The Role and Controversies of Electroencephalogram in Focal versus Generalized Epilepsy

Abstract

As early in 1935, Gibbs et al described electroencephalogram (EEG) features of large slow waves seen in “petit mal” seizures and change in background rhythm to a higher frequency, greater amplitude pattern in “grand mal” seizures. Studies have shown many typical EEG features in focal onset as well as generalized epilepsies.[2] [3] It is usually easy to delineate focal epilepsy cases when EEG onset of seizures is clear as seen in Benign focal epileptiform discharges of childhood.[4] However, it is not uncommon to see cases where epileptiform discharges are not very clear. For example, there can be secondary bilateral synchrony or generalized onset of epileptiform discharges in some cases of focal epilepsy[5] and nongeneralized EEG features is cases of generalized epilepsy like absence seizures.[6]

The awareness of occurrence of focal clinical and EEG features in generalized epilepsy is particularly important to help to select appropriate AEDs and also to avoid inappropriate consideration for epilepsy surgery.[7] Lüders et al[8] have shown that multiple factors like electroclinical seizure evolution, neuroimaging (both functional and anatomical) have to be analyzed in depth before defining an epileptic syndrome. Here, we are providing few examples of different situations where it is still mysterious to figure out focal onset seizures with secondary generalization versus primary generalized epilepsy.

Keywords

electroencephalogram - focal epileptiform discharges - generalized epileptiform discharges - secondary bilateral synchrony

Publication History

Received: 16 November 2020

Accepted: 01 December 2020

Article published online:
19 February 2021

• References

• 1 Gibbs FA, Davis H, Lennox WG. The Electro-encephalogram in Epilepsy and in conditions of impaired consciousness. Arch NeurPsych. 1935; 34 (06) 1133-1148
• 2 Geiger LR, Harner RN. EEG patterns at the time of focal seizure onset. Arch Neurol 1978; 35 (05) 276-286
• 3 Seneviratne U, Cook MJ, D'Souza WJ. Electroencephalography in the diagnosis of genetic generalized epilepsy syndromes. Front Neurol 2017; 8: 499
• 4 Britton JW, Frey LC, Hopp JL. et al. In: Louis St. EK, Frey LC. eds. Electroencephalography (EEG): an introductory text and atlas of normal and abnormal findings in adults, children, and infants. Chicago: American Epilepsy Society; 2016. (EEG in the Epilepsies; ). Available at: https://www.ncbi.nlm.nih.gov/books/NBK390347/
• 5 Kim DW, Lee SY, Lee SK. Focal epileptogenic lesions in adult patients with epilepsy and generalized epileptiform discharges. J Epilepsy Res 2016; 6 (02) 75-78
• 6 Sadleir LG, Farrell K, Smith S, Connolly MB, Scheffer IE. Electroclinical features of absence seizures in childhood absence epilepsy. Neurology 2006; 67 (03) 413-418
• 7 Chaves J, Sander JW. Seizure aggravation in idiopathic generalized epilepsies. Epilepsia 2005; 46 (Suppl. 09) 133-139
• 8 Lüders H, Acharya J, Baumgartner C. et al. Semiological seizure classification. Epilepsia 1998; 39 (09) 1006-1013
• 9 Lüders H, Lesser RP, Dinner DS, Morris HH. Benign focal epilepsy of childhood. In: Lüders H., Lesser R.P.. eds. Epilepsy: Electroclinical Syndromes. Clinical Medicine and the Nervous System. London: Springer; 1987
• 10 Taylor I, Marini C, Johnson MR, Turner S, Berkovic SF, Scheffer IE. Juvenile myoclonic epilepsy and idiopathic photosensitive occipital lobe epilepsy: is there overlap?. Brain 2004; 127 (Pt 8): 1878-1886
• 11 Panayiotopoulos CP, Chroni E, Daskalopoulos C, Baker A, Rowlinson S, Walsh P. Typical absence seizures in adults: clinical, EEG, video-EEG findings and diagnostic/syndromic considerations. J Neurol Neurosurg Psychiatry 1992; 55 (11) 1002-1008
• 12 Tukel K, Jasper H. The electroencephalogram in parasagittal lesions. Electroencephalogr Clin Neurophysiol 1952; 4 (04) 481-494
• 13 Fernandez-Baca Vaca G, Park JT. Focal EEG abnormalities and focal ictal semiology in generalized epilepsy. Seizure 2020; 77: 7-14
• 14 Linane A, Lagrange AH, Fu C, Abou-Khalil B. Generalized onset seizures with focal evolution (GOFE) - A unique seizure type in the setting of generalized epilepsy. Epilepsy Behav 2016; 54: 20-29
• 15 Aliberti V, Grünewald RA, Panayiotopoulos CP, Chroni E. Focal electroencephalographic abnormalities in juvenile myoclonic epilepsy. Epilepsia 1994; 35 (02) 297-301
• 16 Williamson R, Hanif S, Mathews GC, Lagrange AH, Abou-Khalil B. Generalized-onset seizures with secondary focal evolution. Epilepsia 2009; 50 (07) 1827-1832
• 17 Blume WT, Pillay N. Electrographic and clinical correlates of secondary bilateral synchrony. Epilepsia 1985; 26 (06) 636-641
• 18 Sakakibara S, Nakamura F, Demise M. et al. Frontal lobe epilepsy with absence-like and secondarily generalized seizures. Psychiatry Clin Neurosci 2003; 57 (04) 455-456
• 19 Kakisaka Y, Alexopoulos AV, Gupta A. et al. Generalized 3-Hz spike-and-wave complexes emanating from focal epileptic activity in pediatric patients. Epilepsy Behav 2011; 20 (01) 103-106
• 20 Chang EF, Nagarajan SS, Mantle M, Barbaro NM, Kirsch HE. Magnetic source imaging for the surgical evaluation of electroencephalography-confirmed secondary bilateral synchrony in intractable epilepsy. J Neurosurg 2009; 111 (06) 1248-1256