We previously introduced the manual zero potential shifting (MZPS) method into dipole analysis to reduce the influence by error potential at the analytical stage. The source localizations of epileptic spikes as an equivalent current dipole (ECD) were estimated in a patient with symptomatic epilepsy and contrasted with findings obtained by magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT). When spikes were analyzed by the MZPS method, ECDs had high values of dipolarity, an indicator of ECD reliability. Moreover, their locations corresponded with lesions shown by MRI and SPECT. When the same spikes were analyzed by the conventional method, dipolarity values were declined and the locations did not correspond with lesions. These results provide further evidence that the MZPS method is of clinical utility in evaluating the electric source generator of epileptic spikes.