How long does it take to recover from a brain biopsy? (assuming it is negative)

Short time: A stereotactic biopsy does not take much time to recover from at all (hours to a couple of days). Headache is the most common side effect. Open brain biopsy done via a "burr hole" would take slightly longer -- but both are very standardized and neurosurgeons are the specialists with the longest number of years of training: 9 years after medical school. They know what they are doing.