EPIDEMIOLOGY,
PATHOPHYSIOLOGY AND CLINICAL SPECTRUM:
Dengue virus (DENV) infection is one of the most rapidly spreading arboviral infection worldwide.
It is a single stranded RNA virus of flavivirus genus and family flaviviridae.
It has 4 serotypes and serotypes 2 and 3 are associated with severe disease and neurological involvement.
[1,
2,
3]
It is transmitted by mosquitoes of the genus Aedes,
which are widely distributed in subtropical and tropical areas of the world (Figure 1).
Patients typically give history of living in or recent travel to endemic areas.
The incubation period is 3 to 14 days.
Clinical spectrum varies from clinically silent to rapidly progressive alteration in consciousness.
Patients initially present with febrile illness with skin rash and may later develop either dengue hemorrhagic fever or dengue shock syndrome (Figure 2 and 3)
NEUROLOGICAL INVOLVEMENT BY DENGUE VIRUS (Figure 4)
Neurological involvement is usually thought to result from hepatic failure,
cerebral hypoperfusion,
electrolyte disturbances,
hypovolemia and shock,
cerebral edema,
and hemorrhage related to endothelial injury however direct virus entry into CNS has also been implicated to be major cause for the neurological dysfunction.
[4]
DENV is not a neurotropic virus however presence of virus and/ or antibodies in CSF has been implicated in its neurotropism.
The mechanism of entry into CNS may be either through vascular leak due to damaged endothelium or through the infected macrophages and histamine release.
[5,
6]
Dengue encephalitis is mainly a clinical and laboratory diagnosis based on the virus or antibody detection in CSF.
Imaging like CT and MRI plays a supportive role as many of the imaging features are unique to dengue encephalitis.
Hemorrhage is highly specific for making the diagnosis of dengue encephalitis.
[4,
7]
Some patients develop autoimmune response to dengue antigens and present with optic neuritis or ADEM or Guillain- Barre syndrome later in the course of disease.
Cord involvement is also seen in few patients as acute transverse myelitis with or without hemorrhages.