1. In tuberculosis meningitis there is a tuberculosis endarteritis characterized by the formation of intimal tubercles and a diffuse subendothelial, intimal proliferation due to implantation of tubercle bacili from the blood. From the endarteritis the infiltration may spread into the muscular coat and the adventitia, and the whole wall may undergo caseous and hyaline degeneration.
2. Tuberculous proliferation in the adventitia may invade the media and the intima, and the whole wall of the arterial segment may undergo degeneration.
3. The veins are constantly the seat of more or less extensive infiltration, which always results from adjacent extravascular or arterial foci.
4. The epithelioid cells of the subendothelial, tuberculous intimal
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proliferation are most likely derived from the subendothelial layer of connective tissue and not from the endothelial lining.