| Primary reading epilepsy Benjamin G. Zifkin and Frederick Andermann April 24, 2001 Date of update: February 11, 2003 Date of update: May 2004 Medline SEARCH DATE: January 2004 |
ACKNOWLEDGEMENTS AND DISCLOSURESPlease disclose any financial or other conflicts of interest that might bias your contributions, or give rise to the perception of such bias. Relevant financial ties can include consultantships, memberships in speaker's bureaus, grants, research support, salaries, royalties, ownership, equity positions, stock options, or other financial arrangements wherein you stand to gain substantially from an increase of stock value or corporate revenues. Disclosures and acknowledgements will be linked to the author name(s) and will display along with appointments and affiliations. Disclosures, acknowledgements, and affiliations can be entered and updated via the "Update My Profile" link in the Online Submission System. Alternatively, you may send such information along with your updated manuscript. THUMBNAILSo that MedLink Corporation can highlight your clinical summary and your authorship on the MedLink Neurology home page and in our weekly email to subscribers, we ask that you provide here a brief overview of your subject (about 50 to 100 words) aimed at enticing readers to view this clinical summary. For updates, please include a sentence that refers to something new you have added. Refer to yourself in the 3rd person (eg, Dr. Doe of Superior Institution explains the basics…). For more information and examples of thumbnails, please see the Instructions to Authors, which can be downloaded from your "My Writing Assignments" page in the Online Submission System ( http://www.medlinkoss.com). Current thumbnail : Primary reading epilepsy is characterized by seizures induced by reading and is classified as a reflex epilepsy syndrome in the recent proposed diagnostic scheme for epilepsy and seizures. In these patients, reading triggers jaw jerks and unilateral or bilateral myoclonic jerks that may progress to a generalized convulsion if reading continues. Routine imaging studies are normal. Benjamin Zifkin and Frederick Andermann of the Epilepsy Clinic at the Montreal Neurological Hospital review EEG data, and recent high resolution 3-Tesla MRI and functional imaging in reading epilepsy which suggest that a mechanism similar to that seen in pattern-sensitive seizures, in which generalized activity is activated by the occipital cortical stimuli, may operate in many cases of primary reading epilepsy, in which activation of a language related functional network triggers the generalized or bilateral EEG discharges and clinical events.
PATHOGENESIS AND PATHOPHYSIOLOGYStudies of reading epilepsy suggest that increased task difficulty, increased complexity of different types, or duration increase the chance of EEG or clinical activation. No one feature of reading can be identified as a common trigger (Christie et al 1988; Wolf et al 1998). Functional imaging in primary reading epilepsy (Koepp et al 1998; Koutroumanidis et al 1998) has shown that these seizures result from activation of parts of a speech and language network in both hemispheres. Recent fMRI and morphological studies of two subjects with reading epilepsy using a more powerful 3-Tesla magnet showed that silent reading by one subject activated spikes in the left precentral gyrus. However, activation also occurred in the central sulcus and globus pallidus bilaterally. Both subjects had an unusual gyral pattern in the left central region (Archer et al 2003). These findings are in agreement with the proposal (Remillard et al 1998) that the hyperexcitable neuronal tissue forming the critical mass recruited to produce a clinical attack is not necessarily contiguous but is functionally linked. Radhakrishnan (Radhakrishnan 1995) found bilateral symmetric ictal discharges in 75% of subjects and suggested that reading epilepsy was similar to cases of juvenile myoclonic epilepsy with specific triggers of myoclonic jerks, which for nonverbal tasks has been described as “praxis-induction.” A mechanism similar to that seen in pattern-sensitive epilepsy, in