An average humanoid who has been implanted with a surger will experience a high-energy consumption of their brain and nervous system. This is a particularly pernicious weapon as it works slowly and painfully delivering the high energy charge. This weapon is employed by agents of the Romulan Star Empire.
On stardate 8748, in the early 2290s, Professor Peter Erikson was killed by Romulan Commander Agorra's neural surger. Erikson had conspired with Agorra to defect to Romulus with Federation intelligence. After supplying the Romulans with vital information, Agorra supplied Erikson with what the Professor thought was a tracer, but was actually a surger.
Erikson was used to attempt to enlist Saavik to defect, when she was dispatched to recover him by Starfleet. When Saavik proved unwilling to betray her loyalty, Erikson attempted to use the tracer to be recovered by Agorra's transporter. The neural surge began and slowly burnt through his body. He collapsed in Saavik's arms and had several seconds to realize that he had been duped while the burning pain coursed through his body. (TOS comic: "Renegade")