Complex sentence: Patients with the best outcome have no or limited symptoms of respiratory or neurological distress, accumulation of these symptoms leads to decreased levels of statistical survival compared with patients diagnosed with asymptomatic hyperleukocytosis alone.
Split into simpler sentences: Patients with the best outcome have none or limited symptoms of respiratory or neurological distress. An accumulation of these symptoms leads to decreased levels of statistical survival compared to patients diagnosed with asymptomatic hyperleukocytosis alone.