CNS INFECTIONSCT & MRI

DR. MUHAMMAD BIN ZULFIQARPGR 1

Types of Infections• Bacterial• Viral• Spirochetal• Fungal• Protozoal• Prions Disease

Routes of Spread• Hematogenous• Local(trans sinus, mastoid antrum )• During Birth• Transplacental• Iatrogenic• Idiopathic

Presentation of infection •Pia or Subarachnoid space and/or dura or arachnoid•Empyema : epidural or subdural•Cerebritis :Intraparenchymal early stage of abcess formation•Intraparenchymal abcess•Ventriculitis

BACTARIAL infections• ORGANISMS INVOLVED• Neonates:GROUP B Streptococcus,E.Coli,Listeria• Young Children:Heamophilus,E.Coli,Nisseria meningitides• Adults:Streptococcous pneumoniae,,N.Meningitidis• Old age:S.pneumoniae,Listeria

Presentation of bacterial infections•Meningitis( Leptomeningitis, Pachymeningitis)•Empyema•Cerebritis• Brain abcess

Meningitis•Types•Predisposing Factors( Sinusitis, Chronic Pulmonary Infection, Tetrology of Fallot, Transposition of great vessels, other Cyanotic heart diseases)

Imaging Features:a. Initially Normal on C.T.b. Convexity enhancementc. Basilar enhancement(more common on T.B.M.)

COMLICATIONS OF MENINGITIS1. Subdural effusion common in infants and children2. Empyema3. Parenchymal extension (Cerebritis ,Abcess formation)4. Hydrocephalous(communicating>non communicating5. Ventriculitis6. Venous infections secondary to thrombosis

Frontal sinusitis, empyema, and abscess formation in a patient with bacterial meningitis. This contrast-enhanced, axial T1-weighted magnetic resonance image shows a right frontal parenchymal low intensity (edema), leptomeningitis (arrowheads), and a lentiform-shaped subdural empyema (arrows).

Chronic mastoiditis and epidural empyema in a patient with bacterial meningitis. This axial computed tomography scan shows sclerosis of the temporal bone (chronic mastoiditis), an adjacent epidural empyema with marked dural enhancement (arrow), and the absence of left mastoid air.

Brain Abcess

1. Children:(staphylococcal especially after trauma,Streptococcuc,Pneumococcus)

2. Adults:mixed aerobic and anaerobic flora3. Immunosuppression:Toxoplasmosis,Cryptococcus,CandidiasisAspergi

llosis,Nocardiosis,mucormycosis,T.B.Atypical Mycobacteria

• MECHANISM1. Hematogenous Spread(I/V drug abuse,Sepsis)2. Direct Extension• Sinusitis• Otitis,Mastoiditis• Open trauma(penetrating trauma,Surgery3. Idiopathic

Cerebralabscess. (A) Low-density lesion in occipital region with some mass effect. (B) After contrast medium, note thin ring of enhancement round the abscess with oedema anteriorly. (C) Multiple abscesses in frontoparietal area showing capsular enhancemenT after contrast medium (L34, W75).

Axial post-gadolinium T1WI showing ring-enhancing lesion with mass effect in a patient with pyogenic brain abscess.

Acute bacterial meningitis. This contrast-enhanced, axial T1-weighted magnetic resonance image shows leptomeningeal enhancement (arrows).

Tuberculous Meningitis• Most common CNS manifestation of T.B.• Followed by pulmonary T.B.• Intraparenchymal Tuberculoma• Basilar Meningeal involvement• Cranial Nerve Palsies*(commonly Optic nerve)• Hydrocephalous• MRI IS MORE SENSITIVE

Imaging Features•Basilar Meningitis1. Intense contrast enhancement of basilar Meninges(CT&MRI)2. Pituitary and parasellar involvement3. Pituitary or hypothalamic axis involvement4. T2W hypo intense Meninges5. Calcification occur late in disease• Tuberculoma(usually solitary, Nonspecific enhancing mass like

lesion)• Miliary Form: Multiple tiny Intraparenchymal lesions

Enhanced CT of a patient with tuberculous meningitis showing perivascular inflammatory changes and temporal infarction due to vasculitis.

