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Electroencephalography (EEG) in the diagnosis of seizures and epilepsy

Jeremy Moeller, MD
Hiba Arif Haider, MD
Lawrence J Hirsch, MD
Section Editor
Paul Garcia, MD
Deputy Editor
Janet L Wilterdink, MD


The diagnosis of epilepsy is often not straightforward, and misdiagnosis is not rare [1]. A detailed and reliable account of the event by an eyewitness is the most important part of the diagnostic evaluation, but may not be available [2].

Electroencephalography (EEG) is an important diagnostic test in evaluating a patient with possible epilepsy. It can provide support for the diagnosis of epilepsy and also assists in classifying the underlying epileptic syndrome.

However, there are several reasons why EEG alone cannot be used to make or refute a specific diagnosis of epilepsy:

Most EEG patterns can be caused by a wide variety of different neurologic diseases.

Many diseases can cause more than one type of EEG pattern.

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Literature review current through: Nov 2017. | This topic last updated: Aug 03, 2016.
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  1. Scheepers B, Clough P, Pickles C. The misdiagnosis of epilepsy: findings of a population study. Seizure 1998; 7:403.
  2. van Donselaar CA, Stroink H, Arts WF, Dutch Study Group of Epilepsy in Childhood. How confident are we of the diagnosis of epilepsy? Epilepsia 2006; 47 Suppl 1:9.
  3. Buzsaki, G, Traub, et al. The Cellular Basis of EEG Activity. In: Current Practice of Clinical Electroencephalography, Ebersole, JS, Pedley, TA (Eds), Lippincott Williams & Wilkins, Philadelphia 2003. p.1.
  4. Glick TH. The sleep-deprived electroencephalogram: evidence and practice. Arch Neurol 2002; 59:1235.
  5. King MA, Newton MR, Jackson GD, et al. Epileptology of the first-seizure presentation: a clinical, electroencephalographic, and magnetic resonance imaging study of 300 consecutive patients. Lancet 1998; 352:1007.
  6. Marsan CA, Zivin LS. Factors related to the occurrence of typical paroxysmal abnormalities in the EEG records of epileptic patients. Epilepsia 1970; 11:361.
  7. van Donselaar CA, Schimsheimer RJ, Geerts AT, Declerck AC. Value of the electroencephalogram in adult patients with untreated idiopathic first seizures. Arch Neurol 1992; 49:231.
  8. Baldin E, Hauser WA, Buchhalter JR, et al. Yield of epileptiform electroencephalogram abnormalities in incident unprovoked seizures: a population-based study. Epilepsia 2014; 55:1389.
  9. Doppelbauer A, Zeitlhofer J, Zifko U, et al. Occurrence of epileptiform activity in the routine EEG of epileptic patients. Acta Neurol Scand 1993; 87:345.
  10. Goodin DS, Aminoff MJ. Does the interictal EEG have a role in the diagnosis of epilepsy? Lancet 1984; 1:837.
  11. Salinsky M, Kanter R, Dasheiff RM. Effectiveness of multiple EEGs in supporting the diagnosis of epilepsy: an operational curve. Epilepsia 1987; 28:331.
  12. Burkholder DB, Britton JW, Rajasekaran V, et al. Routine vs extended outpatient EEG for the detection of interictal epileptiform discharges. Neurology 2016; 86:1524.
  13. Narayanan JT, Labar DR, Schaul N. Latency to first spike in the EEG of epilepsy patients. Seizure 2008; 17:34.
  14. Walczak T, Scheuer M, Resor S, Pedley T. Prevalence and features of epilepsy without interictal epileptiform discharges. Neurology 1993; 43:287.
  15. Friedman DE, Hirsch LJ. How long does it take to make an accurate diagnosis in an epilepsy monitoring unit? J Clin Neurophysiol 2009; 26:213.
  16. Janszky J, Hoppe M, Clemens Z, et al. Spike frequency is dependent on epilepsy duration and seizure frequency in temporal lobe epilepsy. Epileptic Disord 2005; 7:355.
