Rich focus

More recently a more comprehensive classification of the pathogenesis of tuberculous meningitis has been proposed by Donald et al.:^[1]

1. A Rich focus develops as a result of haematogenous dissemination from the primary complex, including miliary tuberculousis, subsequently rupturing into the sub-arachnoid space.
2. A Rich focus develops within the choroid plexus or ventricular walls as a result of haematogenous dissemination.
3. The mechanism described by Rich and McCordock in which haematogenous dissemination at the time of infection, or later, results in development of a Rich focus which is initially controlled but later ruptures into the subarachnoid space.
4. Direct extension from an adjacent structure such as the vertebrae results in development of meningitis.