In extrapulmonary TB, surgery is often needed to make a diagnosis (rather than to effect a cure): surgical excision of lymph nodes, drainage of abscesses, tissue biopsy, etc. are all examples of this. Samples taken for TB culture should be sent to the laboratory in a sterile pot with no additive (not even water or saline) and must arrive in the laboratory as soon as possible. Where facilities for liquid culture are available, specimens from sterile sites may be inoculated directly following the procedure: this may improve the yield. In spinal TB, surgery is indicated for spinal instability (when there is extensive bony destruction) or when the spinal cord is threatened. Therapeutic drainage of tuberculous abscesses or collections is not routinely indicated and will resolve with adequate treatment. In TB meningitis, hydrocephalus is a potential complication and may necessitate the insertion of a ventricular shunt or drain.