, editor. (Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, has no relevant financial relationships to disclose.)

Dr. Panayiotopoulos of St. Thomas' Hospital had no relevant financial relationships to disclose.

Overview

Primary reading epilepsy is a distinct form of reflex epilepsy in which all, or almost all, seizures are precipitated by reading. There are 2 variants: the most common manifests with jaw myoclonus (myoclonic variant) and the other with focal seizures of alexia (focal variant with alexia). Focal seizures may evolve into generalized tonic-clonic seizures if reading persists. In the myoclonic variant, EEG discharges are brief, bilateral synchronous with a left-sided emphasis, whereas in the focal variant they are prolonged and localized in the dominant posterior temporo-occipital junction. In the myoclonic variant, ictal functional neuroimaging shows multiple cortical hyperexcitable areas that are part of the neuronal network and subserve the function of speech. In the focal variant, ictal functional neuroimaging shows mainly focal hyperexcitability in the dominant posterior temporo-occipital regions. Primary reading epilepsy is nonprogressive but probably lifelong. Optimal treatment is with clonazepam for the myoclonic form and with carbamazepine (or other antiepileptic drugs that are effective for focal seizures) for the focal variant with alexia. In this article, the author details developments in the clinical manifestations, pathophysiology, genetics, EEG, functional neuroimaging, and treatment of primary reading epilepsy.

Key points

Primary reading epilepsy is characterized by:

• Epileptic seizures that are primarily triggered by the act of reading. • A variant with brief (for seconds) jaw myoclonus as the main type of seizures. • A second variant with exclusively focal seizures manifesting with alexia or dyslexia. • Generalized tonic-clonic seizures are rare and mainly occur if reading continues despite the appearance of either jaw myoclonus or alexia. • The latency from the stimulus onset (reading) to the clinical or EEG response is usually long (minutes). • Onset at a peak age of late adolescence (never before the age of 11 years) and persistence in late life though it is not progressive. • Seizures are usually controlled with modification of reading and clonazepam for the myoclonic variant or carbamazepine for the focal variant with alexia.

Historical note and terminology

Bickford and colleagues first described seizures induced by reading and distinguished 2 types of reading epilepsy: ‘‘primary reading epilepsy'' in which seizures occurred only in relation to reading and “secondary reading epilepsy” in which reading was not the sole stimulus (Bickford et al 1956). However, since the original description, the differentiation between primary and secondary reading epilepsy has become less distinct because in many patients clinically identical seizures can also be provoked by linguistic activities other than reading, such as writing or speaking, to the extent that the term “language-induced epilepsy” was proposed (Geschwind and Sherwin 1967; Koutroumanidis et al 1998). However, for historical reasons, this article uses the traditional nomenclature of “primary reading epilepsy.”

Primary reading epilepsy was initially classified by the ILAE together with the benign childhood focal epilepsies (Commission on Classification and Terminology of the International League Against Epilepsy 1989); this was debated by many authorities because reading epilepsy has no common links with benign childhood focal seizures and because it is a purely reflex epilepsy (Radhakrishnan et al 1995; Koutroumanidis et al 1998; Ramani 1998; Bansal and Radhakrishnan 2010). In more recent reports, the ILAE rightly categorizes “reading epilepsy” as a syndrome of reflex epilepsy (Engel 2001) but retains the name “primary reading epilepsy” (Berg et al 2010).

Primary reading epilepsy is defined as follows in the 1989 ILAE classification:

Primary reading epilepsy : All or almost all seizures in this syndrome are precipitated by reading (especially aloud) and are independent of the content of the text. They are simple partial motor (involving masticatory muscles) or visual, and if the stimulus is not interrupted, generalized tonic-clonic seizures may occur. The syndrome may be inherited. Onset is typically in late puberty, and the course is benign with little tendency to spontaneous seizures. Physical examination and imaging studies are normal, but EEG shows spikes or spike-waves in the dominant parieto-temporal region. Generalized spike and wave may also occur (Commission on Classification and Terminology of the International League Against Epilepsy 1989).

