Clinical electroencephalogram (EEG) evaluation is improved by the amplitude asymmetry index

ABSTRACT

Cerebral hemispheres, although similar, are neither completely symmetrical in structure nor equivalent in function. EEG asymmetry studies have been directed more to frequency than to amplitude analysis.

Objective Better definition of normal amplitude asymmetry values on the classical EEG frequency bands.

Results EEG amplitude asymmetry index (AAI) is physiologically low in normal adults, differences usually lesser than 7%.

Conclusion Persistent or intermittent amplitude asymmetry regional differences higher than 7% may be suggestive of pathology after adequate correlation with clinical data and EEG classical visual analysis.

RESUMO

Os hemisférios cerebrais não são simétricos em morfologia ou funções. Tradicionalmente, os estudos de assimetria do EEG focaram mais na análise de frequências do que na de amplitudes.

Objetivo Contribuir para melhor definição dos valores normais de assimetria de amplitudes nas faixas de frequência clássicas do EEG.

Resultados O índice de assimetria de amplitudes é fisiologicamente baixo em adultos, usualmente menor do que 7%.

Conclusão Se adequadamente correlacionadas aos dados clínicos e à análise visual do EEG, assimetrias persistentes ou intermitentes de amplitude acima de 7% podem ser sugestivas de patologia.

Electroencephalography - amplitude - asymmetry

Eletroencfalografia - amplitude - assimetria

• References

• 1 Niedermeyer E. The normal EEG of the waking adult. In: Niedermeyer E, Silva FL, editors. Electroencephalography: basic principles, clinical applications and related fields. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 1999. p. 149-73.
• 2 Putten MJAM. The revised brain symmetry index. Clin Neurophysiol. 2007;118:2362-7.
• 3 Kandel ER. Brain and behavior. In: Kandel ER, Schwartz JH, Jessell TM. Principles of neural science,editors. 3rd Ed. New York: Elsevier; 1991. p. 1-17.
• 4 Kugler J. La electroencefalografia em la clínica y em la practicaMadrid: Alhambra; 1969. El electroebcefakigrana: elementos gráficos: nomenclatura. ; p. 39-57.
• 5 Kellaway P. An orderly approach to visual analysis: the parameters of the normal EEG in adults and children. In: Klass DW, Daly DD, editors., Current practice of clinical electroencephalography. New York: Raven Press; 1979. p. 69-147.
• 6 Delamonica EA. Electroencefalografía. 2nd ed. Buenos Aires: Libreria El Ateneo; 1984. Chapter 4, El EEG Normal del Adulto; p. 87-130.
• 7 Aurlien H, Gjerde IO, Aaserth JJ, Eldoen G, Karlsen, B, Skeidsvoll H et al. EEG background activity described by a large computerized database. Clin Neurophysiol. 2004;115(3):665-73. doi:10.1016/j.clinph.2003.10.019
• 8 Cloostermans MC, Vos CC, Putten MJAM. A novel approach for computer assisted EEG monitoring in the ICU. Clin Neurophysiol. 2011;122(10):2100-9. doi:10.1016/j.clinph.2011.02.035
• 9 Finnigan S, Putten MJAM. EEG in ischaemic stroke: quantitative EEG can uniquely inform (sub)-acute prognoses and clinical management. Clin Neurophysiol. 2013;124(1):10-19. doi:10.1016/j.clinph.2012.07.003
• 10 Lodder SS, Putten MJAM. Quantification of the adult EEG background pattern. Clin Neurophysiol. 2013;124(2):228-37. doi:10.1016/j.clinph.2012.07.007
• 11 Bickford RG, Billinger TW, Fleming NI, Stewart F. The compressed spectral array (CSA): a pictorial EEG. Proc San Diego Biomed Symp. 1972;11:365-70.
• 12 Myslobodsky MS, Coppola R, Bar-Ziv J, Weinberger DR. Adequacy of the International 10-20 Electrode System for Computed Neurophysiologic Topography. J Clin Neurophysiol. 1990;7(4):507-18.
• 13 Brigo F, Cicero R, Fiaschi A, Bongiovanni LG. The breach rhythm. Clin Neurophysiol. 2011;122(11):2116-20. doi:10.1016/j.clinph.2011.07.024