[Severe encephalitis without correlate in MRI]

Encephalitis could be a life-threatening disease depending on localisation and infectious agent. Neuroimaging, especially MRI, is an important component in the diagnosis. The recent investigations demonstrate that diffusion abnormalities are the first and sensitive signs of viral encephalitis. We describe five patients with severe encephalitis with normal MR imaging. Three of five patients were intermittently mechanically ventilated, two of these longer than 4 weeks. The other two patients suffered from a severe psychosyndrome with seriously limited ability to communicate throughout 6 weeks. At the time of first MRI examination all patients were noticeably ill. Four of five patients had at least one follow-up MRI. The MRI examinations included FLAIR sequences and DWI in four of five patients. Contrast-enhancement was detectable in none of our patients. Follow-up examinations revealed that symptoms of encephalitis were noticeably or completely regressive.