Abnormal Fast Activity before the Onset of West Syndrome

Abstract

In our sequential EEG study performed on 68 infants with various pre- and perinatal brain insults, we found peculiar abnormal fast activity (AFAs) in 12 patients. 9 of the 12 patients with AFAs later developed West syndrome (WS) compared with only 3 of the 56 patients without AFAs (p<0.001, χ² test). We analyzed these AFAs using EEG topography, and compared them with ictal fast activity (IFA) corresponding to tonic spasms observed later in the same patients after they had developed WS. We also investigated the clinical and EEG features in these patients. AFAs were first observed commonly at 4–5 months of CA, before the onset of WS. AFA topographic maps revealed posterior predominance in 11 of the 12 patients; IFA maps also showed posterior predominance but were more widely distributed. We propose that, though AFAs and IFAs are different, they share certain aspects of their pathophysiology, and that the maturational process of the occipital cortex plays an important role in the shared aspects. Since AFAs are observed before the onset of WS, they can be considered a sign that WS is imminent.

Key words

West syndrome - infantile spasms - abnormal fast activity - topographic analysis - ictal EEG

References

• 1 Barkovich AJ, Kjos BO, Jackson Jr DE. et al . Normal maturation of the neonatal and infant brain: MR imaging at 1.5 T.  Radiology. 1988;  166 173-180
• 2 Chugani HT, Phelps ME, Mazziotta JC. Positron emission tomography study of human brain functional development.  Ann Neurol. 1987;  22 487-497
• 3 Chugani HT, Shields WD, Shewmon DA. et al . Infantile spasms: I. PET identifies focal cortical dysgenesis in cryptogenic cases for surgical treatment.  Ann Neurol. 1990;  27 406-413
• 4 Cusmai R, Ricci S, Pinard JM. et al . West syndrome due to perinatal insults.  Epilepsia. 1984;  25 317-325
• 5 Endoh F, Yoshinaga H, Kobayashi K. et al . Electroencephalographic changes before the onset of symptomatic West syndrome.  Brain Dev. 2007;  29 630-638
• 6 Fusco L, Vigevano F. Ictal clinical electroencephalographic findings of spasms in West syndrome.  Epilepsia. 1993;  34 671-678
• 7 Iinuma K, Haginoya K, Nagai M. et al . Visual abnormalities and occipital EEG discharges: risk factors for West syndrome.  Epilepsia. 1994;  35 806-809
• 8 Inoue T, Kobayashi K, Oka M. et al . Spectral characteristics of EEG gamma rhythms associated with epileptic spasms.  Brain Dev. 2008;  30 321-328
• 9 Kobayashi K, Oka M, Akiyama T. et al . Very fast rhythmic activity on scalp EEG associated with epileptic spasms.  Epilepsia. 2004;  45 488-496
• 10 Ohtahara S. Clinico-electrical delineation of epileptic encephalopathies in childhood.  Asian Med J. 1978;  21 499-509
• 11 Ohtahara S. Seizure disorders in infancy and childhood.  Brain Dev. 1984;  6 509-519
• 12 Ohtsuka Y, Murashima I, Asano T. et al . Partial seizure in West syndrome.  Epilepsia. 1996;  37 1060-1067
• 13 Oka M, Kobayashi K, Akiyama T. et al . A study of spike-density on EEG in West syndrome.  Brain Dev. 2004;  26 105-112
• 14 Okumura A, Hayakawa F, Kuno K. et al . Periventricular leukomalacia and West syndrome.  Dev Med Child Neurol. 1996;  38 13-18
• 15 Okumura A, Watanabe K. Clinico-electrical evolution in prehypsarrhythmic stage: toward prediction and prevention of West syndrome.  Brain Dev. 2001;  23 482-487
• 16 Panzica F, Binelli S, Canafoglia L. et al . Ictal EEG fast activity in West syndrome: from onset to outcome.  Epilepsia. 2007;  48 2101-2110
• 17 Suzuki M, Okumura A, Watanabe K. et al . The predictive value of electroencephalogram during early infancy for later development of West syndrome in infants with cystic periventricular leukomalacia.  Epilepsia. 2003;  44 443-446
• 18 Yamatogi Y, Ohtahara S. Age-dependent epileptic encephalopathy: a longitudinal study.  Folia Psychiatr Neurol Jpn. 1981;  35 321-332
• 19 Yoshinaga H, Endo F, Kikumoto K. et al . Epilepsy development in infancy with epileptic discharges.  Brain Dev. 2007;  29 217-223
• 20 Yoshinaga H, Kobayashi K, Endo F. et al . Abnormal fast activity in infancy with paroxysmal downwards gaze.  Brain Dev. 2009;  31 435-441
• 21 Watanabe K, Takeuchi T, Hakamada S. et al . Neurophysiological and neuroradiological features preceding infantile spasms.  Brain Dev. 1987;  9 391-398
• 22 Watanabe K. West syndrome: etiological and prognostic aspects.  Brain Dev. 1998;  20 1-8

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