Permanent incapacity of President or Vice-President
Section 144(1) · 1999 Constitution (2004 edition)
What Constitution says
(1) The President or Vice-President shall cease to hold office, if - (a) by a resolution passed by two-thirds majority of all the members of the executive council of the Federation it is declared that the President or Vice-President is incapable of discharging the functions of his office; and (b) the declaration is verified, after such medical examination as may be necessary, by a medical panel established under subsection (4) of this section in its report to the President of the Senate and the Speaker of the House of Representatives.
This is the 1999 Constitution as published in 2004. Later amendments aren't included yet, so a section may have changed since.
Original source
Official Gazette · CFRN 1999 official PDF · printed page 72–73. Original document
Release: draft-c8d50d87fae9. Source scope, review and corrections