[Infections of the central nervous system in the immuno-compromised]

CNS Infections in Immunoincompetent Patients : Neuroradiological and Clinical Features

In patients with immunodeficiency the pathogen spectrum of central nervous system (CNS) infections is broader and different from that of immunocompetent patients. Numerous opportunistic infections are characterized by a high prevalence of viral, bacterial and parasitic pathogens, and depend on the type of impaired immune defense, for example impaired T‑cell or monocyte function, monoclonal antibody treatment, and impaired granulocyte function. Neuroradiological features as well as laboratory findings are often different and versatile in comparison to immunocompetent individuals and pathognomonic imaging findings do not exist; however, knowledge of possible pathways of pathogens in the CNS and preferred tissue affection may help in narrowing down differential diagnoses. Therefore, knowledge of the type of patient and the performed immunomodulatory therapy is essential for the neuroradiological assessment and the differential diagnostic considerations. Moreover, parenchymal reactions in the sense of an immune reconstitution inflammatory syndrome (IRIS) can occur when immunocompetence is restored. This review focus on the most common pathologies in immunocompromised patients, and an overview of imaging features but also of pathology and clinical aspects is given. The synopsis of anamnestic information, clinical findings and structured analysis of the lesion pattern, its spread and short-term follow-up may increase the correct diagnostic classification; however, the gold standard is still determination of the pathogen in the cerebrospinal fluid (CSF), blood cultures or biopsies.

Rickettsiae, protozoa, and opisthokonta/metazoa

Rhizobiales (formerly named Rickettsiales) cause in rare instances meningitis and meningovasculitis, respectively. In case of history of exposure, infection by Rhizobiales needs to be considered since both diagnosis and therapy may be extremely difficult and pathogen-specific. The same applies to protozoa; in this chapter, Babesia species, free-living amoebae and Entamoeba histolytica infection, including severe meningitis and brain abscess, infection by Trypanosoma species (South American and African trypanosomiasis) are discussed with respect to history, epidemiology, clinical signs, and symptoms as well as differential diagnosis and therapy. Parasitic flatworms and roundworms, potentially able to invade the central nervous system, trematodes (flukes), cestodes (in particular, Cysticercus cellulosae), but also nematodes (in particular, Strongyloides spp. in the immunocompromised) are of worldwide importance. In contrast, filarial worms, Toxocara spp., Trichinella spp., Gnathostoma and Angiostrongylus spp. are seen only in certain geographically confined areas. Even more regionally confined are infestations of the central nervous system by metazoa, in particular, tongue worms (=arthropods) or larvae of flies (=maggots). The aim of this chapter is (1) to alert the neurologist to these infections, and (2) to enable the attending emergency neurologist to take a knowledgeable history, with an emphasis on epidemiology, clinical signs, and symptoms as well as therapeutic management possibilities.

Entzündliche Erkrankungen

Unter einer Meningitis versteht man eine Entzündung von Pia mater und Arachnoidea. Das Erregerspektrum ist weit und reicht von Bakterien, die hämatogen-metastatisch, fortgeleitet oder durch offene Hirnverletzung zur eitrigen Meningitis führen, über Viren zu Pilzen und Parasiten. Insbesondere bei den unbehandelt häufig letal verlaufenden eitrigen Meningitiden ist eine rasche Diagnose mit Erregernachweis notwendig. Unverzüglich ist daraufhin eine spezifische, der regionalen Resistenzentwicklung angepasste Therapie einzuleiten. Die meningeale Affektion im Rahmen einer Listeriose oder Tuberkulose verdient aufgrund des klinischen Bildes, des Verlaufs und der spezifischen Therapie besondere Beachtung. Die fungalen Infektionen werden, da klinisch häufig als Meningoenzephalitis imponierend, in Abschn. 33.3 abgehandelt.

[Parasitic diseases of the central nervous system]

Central nervous system infections and infestations by protozoa and helminths constitute a problem of increasing importance throughout all of central European and northern/western countries. This is partially due to the globalisation of our society, tourists and business people being more frequently exposed to parasitic infection/infestation in tropical countries than in moderate climate countries. On top of that, migrants may import chronic infestations and infections with parasitic pathogens, eventually also--sometimes exclusively--involving the nervous system. Knowledge of epidemiology, initial clinical signs and symptoms, diagnostic procedures as well as specific chemotherapeutic therapies and adjunctive therapeutic strategies is of utmost important in all of these infections and infestations of the nervous systems, be it by protozoa or helminths. This review lists, mainly in the form of tables, all possible infections and infestations of the nervous systems by protozoa and by helminths. Besides differentiating parasitic diseases of the nervous system seen in migrants, tourists etc., it is very important to have in mind that disease-related (e.g. HIV) or iatrogenic immunosuppression has led to the increased occurrence of a wide variety of parasitic infections and infestations of the nervous system (e. g. babesiosis, Chagas disease, Strongyloides stercoralis infestation, toxoplasmosis, etc.).

Chronic meningitis

Chronic meningitis is an inflammation of the meninges with subacute onset and persisting cerebrospinal fluid (CSF) abnormalities lasting for at least one month. Several non-infectious and infectious etiologies are known to be causative. The wide range of different etiologies renders the approach to patients with this syndrome particularly difficult. There is no standardized diagnostic procedure, thus, taking an in depth history combined with a complete physical examination is mandatory in every patient.This review aims to present the current knowledge on etiology, neurological course of disease, diagnostic and therapeutic management steps of patients presenting with clinical signs and symptoms of chronic meningitis and meningoencephalitis. Still, the etiology of one third of patients remains unclear, reflecting the diagnostic challenge of this syndrome for each physician or neurologist, respectively. However, most patients with idiopathic chronic meningitis have a relatively good outcome.