CNS infections Flashcards
congenital infections of the fetal and neonatal brain are commonly referred to as the group of ____. they often result in significant brain injury, and congenital brain malformations are more frequently seen with earlier onset of infections in utero due to disruption of the normal CNS development during fetal gestation
TORCH
TORCH infection includes
toxoplasmosis, other infections (syphilis, varicella zoster, lymphocytic choriomeningitis), rubella, cytomegalovirus, herpes simplex
another important virus now recognized prenatal CNS infection aside from TORCH
Zika virus
member of the herpes family of viruses andis the most common congenital CNS infection. In utero transmission occurs hematogeneously during viral reactivation in seropositive pregnant women or primary infection during pregnancy
Cytomegalovirus
30 to 50% of CMV infection is from
transplacental transmission
symptomatic neonates with this viral infection may have hepatosplenomegaly, jaundice, cerebral involvement (psychomotor retardation), chorioretinitis and deafness. virus also preferentially multiplies along the ependyma and germinal matrix resulting in a periventricular pattern of injury and development of dystrophic calcifications
CMV
calcifications of the basal ganglia or cortex are not seen in CMV but are noted in
congenital toxoplasmosis
this viral infection cause loss of periventricular white matter which then forms custs, ventriculomegaly and microcephaly. infection during the first trimester can result in neuronal migration anomalies such as heterotopia and lissencephaly and disorders of cortical organization including schizencephaly, polymicrogyria and cortical dysplasia. delayed myelination and cerebellar hypoplasia are also common findings
CMV
caused by parasite protozoan, results from hematogeneous spread after pregnant woman eats undercooked meat or is exposed to cat feces, both of which can harbor viable oocysts
toxoplasmosis
toxoplasmosis causes
necrotizing encephalitis of fetal brain, during first 2 trimester of gestation, but typically no developmental malformations. microcephaly, chorioretinitis and mental retardation
imaging findings of toxoplasmosis
atrophy, dilated ventricles, dystrophic calcifications scattered in the white matter, basal ganglia and cortex
a rodent-borne arena virus which can closely mimic toxoplasmosis and CMV on neonatal neuroimaging. onset of infection in first trimester often leads to spontaneous abortion. presents with chorioretinitis, either hydrocephalus or microcephaly but with results of accompanying microbiologic and serologic studies being negative for more common congenital pathogens. cerebral calcifications can be periventricular in location and/or distributed between white matter, deep gray nuclei and cortex
lymphocytic choriomeningitis virus (LCMV)
encephalitis in neonates often results from infection during descent through the birth canal when the mother has genital infection with _____
herpes virus type 2
if patient survives with neonatal HSV 2, the following manifestations may be seen
varying degrees of microcephaly, mental retardation, microphthalamia, enlarged ventricles, intracranial calcifications and multicystic encephalomalacia
early in the course of HSV encephalitis, US will show
increased parenchymal echogenicity
CT findings in HSV encephalitis
diffuse brain swelling or bilateral patchy areas of hypodensity in the cerebral white matter and cortex, with relative sparing of the basal ganglia, thalami and posterior fossa structures. these hypodense lesions correspond to areas of T2 hyperintensity on MRI and progress to areas of necrosis and cystic encephalomalacia
true or false: opportunistic infections and neoplasms seen in adults with AIDS are not usually seen in young children
true
affected infants of this viral infection are more susceptible to respiratory infections and diarrhea that can present with encephalopathy, developmental delay and failure to thrive. it primarily affects white matter and basal ganglia, especially globi pallidi, best seen with CT, while MRI alows better demonstration of T2 hyperintense white matter abnormalities. in some cases, there is associated vasculopathy with fusiform dilatation and ectasia of the intracranial arteries
congenital HIV
viral infection that cause diffuse meningoencephalitis, brain infarction and necrosis. infants who survive severe infection present with microcephaly, ocular abnormalities and deafness. CT reveals dystropic calcifications in the deep gray nuclei and cortex, whereas MRI better demonstrates infarcts, white matter loss and occassionally delayed myelination
