"No neurological assessment was carried out in ED before the woman was referred to the general medicine team," the report said.
"This referral was initially declined before a second referral was accepted. The woman discharged herself from the ED and was later found to have a brain tumour."
Hill described the woman's care as "suboptimal" and was critical of staff members' decisions not to offer an adequate neurological review at either visit, and that the general medicine team declined a referral without assessing her.
Hill was also concerned by a lack of documentation which he said could have affected the quality and continuity of services.
He found the DHB to be in breach of the code of Health and Disability Services Consumers' Rights.
He criticised a general medicine consultant for not arranging a CT scan or providing the woman with more formal follow-up advice when she was first discharged.
"A busy environment does not remove the obligation to provide good services, and does not remove the accountability for ensuring that appropriate steps are taken," he said.
He recommended both the consultant and the DHB apologise to the woman, and that the DHB consider a number of changes relating to the overview by consultants of junior doctors' cases, and consultant involvement in cases where patients re-present to ED or where they wish to leave hospital against medical advice; and changes relating to documentation and criteria for urgent CT head scans, including ongoing education in relation to this.
Acting chief medical officer Dr James Entwisle apologised to the patient and family.
"No injury to, or misdiagnosis of, a patient under our care is acceptable," he said in a statement.
"We have undertaken a thorough review to look at what lessons could be learned, and changes made, to try to ensure that such an event does not happen again.
"We take patient safety extremely seriously, and acknowledge that we failed the patient and family in this instance. We also accept the Health and Disability Commissioner's finding that we did not provide services of reasonable care and skill. We have written to the patient and their family to sincerely apologise for that failure."
Entwisle had reviewed the report, and said the DHB was considering how to implement the recommendations.