which generalized activity is activated by the occipital cortical stimuli, may operate in many cases of primary reading epilepsy in whom bilateral myoclonic attacks or bilaterally synchronous epileptiform activity is triggered by a functionally localized task activating a functional network which in affected subjects is hyperexcitable. Evidence for the distribution of this network and for the abnormal activity within it has been obtained from functional imaging (Koepp et al 1998). Pegna and colleagues suggest that seizures triggered by sublexical (nonword) reading involve the left hemisphere preferentially, as compared to those triggered by lexical reading, which have bilateral EEG expression (Pegna et al 1999). More information could be obtained from detailed clinical and EEG assessment with genetic histories and high field strength MRI imaging of patients and families.EPIDEMIOLOGY Reading epilepsy is unusual but may be underdiagnosed. The incidence and prevalence are unknown. PREVENTION No method of prevention is known. DIFFERENTIAL DIAGNOSIS Primary reading epilepsy may be underdiagnosed. If isolated jaw jerks occur without leading to myoclonic jerks, ictal disturbance of spoken language, or a generalized convulsion, the condition may not be recognized as a form of epilepsy. Isolated jaw jerks may be dismissed as a meaningless tic, and associated ictal language disturbance may be ascribed to stuttering or to a movement disorder. Other forms of epilepsy must also be differentiated. Secondary reading epilepsy, typically without jaw jerks, occurs in patients with triggered and spontaneous seizures and must be considered if there are abnormalities on examination, imaging, or the interictal EEG. Pronounced pattern sensitivity may result in seizures during reading due to the pattern of the printed text (Wilkins and Lindsay 1985; Matricardi et al 1991), and some subjects are also sensitive to eye movement. DIAGNOSTIC WORKUP EEG is necessary to confirm the diagnosis. Other usual investigations are normal in primary reading epilepsy. The history may suggest certain texts or conditions which are likely to provoke jaw jerks, and using these, events can usually be easily elicited and recorded. Primary reading epilepsy is characterized electrographically by evoked paroxysmal rhythmic theta activity or spikes either over 1 or both frontocentral, centroparietal, or temporoparietal regions in association with jaw jerks. Typically the left side is involved when activity is unilateral, and it is important to note that bilateral jaw jerks are associated with this unilateral discharge. Many patients with primary reading epilepsy have bilateral or asymmetric myoclonic attacks and bilaterally synchronous spike and wave activity. Unilateral myoclonia have also been reported with bilateral activation (Wolf et al 1998). These clinical and EEG responses may be altered or suppressed in subjects taking antiepileptic drugs. The interictal EEG is normal, and the patients are not typically photosensitive. Imaging studies do not show gross lesions. PROGNOSIS AND COMPLICATIONS Most patients respond well to valproate when drug treatment is needed. There is usually no deterioration in neurologic status or in seizure control. The diagnosis must be reconsidered if either of these occur. MANAGEMENT Some patients with primary reading epilepsy do not want drug treatment, especially if they have not had generalized convulsions, and some may not need it. Nonpharmacologic treatments for reflex epilepsy have been recently reviewed (Wolf 2002). A detailed history must be obtained to devise measures which may reduce the chance of a seizure being triggered. Avoidance of prolonged reading and maneuvers that briefly disrupt comprehension or increase arousal may be helpful, but social and educational handicap may arise from these. Audiotaped texts may be useful. Text masking may help those in whom pattern or eye movement contribute to seizure occurrence (Wilkins and Lindsay 1985). These may also be useful if the response to antiepileptic drugs is not complete or if the patient cannot tolerate them. Basic measures such as avoiding sleep