A portable monitoring device comprises a hearing aid having a housing, a microphone (24), an acoustic signal processing means (43), and an acoustic output transducer (33). The portable monitoring device further comprises an EEG monitoring system arranged at least partly in said housing, and comprising a measuring unit (3) having electrodes (12) arranged external to the housing. The EEG monitoring system comprises a processing unit (42) for analyzing the EEG signal for identifying or predicting specific biological incidences, such as a seizure, in said person, decision means for deciding, based on said analyzed EEG signal, when an alarm or information must be provided to said person, and means for providing said alarm or information through said output transducer (33). The invention further provides a method of monitoring an EEG signal of a hearing impaired person.