Viral Infectionsa) Specific Infections1. RNA VIRUSES• Enterovirus• Arbovirus• Rabies virus• Paramyxovirus

2. DNA VIRUSES• Herpes Simplex Virus• Cytomegalovirus• Herpes zoster• Papova virus• Unidentified viruses(encephalitis lethargica,uveomeningoencephalitis,Behcets disease)

b) Nonspecific Infections (measles,chickenpox,smallpox,rubella)

Herpes Simplex Virus Encephalitis

HSV-1,oral herpes•Children and adults•Activation of latent virus in trigeminal ganglion•Altered mental status•Limbic system, frequently b/l but asymmetrical

HSV-2 genital herpes•Neonatal torch infection•Acquired during parturition•Manifests several weeks after birth•Diffuse encephalitis(non focal)

IMAGING FEATURES•MRI is superior to CT•CT & MRI findings are normal initially•MRI detect changes even 2 to 3 days after disease•Distribution: limbic system , temporal lobe> cingulate gyrus,subfrontal region

1. Acute Stage• Decreased/restricted diffusion in affected areas Gyral oedema( T1W hypo intense/T2W hyperintense) No enhancement

2. Subacute stage Marked increase in edema bilateral asymmetrical involvement gyral enhancement Hemorrhage is common

HSE. T2 weighted MRI showing extensive area of increased signal in right temporal lobe and lesser involvement of the left.

Axial proton density–weighted image in a 62-year-old woman with confusion and herpes encephalitis shows T2 hyperintensity involving the right temporal lobe.

Axial nonenhanced T1-weighted image shows cortical hyperintensity (arrows) consistent with petechial hemorrhage. In general, this is a common pathologic finding but less commonly depicted in herpes encephalitis.

Axial gadolinium-enhanced T1-weighted image reveals enhancement of the right anterior temporal lobe and parahippocampal gyrus. At the right anterior temporal tip is a hypo intense, crescentic region surrounded by enhancement consistent with a small epidural abscess.

Axial diffusion-weighted image reveals restricted diffusion in the left medial temporal lobe consistent with herpes encephalitis. This patient also had a positive result on polymerase chain reaction assay for herpes simplex virus, which is both sensitive and specific. In addition, the patient had periodic lateralized epileptiform discharges on electroencephalogram, which supports the diagnosis of herpes encephalitis.

Coronal T2-weighted image reveals hyperintensity in the left temporal lobe (arrows) in a distribution similar to the restricted diffusion abnormality seen in the previous image. This finding is typical for herpes encephalitis. In patients with HHV6 infection, one series noted that in addition to mesial temporal lobe abnormality, abnormal T2 hyperintensity has been seen in the insular and inferior frontal region, which may suggest the diagnosis. There are felt to be 2 typical imaging appearances: one seen in older adults involves T2 hyperintensity confined to the medial temporal lobe; in young adults, a more varied pattern has been described that includes foci of restricted diffusion with an otherwise normal magnetic resonance, diffuse cortical necrosis, or small focal regions of abnormal T2 hyperintensity.

Progressive multifocal leukoencephalopathy•Papova virus causative organism•Effect patients with compromised immunity•Multifocal demyelinating lesion spread in hemispheres often asymmetrically•MRI superior to CT•Spreading areas of low density seen on CT• Increased signals on T2W & less conspicuous reduced signals on T1W

Neurological outcomes of congenital CMV infection. Examples of computed tomography (A) and magnetic resonance imaging (B and C) of three infants with severe symptomatic congenital CMV infection with CNS involvement are shown. The classical pattern of injury described with congenital CMV infection involving the CNS is characterized by periventricular calcifications (panel A, arrow). Other consequences of fetal brain infection include abnormalities of neuronal migration, leading to polymicrogyria (panel B, arrows) and, in extreme cases, profound structural defects such as porencephalic cysts with associated schizencephaly (panel C, arrow).

Subacute sclerosing panencephalitis. Figure 1. MRI scans of the brain at the time of presentation in the neurology clinic (A and B) and 3 months later (C and D). Panels A and C are T1-weighted images; B and D are T2-weighted images. The initial MRI scan (A and B) reveals a focal abnormality in the subcortical white matter of the left frontal lobe, consisting of a hypointense signal on the T1-weighted image (arrow in A) and a hyperintense signal on the T2-weighted image (arrow in B). In the follow-up scan, the focal abnormality in the left frontal lobe is less obvious than previously (arrow in D), but advanced and diffuse cortical atrophy is present, signified by the ventriculomegaly and markedly enlarged sulci (arrowheads in C).

Axial FLAIR images of a patient with chronic HHV 6 encephalitis showing patchy signal hyperintensities in white matter and cortex.

