Pattern-sensitive Epilepsy: Electroclinical Characteristics, Natural History, and Delineation of the Epileptic Syndrome

Authors


Address correspondence and reprint requests to Dr. D.W. Klass at Section of Electroencephalography, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, U.S.A.

Present address of Dr. Radhakrishnan: Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695 011, India.

Present address of Dr. St. Louis: University of Iowa College of Medicine, 200 Hawkins Drive, Iowa City, IA 52242, U.S.A.

Abstract

Summary: Purpose: To elucidate the electroclinical features and long-term outcome of patients with pattern-sensitive epilepsy.

Methods: We reviewed the clinical and electroencephalographic (EEG) findings of 73 (43 female and 30 male) patients in whom pattern-sensitive epilepsy was diagnosed at Mayo Clinic (Rochester, Minnesota, U.S.A.) from 1950 through 1999. We contacted patients and their relatives by letter or telephone to obtain the latest seizure and quality-of-life outcomes.

Results: The median age at onset of seizures was 12.8 years (range, 0.6–32.9 years). Most patients had absence, myoclonic, or generalized tonic–clonic seizures. Interictal epileptiform discharges in the EEG were detected in 61 (83.6%) patients and were generalized in 54 (74%). Paroxysmal epileptiform discharges in the EEG elicited with standard patterns were all generalized in two thirds of patients but were restricted to the posterior head region in one-third. Eight (11%) patients did not exhibit photosensitivity. Television was the most common precipitant [30 patients (41%)]. Twenty-nine patients gave a clear history of one or more seizures precipitated while viewing environmental patterns such as window screens, garments, tablecloths, and ceiling tiles; the rest of the patients admitted that they preferred to avoid looking at patterned objects because these objects made them uncomfortable. The electroclinical features suggested juvenile myoclonic epilepsy in 14 patients, progressive myoclonus epilepsy in three, progressive familial cerebellar ataxia with myoclonus in two, and severe myoclonic epilepsy of infancy in one. During a median follow-up period of 15.7 years, 25 (45.5%) of 55 patients who were followed up for ≥5 years achieved complete seizure remission. The median age at remission was 24.4 years. The absence of progressive neurologic disease was correlated significantly with remission; a family history of seizures showed a trend in favor of remission. More than two thirds of the patients did not consider the seizures an impediment to their family life or to educational and occupational achievements.

Conclusions: Although pattern sensitivity as a trait occurs in various epileptic syndromes, pattern-sensitive epilepsy is a readily distinguishable subtype of the visually provoked reflex epilepsies. In our opinion, the location and extent of the excitable region or regions within the visual cortex concerned with different attributes of visual function dictate susceptibility to a specific trigger (intermittent light, pattern, or color) or closely related multiple triggers and the resultant electroclinical phenomenon.

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