John Libbey Eurotext

Reading epilepsy in a patient with previous idiopathic focal epilepsy with centrotemporal spikes Volume 1, numéro 3, Septembre 1999

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  • Reading epilepsy in a patient with previous idiopathic focal epilepsy with centrotemporal spikes

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Benign epilepsy with centrotemporal spikes (BECT) [1] is a common childhood epilepsy syndrome, with onset between 5 and 10 years of age. It is characterized by brief, stereotypical, unilateral motor tonic, clonic, or tonic-clonic convulsions involving lips and tongue as well as pharyngeal and laryngeal muscles.

A transient speech impairment, hypersalivation or dysphasia can occur during the ictal or postictal phase. Typically, the seizures are related to sleep, and, in diurnal attacks, consciousness is preserved. Interictal waking EEG shows spike and waves in the central (rolandic) or midtemporal regions. These spikes are activated by sleep and may be unifocal or multifocal occurring in one or both hemispheres, increasing during sleep. Seizures are readily controlled by most antiepileptic drugs such as carbamazepine and phenytoin [1]. Genetic factors are believed to play a role. There is a marked age-dependence of the syndrome implying a hereditary impairment of brain maturation. Recently, a case of benign familial neonatal convulsions (BFNC) followed by BECT was described in two siblings [2], suggesting a common genetic background. These two distinct epileptic syndromes in two siblings are both genetically determined and have a benign course. It is interesting that they are classified in the present classification of epilepsies and epileptic syndromes (International League Against Epilepsy, ILAE, 1989) [3] into different groups, that is generalized and localization-related respectively.

Reading epilepsy (RE) [4] is a benign epileptic syndrome, idiopathic or symptomatic, in which seizures occur in reponse to reading. In some cases, the seizures are precipitated only by one stimulus, such as reading, and can thus be termed "pure reflex epilepsy" (primary reading epilepsy, PRE). In other cases different triggering factors may be recognized (secondary reading epilepsy, SRE). In PRE, seizures start in adolescence, and the semiology consists of sensory-motor or motor speech aura occurring while reading, jaw jerks and, if reading is continued, a generalized seizure.

Interictal EEG is often normal; ictal EEG shows either bilaterally synchronous paroxysmal or a local temporo-parietal discharge in the dominant hemisphere. Seizures respond well to carbamazepine, valproic acid or benzodiazepines [4].

We report the first documented case, to our knowledge, with a clear-cut idiopathic localization-related epilepsy (BECT) evolving into PRE.

Case report

A 30 year-old, right-handed man was examined for epileptic seizures. He had no family history of seizures or personal history of birth trauma, fever convulsions or head injury.

At the age of 8 years, he had had nocturnal partial motor seizures, with clinical and electroencephalographic features typical of BECT. His seizures were characterized by a sudden "throat sound", then he woke up and he usually ran to his parents. They noted a contraction of the left hemiface and clonic movements of the left leg without loss of contact for about 10-15 seconds, with speech impairment. We reviewed the EEG at 8 (figure 1) and 12 years (figure 2). At 8 years of age, EEG recording during drowsiness disclosed spike and wave discharges on a normal background activity over both mid-temporal regions, predominantly on the left side. At twelve years of age, EEG tracings during wakefulness showed spike and wave paroxysmal activity over centro-parietal regions, more evident on the left hemisphere. General and neurological examinations were normal, with normal development and school performance. At that time, treatment with carbamazepine (600 mg/die) and phenobarbital (100 mg/die) considerably reduced the frequency and intensity of seizures. He was then seizure-free during the 5 year follow-up period from the age of 12 to the age of 17, and so stopped the antiepileptic therapy. At age 17 years, he began to note, while reading silently but more often aloud, very frequent episodes of abrupt, involuntary, isolated jaw jerks, associated with a subjective sensation of clicking, mouth trembling, stuttering, difficulty in pronouncing words and eventual speech arrest. These symptoms progressed to a generalized tonic-clonic seizure (GTCS) if the reading was continued, with a variable latency. The patient did not have spontaneous seizures and no other additional non-reading-related stimuli were able to trigger his attacks. The patient often recognized the initial symptoms and he avoided prolonged reading to prevent the GTCS. Results of general and neurological examination were normal, as well as routine blood tests and neuroradiological study (computed tomography and magnetic resonance scans). Video-polygraphic interictal EEG recordings during the awake resting state showed normal background activity with a mild, non-specific bitemporal slowing during light sleep, without evidence of photosensitivity or paroxysmal activity during hyperventilation. Prolonged reading of linguistic material induced repetitive myoclonic jerks in the facial muscles (video 1). The appearance of myoclonias coincided, on EEG (figure 3), with a clear-cut epileptiform spike and wave activity, diffuse in both hemispheres, with anterior predominance. These EEG/EMG correlations were more evident during reading aloud compared with silent reading. The content of the text was not significant in provoking seizures. Treatment with carbamazepine 800 mg/day and valproic acid 800 mg/day considerably reduced seizure frequency.

