  This paper addresses the question of existence of (not necessarily
self-similar) solutions to the 4-vortex problem that lead to total or partial
collision. We begin by showing that energy considerations alone imply that, for
the general $N$-vortex problem, the virial being zero is a necessary condition
for a solution to both evolve towards total collision and satisfy certain
regularity condition. For evolutions assumed to be bounded, a classification
for asymptotic partial collision configurations is offered. This classification
depends on inertia and vorticity considerations. For non-necessarily bounded
evolutions, we discuss the relationship between partial and (non-regular) total
collisions when the virial is not zero and a generic condition on the
vorticities holds. Finally, we give a canonical transformation that, for a
class of 4-vortex systems satisfying a restriction on the vorticities, allows
to formally apply the averaging principle in order reduce the dynamics when two
of the vorticities are near a binary collision. The reduced system is a
one-degree of freedom hamiltonian system.
