Mount Sinai Health System describes kernicterus as having early, middle, and late stages. Early-stage kernicterus is usually easier to treat and may not necessarily result in permanent brain damage
In the middle and late stages of kernicterus, it’s more likely for babies to experience more severe symptoms like fever and coma. The disease can be harder to treat at this point, and the chances of the baby developing significant brain damage and hearing loss are much greater.