  17. Krumholz A, Wiebe S, Gronseth G, et al. Practice Parameter: evaluating an apparent unprovoked first seizure in adults (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society. Neurology 2007; 69:1996.
  18. Fisher RS, Acevedo C, Arzimanoglou A, et al. ILAE official report: a practical clinical definition of epilepsy. Epilepsia 2014; 55:475.
  19. Gotman J, Marciani MG. Electroencephalographic spiking activity, drug levels, and seizure occurrence in epileptic patients. Ann Neurol 1985; 17:597.
  20. Spencer SS, Goncharova II, Duckrow RB, et al. Interictal spikes on intracranial recording: behavior, physiology, and implications. Epilepsia 2008; 49:1881.
  21. Sadleir LG, Scheffer IE. Optimizing electroencephalographic studies for epilepsy diagnosis in children with new-onset seizures. Arch Neurol 2010; 67:1345.
  22. Bruni J, Wilder BJ, Bauman AW, Willmore LJ. Clinical efficacy and long-term effects of valproic acid therapy on spike-and-wave discharges. Neurology 1980; 30:42.
  23. Schmidt D. The influence of antiepileptic drugs on the electroencephalogram: a review of controlled clinical studies. Electroencephalogr Clin Neurophysiol Suppl 1982; 36:453.
  24. Pillai J, Sperling MR. Interictal EEG and the diagnosis of epilepsy. Epilepsia 2006; 47 Suppl 1:14.
  25. Van Cott, AC, Brenner, RP.. Drug Effects and Toxic Encephalopathy. In: Current practice of clinical electroencephalograhy, Ebersole, JS, Pedley, TA (Eds), Lippincott Williams and Wilkins, Philadephia 2003. p.463.
  26. Specchio N, Boero G, Michelucci R, et al. Effects of levetiracetam on EEG abnormalities in juvenile myoclonic epilepsy. Epilepsia 2008; 49:663.
  27. Verma A, Radtke R. EEG of partial seizures. J Clin Neurophysiol 2006; 23:333.
  28. Bennett DR. Spike-wave complexes in "normal" flying personnel. Aerosp Med 1967; 38:1276.
  29. Gregory RP, Oates T, Merry RT. Electroencephalogram epileptiform abnormalities in candidates for aircrew training. Electroencephalogr Clin Neurophysiol 1993; 86:75.
  30. Zivin L, Marsan CA. Incidence and prognostic significance of "epileptiform" activity in the eeg of non-epileptic subjects. Brain 1968; 91:751.
  31. Cavazzuti GB, Cappella L, Nalin A. Longitudinal study of epileptiform EEG patterns in normal children. Epilepsia 1980; 21:43.
  32. Bridgers SL. Epileptiform abnormalities discovered on electroencephalographic screening of psychiatric inpatients. Arch Neurol 1987; 44:312.
  33. Borusiak P, Zilbauer M, Jenke AC. Prevalence of epileptiform discharges in healthy children--new data from a prospective study using digital EEG. Epilepsia 2010; 51:1185.
  34. Hughes JR. Long-term clinical and EEG changes in patients with epilepsy. Arch Neurol 1985; 42:213.
  35. Chung MY, Walczak TS, Lewis DV, et al. Temporal lobectomy and independent bitemporal interictal activity: what degree of lateralization is sufficient? Epilepsia 1991; 32:195.
  36. Fountain NB, Kim JS, Lee SI. Sleep deprivation activates epileptiform discharges independent of the activating effects of sleep. J Clin Neurophysiol 1998; 15:69.
  37. Liporace J, Tatum W 4th, Morris GL 3rd, French J. Clinical utility of sleep-deprived versus computer-assisted ambulatory 16-channel EEG in epilepsy patients: a multi-center study. Epilepsy Res 1998; 32:357.
  38. Eeg-Olofsson O, Petersén I, Selldén U. The development of the electroencephalogram in normal children from the age of 1 through 15 years. Paroxysmal activity. Neuropadiatrie 1971; 2:375.
  39. Kellaway, P. The incidence, significance and natural history of spike foci in children. In: Current clinical neurophysiology: update on EEG and evoked potentials, Henry, C (Eds), Elsevier, Amsterdam 1981. p.151.
  40. Wong VC. Cortical blindness in children: a study of etiology and prognosis. Pediatr Neurol 1991; 7:178.
