Neuroanatomy Atlas in Clinical Context

62 CHAPTER 4 / MENINGES, CISTERNS, VENTRICLES, AND RELATED HEMORRHAGES

B

A

Mastoiditis

Sigmoid sinus

D

C

Middle cerebral artery

Position of tentorium cerebelli

Falx cerebri

Falx cerebri

is almost always accompanied by other disease processes, most notably acute or chronic otitis media . The close association of mastoid air cells to the sigmoid sinus represents one comparatively direct route into the central nervous system. Once an infection of the mastoid accesses the central nervous sys tem, it may involve the venous sinuses ( A ), which appear bright when enhanced. The infection will layer out over the surface of brain within the SAS, enter the sulci, and occupy the SAS immediately above and below the tentorium cerebelli (see arrows in A , B , C ). The SAS and the sulci enhance when the patient is given IV gadolinium ( C , D ) and appear bright in the image. In addition to these features, small enhancements may appear within the SAS ( D , arrows) that indicate the formation of small abscesses. This inflammation may also extend to involve the dura mater in which case it is called pachymeningitis . Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2024

4-2 Examples of meningitis ( A – D , all axial) in the adult. Meningitis is a disease that generally involves the subarach noid space (SAS) and the membranes bordering on this space, namely, the arachnoid mater and pia mater. Consequently, it is commonly called leptomeningitis ( arachnoiditis, or pia-arachnitis ). Meningitis may preferentially affect one side more than the other and, in some cases, present with unilateral deficits. Bacterial meningitis is a medical emergency ; it may present suddenly, progress rapidly, and must be treated quickly or death may result. Patients with viral meningitis may become ill over several days versus potentially hours, and after a short acute period, and with supportive care, most will recover with no per manent deficits. Sources of infections that may lead to meningitis are those involving the paranasal sinuses or the mastoid air cells ( mastoiditis, A ). Mastoiditis