sentences:  It is learned during "Endgame", the final episode of the series, that Tuvok suffers from a degenerative neurological disease, which can only be cured by undergoing a mind meld with a family member.In 2377, he was still well enough to perform his duties.However, in his elderly years, in an alternate timeline, the disease finally ravaged Tuvok's mind as he was not able to return to the Alpha Quadrant in time for a cure.