Ummm, actually yes it does mention full body seizures.
MOVE-BY-WIRE SYSTEM
While usually considered cutting-edge technology, the
move-by-wire system actually predates all other reaction
cyberware, being the prototype from which wired
reflexes and similar systems were drawn. It was simply
too expensive and invasive to the user’s body for
widespread use, and the inferior, but more survivable,
wired reflexes claimed its glory. Researchers have been
struggling with it for decades and still haven’t perfected
it, but it’s at least closer to being usable today than
ever before. The system works by putting the user’s entire
body into a permanent seizure, using electrical impulses
to direct those seizures towards an eventual end
goal, such as “move here” or “stab that guy.” In many
ways, this isn’t unlike a high-end aircraft, where hundreds
of computerized micro-corrections are required
to keep it flying, only using metahuman flesh and bone
instead of high-end carbon and aluminum. Any user
under an active system will be affected by constant
small twitches and tremors due to the complex interactions
of the system, which vanish as soon as the system
engages actual movement, returning whenever they
are once again still. Move-by-wire is incompatible with
any other reaction-enhancing augmentation.
Each Rating point of a move-by-wire system adds
+1 Reaction and +3 Initiative (making it +4 total to Initiative).
Rating 1 move-by-wire does not offer any additional
Initiative Dice, but Rating 2 and Rating 3 offer
+1D6 Initiative Dice, meaning Rating 2 offers +2 Reaction,
+6 Initiative, and +1D6 Initiative Dice, and Rating
3 offers +3 Reaction, +9 Initiative, and +1D6 Initiative
Dice. In addition, the move-by-wire system acts as skillwires
of twice its Rating, but will require a skilljack to
access this functionality. Users of move-by-wire systems
suffer a penalty to their Social limit equal to the system’s
Rating thanks to their constant twitches and tremors.
Wireless Bonus: : +1 to relevant inherent limits when
used as skillwires (see p. 455, SR5).