In medicine, a mass effect is the effect of a growing mass (or tumor in its narrow meaning), for example the consequences of a growing cancer. For example, cancer of the thyroid gland may cause symptoms due to compressions of certain structures of the head and neck; pressure on the laryngeal nerves may cause voice changes, narrowing of the windpipe may cause stridor, pressure on the gullet may cause dysphagia and so on. An intracranial hemorrhage (a bleeding within the skull) can have a mass effect on the brain, increasing intracranial pressure and potentially causing midline shift or deadly brain herniation.