spinal tap

noun
1
a medical procedure in which liquid is removed from the lower part of the spine with a hollow needle, usually in order to diagnose a medical problem (= identify what it is)
نمونه‌گیری مایع نخاعی, پونکسیون مایع نخاعی, پونکسیون کمری, پونکسیون نخاعی