Brain connectivity in West syndrome

PURPOSE Hypsarrhythmia, the pathognomonic EEG pattern of West syndrome, is typically characterized by a high amplitude, arrhythmic, and asynchronous pattern. While this severely aberrant pattern would suggest severe abnormalities in connectivity, coherence has not yet been systematically assessed in hypsarrhythmia. METHODS We evaluated the EEGs of 28 infants, 12 with infantile spasms with hypsarrhythmia and 16 similarly age control infants for coherence and spectral power. RESULTS Children with infantile spasms and hypsarrhythmia EEGs had marked abnormalities in coherence and spectral power compared to normal children of similar ages. During sleep increases in delta, theta, alpha and beta coherences were seen, particularly at long inter-electrode distances while at short inter-electrode distances coherences were decreased in the theta and beta range, particularly in the frontal region. The enhanced coherences at long inter-electrode distances suggest that during sleep in children with infantile spasms widely spread cortical region do not have functional differentiation whereas in the frontal lobe there is reduced functional connectivity and integration of local cortical regions. Children with continued seizures and developmental delay showed persistent abnormalities in coherence. CONCLUSION This study demonstrates that hypsarrhythmic EEGs have marked abnormalities in coherence spectral power and such abnormalities may be related to cognitive impairment.