Opportunities for progression and promotion should be considered in the same way as for any other employee working for you. Of course, the employee will need to meet the criteria, but you should ensure that there are no barriers to promotion because of their injuries that could be avoided, such as the manner of assessment or interview.
You should also consider the criteria carefully to ensure that anything which the employee might have difficulty meeting is reasonably required. (In legal terms, ‘a proportionate means of achieving a legitimate aim’.) Otherwise, a complaint could be made of indirect discrimination under section 19 of the Equality Act 2010.
It may be that the employee’s desire for promotion has changed following their injury. This may be something that they are not even considering initially whilst they get used to being back at work. They may lack confidence in their abilities following their brain injury.
If the employee has not indicated their desire to pause their progression in the workplace, you should discuss promotions with the employee as you would have had the brain injury not occurred.
Any decision to change their route of progression should come from the employee. This will help the employee to feel valued and achieve their best. It will also avoid the employer discriminating against the employee, either on grounds of their disability (contrary to section 13 of the Equality Act 2010), or for any reason arising from their disability, i.e. their symptoms (contrary to section 15 of the Equality Act 2010).
It is important to recognise this and help your employee reach their full potential. By having an open-minded and inclusive environment, an employee should not be put off applying for promotions.