Infections and inflammations Flashcards
What are the common causes of chronic meningitis?
TB, fungi
What are the routes of infection for meningitis?
Hematogenous spread - paranasal sinus/mastoid infection
Otitis media
Penetrating head injury
Prior surgery
What are the general imaging findings associated with meningitis?
Leptomeningeal enhancement and/or ependymal enhancement
High signal CSF on FLAIR - denotes protein (viral, bacterial) in CSF
What is the most common complication in child meningitis?
Hydrocephalus
What are the two common complications from adult meningitis?
Effusions and empyema
What percentage of meningeal effusions turn into empyema?
What is the most common cause of sterile effusion?
What are the complications associated with subdural empyema?
2%
H influenza
Venous thrombosis, infarction, cerebritis, ventriculitis, abscesses
What is the patient population for pyogenic cerebral abscess?
10-30yo male with AIDS
What is the main cause of cerebral pyogenic abscess?
What are the routes of infection?
Bacteria
Hematogenous spread, paranasal sinusitis, otitis media, meningitis, penetrating head trauma
What are the stages of cerebritis?
Early cerebritis (5 days) Late cerebritis (4-11 days) - central necrosis Early abscess (10-18 days) - early capsule formation Late abscess (14-19 days) - rim enhancing lesion, may last up to 8 months
What are the imaging features of a pyogenic cerebral abscess? Early vs late?
Early - nonspecific T2 prolongation with heterogenous enhancement
Late - capsule with low T2/FLAIR high T1 signal, SMOOTH THIN capsule (vs glioma or mets), vasogenic edema, rim is thicker on side of grey matter
What is the main difference in the capsule between glioma/mets and cerebritis abscess?
Abscess rim is THIN and SMOOTH
What are the restricted diffusion characteristics of abscess? Which bugs have decreased relative restriction?
What does persistent restriction indicate?
Cavitary restricted diffusion
TB, toxoplasmosis, fungi may have less prominent restriction
Persistent restriction indicates treatment failure
What bug is most common in viral encephalitis?
Herpes type I
Where does HSV 1 reside prior to reactivation?
Where does it infect?
What is the CT/MRI appearance?
trigeminal ganglia
Mesial temporal lobe, insula and orbital surface of frontal lobes
CT: often normal, can show ill defined hypoattenuation in the affected regions
MR: bilateral T2 signal in medial temporal lobe, insular cortex, cingulate gyrus, and inferior frontal lobe, restricts diffusion
Gyral enhancement later
Which meningites has a propensity for hemorrhagic transformation?
Herpes 1
Who gets HSV2 encephalitis? Where?
Inoculation during vaginal delivery
Diffuse meningoencephalitis involving cerebellum
Who gets CMV encephalitis?
Where is the infection?
What are the CNS manifestations?
AIDS (
What are the associated findings with neonatal CMV?
Chorioretinits, microophthalmia
Periventricular calcifications in the setting of hydrocephalus and fever suggests what?
CMV meningitis
Basal ganglia calcification, atrophy, and microcephaly in a neonates suggests what?
HIV
What are the characteristic features of HIV encephalopathy?
What is the imaging appearance?
Demyelination, gliosis, multinucleated giant cells
MR: Confluent, ill defined T2/FLAIR signal in white matter of FRONTAL and PARIETAL lobes WITHOUT enhancement, diffuse atrophy
Diffuse cerebral atrophy with T2/FLAIR prolongation in periventricular and deep white matter
What is the main difference between HIV encephalopathy and PML?
HIV spares the subcortical U fibers and is symmetric
What is PML?, what is the virus?
Who is at risk? What drug associated with MS has a risk?
Progressive multifocal leukoencephalopathy
JC virus (papovavirus)
AIDS, transplant, hodgkin lymphoma, CLL, immunodeficiency, SLE, sarcoid, amyloidosis, scleroderma
Natalizumab
What is the pathology of PML?
What cell is affected?
What is the imaging appearance?
Demyelination of oligodendrocytes
ASYMMETRIC multifocal white matter lesions with little or no mass effect and NO enhancement
Usually occipitoparietal
INVOLVES subcortical U fibers (unlike HIV)
What is the most common opportunistic infection in AIDS patients? What CD4 count?
Toxoplasmosis
What is the imaging appearance of toxoplasmosis? Where does it occur? What is the associated sign?
Single or multiple ring enhancing lesions in the BASAL GANGLIA and grey white junctions
Ring enhancing lesions with MARKED surrounding edema
Asymmetric target sign - eccentric nodule of enhancement along the enhancing wall of the toxoplasmosis lesion
DOESNT restrict diffusion