Dengue Hemorrhagic Fever-MRI

32 yr adult with clinical and serology positive Dengue fever with acute encephalopathy with low platelet  counts   shows on CEMRI, multiple hemorrhagic   focal lesions in supra and infratentorial locations with relative sparing of basal ganglia and brainstem and varying degrees of  restriction and enhancement ,   possibly explained by different ages of bleed and  therefore varying  degrees  of breakdown of blood brain barrier

Questions in the case

1. Thalami spared?---   variations are reported

2. Enhancement is varied  in different lesions? possibly  related to  different ages of  bleed

3. Meninges normal--  Imaging  is not good  enough for meningitis

4. Cord is normal?--- encephalomyelitis is only  known to occur in some

5. Is comorbidity possible with some other infections?—certainly possible, but since serology and CSF are negative, less likely

Teaching points  for Radiologist  by Dr MGK Murthy. Images by Mr Hariom and Mr Venkat.

·         Dengue fever occurs in about 100 countries ,and is caused by RNA virus of Flavivirdae family

·          Non-neurotropic nature of the virus is now questioned with some  growing from CSF

·         Neurology involvement can be encephalitis (direct virus effects) or more common encephalopathy (usually metabolic, hypotension or haemorrhage  related findings)

·         CSF serology an virus culture are considered as gold standard

·         MRI plays crucial role in altered sensorium patients to  exclude  other causes  as well  show focal lesions apart from  severity and nature

·         Viral encephalitides have predilection for certain sites as below :

HSV: Frontal, Temporal lobes

Japanese Encephalaitis: Thalamus, basal ganglia, cerebellum, brainstem

West Nile fever: Deep grey matter, mesial temporal lobe, cerebellum, brainstem. Difficult to differentiate from JE on imaging alone

Rabies: Hippocampi, basal ganglia, brainstem , temporal lobes.

Chikungunya: cingulated gyrus, Limbic system

Nipah: multiple white matter lesions.