Case Presentation:
A 59 year‐old woman presented with 5 days of fever, headache, photophobia, generalized weakness, and intermittent confusion.
Vital signs: temperature 40.3 C, pulse 96, respirations 17, and blood pressure 124/76. She was alert and oriented to person, place, and time, but was very somnolent and had difficulty remaining awake. She had no nuchal rigidity, equal and reactive pupils, and dry mucous membranes with a non‐focal neurologic exam including negative Kernig and Brudzinski signs.
Labs revealed thrombocytopenia, elevated transaminases, a non anion gap metabolic acidosis, and acute kidney injury. CT head showed no evidence of acute stroke or hemorrhage. There was concern for thrombocytopenic thrombotic purpura/hemolytic uremic syndrome but evaluation of the peripheral smear showed no schistocytes. TSH and acetaminophen/salicylate levels were normal. Cerebrospinal fluid showed elevated protein, but only four WBCs. She was treated empirically for murine typhus while awaiting rickettsial studies. All of her spinal fluid tests came back negative (bacterial cultures, all her viral studies, fungal studies and arbovirus panel). Her serum rickettsial panel was also negative. Upon further questioning, it was determined she had recently started taking lamotrigine and she was diagnosed with a drug‐induced aseptic meningitis.
Discussion:
Bacterial meningitis is a common concern in any patient presenting with fever, headache, and altered mental status. Aseptic meningitis is defined as inflammation of the meninges without a bacterial source. Aseptic meningitis can often mimic a bacterial process with fever, headache, and confusion, making diagnosis difficult. Furthermore, neuroimaging does not typically show any specific abnormalities. In order to properly differentiate between aseptic and bacterial meningitis, cerebrospinal fluid must be obtained and sent for cell count and bacterial, viral, and fungal studies. Typically, the CSF for aseptic meningitis will show a pleocytosis (mononuclear or polymorphonuclear) less than that of bacterial meningitis. Viruses (including enterovirus, cytomegalovirus, herpes virus) are the most common cause of aseptic meningitis. Less commonly, certain medications (NSAID’s, antibiotics, intravenous immunoglobulins, and antiepileptics) can cause a drug induced aseptic meningitis. Since this is a diagnosis of exclusion, it is extremely important to take a thorough medication reconciliation during the initial interview of a patient. While uncommon, several cases of lamotrigine associated aseptic meningitis have been reported.
Conclusions:
Aseptic meningitis should be considered in patients who present with fever, headache, and confusion. Furthermore, a detailed medication history should be obtained in the rare instance the patient has drug induced aseptic meningitis. Our patient’s clinical symptoms and lab abnormalities resolved with cessation of her lamotrigine. She was discharged with instructions not to take the medication again.