Empiric high-dose parenteral antimicrobials may be indicated after a complete diagnostic evaluation with intensive support and, occasionally, neurosurgical intervention. A third-generation cephalosporin plus metronidazole (eventually plus vancomycine or amikacin) is an adequate approach to the early stage of abscess formation (cerebritis). Abscess larger than 2.5 cm should be aspirated before starting an empirical therapy. Treatment must be targeted on the antimicrobial susceptibility tests. The duration of therapy depends on clinical and neuroimaging monitoring, and several weeks of treatment is advised. Intracranial pressure should be managed by the use of IV mannitol and dexamethasone 6–12 mg q6h.

Prior to antibiotics and refinement of neurosurgical techniques, mortality approached 100 %. If the patient is comatose before appropriate treatment, mortality approaches 20–50 %; if the treatment starts when the patient is still alert, the range of mortality decreases to 5 and 10 %. Among the surviving patients, approximately 30 % complain of some neurological disorders, particularly of focal epilepsy.

The standard approach to CNS tuberculosis includes an initial 2-month induction therapy regimen, including isoniazid, rifampin, pyrazinamide, and ethambutol, followed by 7–10 additional months of isoniazid and rifampin as maintenance therapy for an isolate that is sensitive to these agents. Treatment with corticosteroids is strongly recommended in CNS TB, in particular, because it reduces mortality from TBM. In case of severe hydrocephalus, surgical treatment is necessary to reduce the mass effect of tuberculomas and to drain brain abscesses.

The clinical stage at diagnosis, the immunological status of the host, and antimicrobial resistance pattern of the strains are the main determinants of prognosis. Advanced stage, age, focal weakness, cranial nerve palsies, presence of any infarction other than a purely hemispheric infarction, and hydrocephalus are predictors of mortality at 3 months.

CNS tuberculoma is a benign condition with a good prognosis and effective therapy options. TB of the spine may evolve into paraplegia, spinal tumor syndrome, and kyphosis. Early diagnosis and prompt treatment can reverse paralysis and minimize the potential disability resulting from Pott’s paraplegia. When needed, a combination of conservative therapy and surgical decompression yields successful results in most patients with tuberculosis of the spine and who have neurological complications.

The treatment recommendations for patients with neurosyphilis or ocular syphilis is aqueous crystalline penicillin G at 18–24 million units per day, either by continuous infusion or in divided doses, for 10–14-days.

Immunosuppression due to human immunodeficiency virus (HIV) infection supports the development of neurosyphilis with parenchymal affection, predominantly if peripheral blood CD4-cell counts are below 350 cells/uL. The incidence of relapses or reinfections of patients after treatment of an early syphilis is believed to be more likely in HIV patients. Early and effective treatment may not only prevent further disease progression, but may also allow for a complete recovery.

Tertiary neurosyphilis may result in severe sequelae such as dementia paralytica or general paresis and tabes dorsalis not responsive to antibiotic treatment. Bilateral hearing loss may complicate ocular syphilis. Visual loss is common after chorioretinitis [5].

Parenteral treatment regimens with third generation cephalosporins for 10–14 days. There is also a growing body of evidence that oral regimens, particularly with doxycycline can be highly effective.

The outcome after antibiotic treatment is generally good. The pain, typical for Bannwarth’s syndrome, rapidly decreases under antibiotic therapy, and patients might be free of complaints even after one antibiotic dose. In the majority of cases, persisting objective symptoms after an adequate course of antibiotics are either due to irreversible damage (a limb paresis due to axonal loss) or might reflect a misdiagnosis in the majority of cases.

Because facial nerve palsy occurs frequently and is easily diagnosed, this group of patients has been the subject of several recent studies. If untreated, a significant number will develop persistent infection and late sequelae [6]. Some patients may develop a post-Lyme syndrome or chronic Lyme disease characterized by fatigue, malaise, and subjective perceptions of memory and cognitive impairment, but they usually have little compelling evidence of CNS infection or damage.

Overturf’s Diagnostic Criteria for Ventriculoperitoneal Shunt Infection: [7].

Morbidity and mortality depend on the age of the patient, the type of microorganism involved, and the underlying conditions. Fulminant course and fatalities are observed usually among adults with head trauma and postneurosurgical states; in contrast, pediatric cases following premature delivery involve both a more indolent course and a more favorable outcome [8]. Increasing MRSA strains affect treatment and prognosis of these kinds of infections. Prognosis of infections caused by Gram-negative bacteria is considered particularly poor: they are difficult to suspect because patients often appear relatively well at presentation, and are usually of mixed infections.

Intravenous (IV) antibiotic treatment for 4–6 weeks (targeted on the isolated microorganism). Forty percent of patients with infective endocarditis will need cardiac surgery, primarily for valve repair or replacement. Timing of surgery in patients with infective endocarditis and embolic stroke remains controversial, but a report suggested that surgery can be performed relatively safely within 3 days of stroke, if heart failure is severe; otherwise, a delay of 2–4 weeks is preferable. In patients with associated hemorrhage, a delay of at least 4–6 weeks is preferred. Operative mortality is variable, but has been reported as 7.6 %. Anticoagulants are contraindicated because of the increased risk of CNS hemorrhage.

Endocarditis can have profound and devastating neurological consequences [9]. In most cases, the neurological sequelae are present before the initiation of antimicrobial therapy (76 %). Studies have shown that the mortality of patients with bacterial endocarditis with CNS involvement is much greater (58–74 %) than that of patients who do not have CNS involvement (20–56 %). In one study, during the acute phase of infective endocarditis, 24 % of patients with neurological complications died, while only 10 % of those without neurological complications died. Among the patients with neurologic involvement, mortality was 25 % in those treated medically and 20 % in those treated surgically. In one series, 38 major embolic events occurred in 37 patients; 30 of these 37 patients died (81 % mortality).

The genus Aspergillus is an anamorphic member (asexual form) of the family Trichocomaceae. Aspergillus species are filamentous fungi spread worldwide, usually acquired by inhalation of Aspergillus conidia. CNS aspergillosis may result from: hematogenous dissemination, directed extension from the paranasal sinuses or eye, or direct inoculation. The most relevant risk factors for invasive aspergillosis include hematological disorders, prolonged and profound neutropenia (<100 neutrophils/ul), neoplastic diseases, solid organ transplantation, and allogenic hematopoietic stem cell transplantation. In this setting, the frequency of CNS infections ranges from 14 to 42 %.

Cerebral abscesses, paranasal sinusitis, meningitis (usually associated with adjacent cerebral lesion), meningoencephalitis, arachnoiditis, and ventriculitis. Mycotic aneurysms, cerebral infarcts, multifocal cerebritis.

Candida species are yeasts. C. albicans is the most common species responsible for candidal brain abscess (90 %). The organism is a normal commensal of humans. Usually, CNS candidiasis results from hematogenous dissemination, but Candida meningitis may result from infection from a ventricular shunt. Risk factors for neurocandidiasis are broad-spectrum antibiotic therapy, prematurity, parenteral nutrition, malignancy, treatment with corticosteroids, transplantation, indwelling devices, abdominal surgery, diabetes, dialysis, multiple sites colonization, and parenteral drug abuse.