The epidural and subdural spaces can be involved by bacterial or fungal infections, usually as a consequence of direct local spread. Epidural abscesses arise from an adjacent focus of infection, such as sinusitis or osteomyelitis. When abscesses occur in the spinal epidural space, they may cause spinal cord compression and constitute a neurosurgical emergency. Infections of the skull or air sinuses may also spread to the subdural space, producing subdural empyema. The underlying arachnoid and subarachnoid spaces usually are unaffected, but a large subdural empyema may produce a mass effect. In addition, thrombophlebitis may develop in the bridging veins that cross the subdural space, resulting in venous occlusion and infarction of the brain. Most patients are febrile, with headache and neck stiffness, and if untreated may develop focal neurologic signs referable to the site of the infection, lethargy, and coma. With treatment, including surgical drainage, resolution of the empyema occurs from the dural side; if resolution is complete, a thickened dura may be the only residual finding. With prompt treatment, complete recovery is usual.
Meningitis is an inflammatory process involving the leptomeninges within the subarachnoid space; if the infection spreads into the underlying brain, it is termed meningoencephalitis. These terms are also used in non-infectious settings such as chemical meningitis, a response to a nonbacterial irritant such as debris from a ruptured epidermoid cyst, and carcinomatous meningitis, the spread of metastatic cancer cells to the subarachnoid space.
Infectious meningitis can be broadly divided into acute pyogenic (usually bacterial), aseptic (usually viral), and chronic (usually tuberculous, spirochetal, or fungal) subtypes. Examination of the CSF is often useful in distinguishing among the various causes of meningitis.
http://ebooksmedicine.net
EmpyemaPolymicrobial(staphylococci,anaerobicgram-negative)
Rickettsia, Spirochetes, and Fungi
The most likely causes of bacterial meningitis vary with patient age. In neonates, common organisms are Escherichia coli and group B streptococci. In adolescents and young adults, Neisseria meningitidis is the most common pathogen; in older adults, Streptococcus pneumoniae and Listeria monocytogenes are more common. Across ages, patients typically show systemic signs of infection along with meningeal irritation and neurologic impairment, including headache, photophobia, irritability, clouding of consciousness, and neck stiffness. Lumbar puncture reveals an increased pressure; examination of the CSF shows abundant neutrophils, elevated protein, and reduced glucose. Untreated pyogenic meningitis is often fatal, but with prompt diagnosis and administration of antibiotics, most patients can be saved.
MORPHOLOGYInacutemeningitis,anexudateisevidentwithintheleptomeningesonthesurfaceofthebrain(