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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.
HISTORICAL NOTE AND NOMENCLATURE
Bickford and colleagues first described seizures induced by reading and delineated most of the cardinal clinical features of primary reading epilepsy, defined in patients without spontaneous seizures in whom all attacks were triggered by reading (Bickford et al 1956). Focal, regional, and generalized reflex EEG paroxysmal activity was described in primary reading epilepsy, and the definition of the syndrome did not appear to depend on any single type or localization of EEG abnormality (Ramani 1998). The classification of primary reading epilepsy was thus a matter of interest and debate. Primary reading epilepsy is classified as an idiopathic localization-related epilepsy (Anonymous 1989) but in the proposed revision (Engel 2001) is admitted as a reflex epilepsy syndrome without specifying whether it is generalized or focal. In this proposal, an epilepsy syndrome is “a complex of signs and symptoms that define a unique epilepsy condition with different etiologies" , and reflex epilepsy syndromes are those “… in which all epileptic seizures are precipitated by sensory stimuli. Reflex seizures that occur in focal and generalized epilepsy syndromes that are also associated with spontaneous seizures, are listed as seizure types.” Other seizures induced by reading and by other language tasks have also been described in these patients, and in others with evident brain lesions. The original descriptions of primary reading epilepsy predate the CT scan and widespread video-EEG recording: many reports can be difficult to interpret due to different methods of stimulation, recording, and interpretation of the results.
CLINICAL MANIFESTATIONS
Primary reading epilepsy consists of seizures triggered by reading, without spontaneous seizures (Bickford et al 1956; Radhakrishnan et al 1995; Koutroumanidis et al 1998; Ramani 1998). Seizures usually begin in adolescence, and onset is unusual in younger children or adults over 30 years of age. Patients report jaw jerking or clicking while reading, often with jerks of the arms, and if reading continues, a generalized convulsion may occur. Transient cognitive impairment and speech arrest has also been noted with the jerks. Patients may present with a first convulsion, and a longer history of reading-induced jerks may only then be obtained retrospectively. The developmental history, neurologic examination, interictal EEG, and CT scan are normal. More prolonged reading-induced partial seizures with ictal dyslexia or alexia, possibly speech arrest, and reading-induced bilateral myoclonic seizures and absences have also been reported. A family history of epilepsy is common, and familial reading epilepsy may occur. Wolf reviewed 111 patients with reading epilepsy: of 69 index patients, 28 (41 %) had a family history of seizures and of 20 first-degree family members with sufficient information, 11 also had reading epilepsy (Wolf 1992). Koutroumanidis and colleagues noted that many patients had similar seizures with other linguistic tasks (Koutroumanidis et al 1998); reading epilepsy may indeed be a subset of a more broadly-defined reflex epilepsy involving a network for language but this has not yet been sufficiently explored, although it has been reported earlier by Geschwind and Sherwin, and is not defined as a reflex epilepsy syndrome (Geschwind and Sherwin 1967). Activation by reading and by other language tasks in the same patient can also occur in symptomatic epilepsies (Ritaccio et al 1992), and as illustrated with video documentation by Canevini and colleagues (Canevini et al 2001).
CLINICAL VIGNETTE
No information was provided by the author.
ETIOLOGY
The etiology of primary reading epilepsy is unknown. See Pathogenesis and pathophysiology section for more information..
PATHOGENESIS AND PATHOPHYSIOLOGY
Studies 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
ILAE Copyright Notice
ABBREVIATIONS
CT:computed tomography
EEG:electroencephalogram
MRI:magnetic resonance imaging
ICD CODE
345.0
MCKUSICK MIM NUMBER
132300
MAJOR KEYWORD DESCRIPTORS
absences
alexia
arm jerks
cognitive processes
epilepsy syndrome
generalized convulsions
ictal dyslexia
idiopathic localization-related epilepsy
jaw jerks
myoclonic attacks
partial seizures
reading-induced partial seizures
reflex epilepsy
reflex seizures
tonic-clonic seizures
transient cognitive impairment
MINOR KEYWORD DESCRIPTORS
comprehension
hyperexcitability
language
reading
recitation
seizures
speech arrest
AGE OF PRESENTATION
06-12 years
13-18 years
19-44 years
45-64 years
AGE OF TYPICAL PRESENTATION
06-12 years
13-18 years
19-44 years
POPULATION GROUP(S) PREFERENTIALLY AFFECTED
none selectively affected
OCCUPATION GROUP(S) PREFERENTIALLY AFFECTED
none selectively affected
SEX
male=female
FAMILY HISTORY
family history may be obtained
HEREDITY
heredity may be a factor
GLOSSARY
primary reading epilepsy:a reflex epilepsy syndrome in
which seizures are induced by reading, without spontaneous seizures
reflex epilepsy syndrome: a syndrome in which all epileptic
seizures are precipitated by sensory stimuli
epilepsy syndrome: a complex of signs and symptoms that
define a unique epilepsy condition with different etiologies
etc
PERMUTED TOPIC, SYNONYMS, VARIANTS
Primary reading epilepsy
reading epilepsy, Primary
epilepsy, Primary reading
RELATED TOPICS
Complex reflex epilepsy
Epilepsy
Seizures induced by thinking
DIFFERENTIAL DIAGNOSIS
isolated jaw jerks
tics
stuttering
movement disorder
secondary reading epilepsy
pronounced pattern epilepsy
eye movement-induced seizures
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