White things crusted at ear tips of 16 yr old female shit zhu

Hi my dog is an older female shih tzu. For several months she has had this ear crust at the tips of her ears . It’s not noticeable until you start look at her ears and then you pull out the white things that are all stuck to the tips Of her ears . Then you see black spots as well. She has been diagnosed with Cushings disease and is currently taking medication

Hello   White crusty or flaky ear-tips can be a signs of various different diseases in older dogs, from the mild to the severe.  Ideas include sebhorrhea (waxy plugs adherent to the hair shafts), sarcoptic mange (skin mites), a lack of blood flow to the ears (leading to crustiness and necrosis at the extremities), endocrine diseases and ringworm.  All of these are treated differently and Ringworm is infectious to people.  Sometimes, the most superficial-seeming of these possibilities can be signs of more severe underlying disease in the patient, so while ear crusting can be easily dismissed, it is worth taking the time to understand what has changed.