Objective: Mesial temporal sclerosis with associated extra hippocampal pathology is considered ‘dual pathology’ that could influence the progression and clinical outcome of complex partial seizures. This study is undertaken to evaluate and compare the clinical outcome and pathology of the temporal lobe and hippocampus in cases of mesial temporal sclerosis (MTS) alone and MTS with associated pathological changes in the extrahippocampal temporal lobe (dual pathology). Methods: The clinical and presurgical evaluation data and post surgical follow up (2 years) were reviewed retrospectively from medical records of 15 cases with MTS alone and 11 cases having dual pathology. Specific pathological changes were recorded after reviewing the material from hippocampus and temporal lobe and immunostaining with antibodies to synaptophysin, and neurofilament to delineate dystrophic neurons and synaptic pathology and S-100 protein for glial elements. Results: Among the 11 patients with dual pathology, 2 patients had mild cortical dysplasia (MCD) and 9 had focal cortical dysplasia (FCD) in the adjacent temporal cortex, as described by Palmini et al. High resolution MRI (1.5 Tesla) did not detect the presence of the second pathology reported in this series. Thirteen of the 15 patients with MTS alone and 6 of the 11 patients with dual pathology had good post surgical outcome. Six (2 MTS + 4 dual pathology) out of 7 patients who failed to show good clinical outcome had significant loss of neurons in CA3 sub-field of Ammon’s horn, whereas only 12 out of 19 patients who had good outcome had CA3 neuronal loss. Various types of cytoskeletal and synaptic pathology are found in the dysplastic neurons in the zones of cortical dysplasia. Conclusion: Two types of structural lesions underlie complex partial seizures, MTS with or without associated extrahippocampal lesions of neuronal cytoarchitectural abnormality may influence the prognosis. Neuronal loss in CA3 subfield of Ammon’s horn seems to have a role in negative clinical outcome, though this feature needs to be further validated.