Many patients are aware of chronic headaches at onset,[4] and 48% have vestibulocochlear neuropathy.[5] Idiopathic HP is usually not associated with elevated angiotensin I-converting enzyme, myeloperoxidase anti-neutrophil cytoplasmic antibody, PR3-ANCA, rheumatoid factor, and antinuclear antibodies. This evidence concerns the gene MPO and headache disorder.