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251 Walsh & Hoyt: Mucoceles, Pyoceles, and SinusitisBarrett J. Katz, MD, MBA, Montefiore Medical CenterAlthough mucoceles, pyoceles, and sinusitis are not infections of neural tissue, they not infrequently produce neuro-ophthalmologic symptoms and signs through their effects on adjacent neural and vascular structures. In most cases, damage is caused by compression by an expanding mass; however, in so...
252 Walsh & Hoyt: NeuritisBarrett J. Katz, MD, MBA, Montefiore Medical CenterNeuritis is a generic term indicating inflammation of a nerve. The inflammation may result from the direct effects of an organism, from its antigenic effects on the immune system, or from mechanisms unrelated to current or previous infection or insult. Organisms capable of producing neuritis by dire...
253 Walsh & Hoyt: Cerebral EdemaBarrett J. Katz, MD, MBA, Montefiore Medical CenterCerebral edema is an increase in brain volume caused by increased tissue water content. The causes of cerebral edema include an increase in intravascular pressure, damage to and increased permeability of the cerebral vascular wall, and a decrease in plasma colloid osmotic pressure. Aquaporins, a fam...
254 Walsh & Hoyt: Immunity and Infectious DiseaseBarrett J. Katz, MD, MBA, Montefiore Medical CenterThe increasing recognition of the role of cellular and humoral reactions in disease has led to a greater understanding of the pathogenesis of infection of the CNS. Depending on the immune response, the same organism may produce no, mild, recurrent, or fatal disease. The CNS is at a disadvantage when...
255 Walsh & Hoyt: AbscessesBarrett J. Katz, MD, MBA, Montefiore Medical CenterAn abscess is a circumscribed area of pus. Intracranial abscesses may be epidural, subdural, or intracerebral. An epidural abscess initially tends to be small and flat because the dura develops an increasingly strong adhesion to the bone of the skull throughout life, and it becomes more difficult to...
256 Walsh & Hoyt: Meningitis (Including Pachymeningitis)Barrett J. Katz, MD, MBA, Montefiore Medical CenterMeningitis is an infection of the leptomeningesthe surrounding surfaces of the brain. It is caused by a variety of organisms, including bacteria, viruses, fungi, and protozoa. The subarachnoid space offers little resistance to infection, and the CSF facilitates its spread over the brain and spinal c...
257 Walsh & Hoyt: Encephalitis (Meningoencephalitis)Barrett J. Katz, MD, MBA, Montefiore Medical CenterEncephalitis is inflammation confined to the brain; meningoencephalitis is inflammation of both the brain and the leptomeninges. Both encephalitis and meningoencephalitis are characterized by infection and destruction of neurons and glial cells. They are primarily diseases of children, with the youn...
258 Walsh & Hoyt: DemyelinationBarrett J. Katz, MD, MBA, Montefiore Medical CenterDestruction of myelindemyelinationoccurs in a variety of diverse inflammatory disorders. In some of these disorders, myelin breakdown is secondary to destruction of neurons: neuronolytic demyelination. In others, demyelination is the primary process and associated with relative preservation of affec...
259 Walsh & Hoyt: VasculitisBarrett J. Katz, MD, MBA, Montefiore Medical CenterIntracranial arteries and veins may become infected by a variety of organisms. The infection may be a primary process within the vascular system itself or may result from the effects of an acute, subacute, or chronic contiguous process that penetrates the vessel. The inflammatory response varies gre...
260 Walsh & Hoyt: Mucoceles and PyocelesBarrett J. Katz, MD, MBA, Montefiore Medical CenterA mucocele is formed when drainage of mucus from one of the paranasal sinuses becomes blocked by obstruction of its ostium. If the contents of a mucocele become secondarily infected, the resulting mass is called a pyocele or mucopyocele. A mucocele or pyocele may develop in any of the paranasal sinu...
261 Walsh & Hoyt: Routes of InvasionBarrett J. Katz, MD, MBA, Montefiore Medical CenterDespite the protection provided by skin, bone, meninges, and vascular barriers, organisms can enter the intracranial cavity and vertebral canal. Such organisms reach the CNS in one of two ways: via the bloodstream (hematogenous spread) or by extension from local sources.
262 Walsh & Hoyt: EncephalomyelitisBarrett J. Katz, MD, MBA, Montefiore Medical CenterAn encephalomyelitis produces signs of an encephalitis combined with a myelitisan inflammation of the spinal cord. Indeed, the main pathologic process is an infection of neurons in the anterior horn cells of the spinal cord, in the motor nuclei of the brainstem, and, to a lesser degree, in motor cor...
