During the 15-minute hearing at Hammersmith, west London, Dr John Burton, the west London coroner, said a full inquest would take place in about a month after police inquiries are completed.
None of the 45-year-old Eastleigh MP's family was at the hearing, though they had been invited. The only witness, Detective Superintendent Brian Edwards, who is leading the investigation, told the inquest that further interviews were necessary to prove no one else was involved in Mr Milligan's death at his home in Hammersmith, on 7 February.
Det Supt Edwards said: 'We are trying to exhaust every possibility to show that no one else was involved. We are keeping an open mind.'
Dr Burton said that even though the inquiries were continuing he would release Mr Milligan's body so that his family could make funeral arrangements.
The coroner also asked Det Supt Edwards about the inquiry into the way news of the MP's death leaked to the media, but the officer said it did not form part of his inquiry.