The first case of mild encephalopathy with a reversible splenial lesion due to Japanese encephalitis virus infection

MR imaging of adult acute infectious encephalitis

BACKGROUND

Imaging is a key tool for the diagnosis of acute encephalitis. Brain CT scan must be urgently performed to rule out a brain lesion with mass effect that would contraindicate lumbar puncture. Brain MRI is less accessible than CT scan, but can provide crucial information with patients presenting with acute encephalitis.

METHOD

We performed a literature review on PubMed on April 1, 2015 with the search terms "MRI" and "encephalitis".

RESULTS

We first described the various brain MRI abnormalities associated with each pathogen of acute encephalitis (HSV, VZV, other viral agents targeting immunocompromised patients or travelers; tuberculosis, listeriosis, other less frequent bacterial agents). Then, we identified specific patterns of brain MRI abnomalies that may suggest a particular pathogen. Limbic encephalitis is highly suggestive of HSV; it also occurs less frequently in encephalitis due to HHV6, syphillis, Whipple's disease and HIV primary infection. Rhombencephalitis is suggestive of tuberculosis and listeriosis. Acute ischemic lesions can occur in patients presenting with severe bacterial encephalitis, tuberculosis, VZV encephalitis, syphilis, and fungal infections.

CONCLUSION

Brain MRI plays a crucial role in the diagnosis of acute encephalitis. It detects brain signal changes that reinforce the clinical suspicion of encephalitis, especially when the causative agent is not identified by lumbar puncture; it can suggest a particular pathogen based on the pattern of brain abnormalities and it rules out important differential diagnosis (vascular, tumoral or inflammatory causes).

Transient elevation of cerebrospinal fluid protein in a patient of mild encephalitis with reversible lesion in the splenium: a case report

Mild encephalitis with reversible lesion in the splenium (MERS) is a clinicoradiological syndrome presenting as a solitary lesion in the central portion of the splenium of the corpus callosum (SCC) with a radiological finding of restricted diffusion and low apparent diffusion coefficient (ADC) values. Complete resolution of the lesion on follow-up imaging and full clinical recovery are the hallmarks of this syndrome, even with only supportive therapy. MERS is usually associated with normal Cerebrospinal fluid (CSF) findings and an excellent prognosis, even without corticosteroid therapy. Magnetic resonance imaging (MRI) is the ideal modality for initial diagnosis and follow-up. Not many cases of this uncommon clinicoradiological syndrome with transient elevation of CSF proteins have been reported. In the subsequent sections, we present a case report of this unusual clinicoradiological entity with raised CSF protein. We also elaborate on possible differential diagnoses and the syndrome's proposed pathophysiology.