viral meningoencephalitis ad.pptx viral meningitis

Viral meningitis

1. 4 yr female child Ch wd II Presented with rt focal seizure x7 days followed by fever x 5 days n became comatose. MRI brain was requested

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3. 1 st possibilty : Herpes meningoencephalitis . IMPRESSION

4. Encephalitis Acute, diffuse, inflammatory process affecting brain parenchyma Most commonly viral Pathogenesis of viral encephalitis -Direct viral destruction of cells -Para or post-infectious inflammatory or immune- mediated response Most viruses primarily infect brain parenchyma and neuronal cells Some cause vasculitis Demyelination may follow infection

5. Herpes encephalitis Most common cause of sporadic  viral encephalitis , with a predilection for the temporal lobes. In adults, HSV-1 accounts for 95% of all fatal cases of sporadic encephalitis and usually results from reactivation of the latent virus . The clinical findings and neuroimaging appearance are both consistent with spread of the virus from a previously infected ganglion.

6. Presentations and natural history Patients usually presents with altered mental status . Seizures, fever, and headaches are also common. Early diagnosis and prompt treatment are essential Mortality rate:-50-70% Definitive diagnosis :- Serology and CSF-PCR Imaging findings are highly suggestive of HSE.

7. Location Limbic system : Temporal lobes, insula, subfrontal area and cingulate gyri typically Cerebral convexity and posterior occipital cortex may become involved Typically bilateral disease, but asymmetric Basal ganglia usually spared Atypical patterns seen in infants, children Rarely, may affect midbrain and pons ( mesenrhombencephalitis ) Involvement may initially appear unilateral but is typically followed by less severe contralateral disease . This sequential bilaterality is highly suggestive of HSE-1

8. CT Findings NCCT: CT often normal early Low attenuation, mild mass effect in medial temporal lobes, insula Hemorrhage is typically a late feature Predilection for limbic system, basal ganglia spared Earliest CT findings at 3 days after symptom onset CECT: Patchy or gyriform enhancement of temporal lobes , a late feature

9. MR Findings MRI is more sensitive than CT in detecting early changes of HSE-1 TlWI :- Decreased signal in gray and white matter, loss of gray-white junction, mass effect May see subacute hemorrhage as increased signal within edematous brain. Atrophy and encephalomalacia , in chronic cases. T2WI :-Increased signal in gray, subcortical white matter. Typically bilateral, but asymmetric. May see subacute hemorrhage as increased signal within edematous brain. PD/Intermediate : Increased signal in affected areas. FLAIR : Hyperintense swollen cortex/ subcortical white matter.

10. T2* GRE : If hemorrhagic, hypointensity " blooms“ within edematous brain DWI/ADC : restricted diffusion Tl C+ :-May see mild, patchy enhancement early Gyriform enhancement usually seen 1 week after initial symptoms Meningeal enhancement occasionally seen Enhancement seen in temporal lobes, insular cortex,subfrontal area and cingulate gyrus MR findings may be seen within 2 days of symptoms

11. Role of Diffusion Imaging Cortical lesions are more readily detected on DWI images compared with FLAIR and T2-weighted images. Some lesions that are mildly hyperintense on T2-weighted and FLAIR images are easily detectable on DWI images . W ith progression OR follow up imaging , FLAIR imaging depicts lesions more extensively than DWI and lesions lose signal intensity on DWI imaging

12. DWI could be positive in the early disease phase, even when PCR findings are negative . Lesions could be recognized as early as 40 h after symptom onset in adults. ADC mapping, along with DWI, is used to look for true restriction of diffusion and its quantification and this technique may help to rule out the T2 shine-through effect , and to differentiate vasogenic and cytotoxic oedema . Cytotoxic oedema may indicate a poor prognosis.

13. (Left) Axial FLAIR MR IN 52 year old male with fever and seizures. Shows hyperintense signal in the right temporal lobe, right insula , and bilateral medial frontal lobes. ( Right) Axial NECT shows hypodensity in the right temporal and inferior frontal lobes 2 days after the MR study . His initial CT was "normal ". CT findings can often only be seen 3 days after symptom onset.

14. (Left) Coronal FLAIR MR shows classic bilateral, asymmetric involvement of the medial temporal lobes and right insula in this 46 year old female with herpes encephalitis . Basal ganglia sparing is typical. (Right) Axial TlWI MR shows Tl hyperintensity representing subacute blood products in the right insula (arrow) on this follow-up study. Hemorrhage is typically a late feature of herpes encephalitis .

15. (Left) 25 year old male with altered mental status and aphasia. Axial NECT shows hemorrhage in the left temporal lobe with surrounding edema and mass effect. Poor prognosis despite early Acyclovir therapy . (Right) 50 year old with fever and confusion. Axial DWl MR shows diffusion restriction in the right temporal lobe and hippocampus . D Wl is very sensitive for encephalitis. Unilateral disease is atypical.

16. Axial diffusion-weighted image reveals restricted diffusion in the left medial temporal lobe consistent with 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.  

17. MRS – helpful in disease progression increase in Cho/Cr with progressive decrease in NAA/Cr – demyelination with neuronal dysfunction Sequalae – Encephalomalacia , atrophy & calcification Diagnosis – CSF PCR (95%)

18. JAPANESE ENCEPHALITIS With the presence of temporal lobe involvement in the clinical setting of acute viral encephalitis, lesions typical of JE in the thalami, SN, and basal ganglia are helpful in differentiating JE from HSE in these patients. Temporal lobe involvement pattern in JE is different from that in HSE; the posterior hippocampus is commonly involved . The anterior temporal lobe is usually spared and insular involvement is rare, unlike HSE. It is possible, however, that a more virulent strain of the JE virus may involve other areas of the temporal lobe by contiguous spread, when the involvement pattern may resemble that of HSE and differential diagnosis may be a problem . Corpus callosum involvement also has been reported in JE.

19. THANK YOU References : - Diagnostic N euroradiology by Osborn Diagnostic Imaging Brain by Osborn Magnetic Resonance and Diffusion weighted Imaging Findings of Herpes Simplex Encephalitis. HERPES 15:1 2008