Background: Transient neurological symptoms in patients with subdural hematoma (SDH) are often attributed to secondary epilepsy despite a negative workup. We believe a significant proportion of these patients could rather suffer from cortical spreading depolarization (CSD). Methods: We performed a retrospective case-control study of patients with transient neurological symptoms post-SDH evacuation between 1996 and 2017. The clinical features of patients with negative EEG were compared to those with positive EEG (ictal or interictal abnormalities) and a clinical scoring system was created. Results: 59 patients were included, 20 (34%) with a positive EEG. Speech-related symptoms (OR 4.8, p=0.018) and prolonged episodes (OR 23.1, p=0.001) were associated with a negative EEG. Clonic movements (OR 0.014, p<0.0005), impaired awareness (OR 0.013, p<0.0005), positive symptoms (OR 0.05, p<0.0001), complete response to standard antiepileptic drugs (OR 0.06, p=0.007) and mortality (OR 0.021, p=0.003) were associated with a positive EEG. We built a clinical score based on these features, which showed a 90% sensitivity and 100% specificity. Conclusions: We believe that the differences observed between both groups were driven by the presence of CSD rather than seizure in the case group. Our proposed scoring system can help predict EEG results and may be useful to identify CSD in future trials.