We report cases of two elderly women with dementia who presented with a new-onset seizure disorder characterized by subtle, rhythmic muscular contractions involving the buccolingual region and the four limbs, persistent jaw opening, and abnormal cervical posture that mimicked myoclonus-dystonia syndrome and oromandibular dystonia. The symptoms lasted several minutes to a few hours. Video-polygraphic recordings revealed an electromyographic (EMG) pattern of brief, shock-like muscular contractions consistent with myoclonus that correlated with a high-amplitude (70-90 µV), 11-14 Hertz, bilaterally symmetric electroencephalographic (EEG) rhythm over the frontocentral regions. A time-locked relationship between the frontocentral EEG activity and the EMG myoclonic potentials demonstrated the cortical origin of myoclonus and therefore the epileptic nature of the disorder, whereas the oromandibular and cervical dystonic-like postures suggested the pathogenic involvement of subcortical structures. The intravenous administration of diazepam suppressed the clinical symptoms and the EEG-EMG correlate of myoclonus. The clinical and neurophysiological findings illustrate a form of myoclonic status epilepticus (SE) with dystonia-like symptoms resulting from the functional involvement of cortical and subcortical structures. The manifestation of subtle, rhythmic myoclonus and dystonic-like postures in patients with atypical EEG patterns of SE may require challenging differential diagnoses with myoclonus-dystonia syndrome and oromandibular dystonia.