The longest surgery on record occurred in 2001 and lasted more than four straight days—103 hours to be exact. A team of 20 doctors at Singapore General Hospital worked in shifts to separate Ganga and Jamuna Shrestha, 11-month-old twins conjoined at the head. Not only did the girls share a cranial cavity, their brains were partially fused. Typically such separation procedures might take 30 hours—still an eternity in surgical terms—but once underway, doctors discovered that the girls’ brains were even more tightly enmeshed than expected.