There aren't many hospitals that test for autonomic nervous system disorders

My son has been experiencing symptoms of depression, headaches, and tachycardia. He had been taking antidepressants for a few years and was doing better, but his condition has recently worsened again. After looking into it, I suspected it might be an autonomic nervous system disorder, so I went to a general hospital for testing, but they told me they don't perform those kinds of tests.
I finally managed to find one place to get tested, and as expected, there is an abnormality. It seems like an area that doctors haven't researched much yet. It feels like it might be a lingering effect of COVID-19.
I have already made an appointment with a famous neurosurgery clinic in Seoul. It's heartbreaking. I wish we had known sooner..