Overview.
Lymphocytic choroid plexus meningitis (LCM) is an acute infectious disease caused by the LCM virus. The clinical course of the disease ranges from influenza-like symptoms to meningitis and encephalitis. The course of the disease is self-limiting and the prognosis is good. The disease is an animal-based infection, and the natural host of LCM virus is the brown house mouse.
Etiology
The pathogenesis of the disease has not been fully elucidated. When the virus first invades the respiratory tract, it can reproduce in large quantities in the epithelial cells, so many patients manifest upper respiratory tract infection or “flu-like” symptoms. The virus enters the bloodstream and causes viremia, which can pass the blood-brain barrier and infect meningeal cells.
Symptoms
The incubation period of the disease is from 6 to several weeks, with various clinical manifestations.
1. Influenza-like type
The onset of the disease is mostly acute, with fever up to 39℃ or above, accompanied by back pain, headache and generalized muscle pain. Some patients complain of nausea, vomiting, photophobia, lymph node swelling and pain, diarrhea, rash or sore throat, nasal congestion and runny nose, cough and other symptoms. The duration of the disease is about 2 weeks, with occasional relapses. The feeling of weakness after the disease can last for 2 to 4 weeks.
2. Meningitis type
It may appear after “flu-like” symptoms (often with a short period of remission), or start directly with meningitis. The onset of the disease is rapid, characterized by fever, headache, vomiting, meningeal irritation, etc. Convulsions are rare, except in young children. Mental status is generally unchanged. The course of the disease is about 2 weeks.
3. Others
Meningoencephalitis type and encephalomyelitis type are rare, manifested by severe headache, delirium, coma, convulsions, paralysis and mental disorder. Some cases have neurological sequelae, such as aphasia, deafness, arachnoiditis, paralysis of different degrees, ataxia, diplopia, strabismus, etc.
Examination
Peripheral blood picture shows normal or decreased total number of white blood cells and relative increase of lymphocytes. In patients with meningitis type, the cell count of cerebrospinal fluid may increase to 100~3000/mm3, of which more than 90% are lymphocytes; protein is increased, but usually not more than 100mg/dl; sugar is normal or slightly decreased, and chloride is normal. Pressure is normal or slightly increased.
Blood or cerebrospinal fluid of patients in the acute stage can be inoculated in the brain or peritoneal cavity of mice to isolate the pathogen, and serum immunofluorescence test can be positive in the first week of the course of the disease, which is conducive to early diagnosis. Complement binding test is positive at 10-14 days of the disease, and the titer peaks at 5-8 weeks and disappears within 4-6 months. Neutralization test is only used for epidemiological investigation.
Diagnosis
A history of contact with voles and mice, or the presence of mice in the residence and neighborhood of the same patients, a brief remission of “flu-like” symptoms followed by meningeal irritation, increased cerebrospinal fluid with almost exclusively lymphocytes, and a normal chloride with a relative decrease in glucose are all important references. Confirmation of the diagnosis depends on serologic testing or virus isolation.
Treatment
There is no specific treatment for this disease. Symptomatic treatment is given when the headache is severe, and dehydrating agents such as mannitol can be used if the cerebral pressure is increased.