Quantitative phase imaging techniques including digital holographic microscopy (DHM) have emerged recently in life sciences and can be aimed at monitoring and quantifying, in a non-invasive way, cellular processes. Due to its interferometric nature, the DHM phase signal or optical path difference (OPD), which depends on both cell thickness and integral RI can be measured with a high sensitivity. Here, we present an application of digital holographic microscopy (DHM) dedicated towards early and label free detection of neuronal death. Practically, through the quantitative measurements of OPD, the early neuronal cell volume regulation, following glutamate-mediated excitotoxicity, has been accurately monitored. Finally, the efficiency of this early cell volume regulation process has been successfully correlated with the occurring of the subsequent neuronal death assessed with the widely accepted trypan blue viability method.