However, this definition refers to reading epilepsy manifested mainly with jaw myoclonus only though advances also document another variant of pure focal epileptic seizures provoked by reading that manifest with alexia lasting for minutes and without jaw jerks (Koutroumanidis et al 1998; Bansal and Radhakrishnan 2010; Gavaret et al 2010; Maillard et al 2010; Osei-Lah et al 2010; Koutroumanidis et al 2017) (see Table 1). Therefore, the following definition of primary reading epilepsy may be more appropriate:

Primary reading epilepsy is a distinct form of reflex epilepsy in which all, or almost all, seizures are precipitated by the reading. There are two variants; the most common variant manifests with jaw myoclonus (myoclonic variant) and the other with focal seizures of alexia (focal variant with alexia). Image: Reading-induced seizures, jaw myoclonus, and alexia (ictal EEG) Image: Reading-induced focal seizure with alexia (ictal video EEG) Gregory and Broomall 2013). In the myoclonic variant, EEG discharges are brief, bilateral synchronous with a left-sided emphasis or focal, while in the focal variant they are prolonged and localized in the dominant posterior temporo-occipital junction. In the myoclonic variant, ictal functional neuroimaging shows multiple cortical hyperexcitable areas that are part of the neuronal network that subserves the function of speech. In the focal variant, ictal functional neuroimaging shows mainly focal hyperexcitability in the dominant posterior temporo-occipital regions. Primary reading epilepsy is nonprogressive but probably lifelong. Optimal treatment is with clonazepam for the myoclonic form and with carbamazepine or other antiepileptic drugs that are effective for focal seizures.

Herbert Spencer, the nineteenth-century philosopher, probably suffered from reading epilepsy, with onset at the age of 35 years (Raitiere 2011).

Table 1. Primary Reading Epilepsy: Myoclonic Variant Versus Focal Variant With Alexia

Myoclonic reading epilepsy Focal reading epilepsy with alexia Sex Males predominate Males predominate Age at onset Mainly 15 to 18 years Mainly 15 to 18 years Family history Yes No Main symptoms of seizures Jaw myoclonus Alexia Duration of seizures Brief in seconds Longer in minutes Progression to secondarily GTCS Yes Yes Other types of seizures Myoclonic jerks Probably GTCS Precipitating factors Reading but also other linguistic activities (writing, talking) Reading only Ictal EEG Mainly bilateral singular sharp waves predominating in the left temporo-parietal regions Focal discharges of slow waves and spikes localized in the dominant posterior temporo-occipital regions Pathophysiology Probably a diffusely hyperexcitable network subserving reading Focal hyperexcitability in the dominant temporo-occipital junction (mainly angular gyrus) Prognosis Relatively good but lifelong and causing disability of reading Relatively good but lifelong and causing disability of reading Treatment Modification of reading and other precipitating factors Modification of reading and other precipitating factors Prophylactic treatment with antiepileptic drugs Mainly clonazepam Mainly carbamazepine or other drugs for focal epileptic seizures

Neither reflex nor reading seizures/epilepsy are considered in the new operational ILAE classifications (Fisher et al 2017a; Fisher et al 2017b; Scheffer et al 2017). However, in the new online diagnostic manual of the epilepsies by the ILAE Commission on Classification and Terminology, reading epilepsy is classified amongst reflex epilepsies of variable age at onset with the following description, which refers to the myoclonic variant only (Commission on Classification and Terminology of the International League Against Epilepsy 2014):

“Reading epilepsy is characterized by seizures that start between 12 and 19 years of age. There is a male predominance (1.8M:F). Seizures are elicited by reading (aloud or silently). Prognosis is good as seizures are usually minor and can be avoided through reducing exposure to the stimulus.

Seizures are exclusively induced by reading and can start minutes to hours after reading. Myoclonic jerks of the masticatory, perioral and oral muscles are the commonest seizure seen in this syndrome resulting in a clicking sensation. If reading continues, the jerks may increase and spread or a generalized convulsion may occur. Seizures with inability to read or possibly dysphasia may occur and may be prolonged. Absence seizures may occasionally occur. Seizures are typically well controlled once the stimulus is recognized. Seizures may be provoked by talking, writing or chewing in some patients.

The interictal EEG is usually normal. Ictal EEG may be obscured by artifact due to myoclonic jerks of the jaw and head. Ictal EEG findings of sharp-wave discharges have been reported, when these are noted they are bilateral but with a dominant hemisphere (temporo-parietal) maximum.

Neuroimaging is normal.

Reading epilepsy is thought to be genetically determined. Familial cases have been reported.

It is usually not difficult to distinguish reading epilepsy from other epilepsies if correct history is obtained.” (Commission on Classification and Terminology of the International League Against Epilepsy 2014).