Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are clear . There is no effusion or pneumothorax . Known pneumomediastinum was more clearly delineated on prior CT . There is subcutaneous gas at the base of the neck on the right . Cardiomediastinal silhouette is within normal limits . There is no free intraperitoneal air .
    OUTPUT:
    
Known pneumomediastinum better seen on earlier CT scan .