Marzia Puccioni-Sohler, MD, PhD, Head of the Cerebrospinal Fluid Laboratory and Clinical Pathology Service at the Clementino Fraga Filho Hospital of the Federal University of Rio de Janeiro (HUCFF/UFRJ) and Professor of Neurology at the University of the State of Rio de Janeiro (UNIRIO) discusses her paper "Neurological dengue manifestations associated with intrathecal specific immune response" that was recently published in Neurology® (2009:73:1413-17). She spoke with José G. Merino, MD, Science Editor of AAN.com.
AAN.com: Can you summarize the methodology and major findings of your study?
Puccioni-Sohler: We wanted to determine if patients with dengue-related neurologic syndromes produce specific IgG antibodies in the central nervous system (CNS) and to determine the clinical and physiopathological relevance of these antibodies. We studied 10 dengue-IgM seropositive patients (six female, age 22 to 74 years; duration of disease five to 30 days) who had myelitis, encephalitis, optic neuromyelitis, and Guillain-Barré syndrome (GBS). We performed enzyme-linked immunosorbent assay (ELISA) to look for dengue IgM and IgG in serum and cerebrospinal fluid (CSF), and used the specific antibody index method described by Reiber & Felgenhauer. Nine of the 10 patients had IgG antibodies, but only three (all of them with myelitis) had intrathecal synthesis of the IgG.
AAN.com: What were the CSF findings in your patients?
Puccioni-Sohler: All our patients had abnormal CSF, with the exception of one patient, who was diagnosed with GBS after showing symptoms for 17 days. Patients with myelitis and encephalitis had an inflammatory CSF profile with pleocytosis, high protein concentration, evidence of blood-CSF barrier dysfunction, and intrathecal synthesis of immunoglobulins. Four of the five patients with GBS and the patient with neuromyelitis had protein-cytological dissociation. In general, the highest protein levels in GBS were observed 10 to 20 days after the onset of the disease.
Dengue IgG and IgM antibodies were detected in the CSF on days five and seven from the onset of neurologic symptoms, respectively, indicating that both can be found in the early stages of the infection. We found specific IgM antibodies in the CSF of the three patients with myelitis, two patients with GBS and the patients with encephalitis and optic neuromyelitis. The detection of specific IgM antibodies in the CSF with ELISA has high specificity (97 percent) but low sensitivity (46 percent) for neurologic syndromes associated with dengue. This means that, in patients with neurologic manifestations and a positive IgM in CSF, there is a high probability that the symptoms are due to dengue infection and, conversely, that negative IgM results in CSF don't exclude the possibility that the neurologic signs are dengue-related. In the patients with GBS and optic neuromyelitis, the blood-CSF barrier dysfunction may have contributed to the transfer of serum IgM to the CSF rather than local synthesis. We found IgG antibodies in the CSF of all of the patients in this study, with the exception of one patient with GBS who had negative specific IgM and normal CSF. In endemic areas, the majority of the population may have these antibodies in their serum as a result of a prior asymptomatic dengue infection, and these antibodies cross the blood-CSF barrier. Thus, the demonstration of dengue IgG antibodies in CSF does not help with diagnosis.
AAN.com: What are the clinical features of dengue?
Puccioni-Sohler: Dengue is an acute febrile illness caused by a flavivirus that is transmitted by the mosquitoes Aedes aegypti (in subtropical and tropical Americas) and Aedes albopictus (in Asia). Dengue is endemic in areas where the environmental and socio-economic conditions allow the development of the vector. Epidemics of dengue fever are common throughout the world: 50–100 million cases are registered every year and 2.5 billion people live in risk areas encompassing over 100 different countries. Despite this diversity, 80 percent of the cases in the Americas occur in Brazil. There are four virus serotypes and the incubation period of these viruses ranges from three to 15 days. The majority of people infected with dengue are asymptomatic. Among symptomatic patients, there are two clinical syndromes. The first one, the classical form, presents with high fever, severe frontal headache, retro-ocular pain, muscle and joint pain, rash, nausea and vomiting, and abdominal pain. This form is rarely fatal. The second syndrome, dengue hemorrhagic fever, is more severe and is characterized by fever, increased vascular permeability, thrombocytopenia, hematomegaly, and hemorrhagic manifestations. In rare cases, it can lead to shock. When this occurs, the mortality rate is high.
AAN.com: How is dengue diagnosed?
Puccioni-Sohler: To confirm dengue infection, a lab test must detect the viral antigen (isolation of the agent or by polymerase chain reaction) in the first seven to nine days after the onset of the symptoms. Serological methods can also be used to detect IgM antibodies in a single serum sample or an increase of the IgG antibody titer in paired samples. There is cross-reactivity with other viruses of the flavivirus group (St. Louis encephalitis, Japanese encephalitis, West Nile fever, and yellow fever).
