A Rich focus is a

tuberculous Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

granuloma A granuloma is an aggregation of macrophages (along with other cells) that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such sub ...

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 ...

meninges In anatomy, the meninges (; meninx ; ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in the subarachnoid spac ...

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 ner ...

. The Rich focus is named for

Arnold Rice Rich Arnold Rice Rich (March 28, 1893 – April 17, 1968) was an American pathologist. Career Born March 28, 1893, in Birmingham, Alabama, Rich attended the University of Virginia, majoring in biology, and then the Johns Hopkins Medical School ...

, a pathologist at

Johns Hopkins Hospital Johns Hopkins Hospital (JHH) is the teaching hospital and biomedical research facility of Johns Hopkins School of Medicine in Baltimore, Maryland. Founded in 1889, Johns Hopkins Hospital and its school of medicine are considered to be the foundin ...

, who along with his colleague Howard McCordock 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 Miliary tuberculosis is a form of tuberculosis that is characterized by a wide dissemination into the human body and by the tiny size of the lesions (1–5 mm). Its name comes from a distinctive pattern seen on a chest radiograph of many tiny ...

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