Spatially isolated disordered zones have been produced in silicon by irradiating with Xe+ ions in situ in a transmission electron microscope to fluences in the range of 1011 to 1012 ions cm-2. At these levels of fluence, the zones are clearly visible with minimal overlap with typical effective radii of the order of 1 nm. Studies of the isochronal recrystallization of zones with similar starting radii have shown that although most zones behave as expected and immediately begin to reduce their effective radius, in a small number of cases, some of the zones increase in size following an isochronal recrystallization step. Kinetic Monte-Carlo simulations have indicated that this behaviour may result when a high density of point defects surrounds an amorphous core. Upon recrystallization, the system relaxes to a configuration which can give rise to an increase in volume of the disordered zone of up to 50%. The kinetic Monte-Carlo simulations have shown that the defect most likely to be responsible for this anomalous growth is the interstitial-vacancy (IV) pair and the configuration of the IV pairs around an amorphous zone has a strong influence on the maximum re-growth of the zone.