Pain insensitive structure in brain is :

Choroid plexus Choroid plexus is pain insensitive structure. Harrison writes:-"relatively few cranial structures are pain- producing; these include the slap' middle meaningeal aery, dural sinuses, falx cereberi, and proximal segments of the large pail aeries. The ventricular ependyma, choroid plexus, pail veins, and much of the brain parenchyma are not pain-producing."