This compression could be caused by a cervical rib, which is a congenital anomaly where an extra rib is located above the first rib; or by a Pancoast tumor, a type of lung cancer where tumor forms at the tip of the lung.

这种压迫可能由颈肋引起，颈肋即一种先天性异常：在第一肋上方出现一个额外的肋骨；也可能由肺上沟瘤引起，即肺尖处的一种肿瘤。