Primary Reading Epilepsy

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 currently classified as an idiopathic localization-related epilepsy (Commission on Classification and Terminology of the International League Against Epilepsy 1989) and in the proposed revision (which is still in press) is admitted as an 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."


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 old. 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 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. Koutroumanidis and colleagues noted that many patients had similar attacks 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. This has not yet been sufficiently explored, although it has been reported earlier by Geschwind and Sherwin (Geschwind and Sherwin 1967) and is not defined as a reflex epilepsy syndrome.


CLINICAL VIGNETTE

No information was provided by the author.


ETIOLOGY

The etiology of primary reading epilepsy is unknown.


BIOLOGICAL BASIS

Studies of reading epilepsy suggest that increased task difficulty, increased complexity of different types, and long duration of reading increase the chance of EEG or clinical activation (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, confirming that the hyperexcitable neuronal tissue forming the critical mass recruited to produce a clinical attack is not necessarily contiguous but is functionally linked (Wolf 1994; Remillard et al 1998). 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 primary reading epilepsy, 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 (non word) reading involve the left hemisphere preferentially, as compared to those triggered by lexical reading, which have bilateral EEG expression (Pegna et al 1999).


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 or symptomatic 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 helps to confirm the diagnosis. The history may suggest certain texts which are likely to provoke jaw jerks, and using these, events can often be 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 has also been reported with bilateral activation (Wolf et al 1998) 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 or to small doses of clonazepam and 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. The patient's particular history must be obtained in detail to devise measures which may reduce the chance of a seizure being triggered. Avoidance of prolonged reading, along with 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 USA) or clonazepam may also be needed.


PREGNANCY

Not applicable.


ANESTHESIA

No contraindications with anesthesia and primary reading epilepsy are known.


REFERENCES CITED

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.

Christie S, Guberman A, Tansley BW, Couture M. Primary reading epilepsy: investigation of critical seizure-provoking stimuli. Epilepsia 1988;29(3):288-93.

Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989;30:389-99.

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;121:1409-27.

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;35:101-11.

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;118:75-89.

Ramani V. Reading epilepsy. In: Zifkin BG, et al, 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, et al, editors. Reflex epilepsies and reflex seizures. Advances in neurology. Vol 75. Philadelphia: Lippincott-Raven Press, 1998:227-40.

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: Wolf P, editor. Epileptic seizures and syndromes. London: John Libbey, 1994:67-73.

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.