  41. Malow BA, Reese KB, Sato S, et al. Spectrum of EEG abnormalities during clozapine treatment. Electroencephalogr Clin Neurophysiol 1994; 91:205.
  42. Hughes JR, Schreeder MT. EEG in dialysis encephalopathy. Neurology 1980; 30:1148.
  43. Hirsch LJ, LaRoche SM, Gaspard N, et al. American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology: 2012 version. J Clin Neurophysiol 2013; 30:1.
  45. Markand ON, Daly DD. Pseudoperiodic lateralized paroxysmal discharges in electroencephalogram. Neurology 1971; 21:975.
  46. Fitzpatrick W, Lowry N. PLEDs: clinical correlates. Can J Neurol Sci 2007; 34:443.
  47. Gurer G, Yemisci M, Saygi S, Ciger A. Structural lesions in periodic lateralized epileptiform discharges (PLEDs). Clin EEG Neurosci 2004; 35:88.
  48. Baykan B, Kinay D, Gökyigit A, Gürses C. Periodic lateralized epileptiform discharges: association with seizures. Seizure 2000; 9:402.
  49. Orta DS, Chiappa KH, Quiroz AZ, et al. Prognostic implications of periodic epileptiform discharges. Arch Neurol 2009; 66:985.
  50. PeBenito R, Cracco JB. Periodic lateralized epileptiform discharges in infants and children. Ann Neurol 1979; 6:47.
  51. Snodgrass SM, Tsuburaya K, Ajmone-Marsan C. Clinical significance of periodic lateralized epileptiform discharges: relationship with status epilepticus. J Clin Neurophysiol 1989; 6:159.
  52. de la Paz D, Brenner RP. Bilateral independent periodic lateralized epileptiform discharges. Clinical significance. Arch Neurol 1981; 38:713.
  53. Chong DJ, Hirsch LJ. Which EEG patterns warrant treatment in the critically ill? Reviewing the evidence for treatment of periodic epileptiform discharges and related patterns. J Clin Neurophysiol 2005; 22:79.
  54. Foreman B, Claassen J, Abou Khaled K, et al. Generalized periodic discharges in the critically ill: a case-control study of 200 patients. Neurology 2012; 79:1951.
  55. Gilmore PC, Brenner RP. Correlation of EEG, computerized tomography, and clinical findings. Study of 100 patients with focal delta activity. Arch Neurol 1981; 38:371.
  56. Maytal J, Novak GP, Knobler SB, Schaul N. Neuroradiological manifestations of focal polymorphic delta activity in children. Arch Neurol 1993; 50:181.
  57. Marshall DW, Brey RL, Morse MW. Focal and/or lateralized polymorphic delta activity. Association with either 'normal' or 'nonfocal' computed tomographic scans. Arch Neurol 1988; 45:33.
  58. Watemberg N, Alehan F, Dabby R, et al. Clinical and radiologic correlates of frontal intermittent rhythmic delta activity. J Clin Neurophysiol 2002; 19:535.
  59. Dalby, MA. Epilepsy and 3 per second spike and wave rhythms. A clinical, electroencephalographic and prognostic analysis of 346 patients. Acta Neurol Scand 1969; Suppl 40:3+.
  60. Holmes GL, McKeever M, Adamson M. Absence seizures in children: clinical and electroencephalographic features. Ann Neurol 1987; 21:268.
  61. Watemberg N, Linder I, Dabby R, et al. Clinical correlates of occipital intermittent rhythmic delta activity (OIRDA) in children. Epilepsia 2007; 48:330.
  62. Gullapalli D, Fountain NB. Clinical correlation of occipital intermittent rhythmic delta activity. J Clin Neurophysiol 2003; 20:35.
  63. Di Gennaro G, Quarato PP, Onorati P, et al. Localizing significance of temporal intermittent rhythmic delta activity (TIRDA) in drug-resistant focal epilepsy. Clin Neurophysiol 2003; 114:70.
  64. Geyer JD, Bilir E, Faught RE, et al. Significance of interictal temporal lobe delta activity for localization of the primary epileptogenic region. Neurology 1999; 52:202.
  65. Gaspard N, Manganas L, Rampal N, et al. Similarity of lateralized rhythmic delta activity to periodic lateralized epileptiform discharges in critically ill patients. JAMA Neurol 2013; 70:1288.
  66. Boylan LS, Labovitz DL, Jackson SC, et al. Auras are frequent in idiopathic generalized epilepsy. Neurology 2006; 67:343.
