A young woman (in her 30’s) presented with a 3-day history of severe headache, low-grade fever (37.8 degrees Celsius) and photophobia. Clinical examination was unremarkable except for mild photophobia and mild neck stiffness. A CT head (non-contrast) done at the Emergency Department was normal, as was her full blood count and renal function panel.

She had been hospitalised 7 years ago for a “brain infection”, for which she stayed almost two weeks in the hospital. In keeping with the tradition of that time, the cause of the brain infection was not made known to her. Since then, however, she had recurrent “special” headaches every 2-3 months that she described as being different from other headaches. These were occasionally associated with mild photophobia and/or low-grade fever, and rarely nausea and vomiting. Each episode had settled with NSAIDs are bed-rest after a few days, but this current episode was the most severe in 7 years.

She had previously worked as an airline stewardess, but had not traveled out of Singapore for the year prior to this hospitalisation. No significant contact history of note. Has goldfish at home but no other pets.

A lumbar puncture was performed, with clear cerebrospinal fluid obtained. CSF analysis results were as follows:

• Cell count = 93 cells/ml (78% lymphocytes).
• Protein = 0.5 g/L (normal range = 0.1 – 0.4).
• Glucose = 3.2 mmol/L (concurrent serum glucose was 5.1 mmol/L)
• Gram stain, India ink and Ziehl-Neelsen stain were all negative.

Question: What is the likely diagnosis?

[Updated 23rd May 2015]

The history of recurrent lymphocytic meningitis, with the majority of episodes being self-limiting without the need of therapy, suggests the diagnosis of Mollaret’s meningitis. Although an etiology cannot be found in some cases, the majority are caused by herpes simplex virus type 2 (HSV-2). There is some controversy over the use of acyclovir for its treatment, however, because most episodes – as with this patient – are self-limiting. However, acyclovir has been found to be useful for the treatment of more severe cases. Because of the frequency of the episodes, I had finally prescribed this patient prophylactic valacyclovir, which for a couple of years appeared to prevent further episodes of meningitis in this patient. This was done years before we really had good evidence for clinical practice – in 2012, Swedish investigators published a 7-year-long clinical trial that showed long-term valacyclovir prophylaxis was not beneficial in patients with recurrent HSV-2 meningitis.