rubella
is a flavivirus which originated in Africa and southeast asia and is transmitted by several species of mosquitoes, especially Aedes aegypti. presents with congenital microcephaly and CNS malformations. unlike CMV, it does not have predilection for the germinal matrix
Zika virus
this virus impairs cell proliferation and promotes apoptosis and cell death. CT best demonstrates both punctate or linear calcifications which localize predominantly to the gray-white junction in the frontal and parietal lobes, and to a lesser extend along the deep gray nuclei and periventricular zone. MRI may show brain volume loss, ventriculomegaly, abnormal myelination, callosal dysgenesis, heterotopia, lissencephaly and polymicrogyria
Zika virus
these extra-axial collections are generally confined by dural attachments which prevent rapid expansion of abscesses and account for their lentiform shape and convex inner margins
epidural
these extra-axial collections can spread more easily thoough the subdural space and be more acutely life threatening, thus requiring rapid neurosurgical intervention
subdural empyemas
frontal sinusitis in children can be complicated by osteomyelitis, with subperiosteal, epidural or subdural abscesses. this is referred to as
pott puffy tumor
how to differentiate subdural empyemas from subdural effusions in MRI
subdural empyemas can be hyperintense on DWI allowing them to be distinguished from subdural efusions which can also enhance mildly
Mild, smooth dural or meningeal enhancement may be seen after craniotomies and in patients with ventriculostomy catheters, especially with MRI. this enhancement can persist for years and should be considered benign in this clinical setting. it is most likely reflects a _____ from perioperative hemorrhage and/or dural scarring
chemical meningitis
bacterial meningitis is caused by ___ in children, ____ in teens and young adults, _____ in older adults, _____ in neonates, _____ in premature newborns
Haemophilus influenzae- children
Neisseria meningitidis- teens and young adults
Streptococcus pneumonia- older adults
Group B streptococcus and E.coli meningitis -neonates
Citrobacter meningitis -premature newborns
inflammatory exudate caused by meningitis appears ___ on CT and FLAIR
hyperdense on CT and hyperintense on FLAIR
most common form of CNS tuberculosis
tuberculous meningitis
true or false: in TB meningitis, chest radiograph may be normal in 40 to 75% of cases
true
CSF findings in TB meningitis
pleocytosis, elevated protein, markedly reduced glucose levels
this type of meningitis will show thickened and enhancing meninges, especially along the basal cisterns, corresponding to a thick gelatinous inflammatory exudate
TB meningitis
meningeal enhancement in this type of meningitis is usually more peripherally distributed and less thick when compared to TB and other granulomatous meningitides
bacterial meningitis
most common complication of TB meningitis
infarct due to extension of inflammatory exudates in the basal cisterns, along the perivascular spaces causing an arteritis with irregular narrowing or occlusion of vessels, most commonly along the distribution of lenticuolstriates and thalamoperforating arteries in the deep gray nuclei
this type of meningitis also cause thick meningeal enhancement of the basal cisterns just like in TB, but with varying degrees of enhancement, based on the immunocompetence of the patient. extension of this type of meningitis to the brain also occurs less often than with TB or pyogenic meningitis
Fungal meningitis; except in aspergillosis and mucormycosis wherein brain extension is also common
occurs when the larvae of the pork tapeworm Taenia solium infest the subarachnoid space, especially the basal cisterns. the larval cysts may grow in grape-like clusters or conform to the shape of the involved cisterns
Meningobasal or racemose cysticercosis
common complications of meningobasal or racemose cysticercosis
cysts may obstruct the foramen of Monro, sylvian aqueduct, third and fourth ventricles, resulting in hydrocephalus. death may result from acute hydrocephalus and ventriculitis
viral meningitis are more commonly caused by what agents
enteroviruses, mumps, Epstein-Barr virus, togavirus, lymphocytic choriomeningitis virus, HIV
true or false: in viral meningitis, patients do not require tx and neurologic deficits are uncommon unless infection progresses to encephalitis. neuroimaging are typically normal but mild meningeal enhancement may occur
