This document provides an overview of various infections that can affect the central nervous system, including bacteria, viruses, parasites, and fungi. It discusses specific conditions like bacterial meningitis, neurosyphilis, herpes simplex encephalitis, poliomyelitis, rabies, and more. For each, it covers topics like causes, clinical manifestations, diagnosis, treatment and prognosis.

5. BACTERIAL MENINGITIS

7. • Beyond the neonatal period, the 3 most common organisms that cause acute bacterial meningitis are Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b (Hib). • Neonates - Group B or D streptococci, nongroup B streptococci, Escherichia coli, and L monocytogenes • Infants and children -H influenzae (48%), S pneumoniae (13%), and N meningitidis • Adults -S pneumoniae, (30-50%), H influenzae (1-3%), N meningitidis (10-35%), gram-negative bacilli (1-10%), staphylococci (5-15%), streptococci (5%), and Listeria species (5%)

9. The classic presentation of meningitis includes the triad fever, sever neck stiffness/rigidity, called meningismus, and change in mental status (eg, lethargy, confusion, irritability, delirium, and coma) Signs of meningeal irritation are observed in only approximately 50% of patients with bacterial meningitis, and their absence certainly does not rule out meningitis.

10. Brudzinski Sign of Meningitis: • Brudzinski sign: is positive if the patients hips and knees flex automatically when the examiner flexes the patients neck while the patient is supine.

11. Kernig’s Sign of Meningitis: Kernig sign: flex patients hip to a 90° angle and then attempting passively straighten the leg at the knee produces pain in the hamstrings and resistance to further extension. Should present bilaterally to support the meningitis diagnosis.

13. Systemic findings upon physical examination may provide clues to the etiology. Skin findings range from a nonspecific blanching, erythematous, maculopapular rash to a petechial or purpuric rash, most characteristic of meningococcal meningitis. Commonly affects the trunk and extremities. Symptoms in infants Cardinal signs of meningitis (eg, fever, vomiting, stiff neck) are rarely present. For neonatal meningitis, these signs are the exception, rather than the rule. • Lethargy and/or change in level of alertness • Poor feeding and/or vomiting • Respiratory distress • Bulging fontanelle • Paradoxic irritability (ie, quiet when stationary, cries when held) • High-pitched cry • Hypotonia • Approximately 6% of affected infants and children show signs of disseminated intravascular coagulopathy and endotoxic shock. These signs are indicative of a poor prognosis.

14. General guidelines The cornerstone in the diagnosis of meningitis is examination of the CSF. Measure the opening pressure and send the fluid for cell count (and differential count), chemistry (ie, CSF glucose and protein), and microbiology (ie, Gram stain and cultures).The opening pressure of CSF should be measured in older children. Similarly, the color of the CSF (eg, turbid, clear, bloody) should be recorded.

17. CSF Characteristics Bacterial Viral Fungal TB Opening Pressure Elevated Slightly elevated Normal or High Ususally high Glucose Low Normal Low Low Protein Very high Normal High High Rbcs Few None None None Wbcs (c/mm3) >200 <200 <50 20-30 Diff PMNs Mono Mono Mono Appearance Turbid Clear Turbid Cob-web

19. Neonatal Initiate treatment as soon as bacterial meningitis is suspected. Ideally, blood and cerebrospinal fluid (CSF) cultures should be obtained before antibiotics are administered. Fluid and electrolyte management Ampicillin and an aminoglycoside combination (ampicillin and cefotaxime Resistant bugs- Vancomycin and either ceftriaxone or cefotaxime Dexamethasone-Decreased inflammation, reduction in cerebral edema

35. Axial FLAIR MRI in herpes simplex encephalitis shows extensive signal change in the right temporal lobe (arrow). Destruction of inferior frontal and anterior temporal lobes – necrotizing inflammation

45. Rabies Virus (Rhabdovirus)-Treatment Post-exposure prophylaxis (PEP) , One dose of human rabies immunoglobulin (HRIG) and four doses of rabies vaccine over a fourteen day period . As much as possible of this dose should be infiltrated around the bites, with the remainder being given by deep intramuscular injection at a site distant from the vaccination site.

51. TUBERCULOMA T1 w MRI IMAGE Tuberculoma is the round gray mass in the left corpus callosum. The red meninges on the right are consistent with irritation and probable meningeal reaction to tuberculosis. Tuberculomas are conglomerate caseous foci within the substance of the brain. Under conditions of poor host resistance, this process may result in focal areas of cerebritis or frank abscess formation, but the usual course is coalescence of caseous foci and fibrous encapsulation (ie, tuberculoma).