AIDS•A neurotropic Virus•Can effect brain directly or can predispose to opportunistic infections•Common HIV –related infections include1. HIV encephalopathy2. Toxoplasmosis most common opportunistic infection of CNS3. Cryptococcosis4. Progressive multifocal leukoencephalopathy5. TB6. Syphilis7. Varicella8. CMV

HIV ENCEPHALOPATHY•Progressive sub acute sub cortical dementia secondary to HIV itself.•60% patients effected

•IMAGING FEATURES•Atrophy most common finding•T2W bright WM lesion in frontal & occipital lobe and peri ventricular location(gliosis, demyelination)•No enhancement or mass effect of WM lesions•CT:diffuse white matter low attenuation •Most of AIDS findings seen are due to associated Viruses

Fungal Infections•Fungal infections of CNS only rarely seen in healthy people•Common Infections1. Cryptococcosis2. Aspergillosis3. Candidiasis4. Mucormycosis• Less common are

Histoplasmosis,coccididomycosis,blastomycosis,cladosporiasis,nocardiosis,actinomycosis

Cryptococcal Infection•Meningitis spread along perivascular spaces•Multiple areas of enhanced signals on T2W images of basal ganglia and brainstem•Cystic lesions also seen

(A,B) Bilateral basal ganglia cryptococcomas, which have a slightly punctuate appearance on the T 2 -weighted images. On the T, coronalimages, the lesions are slightly hypointense and those on the right exert some mass effect on the right frontal horn.

(C,D) Axial and coronal sectionsT2-weighted and T,-weighted show small enhancing abscess impinging on the right ventricle.

Aspergillosis•Hemorrhagic infarcts from vascular invasion•T2W isointense to hypointense masslike lesions

Coronal T1WI after gadolinium enhancement. Patient after bone marrow transplantation with aspergillus encephalitis. Ring-enhancing lesion with perifocal edema and mass effect compressing the lateral ventricle.

Parasitic Infections•Protozoal:1. Toxoplasmosis2. Amoebiasis3. Malaria4. Trypanosomiasis5. Chaga’s disease

• Metazoal:• Tapeworm ( cestodiasis)• Fluke ( trematodes)

Toxoplasmosis •Toxoplasma Gondi•Two types(congenital & adult)•Commonly associated with AIDS

•Congenital:•Gross degree of venticular dilatation•Extensive calcification ofa) Basal gangliab) Subcortical regions

(A,C) Congenital toxoplasmosis. Grossly dilated ventricles and calcified granulomas in atrophic cortex and basal ganglia

Adult toxoplasmosisCommonly associated with AIDS

IMAGING FEATURES:•Single or multiple ring enhancing lesions with surrounding edema•Target appearance of lesion is common•Major consideration in D.D. is CNS LYPHOMA•Periventriclar location and subependymal spread favors lymphoma•Multiple lesions are suggestive of lyphoma

(A) Toxoplasmic encephalitis in a patient with AIDS.Multiple small abcesses with ring enhancement .A ring enhancing lesion proven to

toxoplasmosis abcess is shown periphally in the left frontal lobe on the T2 axial(B) and T, coronal postcontrast imaging(C).the appearences are

non-specific and there is a large amount of assosiated vasogenic edema.Multiple small enhancing nodules are present predominently at

the grey-white matter junction in this T,axial image

(D) ASSOCIATED PERILESIONAL EDEMA IS CLEARLY SEEN ON T2 AXIAL IMAGE

(E)This patient was known to have Aids And have MultipleToxoplasmosis abcesses

•Taenia solium •Cysticercus cellulosae is larval stage•Acute stage shows small rounded low density lesion enhance with CM on CT•Chronic stage shows punctuate calcifications, obstructive hydrocephalous on CT•MRI demonstrate lesion well even in very early stage.

Cysticercosis

Human Coenurosis

Manifestation of palsy of left seventh cranial nerve in 10-year-old male patient with recent history of camping. Transverse T1-weighted postcontrast MR image shows enhancement of left seventh cranial nerve (arrow).•Borrelia burgdorferi is the causative agent

Right facial numbness, pain, and paralysis in 42-year-old female patient. T1-weighted postcontrast coronal MR images depict enhancement of (a) right trigeminal nerve (arrow)

NEUROSYPHILIS

Figure 2a. Sporadic Creutzfeldt-Jakob disease in a 65-year-old man 10 weeks after the onset of dementia, insomnia, and optical hallucinations and 4 weeks before the appearance of periodic synchronous discharges on the EEG. Diffusion-weighted image shows bilateral areas of abnormal high signal intensity in the cerebral cortex, caudate nuclei, putamen, and thalamus.

Diffusion-weighted image shows areas of abnormal high signal intensity in the left cerebral cortex and the bilateral caudate nuclei.

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