Drop seizures are extremely common among individuals with MECP2 duplication syndrome. There is a sudden loss of muscle tone, and if the individual is not supported, he or she drops suddenly to floor, sometimes resulting in injury. Usually these are brief and it is over in a second, but sometimes they come in clusters.
While these drops are certainly one of the most, if not the absolute most, common seizures in MECP2 duplication syndrome, there are actually two kinds of “drops” that look pretty much the same, but are fundamentally very different. It is hard to tell them apart, and at least some individuals with MECP2 duplication syndrome, have both kinds. It may be helpful to figure out which kind is occurring, but it can be really hard to figure out, and it appears that at least some individuals experience both atonic and myoclonic drops.
So what’s the difference? ATONIC VS MYOCLONIC-ATONIC
ATONIC DROPS occur when there is a sudden and extreme loss of muscle tone. If a person is standing or walking, they are suddenly limp and gravity takes over taking them to the ground. Sometimes this drop is such a brief fraction of second that an individual can regain muscle tone and regain their balance and posture before falling but usually, he or she will just drop. If the individual is sitting or laying down, the drop may only result in their head drooping, and depending how well they are supported.
MYOCLONIC DROPS occur when there is a sudden INCREASE in muscle tone in some muscles. If the person is standing or walking, he or she will be thrown to the ground forcefully. Usually there are actually two phases that happen within a fraction of a second: first, the muscles spasm, and then the they lose tone. These are called Myoclonic-Atonic seizures or Myoclonic-Astatic seizures.
Most of the time when people talk about Drop Seizures, people assume that these are Atonic Seizures, but for individuals with MECP2 duplication syndrome, we are often talking about Myoclonic-Atonic Seizures.
In our case, when Dave first started having drops, we assumed they were atonic seizures. As time went on, there were a number of clues that they were myoclonic. One was seeing how hard he would slam down on a table he was sitting at; it was hard to explain just by gravity. Another was to see him have these spasms when he was laying in bed, and he would jacknife his body against gravity. That’s not just loss of tone.
Eventually, however, we saw Dave having longer lasting atonic episodes. Sometimes it would be just his head and neck that went limp. Others it would be his whole body. Sometimes it would last for a few seconds, other times it would last for several minutes. He was clearly awake and conscious, and when it was just his head and neck affected, he could use his hands. So, it took a long time to figure it out, but in his case, he has both atonic and myoclonic-atonic seizures.
I know other kids with this syndrome have drops and I am pretty certain that a lot of them are myoclonic-astonic seizures, but other parents have also reported episodes that sound more like atonic seizures. So, I suspect that having both these kinds of seizures is at least fairly common in our kids.