263 Walsh & Hoyt: Lesions Produced by InfectionBarrett J. Katz, MD, MBA, Montefiore Medical CenterA variety of lesion types may be produced by infections and inflammations. These include abscesses, aneurysms, areas of demyelination, cerebral edema, empyemas, encephalitis, granulomas, meningitis, mucoceles and pyoceles, neuritis, and vasculitis. In this section, we consider the origin, pathologic...
264 Walsh & Hoyt: GranulomaBarrett J. Katz, MD, MBA, Montefiore Medical CenterGranulomatous inflammation is a specialized form of chronic inflammation in which an accumulation of macrophages is the major part of the inflammatory infiltrate. Two defining maturations of this cell type are characteristically found in a granuloma: the epithelioid cell and the inflammatory giant c...
265 Walsh & Hoyt: Aneurysms Caused by Infection (""Mycotic"" Aneurysms)Barrett J. Katz, MD, MBA, Montefiore Medical CenterBacteria, fungi, spirochetes, and other organisms have the potential to infiltrate the walls of intracranial and other arteries. In some instances, this results in the formation of one or more aneurysms. In 1885, Sir William Osler used the term ""mycotic"" to refer to such aneurysms. Although this t...
266 Walsh & Hoyt: Barriers to InfectionBarrett J. Katz, MD, MBA, Montefiore Medical CenterThe structures of the CNS that limit the pathogenesis of infection include bone and fibrous membranes that cover the brain and spinal cord. These protective coverings may be overcome by transport of organisms from the scalp or face, by emissary veins, or by diploic veins that anastomose within the s...
267 Walsh & Hoyt: EdemaBarrett J. Katz, MD, MBA, Montefiore Medical CenterA common response of the brain to a variety of insults is edema. Infections and inflammations of the CNS produce several types of edema: vasogenic, cytotoxic, interstitial, and hypo-osmotic. Some of these types can be distinguished by MR imaging. A variety of organisms produce toxins that can cause ...
268 Walsh & Hoyt: SinusitisBarrett J. Katz, MD, MBA, Montefiore Medical CenterInfection of the paranasal sinuses by bacteria or other organisms may produce neuro-ophthalmologic symptoms and signs by extension of the process into the adjacent orbit, intracranial cavity, or both. Acute, bacterial sinusitis may produce meningitis, brain abscess, epidural or subdural empyema, orb...
269 Meningitis (Including Pachymeningitis)Barrett J. Katz, MD, MBA, Montefiore Medical CenterMeningitis is an infection of the leptomeninges-the surrounding surfaces of the brain.
270 Mucoceles and PyocelesBarrett J. Katz, MD, MBA, Montefiore Medical CenterA mucocele is formed when drainage of mucus from one of the paranasal sinuses becomes blocked by obstruction of its ostium.
271 LESIONS PRODUCED BY INFECTIONS AND INFLAMMATIONS OF THE CNS: Cavernous Sinus ThrombosisBarrett J. Katz, MD, MBA, Montefiore Medical CenterThe clinical features of septic thrombosis of the cavernous sinus can be separated into those caused by the thrombosis and those related to the infection (1114). General symptoms and signs include headache, giddiness, nausea, vomiting, and somnolence. Fever usually is present and may be intermittent...
272 Walsh & Hoyt: Amphotericin BJoel M. Weinstein, MD, Penn State Milton S. Hershey Medical CenterAmphotericin B is the mainstay of treatment in almost all systemic fungal infections, particularly those that affect the CNS. It destroys fungi primarily by binding to one or more sterols in their cytoplasmic membrane, thus altering membrane permeability. Almost all systemic mycoses respond to treat...
273 Walsh & Hoyt: General ConceptsJoel M. Weinstein, MD, Penn State Milton S. Hershey Medical CenterFungi (from the Latin fungus, meaning ""mushroom"") are nonmotile organisms composed of eukaryotic cells whose nuclei contain multiple chromosomes and are surrounded by membrane. They differ from bacteria in that they have a rigid cell wall that usually contains chitin and polysaccharides. Inside t...
274 Walsh & Hoyt: Histoplasma Capsulatum (Histoplasmosis)Joel M. Weinstein, MD, Penn State Milton S. Hershey Medical CenterHistoplasma capsulatum exists in the soil in the mycelial phase but converts to a yeast phase at the body temperature of mammals: 37C. The mycelial form consists of septate branching hyphae that bear spores at both lateral and terminal positions. The hyphae measure 12 micrometers in width, and the s...
275 Walsh & Hoyt: Imidazoles and TriazolesJoel M. Weinstein, MD, Penn State Milton S. Hershey Medical CenterAzoles, also called imidazoles, are synthetic organic compounds that are characterized by at least one five-member ring that usually contains two nitrogen molecules (the azole ring). This ring is responsible for the antifungal properties of these substances. The addition of a third nitrogen to the a...
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