Discussion

Reading epilepsy was first described [5] as an uncommon form of reflex epilepsy in which seizures are precipitated by reading, and was divided into primary and secondary reading epilepsy (PRE and SRE). The diagnosis of PRE or SRE was based on clinical and electrophysiological criteria. PRE was characterized by idiopathic origin, initial jaw clicking, GTCS on prolonged reading, normal resting EEG, and generalized 3-6 c/s paroxysmal EEG discharges with a parieto-occipital maximum on reading. The criteria for SRE were less precise [5], including patients with seizures that occured either spontaneously, or during reading, or in response to other stimuli unrelated to reading. Proprioceptive impulses from the jaw muscles were postulated as the principal pathophysiological mechanism of epileptogenesis [5]. Since then several reports in the literature supported the original classification [6, 7], and additional putative pathophysiological hypotheses underlying reading-induced seizures have been suggested [8]. The importance of a cumulative effect of multiple factors for seizures provocation was noted [9], examining the relative contribution of the many variables implied in reading: saccadic eye movements, reading aloud versus reading silently, linguistic complexity of the text, and concentration. The recognition of familial cases has emphasized the possible role of a genetic component in this condition [10-12]. Several findings suggest that RE does not represent an homogeneous entity, but a spectrum of different electroclinical subtypes. The variability of triggering factors in SRE indicates a difference in specificity of the syndrome because the specific trigger may be eye and mouth movements, visual pattern stimulation, right-to-left reading [13], or the difficulty of the reading material, i.e. foreign languages [6, 13]. Another triggering factor in precipitating seizures may be a cortical linguistic process related to the grapheme-to-phoneme transformation described [14] in a young patient with an acquired RE after removal of a left frontal arteriovenous malformation. The pathophysiological and neuroanatomical bases of epileptogenesis in RE remain to date, unconfirmed.

A recent paper [15] discussed the difficulties in re-classifying RE, both for the terms "primary" and "secondary", used in the context of etiology (idiopathic and acquired) and the terms "focal" and "generalized". In the present classification [3] RE is included among the localization-related idiopathic epilepsies. Genetic, clinical and EEG data [16, 17] indicate that PRE should be included among the idiopathic localization-related epilepsies, with an age-related onset, like the BECT. On the other hand, the clinical and EEG features of RE and juvenile myoclonic epilepsy resemble each other [18], suggesting RE should be included in the group of idiopathic generalized syndromes. Moreover, absence seizures have been induced by reading [13]. A recent clinical and video-EEG study of 17 patients with PRE [19] concluded that RE does not fit into any category of the present classification of ILAE, representing a distinct form of reflex epilepsy neither partial nor generalized, in which the epileptogenesis may be based on a cortical hyperexcitability, genetically determined and age-modulated. In his critical review, Ramani [15] suggested that different subtypes of RE can be distinguished, depending on clinical and EEG findings, that may be classified separately into the group of idiopathic generalized (age-related), idiopathic localization-related and symptomatic localization-related epilepsies. Our case is the first documented report of BECT followed by RE. Because of the relative frequency of BECT in young children, we cannot exclude the possibility of a casual association of these two syndromes in this patient. However, we believe that it is not a coincidental association, because both syndromes have an age-related onset, a benign course and an idiopathic origin, thus supporting the present ILAE classification of RE among the idiopathic localization-related epilepsies, like BECT.

CONCLUSION

Acknowledgment:

We thank Elena Zoni, Carlo Grassi and Fabio Bisquoli for technical assistance in preparing figures and videotapes.