  67. International League Against Epilepsy. Electrophysiology. Epilepsia 2003; 44 Suppl 6:27.
  68. Worrell GA, Lagerlund TD, Buchhalter JR. Role and limitations of routine and ambulatory scalp electroencephalography in diagnosing and managing seizures. Mayo Clin Proc 2002; 77:991.
  69. Seneviratne U, Cook M, D'Souza W. The electroencephalogram of idiopathic generalized epilepsy. Epilepsia 2012; 53:234.
  70. Mendez OE, Brenner RP. Increasing the yield of EEG. J Clin Neurophysiol 2006; 23:282.
  71. Holmes MD, Dewaraja AS, Vanhatalo S. Does hyperventilation elicit epileptic seizures? Epilepsia 2004; 45:618.
  72. Raybarman C. Is hyperventilation an effective ''activating'' procedure in routine clinical EEG studies in children? J Child Neurol 2009; 24:1294.
  73. Jonas J, Vignal JP, Baumann C, et al. Effect of hyperventilation on seizure activation: potentiation by antiepileptic drug tapering. J Neurol Neurosurg Psychiatry 2011; 82:928.
  74. Kasteleijn-Nolst Trenité D, Rubboli G, Hirsch E, et al. Methodology of photic stimulation revisited: updated European algorithm for visual stimulation in the EEG laboratory. Epilepsia 2012; 53:16.
  75. Tartara A, Moglia A, Manni R, Corbellini C. EEG findings and sleep deprivation. Eur Neurol 1980; 19:330.
  76. Roupakiotis SC, Gatzonis SD, Triantafyllou N, et al. The usefulness of sleep and sleep deprivation as activating methods in electroencephalographic recording: contribution to a long-standing discussion. Seizure 2000; 9:580.
  77. Mattson RH, Pratt KL, Calverley JR. Electroencephalograms of epileptics following sleep deprivation. Arch Neurol 1965; 13:310.
  78. Leach JP, Stephen LJ, Salveta C, Brodie MJ. Which electroencephalography (EEG) for epilepsy? The relative usefulness of different EEG protocols in patients with possible epilepsy. J Neurol Neurosurg Psychiatry 2006; 77:1040.
  79. Britton JW, Kosa SC. The clinical value of chloral hydrate in the routine electroencephalogram. Epilepsy Res 2010; 88:215.
  80. Ashrafi MR, Mohammadi M, Tafarroji J, et al. Melatonin versus chloral hydrate for recording sleep EEG. Eur J Paediatr Neurol 2010; 14:235.
  81. Sperling MR, Mendius JR, Engel J Jr. Mesial temporal spikes: a simultaneous comparison of sphenoidal, nasopharyngeal, and ear electrodes. Epilepsia 1986; 27:81.
  82. SILVERMAN D. The anterior temporal electrode and the ten-twenty system. Electroencephalogr Clin Neurophysiol 1960; 12:735.
  83. Goodin DS, Aminoff MJ, Laxer KD. Detection of epileptiform activity by different noninvasive EEG methods in complex partial epilepsy. Ann Neurol 1990; 27:330.
  84. Homan RW, Jones MC, Rawat S. Anterior temporal electrodes in complex partial seizures. Electroencephalogr Clin Neurophysiol 1988; 70:105.
  85. Sadler RM, Goodwin J. Multiple electrodes for detecting spikes in partial complex seizures. Can J Neurol Sci 1989; 16:326.
  86. Benbadis SR, Tatum WO. Overintepretation of EEGs and misdiagnosis of epilepsy. J Clin Neurophysiol 2003; 20:42.
  87. Fowle AJ, Binnie CD. Uses and abuses of the EEG in epilepsy. Epilepsia 2000; 41 Suppl 3:S10.
  88. Krauss GL, Abdallah A, Lesser R, et al. Clinical and EEG features of patients with EEG wicket rhythms misdiagnosed with epilepsy. Neurology 2005; 64:1879.
  89. Tatum WO 4th, Husain AM, Benbadis SR, Kaplan PW. Normal adult EEG and patterns of uncertain significance. J Clin Neurophysiol 2006; 23:194.
  90. Mushtaq R, Van Cott AC. Benign EEG variants. Am J Electroneurodiagnostic Technol 2005; 45:88.
  91. Gilbert DL, Sethuraman G, Kotagal U, Buncher CR. Meta-analysis of EEG test performance shows wide variation among studies. Neurology 2003; 60:564.
  92. Williams GW, Lüders HO, Brickner A, et al. Interobserver variability in EEG interpretation. Neurology 1985; 35:1714.