Case 4: Recurrent bacterial meningitis in an adolescent female

A 17-year-old female was transferred to the authors' institution from another hospital, where she had been admitted with rhinorrhea followed by a progressively worsening headache associated with nausea and photophobia, suggestive of meningitis. On initial examination, she was febrile, with a temperature of 38.7°C and other vital signs within normal limits. She was alert and oriented, with evidence of neck stiffness but no other meningeal signs. The remainder of her neurological examination was normal aside from photophobia. A lumbar puncture performed after a single dose of cefotaxime and vancomycin showed a glucose level of 3.6 mmol/L, protein level of 1.63 g/L, total white blood cell count of 3399×106/L (93% neutrophils) and 1173×106/L red blood cells. Her medical history revealed that she had experienced three previous episodes of bacterial meningitis with pneumococcal bacteremia (2006, 2007 and 2008). Following the first episode of meningitis, she received the 7-valent pneumococcal conjugate and meningococcal conjugate monovalent vaccinations and was referred to immunology and neurosurgery for further workup. Magnetic resonance imaging (MRI) performed after her second episode was interpreted to be unremarkable. She had also undergone an immunological work-up, which revealed normal complement levels. Following the third episode of meningitis, she was started on penicillin prophylaxis, which she had discontinued seven months before presentation. Our patient met the criteria for recurrent bacterial meningitis on the basis of multiple episodes of meningitis caused by the same organism with intervals between completion of therapy for a given episode and onset of the next of >3 weeks. Timely identification of any underlying pathology is important in such patients for the prevention of further episodes and to improve long-term outcomes. Although bacterial meningitis is believed to result predominantly from invasion of the cerebrospinal fluid (CSF) space via the choroid plexus from blood-borne bacteria, a number of cranial and spinal anatomical defects can allow abnormal communication with the CSF, facilitating migration of bacteria into the intradural and subarachnoid spaces. These portals of entry typically result from defects in the frontal, ethmoid or sphenoid bones (comprising the anterior skull base), or the temporal bone. Such defects may be congenital (relating to mesodermal defects), spontaneous (typically arising at the site of aberrant arachnoid granulations) or secondary (eg, post-traumatic or postsurgical). The patient's history of recurrent episodes of meningitis in the absence of other serious bacterial infections was concerning for an underlying structural etiology. In such patients, evaluation with MRI and/or computed tomography is indicated, with computed tomography cisternography and radionuclide cisternography playing a role when a defect is not identified with initial imaging. Individuals with recurrent bacterial meningitis and no obvious history or clinical findings suggestive of an anatomical abnormality should undergo immunological evaluation. The results of our patient's initial work-up for recurrent meningitis were reviewed. Immunological work-up was normal and, contrary to documentation of a previous normal MRI in multiple reports, there was, in fact, documentation of image distortion due to artifact secondary to dental braces in the radiologist's report. A recommendation to consider repeating the MRI after removal of the dental braces had been made. Given the ongoing concern for a structural abnormality, a repeat MRI was requested and the neurosurgery team was reconsulted. The MRI demonstrated a focal osseous defect of the superior wall of the left frontal sinus and adjacent fovea ethmoidalis/anterior cranial fossa floor with a small associated meningocele. This was highly suspicious for a site of CSF leak. She initially provided no history of trauma, but on repeat questioning, disclosed a fall into a ditch while riding her bicycle at seven years of age (2004) at which time she hit her head on a rock. There was no resultant loss of consciousness and she did not seek medical attention. Based on the MRI findings, a plan for frontal sinus defect repair following completion of therapy for meningitis was made. The patient's blood culture drawn before the empirical administration of antibiotics grew Streptococcus pneumoniae. Further serotyping results identified serotype 23B, a serotype not covered by any available pneumococcal vaccine. Although CSF cultures were negative, polymerase chain reaction-based CSF testing was positive for S pneumoniae. The patient was immunized with the 13-valent pneumococcal conjugate vaccine (Prevnar-13; Pfizer, USA) and the meningococcal conjugate quadrivalent vaccine (Menactra; Sanofi-Pasteur, Canada). Advice was given to provide the 23-valent pneumococcal polysaccharide vaccine eight weeks after administration of Prevnar-13 (1). Pneumococcal vaccination is important in patients with structural abnormalities; one review of the literature (2) found that S pneumoniae accounted for 179 (72%) of 247 culture-positive episodes of meningitis in children with abnormal CSF connections in a cranial location. The patient's spectrum of antibiotics was also narrowed to complete a 10-day intravenous antibiotic course with penicillin. She was subsequently continued on levofloxacin until she underwent bifrontal craniotomy and anterior cranial fossa repair approximately five weeks after presentation of her fourth episode of bacterial meningitis. Adhesions were not visualized intraoperatively; however, biopsies were not taken to assess for chronic inflammation histopathologically. In cases of recurrent bacterial meningitis, the timely identification of an underlying pathology is crucial for the prevention of further episodes and to minimize long-term consequences. Diagnosis of anatomical defects leading to recurrent meningitis can be challenging and multiple radiological investigations may be required for the diagnosis of occult CSF leaks. Furthermore, imaging artifact may interfere with visualization of subtle abnormalities; caution should be taken when interpreting results of imaging studies affected by artifact. Review of a patient's immunization history can provide opportunities for further preventive care.

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