true
subdural effusion are common with what type of viral meningitis
H. influenzae
noninfectious granulomatous disease of unclear etiology which involves the CNS in up to 14% of patients at autopsy. helpful for diagnosis involve increased seruma and CSF levels of angiotensin-converting enzyme
sarcoidosis
this type of meningitis primarily affects the leptomeninges, and abnormal leptomeningeal and dural enhancement can be seen with both CT and MRI. thickening and enhancement of the cranial nerves and the hypothalamic-pituitary axis are not uncommon. calcifications are not typical
sarcoidosis
most common organisms that cayse pyogenic cerebritis and abscess
anaerobic
infection with this bacteria is common after surgery or trauma
Staphylococcys aureus
with pyogenic cerebritis or abscess resulting from hematogeneous spread, this lobes are most commonly involved, with the abscess centered at the gray-white junction
frontal and parietal lobes (MCA distribution)
this lobe is most commonly affected with spread of sinus infection
frontal lobes
usually involved in patients with spread from otomastoiditis
temporal lobes or cerebellum
true or false: in pyogenic cerebritis or abscess, fever is absent more than 50% if the time. Meningeal signs are present in only 30% of patients
true
Solitary abscess is usually treated with
stereotactic needle aspiration followed by antibiotic therapy, in an eloquent area of the brain. if there is significant mass effect or the lesion is in a relatively “safe” area, a formal drainage or resection is performed
four pathologically described stages of cerebritis and brain abscess
early cerebritis, late cerebritis, early capsule and late capsule
in this stage or cerebritis and abscess, the infected portion of the brain is swollen and edematous. Areas of early necrosis are filled with inflammatory polymorphonuclear leukocytes, lymphocytes and plasma cells. organisms are present in both the center and the periphery of the lesion which has ill-defined margins. CT scan may be normal or show an area of low density. On MRI, lesion is hypointense or isointense on T1 and hyperintense on T2 and FLAIR images. There may be mild mass effect and patchy areas of enhancement within the lesion on both CT and MRI. a ring of enhancement is not present on this stage
early cerebritis
stage of cerebritis and abscess that occurs within 1 or 2 weeks of infection. central necrosis progresses and begins to coalesce, with fewer organisms detected pathologically. there is vascular proliferation at the periphery of the lesion, with more inflammatory cells and early granulation tissue, which represent the brain’s effort to contain the infection. centrally, there is increased hypodensity on CT, hypointensity on T1 and hyperintensity on T2 and FLAIR sequences. DWI may show some increased signal intensity within the center of the lesion. there is worsening vasogenic edema present outside the enhancing rim and overall increased mass effect. No discrete capsule is evident
Late cerebritis
stage of cerebritis and abscess that occurs within 2 weeks, the infection is wall off as capsule of collagena dn reticulin forms along the inflammatory vascular margin of the infection. Macrophages, phagocytes and neutrophils are also present in the capsule. CT and MR shows a well-defined, usually smooth and thin, rim of enhancement
Early capsule stage
stage of cerebritis or abscess wherein the rim of enhancement becomes even better defined and thicken, reflecting more complete collagen in the abscess wall. Multiloculation is common. CT or MR scans reveal enhancement of the ependymal lining of the ventricles and altered density and signal intensity of the intraventricular CSF
Late capsule stage
this clinical features of prominent central hyperintensity on DWI, smooth complete enhancing rim, significant surrounding vasogenic edema, and T2 hypointensity of the capsule should strongly suggest a
brain abscess
an incomplete ring of enhancement and accompanying characteristic white matter lesions favor this diagnosis rather than abscess
demyelinating lesions
MRS findings in confirming cerebral abscess
elevated lactate and amino acids in the center of the lesion
presents with a thicker, more irregular ring of enhancement that persists within an area of infarction should suggest the diagnosis of
septic embolus
septic emboli may lead to _____, which can result in intraparenchymal or subarachnoid hemorrhage
mycotic aneurysm formation
