Expandable and collapsible brain cannula

A cannula system for accessing a target site within a brain of a patient, said system comprising:

• a cannula comprising a resiliently expandable tube, said cannula having a distal end adapted for insertion into the brain of the patient and a proximal end;
• an insertion tube having a first length and adapted for insertion into the brain of the patient;
• wherein the cannula is compressible to a small diameter configuration to fit inside the insertion tube, and expandable to an unconstrained large diameter configuration;
• and
• an extraction tube that fits over the cannula, the extraction tube having a diameter smaller than the cannula in the unconstrained large diameter configuration.