Subject to the provisions of regulation 30 and notwithstanding the provisions of section 110(5) (leave of medical appeal tribunal required to review assessment in certain cases), a life assessment in respect of occupational deafness made by a medical board or a medical appeal tribunal shall not be reviewed in accordance with section 110(2) (review of assessment in case of unforeseen aggravation) without leave of a medical appeal tribunal, and in the case of a provisional assessment in respect of occupational deafness no such leave shall be required.