LETTERS/COMMENTARY

EEG Features in Idiopathic Generalized Epilepsy:Clues to Diagnosis

To the Editor:We read with interest the article by Betting et al.,

2006 entitled “EEG Features in Idiopathic GeneralizedEpilepsy: Clues to Diagnosis (1).” The authors investi-gated the contribution of EEG recordings for diagnosisand management of 180 patients with a clinical diagnosisof idiopathic generalized epilepsy (IGE). They found thatthe first EEGs yielded 45% with normal activity, 55% withabnormal activity, and only 33% indicated typical abnor-malities. Patients with absence epilepsy were most likelyto exhibit specific EEG abnormalities. At the time of EEGevaluation 92% of the patients were taking an AED and80% of the patients had remained seizure free for ≥ 1 year.From this information the authors concluded that clinicalhistory contributes more to the diagnosis of IGE and thattreatment may be inappropriately delayed while “waiting”for a typical abnormal pattern on EEG.

Significant studies on the predictive value of EEG afterthe first unprovoked seizure have revealed contradictoryresults. Some studies have shown EEG abnormalities in upto 70% of patients after an initial unprovoked seizure (2).Others have shown that obtaining an EEG provides littleadditional information in further treatment of the patients(3). In fact, our group has previously shown that extendedEEG monitoring is important in establishing the diagnosisof the type of epilepsy and making an appropriate choiceof antiepileptic drug (AED) therapy in the future care ofpatients (4,5). Indeed, the accurate diagnosis of idiopathicgeneralized epilepsy was confirmed after prolonged EEGmonitoring in only 29% of patients (5). Further contro-versy exists on whether risk for seizure recurrence is in-creased by the presence of an abnormal EEG on first ex-amination. Several studies have demonstrated that the riskof recurrence doubles with an abnormal EEG (6,7).

We recommend caution when interpreting the resultsof this study. Our main reservation is that EEG interpreta-tions were performed independent of whether the patientwas receiving AED treatment or not. Studies have demon-strated normalization of EEGs while on AED therapy (8).Moreover, the EEG data was not assessed in patients withnew onset seizures only. Initial EEGs were performed insome patients up to 44 years after seizure onset.

We understand that in situations where resources arelimited, there may be delays before performing an EEG.In this situation, we agree with the authors that AED treat-ment should not be withheld from a patient with seizureswhile “waiting” for an EEG. However, EEG is and willcontinue to be an important investigation in the diagnosis,treatment, and prognosis of patients with epilepsy.

Christine Whylings, MSIV, B.S.Agustin Legido, M.D., PhD, M.B.A.

Sanjeev V. Kothare, M.D.Department of Pediatrics, Section of Neurology

St. Christopher’s Hospital for ChildrenDrexel University College of Medicine

Philadelphia, PA

REFERENCES

1. Betting LE, Mory SB, Lopes-Cendes I, et al. EEG Features inIdiopathic Generalized Epilepsy: Clues to Diagnosis. Epilepsia2006;47:523–528.

2. Schreiner A, Pohlmann-Eden B. Value of the Early Electroencephalo-gram After a First Unprovoked Seizure. Clin Electroencephalogr2003;34:140–144.

3. Gilbert DL, Buncher CR. An EEG should not be obtained routinelyafter first unprovoked seizure in childhood. Neurology 2000;54:635–641.

4. Kothare SV, Khurana DS, Valencia I, Melvin JJ, Legido A. Use andvalue of ordering emergency electroencephalograms and videoelec-troencephalographic monitoring after business hours in a Children’sHospital: 1-Year experience. J Child Neurol 2005;20:416–419.

5. Foley CM, Legido A, Miles DK, Chandler DA, Grover WD. Long-term computer-assisted outpatient electroencephalogram monitoringin children and adolescents. J Child Neuro 2000;15:49–55.

6. Shinnar S, Kang H, Berg AT, Goldenshohn ES, Hauser WA, MosheSL. EEG abnormalities in Children with a First Unprovoked Seizure.Epilepsia 1994;35:471–476.

7. Winkler MIB, Rotta NT. Clinical and electroencephalographicfollow-up after a first unprovoked seizure. Pediatr Neurol 2004;30:201–206.

8. Appleton RE, Beirne M. Absence epilepsy in children: the role ofEEG in monitoring response to treatment. Seizure 1996;5:147–148.

Response: EEG Features in Idiopathic GeneralizedEpilepsy: Clues to Diagnosis

To the Editor,We thank Dr. Whylings and colleagues for the interest

in our work (1). Their observations are very relevant, butapparently they misunderstood the message of our paper.We strongly agree that EEG is of extreme importance forevaluation of patients with epilepsy. In fact, our study high-lighted this importance. We would not have acquired se-rial EEGs in patients with idiopathic generalized epilepsy(IGE), if we did not consider it important.

