The hospitalised leader has affixed her left thumb impression to by-election nomination papers as she "is temporarily unable" to sign them, a surgeon's certificate said.
The attestation became a necessity to enable AIADMK candidates to fight the by-elections to four Assembly seats in Tamil Nadu and Puducherry on November 19.
As general secretary of the AIADMK, Jayalalithaa alone is authorised to sign the Form B that allots the party symbol to candidates.
When the by-election schedule was announced on October 16 - Jayalalithaa has been in hospital since September 22 - questions were asked how she would sign the forms.
Two announcements a week ago had preceded the attestation. In the latest medical bulletin issued on October 22, Apollo Hospital had said Jayalalithaa was "improving gradually and interacting". After a visit on the same day, the acting governor too had said she was progressing well.
The forms have been attested by Dr P. Balaji, a senior surgeon at the government-run Rajiv Gandhi Hospital, opposite the Chennai Central railway station.
The doctor has certified that "since the signatory had undergone tracheostomy recently and has an inflamed right hand, she is temporarily unable to affix her signature. Hence she has affixed her left thumb impression on her own in my presence."
Dr Babu Abraham of Apollo Hospitals signed as witness.
A tracheostomy, a surgical procedure in which an opening is made through the front of the neck into the windpipe, is intended to help a patient breathe when normal breathing is not possible. A tracheostomy is sometimes performed to assist long-term ventilation, said a critical care medicine specialist in New Delhi.
"A tracheostomy will not lead to an inflamed right hand - some other underlying condition may have led to the inflammation," the doctor said, adding that he was speculating because he was unfamiliar with the case.
According to a senior lawyer, the elaborate steps were taken to ensure that the nomination forms were not rejected at the time of scrutiny, when candidates from other parties can challenge the entries