A further 1,044 patients seen by consultant neurologist Dr Michael Watt are being recalled.
Those affected are people who were seen by Dr Watt and then discharged to the care of their GP.
Review appointments will now ensure they are on the right treatment.
It comes six months after the unprecedented recall of more than 2,500 former patients due to "safety concerns" around the experienced doctor's work.
This followed a year-long independent investigation by the Royal College of Physicians, with the review - the biggest ever recall by the Belfast health trust - costing around £1 million so far.
Read more:
- Who is Dr Michael Watt?
- Restrictions placed on consultant at centre of patient recall
- People affected by neurology scandal urged to air views in independent probe
Patients who were being actively treated by Dr Watt have already been seen.
The latest group of 1,044 people who had been discharged to the care of their GP and prescribed medications for neurological conditions will be offered appointments within the next four months, starting this weekend.
They include around 700 treated by Dr Watt within the health service and almost 350 private patients at the Ulster Independent Clinic or Hillsborough Private Clinic.
The medications include anti-epileptic drugs, immunosuppressants and disease modifying therapies which are used to treat conditions like epilepsy and Multiple Sclerosis.
Northern Ireland's chief medical officer Dr Michael McBride said: "We provided a commitment at the outset that we would carefully consider anyone who had previously been seen by Dr Watt and discharged, and then recall any key groups of people who, based on the advice of the consultant neurological team, required a review.
"Based on our learning from the inital recall of patients, individuals have now been identified by the specialised medicines they are being prescribed.
"We want to apologise for any distress and uncertainty that this process brings.
"It is clearly our responsibility to act on clinical advice and the emerging outcomes from the first phase of the recall."
The decision on who to offer appointments to has been shared with the Royal College of Physicians.
It described the action as "very sensible" and in line with its initial findings.
Additional clinics have been secured from the independent sector to support consultants at Northern Ireland's largest public healthcare provider, the Belfast Health and Social Care Trust.
All patients in the first stage of the review, announced earlier this year, have already received a first appointment and more than 600 have been discharged.
A significant number of other patients have been referred separately from the main recall process.
Belfast Trust consultant neurologist Dr John Craig said: "We wish to reassure everyone who has received a letter that our primary focus is to provide assurance that they are on the correct treatment and request that they should not stop or make adjustments to their medication until they have been reviewed by a consultant neurologist at their appointment.
"It is crucial that everyone who does not receive a letter understands that they have no action to take and do not need to get in touch.
"This latest review process is being concentrated on specific groups of patients taking specific, specialised medicines."
Read more:
- Secrecy about Dr Watt report continues as Belfast trust refuse to release documents
- Woman with brain lesions and MS faces year-long wait to see neurologist
David Galloway, director of MS Society NI, said the news will obviously be concerning for people and it would encourage those who have received a letter to contact the appointment line.
"This recall has been a stressful time for people, I know our counselling team at the MS Society have been providing support to some of those affected in phase 1 of the recall and I am pleased the Belfast Trust are proactively signposting emotional support services to those affected in this second stage.”
He said while many patients have had a positive experience of the recall up to now, others have faced "life-changing news" after it emerged they had been misdiagnosed and incorrectly treated.
"We continue to engage with the Belfast Trust and Department of Health to ensure people affected receive the care and support they need. While understandably the focus has been on individuals and clinical responses put in place, people affected have understandable and legitimate concerns and questions about how this came about.
"There are reviews and investigations in place and the MS Society is keen findings from those are shared with people affected and indeed published as soon as possible.”
SDLP deputy leader Nichola Mallon said the latest recall confirms the unprecedented scale and seriousness of this situation.
“The number one priority is making sure all patients have the right diagnosis and are on the right treatment and care plan. I would urge every one of the 1,044 patients receiving recall letters today to make a review appointment to ensure they have been correctly diagnosed and are on the correct medication," she said.
"The SDLP has been calling for months for the Department of Health and Belfast Trust to set out clearly the pathway for reassurance for discharged patients who were formerly under the care of Dr Watt, many of whom have been left very distressed, not knowing what to do or how they may have been affected since the recall of neurology patients was first announced back in May.
"One of the most common concerns of patients at the heart of this is the lack of information and communication from the Belfast Trust as to what is happening and the next steps for them. Lessons around all of this, based on patient feedback, must be listened to and acted on so that the stresses of patients are not added to by leaving them feeling they are completely in the dark."
Sinn Fein MLA Pat Sheehan MLA said: "This will be a distressing time for patients who have received a letter as part of this recall but it's important people contact the health authorities to ensure their treatment is appropriate.
“My engagement with the Department of Health and neurology consultants suggests a shortage of neuro-psychologists to meet demand from affected recall patients.
“While I appreciate the challenges involved in the neurology recall I am not convinced sufficient action is being taken to address the shortage in neuro-psychologists.
“I will continue to engage regularly with the department on both neurology recalls to make sure affected patients are receiving the care and support they need."
:: A dedicated advice line - 0800 980 1100 - is available for anyone with any concerns in advance of a recall appointment. It is open from Monday to Friday, 9am to 8pm.