59. Neuro-Cyptococcosis-Pathophysiology Multicystic form of cerebral cryptococcosis: lesions in basal ganglia and cerebellum The fungus enters the human body through inhalation into the lungs. The cerebrospinal fluid is an ideal site for infection as it lacks complements and immunoglobulins.

60. Opaque thick fibrotic CSF obstruction - hydrocephalus. Gelatinous material within the subarachnoid space and small cysts within the parenchyma (&quot;soap bubbles“) Specially in the basal ganglia. Neuro-Cyptococcosis-Pathology

61. Neuro-Cyptococcosis-Treatment Amphotericin B 0.7-1.0 mg/kg/day + 5-flucytosine 100 mg/kg/day for 6-10 weeks. + fluconozole consolidation 6-12 months . Prognosis The majority of the patients improve with adequate therapy. Mortality is seen in about 10% and more common in HIV-positive individuals.

67. Neurocysticercosis Viable cysticercus cellulosae LIVING ( viable ) Stage : CT - appears as hypodense lesion that doesn’t show ring enhancement or perilesional oedema “ HOLE with DOT appearance ” Similar findings in T1w Images.

68. Neurocysticercosis Multiple parenchymal calcifications CALCIFIED Stage : Not visualised in MRI CT- hyperdense nodules with no edema or enhancement. Old nonviable cysts eventually calcify simplifying detection.

73. Toxoplasmosis Diagnosis The indirect fluorescent Ab test measuring IgG Ab is the most widely used diagnostic tool. Detection of T. gondii in human blood samples may be also achieved by using the PCR . Treatment Acute • Pyrimethamine (antimalarial) 4-6 weeks • Sulfadiazine -in combination with pyrimethamine. • Clindamycin • Cotrimoxazole or spiramycin-used for pregnant women to prevent the infection of their child. Latent • In people with latent toxoplasmosis, the cysts are immune to these treatments, as the antibiotics do not reach the bradyzoites in sufficient concentration. • Atovaquone+Clindamycin Pyrimethamine spiramycin Atovaquone Clindamycin

75. Prion Related Diseases • The prion diseases are a large group of related neurodegenerative conditions, which affect both animals and humans. • Prion diseases are unique in that they can be inherited, they can occur sporadically, or they can be infectious. • These diseases all have long incubation periods but are typically rapidly progressive once clinical symptoms begin. Table. Prion-Related Diseases, Hosts, and Mechanism of Transmission Disease Host Mechanism Kuru Human Cannibalism! Sporadic CJD Human Spontaneous PrP C to PrP Sc conversion or somatic mutation Iatrogenic CJD Human Infection from prion-containing material Familial CJD Human Mutations in the PrP gene vCJD Human Infection from BSE GSS Human Mutations in the PrP gene FFI Human D178N mutation in the PrP gene, with M129 polymorphism Sporadic fatal insomnia Human Spontaneous PrP C to PrP Sc conversion or somatic mutation Scrapie Sheep Infection in susceptible sheep BSE Cattle Infection from contaminated food

78. Prion Related Diseases -Diagnosis Imaging Studies MRI is an important imaging test. MRI may show hyperintense signals in the cortical ribbon, basal ganglia, and the thalamus Two characteristic radiological signs have been described. The &quot;hockey stick&quot; sign , which refers to increased signal in the putamen and head of the caudate nucleus resembling a hockey stick, and the &quot;pulvinar&quot; sign, which corresponds to a usually bilaterally increased signal in the pulvinar thalamic nuclei. Shows characteristic signal changes of an MRI taken from a patient with sporadic CJD, using diffusion-weighted imaging (DWI). An abnormal signal is shown in both the basal ganglia (red arrows) and the cortical ribbon (yellow arrow).

81. Tetanus Tetanus, -characterized by a prolonged contraction of skeletal muscle. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani. Infection generally occurs through wound contamination and often involves a cut or deep puncture wound. Risus sardonicus is a highly characteristic, abnormal, sustained spasm of the facial muscles that appears to produce grinning. The name of the condition derives from the appearance of raised eyebrows and an open &quot;grin&quot; - which can appear malevolent to the lay observer - displayed by those suffering from these muscle spasms. Opisthotonos ( o-pis-to-ton-is )

87. That’s all folks!