptic patients (Arroyo and Santamaria, 1997). A similar conclusion was recently reached by Yalcin et al (2002), who reported that seizure type and EEG abnormalities corresponded to arachnoid cyst location in only one out of eight patients.…”

A rare brain developmental anomaly in a patient with Usher’s syndrome

“…Incidence is 0.5% in autopsy series [7]. However, there are also different percentages reported in the literature: 0.23% in head trauma, 1.96% in epilepsia, and 2.6% in headache [8][9][10]. Generally arachnoid cysts remain asymptomatic but may cause headache, nausea, vomiting, lethargy, seizures, and focal symptoms of space-occupying lesion.…”