Lennox-Gastaut syndrome with series of spasms intermixed with tonic seizures

A patient with Lennox-Gastaut syndrome developed an unusual feature of periodic spasms (PS), intermixed with tonic seizures. At age 14, she began to have unilateral seizures on awakening, followed by series of spasms. Each spasm consisted of rotation of the head to the left and global muscle contraction of the whole body lasting for 0.5~1 second. Ictal EEGs revealed diffuse high voltage slow waves (HVSW), sometimes superimposed upon by diffuse low voltage fast activity, which was related to the increase of muscle activity following the spasms. When the duration of the fast activity on EEG became longer than 2 seconds, the peculiar seizures consisting of combination of asymmetrical spasms and tonic seizures occurred. It is speculated that the fast activity superimposed on HVSW seen in PS represents a transition from PS to tonic seizures.