MENINGITIS… INFECTIOUS MENINGITIS And Its Complications: • Clinical presentation • Headache ± fever, nuchal rigidity Radiologic-Pathologic Correlations • AMS (acute febrile encephalopathy) • Etiologies vary • Pyogenic • Viral • Granulomatous • Pathology similar • Dense, purulent exudate • Covers pial surface of brain • Often fills subarachnoid spaces • Variable extension into brain via PVSs Anne G. Osborn, M.D. • ± Involvement of blood vessels ( vasculitis) ACUTE MENINGITIS CT OF ACUTE MENINGITIS Generic Imaging Patterns • May be normal early! Mild ventricular enlargement + “featureless” brain Most common = pia-subarachnoid Less common = focal or diffuse dura- • Findings space exudates (acute > chronic) arachnoid thickening (chronic > acute) • Nonspecific hydrocephalus • Sulcal/cisternal effacement • Pia/subarachnoid enhancement “Effaced” sulci on NECT; enhancing on CECT MR OF MENINGITIS MR OF MENINGITIS T1WI FLAIR Sulci “bright”on FLAIR, ± slightly ↑ • General features Pus fills in sulci • “Dirty” CSF • Iso- (“gray-ish” CSF) on T1WI • Hyperintense on T2WI (hard to see!) • Hyperintense on FLAIR (nonspecific) • Sulcal-cisternal enhancement on T1C+ • Post-contrast FLAIR • More sensitive than T1C+FS! • Other findings • ± Foci of restricted diffusion • Sulci, parenchyma T1C+FS Pus in sulci restricts on DWI (these aren’t strokes!) Page 1 DDX FLAIR HYPERINTENSE CSF COMPLICATIONS OF MENINGITIS Baseline MR • Altered CSF flow, resorption → • Subarachnoid hemorrhage • Hydrocephalus • Meningitis • Often earliest (sometimes only) finding! • Leptomeningeal carcinomatosis • Spread of infection → • Fat in CSF • Ventriculitis/pyocephalitis • “Ivy sign” • Cerebritis/abscess • Slow flow (stroke, SWS, moyamoya) • Empyema • Artifact • Incomplete CSF suppression • Cerebrovascular → • High inspired oxygen • Vasculitis • Recent gadolinium administration • Arterial ischemia/infarction • Venous thrombosis, infarction 24h ltr, propofol anesthesia 100% inspired O2 ACUTE, SEVERE OBSTRUCTIVE MENINGITIS AND HYDROCEPHALUS HYDROCEPHALUS “Blurred” or “fuzzy” margins caused • Remember by periventricular fluid accumulation • “Hydrocephalus” = imaging observation • Not a diagnosis! • Find the cause! T2 hyperintense • “Hydrocephalus” • Often first/only finding in early meningitis • Ventricular enlargement on NECT • Look for etiology FLAIR periventricular “fingers” Meningitis + early hydrocephalus EVOH EVOH Meningitis Meningitis Lateral, 3rd, 4th T2WI with ventricles enlarged periventricular fluid around enlarged 4th Contrast injected via Lateral recesses ventriculostomy, enlarged stops at outlets Obstruction at foramina of Luschka, Magendie Page 2 COMPLICATIONS OF MENINGITIS VENTRICULITIS/PYOCEPHALUS • Altered CSF flow, resorption → • Hydrocephalus • Ventriculitis • Often earliest (sometimes only) finding • Rare cerebral infection • Often meningitis complication • Spread of infection → • Infection of ependymal lining • Ventriculitis/pyocephalitis • ± Choroid plexitis • Cerebritis/abscess • Pyocephalus • Intraventricular empyema • Empyema • Purulent fluid • Cerebrovascular → • Intraventricular abscess rupture • Meningitis less common • Vasculitis • Often fatal • Arterial ischemia/infarction • Venous thrombosis, infarction VENTRICULITIS VENTRICULITIS + CHOROID PLEXITIS FLAIR ependymal hyperintensity, enhancement, restricted DWI PYOCEPHALUS COMPLICATIONS OF MENINGITIS Intraventricular debris, fluid-fluid level, DWI restriction • Altered CSF flow, resorption → • Hydrocephalus • Often earliest (sometimes only) finding • Spread of infection → • Ventriculitis/pyocephalitis • Cerebritis/abscess • Empyema • Cerebrovascular → • Vasculitis • Arterial ischemia/infarction • Venous thrombosis, infarction Pyocephalus 2º to intraventricular abscess rupture Page 3 MENINGITIS → EARLY CEREBRITIS CEREBRITIS/ABSCESS 63yM 2d headache, confusion, L hemiplegia 41yF frontal sinusitis → meningitis → late cerebritis EMPYEMA SUBDURAL EMPYEMA Acute • Rare focal pus collection • Imaging • 1%-2% of CNS infections • Hypodense on CT • Potentially lethal • Hyperintense on FLAIR • May progress rapidly • Enhancing membranes • Neurosurgical emergency • SDE restricts • Etiology • Complications • Infants/young children: Meningitis • Cerebritis • Older children/adults: Sinus/ear infections • Ischemia • Location • DDx • Extraaxial (subdural > epidural) • Chronic SDH • 85% supratentorial • Subdural hygroma • 15% infratentorial • Subdural effusion Chronic EDE SUBDURAL EFFUSIONS Often associated with sinusitis, mastoiditis etc. Post-meningitis sterile CSF-like fluid collections (5-10% of cases) No restriction, no enhancement Page 4 COMPLICATIONS OF MENINGITIS VASCULAR COMPLICATIONS Pyogenic meningitis → bilateral LSA infarcts • Altered CSF flow, resorption → • Hydrocephalus • Often earliest (sometimes only) finding • Spread of infection → • Ventriculitis/pyocephalitis • Arterial ischemia/infarction • Cerebritis/abscess • Vasculitis • Empyema • Venous thrombosis, infarction • Cerebrovascular → • Vasculitis • Arterial ischemia/infarction • Venous thrombosis, infarction VASCULITIS MENINGITIS → DISTAL STROKES Cocci Meningitis with VWI T2 SPACE T1C+FS DANTE DSA L ICA DSA R VA VENOUS INFARCTS NON-INFECTIOUS MENINGITIDES COMMON LESS COMMON/RARE • CSF metastases • Inflammatory amyloid • Neurosarcoid • SLE • Susac syndrome • Rheumatoid arthritis Petechial cortical, subcortical hemorrhages ± focal SAH Page 5 “CARCINOMATOUS MENINGITIS” NEUROSARCOID SUMMARY • General features of meningitis • Clinical, pathology • Imaging → generally similar regardless of etiology • Infectious, non-infectious look alike! • Complications (may be even more severe) • Hydrocephalus (often earliest finding on NECT) • Spread of infection → • Ventriculitis/pyocephalitis • Cerebritis/abscess • Empyema • Cerebrovascular → • Vasculitis • Arterial ischemia/infarction • Venous thrombosis, infarction Page 6.