deprivation and alcohol excess also apply to these patients. Reading epilepsy has been reported to respond well to valproate, and some patients may worsen with carbamazepine (Wolf et al 1998), but clobazam (not marketed in the United States) or clonazepam may also be needed. Some patients will nevertheless require drugs for partial seizures. PREGNANCY Not applicable. ANESTHESIA No contraindications with anesthesia and primary reading epilepsy are known. REFERENCES CITED Anonymous. Proposal for revised classification of epilepsies and epileptic syndromes. Commission on Classification and Terminology of the International League Against Epilepsy. Epilepsia 1989;30(4):389-99. Archer JS, Briellmann RS, Syngeniotis A, Abbott DF, Jackson GD. Spike-triggered fMRI in reading epilepsy: involvement of left frontal cortex working memory area. Neurology 2003;60(3):415-21. Bickford RG, Whelan JL, Klass DW, Corbin KB. Reading epilepsy: clinical and electro-encephalographic studies of a new syndrome. Trans Am Neurol Assoc 1956;81:100-2. Canevini MP, Vignoli A, Sgro V, et al. Symptomatic epilepsy with facial myoclonus triggered by language. Epileptic Disord 2001;3(3):143-6 Engel J Jr; International League Against Epilepsy (ILAE). A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology. Epilepsia 2001;42(6):796-803. Geschwind N, Sherwin I. Language-induced epilepsy. Arch Neurol 1967;16:25-31. Koepp MJ, Hansen ML, Pressler RM, et al. Comparison of EEG, MRI and PET in reading epilepsy: a case report. Epilepsy Res 1998;29(3):251-7. Koutroumanidis M, Koepp MJ, Richardson MP, et al. The variants of reading epilepsy. A clinical and video-EEG study of 17 patients with reading-induced seizures. Brain 1998;121(Pt 8):1409-27. Matricardi M, Brinciotti M, Paciello F. Reading epilepsy with absences, television-induced seizures, and pattern sensitivity. Epilepsy Res 1991;9:145-7. Pegna AJ, Picard F, Martory MD, et al. Semantically-triggered reading epilepsy: an experimental case study. Cortex 1999;35(1):101-11. Radhakrishnan K, Silbert PL, Klass DW. Reading epilepsy. An appraisal of 20 patients diagnosed at the Mayo Clinic, Rochester, Minnesota, between 1949 and 1989, and delineation of the epileptic syndrome. Brain 1995;118(Pt 1):75-89. Ramani V. Reading epilepsy. In: Zifkin BG, Andermann F, Beaumanoir A, Rowan AJ, editors. Reflex epilepsies and reflex seizures. Advances in neurology. Vol 75. Philadelphia: Lippincott-Raven Press, 1998:241-62. Remillard GM, Zifkin BG, Andermann F. Seizures induced by eating. In: Zifkin BG, Andermann F, Baumanoir A, Rowan AJ, editors. Reflex epilepsies and reflex seizures. Advances in neurology. Vol 75. Philadelphia: Lippincott-Raven Press, 1998:227-40. Ritaccio AL, Hickling EJ, Ramani V. The role of dominant premotor cortex and grapheme to phoneme transformation in reading epilepsy. A neuroanatomic, neurophysiologic, and neuropsychological study. Arch Neurol 1992;49(9):933-9. Wilkins AJ, Lindsay J. Common forms of reflex epilepsy: physiological mechanisms and techniques for treatment. In: Pedley TA, Meldrum BS, editors. Recent advances in epilepsy II. Edinburgh: Churchill Livingstone, 1985:239-71. Wolf P. Reading epilepsy. In: Roger J, Dravet D, Bureau M, Wolf P, Dreifuss FE, Dravet C, editors. Epileptic syndromes in infancy, childhood and adolescence: Current problems in epilepsy. 2nd ed. London: John Libbey, 1992:281-98. Wolf P, Mayer T, Reker M. Reading epilepsy: report of five new cases and further considerations on the pathophysiology. Seizure 1998;7(4):271-9. Wolf P. The role of nonpharmaceutic conservative interventions in the treatment and secondary prevention of epilepsy. Epilepsia 2002;43(Suppl 9):2-5. ILAE ABBREVIATIONS ICD CODE MCKUSICK MIM NUMBER MAJOR KEYWORD DESCRIPTORS MINOR KEYWORD DESCRIPTORScomprehensionhyperexcitability language reading recitation seizures speech arrest AGE OF PRESENTATION AGE OF TYPICAL PRESENTATION POPULATION GROUP(S) PREFERENTIALLY AFFECTED OCCUPATION GROUP(S) PREFERENTIALLY AFFECTED SEX FAMILY HISTORY HEREDITY GLOSSARY PERMUTED TOPIC, SYNONYMS, VARIANTS RELATED TOPICS DIFFERENTIAL DIAGNOSIS
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