In tertiary specialized centers, like ours, EEG is easilyavailable; it is not only a question of limited resources.However, most patients with IGE are followed in primarycare centers. In these situations, there may be a delay inrecording the first EEG. Moreover, even when the EEGis performed immediately after the onset of seizures, itmay be normal or may show atypical abnormalities. Un-der these circumstances, the treatment should be initiatedaccording to the main clinical features determined by adetailed history.

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Therefore, Whylings and colleagues are absolutely cor-rect when they mentioned that our “EEG data was notassessed in patients with new onset seizures only. InitialEEGs were performed in some patients up to 44 years af-ter seizure onset.” We chose to investigate this group ofpatients because we believe that this is a more realistic wayof analyzing the importance of EEG in daily practice. Inmost parts of the world, it is not feasible to perform routineEEG immediately after the first or second seizure, beforeintroduction of AED as Whylings and colleagues appearto suggest. Much less likely is to have available prolongedEEG monitoring for these patients. To put this issue intoperspective, it is important to mention that approximately80% of people with epilepsy worldwide are living in de-veloping countries (2). Access to appropriate medical careand treatment gap are major issues in these countries (3).

As we clearly indicated in the introduction, the objec-tive of our study was not to evaluate the EEG in newlydiagnosed epilepsy (1). The population described in ourstudy was not uniform. This heterogeneous population isexactly what neurologists will find in the daily practice,where the majority of patients are referred by primary carephysicians. Diagnosis delay in patients with IGE may lastfor years. It is a well documented problem, and occur indeveloped countries as well (4,5). Patients with IGE maybe referred as having partial refractory epilepsy (4). Thesepatients may present a history of long lasting seizures andmay be under inappropriate therapy (5). As indicated inour paper, the EEG in these patients most likely will showfocalities or atypical features, and this is an important con-cept for clinical practice.

Luiz Eduardo Betting, MDFernando Cendes, MD, PHD

Department of NeurologyUniversity of Campinas

UNICAMP, Brazil

REFERENCES

1. Betting LE, Mory SB, Lopes-Cendes I, et al. EEG Features inIdiopathic Generalized Epilepsy: Clues to Diagnosis. Epilepsia2006;47:523–528.

2. Scott RA, Lhatoo SD, Sander JW. The treatment of epilepsy in de-veloping countries: where do we go from here? Bull World HealthOrgan 2001;79(4):344–351.

3. Mac TL, Le VT, Vu AN, Preux PM, Ratsimbazafy V. AEDs avail-ability and professional practices in delivery outlets in a city centerin southern Vietnam. Epilepsia 2006;47(2):330–334.

4. Lancman ME, Asconape JJ, Penry JK. Clinical and EEG asym-metries in juvenile myoclonic epilepsy. Epilepsia 1994;35:302–306.

5. Thomas P, Valton L, Genton P. Absence and myoclonic status epilep-ticus precipitated by antiepileptic drugs in idiopathic generalizedepilepsy. Brain 2006;129:1281–1292.

NEXT MONTH IN Epilepsia

The featured theme of the September issue is Hormonesand Epilepsy. The theme will be introduced by two criti-cal reviews that focus on the special hormone-related is-sues involved in understanding and treating women withepilepsy. Helen Scharfman and Neil MacLusky discuss“The Influence of Gonadal Hormones on Excitability,Seizures, and Epilepsy in the Female.” And MichaelO’Brien and John Guillebaud present a critical reviewon “Contraception for Women with Epilepsy.” These re-views are followed by a series of original research arti-cles that deal with a variety of issues involving hormones,antiepileptic drugs, and epilepsy. Among the topics ofthese articles are:

Effects of AEDs on reproductive endocrine function inwomen

Hormone replacement therapyLH secretion in men with TLEEffects of valproate on insulin secretion

In addition to papers related to hormonal function, this is-sue presents papers on a variety of other topics, including:

Imaging and recording studies on dysplastic cortex, andSeizures – including non-convulsive seizures and status

epilepticus – in childhood.

Finally, the September issue features a report from theILAE Classification Core Group. This report focuses onestablishing scientifically rigorous criteria for identifyingspecific epileptic seizure types and epilepsy syndromes asunique diagnostic entities.

Online Early

The following hormone papers, as well as many other still-to-be-printed Epilepsia articles, have been published andcan be accessed now, on Online Early:

Harden et al., “Hormone Replacement Therapy inWomen with Epilepsy: A Randomized, Double-blind, Placebo-controlled Study”

Lofgren et al., “Effects of Carbamazepine and Oxcar-bazepine on the Reproductive Endocrine Function inWomen with Epilepsy”

Pylvanen et al., “Characterization of Insulin Secretionin Valproate Treated Patients with Epilepsy”

Contin et al., “Variation in Lamotrigine Plasma Con-centrations with Hormonal Contraceptive MonthlyCycles in Patients with Epilepsy”

Epilepsia, Vol. 47, No. 8, 2006