Cerebrospinal fluid may contain cancer cells. viagra online Specialized tests can sometimes help with the diagnosis. generic viagra For example, blood and cerebrospinal fluid may also be tested to check for substances secreted by tumors called tumor markers and for gene abnormalities that are characteristic of certain tumors. generic viagra In these people, removing cerebrospinal fluid during a spinal tap may cause the tumor to move, resulting in herniation of the brain. generic viagra However, a spinal tap cannot be done in people who have a large tumor that is increasing pressure within the skull.generic viagra generic viagra