Children with aberrant development, including those with autistic disorders, may have atonic or more dramatic syncopal seizures compulsively self-induced by something akin to a Valsalva or Weber maneuver (3,54). Such episodes may be very severe and, indeed, may have a fatal outcome (55). The child seems able to obstruct the cerebral circulation completely, so that an anoxic seizure results. Perhaps, because of the cerebral abnormality already present, this is one situation in which anoxic-epileptic seizures (see Anoxic-Epileptic Seizures below) may result (56-58). If the episodes are very frequent, as is often the case, detailed analysis by videorecording and polygraphic registration (55) may allow a precise elucidation of the diagnosis. Clues include the video-picture of true "breath-holding" for about 10 seconds, this time in inspiration, reduction of the amplitude of the QRS complexes on ECG, and then a burst of high-voltage slow waves on EEG. Sometimes, hyperventilation precedes the Valsalva maneuvre, as in Case Study 4 (see published video in ), and as in the experimental syncopes described by Lempert, Bauer and Schmidt (23). It is likely that many of the reported seizures in Rett syndrome are of this nature (59).
Case study #4. A boy of school age presented with an apparent recurrence of seizures. He had an early history of infantile spasms; that is, epileptic spasms with hypsarrhythmic EEG in the first year of life. The spasms remitted but he was left asymbolic—that is without the understanding of meaning—and without imaginative play or social interaction. His main enjoyments seemed to be twirling or spinning dinner plates and intermittently hyperventilating and holding his breath. He was referred back because of numerous daily tonic seizures. Videorecording demonstrated a consistent stereotyped sequence. While twirling a plate, he hyperventilated, then took a deep breath in inspiration, then made a powerful Valsalva maneuver for 10 to 11 seconds, and finally with a groan he collapsed with brief tonic extension and elevation of his upper limbs. He recovered instantly. His mother said "that's a seizure, isn't it?" It was, but an anoxic seizure, not an epileptic seizure (3).
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