He may be a neurologist who does actually specialize in Parkinson's Disease; however, that does not mean that he went to the White House to see President Biden. President Biden is not the only person at the White House.
[My late ex-husband, while on active duty, started having seizures. He was seen frequently by a neurologist. He was medically discharged because he wasn't controlled. No medication could keep him from having breakthrough seizures and there was no warning before he had them. He later developed Parkinson's Disease. ALL that information would be covered by HIPAA, so reporters wouldn't know who the doctor was seeing or why the person who may specialize in Parkinson's Disease was treating someone. It could be for epilepsy, TBIs, TIAs, etc.]
[President Biden being seen three times is in keeping with his having three annual exams.]