Mollaret's meningitis also referred to as recurrent benign lymphocytic meningitis, is characterized by a transient and recurrent onset of neurological symptoms such as headaches, fever, meningismus and various neurological deficits that last for a few days in a self-limiting fashion. Herpes simplex type 2 virus is the causative agent in virtually all cases. CSF examination and polymerase chain reaction (PCR) testing to detect viral DNA are recommended steps in the diagnostic workup.
Although it was initially described the 1940s, the cause of Mollaret's meningitis was revealed later to be an infection due to the reactivation of herpes simplex viruses (HSV-2), much more commonly HSV-2   . Due to still undisclosed reasons, Mollaret's meningitis is more commonly seen in females and predominantly affects adults around 35 years of age, but the infection is described across all age groups    . The clinical presentation is distinguished by a recurring and sudden onset of headaches that may be quite severe, fever, photophobia, radiculopathy, paresthesias, arthralgia and in about 50% of cases, neurological symptoms - hallucinations, cranial nerve deficits, diplopia, seizures, or even altered consciousness    . Patients report maximal discomfort and pain in the first few hours of symptom appearance, after which a gradual decline in severity is observed . Because of a relatively short duration of symptoms (about 1-7 days in most cases), their recurrence (weeks, months or sometimes even years can pass between attacks), as well as their self-limiting nature that does not pose any harm to the patient, the term benign recurrent lymphocytic meningitis (BRLM) is often used to describe Mollaret's meningitis in the literature   . The recurrent appearance of symptoms usually lasts over a period of 3-5 years, followed by a spontaneous resolution in virtually all cases   .
The diagnosis of Mollaret's meningitis may be difficult to make without adequate clinical suspicion, which can only be raised if a complete patient history is obtained. The duration of symptoms, their pattern, as well as recurrence and remission, are highly specific signs of Mollaret's meningitis. In fact, certain reports have emphasized that at least three episodes are necessary in order to consider Mollaret's meningitis in the differential diagnosis . A complete physical examination may confirm signs and symptoms suggestive of a meningeal irritation. In that case, appropriate laboratory tests should be obtained. Cerebrospinal fluid (CSF) examination is recommended in all patients who exhibit signs of a central nervous system (CNS) infection, and a lumbar puncture is necessary to evaluate the CSF contents, but only after an imaging study of the endocranium (computed tomography) is performed. Lymphocytic pleocytosis (an increased number of lymphocytes in the CSF) is one of the most important signs of viral meningitis, while the presence of large granular plasma cells is a distinguishing feature of Mollaret's meningitis . However, they can be detected only in the first 24 hours after symptom onset, and their monocytic-macrophage origin suggests that neutrophilic pleocytosis is also a possible finding, a rare feature seen in West Nile encephalitis as well  . Protein levels might be elevated, whereas glucose levels are normal . In addition to clinical and CSF criteria, detection of HSV (either HSV-1 or HSV-2) genetic material (DNA) in CSF by PCR methods is the gold standard for confirming the diagnosis    . Because HSV is a rather common cause of viral meningitis, PCR testing should be done whenever CSF shows lymphocytic predominance .