There is no evidence that the drop in antibiotic prescribing for otitis media has increased the incidence of mastoiditis, raising the possibility that the drop in reported cases is due to a confounding factor such as childhood immunizations against "Haemophilus" and "Streptococcus". Untreated, the infection can spread to surrounding structures, including the brain, causing serious complications. While the use of antibiotics has reduced the incidence of mastoiditis, the risk of masked mastoiditis, a subclinical infection without the typical findings of mastoiditis has increased with the inappropriate use of antibiotics and the emergence of multidrug-resistant bacteria.