A Rich focus is a tuberculous granuloma occurring within the

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

or meninges of the brain that ruptures into the subarachnoid space, causing

tuberculous meningitis Tuberculous meningitis, also known as TB meningitis or tubercular meningitis, is a specific type of bacterial meningitis caused by the '' Mycobacterium tuberculosis'' infection of the meninges—the system of membranes which envelop the central ...

. The Rich focus is named for Arnold Rice Rich, a pathologist at

Johns Hopkins Hospital The Johns Hopkins Hospital (JHH) is the teaching hospital and biomedical research facility of the Johns Hopkins School of Medicine, located in Baltimore, Maryland, U.S. It was founded in 1889 using money from a bequest of over $7 million (1873 m ...

, who along with his colleague

Howard McCordock Howard is an English-language given name originating from Old French Huard (or Houard) from a Germanic source similar to Old High German ''*Hugihard'' "heart-brave", or ''*Hoh-ward'', literally "high defender; chief guardian". It is also probabl ...

first described the post-mortem finding of caseous foci within the cerebral cortex or meninges which appeared to predate the development of meningitis. Prior to their research the prevailing view had been that meningitis occurred as a result of the dissemination of tuberculous bacilli associated with

miliary tuberculosis To disseminate (from lat. ''disseminare'' "scattering seeds"), in the field of communication, is to broadcast a message to the public without direct feedback from the audience. Meaning Dissemination takes on the theory of the traditional vie ...

and that these processes occurred at the same time. __TOC__

Developments

More recently a more comprehensive classification of the pathogenesis of

has been proposed by Donald et al.: # A Rich focus develops as a result of haematogenous dissemination from the primary complex, including miliary tuberculousis, subsequently rupturing into the sub-arachnoid space. # A Rich focus develops within the choroid plexus or ventricular walls as a result of haematogenous dissemination. # 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. # Direct extension from an adjacent structure such as the vertebrae results in development of meningitis.

References

Neurological disorders {{nervoussystem-disease-stub