The perisylvian syndrome: case report and review of the literature
KIMISKIDIS V.K., OXBURY J., OXBURY S., KAZIS D.A., KOUVATSOU Z., LOUKOPOULOU E., PITA R., PAPAGIANNOPOULOS S.,VASILIADIS G., KAZIS A.D.

The congenital perisylvian syndrome is a rare neurological entity that is usually described in the context of malformations of cortical organization. The most common clinical presentation of these patients comprises pseudobulbar palsy, cognitive deficits and drug-resistant epilepsy, while neuroimaging studies reveal cortical malformations mainly in the perisylvian regions bilaterally. We describe a variant case of this syndrome with epilepsy commencing at 12 years of age with two types of seizures. The most common types begin with a vague premonitory sense followed by loss of awareness, automatisms and sometimes incomprehensible speech but without post-ictal aphasia. The duration of these seizures is less than a minute and they occur at a frequency of approximately a hundred per year. Their characteristic is that they are particularly prone to appear under stressful conditions. The second type of seizures consists of clonic movements of the right limbs developing to a generalized convulsion. This type ceases to occur after 18 years of age. The patient was initially treated with carbamazepine and oxcarbazepine, to which she proved to be allergic. Because of the drug-resistant nature of her seizures, the patient was treated over the years with various combinations of phenytoin, primidone, topiramate, valproate, lamotrigine, clobazam, vigabatrin and levetiracetam. None of these regimens, however, offered a significant therapeutic effect. The patient was referred to our department at the age of 29 for the purpose of investigating the possibility of treating her drug-resistant epilepsy surgically. On neurological examination she had nasal speech, mild difficulty in tongue movements and hyperextension of both large and small joints of her body. She was also complaining of memory impairment and difficulty in verbalization, which had become increasingly noticeable over the last few years. A high-resolution brain MRI scan showed evidence of a fairly extensive cortical dysplasia extending from the posterior aspect of the left sylvian fissure to a deep post-central sulcus. The cortex in this area was thickened with an irregular grey/white matter interface. Similar, but less marked changes occur on the right hemisphere again extending from the sylvian fissure posteriorly. Extensive study of both hippocampi failed to reveal any asymmetries, abnormal increases in their signal intensity or derangement of their internal architecture. The patient underwent a pharmacologically activated EEG (after intra-venous administration of etomidate) that revealed frequent bursts of spike-wave complexes, sharp and slow waves. These bursts lasted from 2 to 8 seconds. Epileptic discharges had maxima at the left superior frontal electrode (F3) but were also independently seen at the right fronto-temporal area, the right posterior temporal-occipital area and the left middle temporal region. In order to investigate the possibility that her epileptic seizures might be surgically treated, the patient underwent video-telemetry (for four consecutive days) after abrupt antiepileptic drug withdrawal. A number of myoclonic jerks (not always accompanied by electroencephalographic findings) and a lot of seizures were recorded during this period. Two of these seizures were secondarily generalized. From an electrophysiological point of view, the latter started as generalized high frequency discharges followed by slow frequencies of bilateral distribution. In view of the patient's complaint of significant memory impairment and the clinical suspicion of cognitive dysfunction, a thorough neuropsychological examination was undertaken. The psychological assessment revealed specific cognitive deficits including a marginal mental retardation with a composite I.Q. score of 75 (verbal I.Q.=79, performance I.Q.=71). In addition, a slight difficulty in naming was noted, which could not be attributed to the overall cognitive dysfunction.

In conclusion, the present case highlights the heterogeneity of the perisylvian syndrome in terms of symptomatology, clinical, electrophysiological and neuroradiological findings. It is suggested that a high level of clinical suspicion is required in order to reach a correct diagnosis in atypical cases.

Key words: Perisylvian syndrome; cortical dysplasia; polymicrogyria; drug-resistant epilepsy.