AAN.com: What are the neurologic features of dengue infection?
Puccioni-Sohler: Approximately one to five percent of patients infected with dengue have neurologic manifestations. Encephalitis is the most common neurologic manifestation. Encephalitis, encephalopathy, cerebro-meningeal hemorrhage, myelitis, and meningitis occur during the acute infection. Post-infection disorders include acute disseminated encephalomyelitis, Guillain-Barrè syndrome, and facial and ulnar mononeuropathy.
AAN.com: In your study, what were the most common clinical neurologic features of dengue infection?
Puccioni-Sohler: In our study, the most common neurologic syndromes in patients with dengue were Guillain-Barré syndrome (GBS; 50 percent), myelitis (30 percent), and encephalitis and neuromyelitis optica (both 10 percent). All our patients met the World Health Organization criteria: neurologic manifestations coupled with positive IgM dengue serology. The time period between the onset of the febrile period caused by the dengue infection and the onset of neurologic symptoms ranged from five days to 30 days. Acute flaccid paraparesis ascending to tetraparesis was dominant in four out of five cases of GBS. Patients with myelitis had spastic paraparesis, a sensory level and sphincteric disturbance. The symptoms of the patient with encephalitis included transitory mental confusion and spontaneous improvement after 24 hours. The single case of neuromyelitis optica suffered from acute paraparesis, sensory level, urinary incontinence, and blurred vision.
AAN.com: What is the differential diagnosis of patients with dengue and neurologic features?
Puccioni-Sohler: Diagnosis is difficult because the neurologic symptoms and routine analysis of CSF are not specific to dengue. In our study we excluded other inflammatory, neoplastic, and vascular diseases with serum and CSF analysis and MRI. All patients had routine hematological, biochemical, and hepatic tests as well as tests for rheumatic diseases and hepatitis B and C antibodies. We also analyzed the antibodies in serum and CSF for HIV-1, HTLV-1, CMV, EBV, and HSV to exclude other viral infections. The routine CSF exam included cell count, protein and glucose concentration analysis, and smear and culture for bacteria and fungi. To evaluate the blood-CSF barrier we used the albumin quotient (CSF/serum).
AAN.com: What are the mechanisms through which dengue leads to neurologic symptoms?
Puccioni-Sohler: There are several potential mechanisms for the dengue-related neurologic manifestations: direct CNS viral invasion; an auto-immune reaction secondary to systemic infection or post-infection related to immunoallergic mechanisms; metabolic disturbance; and hemorrhage due to thrombocytopenia. The dengue virus has neurotropic and neuroinvasive properties. Because the detection of local synthesis of specific antibodies is evidence of neurotropism of the infectious agent, our findings suggest that myelitis in patients with dengue is due to viral invasion of the spinal cord. We did not find intrathecal production of antibodies among patients with dengue and GBS or optic neuromyelitis: the neurologic syndromes in these patients may have an autoimmune etiology.
AAN.com: What is the treatment for dengue?
Puccioni-Sohler: Unfortunately, there is no available vaccine for dengue or any specific treatment for the disease. Prevention is currently the only way of avoiding a dengue epidemic. Symptoms of the classical form of dengue can be treated with analgesics and antipyretics. We avoid salicylates and NSAIDs because they may increase the risk of hemorrhagic complications. Patients with hemorrhagic fever need close monitoring for signs of shock. The critical period is during the transition to the disappearance of the fever, which tends to occur after the third day of illness
The treatment of the neurologic manifestations depends on the syndrome. In a previous study we found that the characteristic and prognosis of dengue-associated GBS are similar to those of GBS associated with other infections. Some of the neurologic manifestations associated with dengue are benign and recovery is spontaneous, as was the case with our patients with encephalitis and some of the GBS patients. Our patient with neuromyelitis was treated with methylprednisolone, IVIG, and plasmaphersis, and was discharged after a complete recovery. The patient with myelitis had a more malignant course and, despite treatment with methylprednisolone, had significant sequelae: spastic paraparesis, urinary retention, or lower limbs paresthesias.
AAN.com: When should neurologists in non-endemic areas consider the diagnosis of dengue for patients presenting with myelitis or Guillain-Barré syndrome?
Puccioni-Sohler: Neurologists should consider dengue whenever a patient develops myelitis, Guillain-Barré syndrome, or the other neurologic symptoms after travelling to an endemic region. In such instances, patients should be tested for dengue, even if they have no previous history of the infection. In a previous study we found that while six out of seven cases of GBS and dengue did not have typical dengue symptoms, they did have positive IgM serologies.
In the last five years, Dr. Puccioni-Sohler received research support from two Brazilian governmental entities: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for dengue studies
Dr. Merino performed a one-time consultation with staff from Bell, Falla and Associates.