A 32-year-old patient comes in with a complaint of right-sided hearing loss. He states that his hearing has been low for the past six years on the right side. He had two episodes of meningitis in the past year. He has had two surgeries on the temporal lobe of the brain to help improve previous seizure problems. His last surgery was two years ago. He was already seen by two other otolaryngologists who noted that he may have Eustachian tube dysfunction. His examination shows some serous-like fluid in the right ear. His audiogram is on the right (Fig. 1). What is your diagnosis?
Diagnosis: Recurrent Meningitis With CSF Leak
Meningitis is a life-threatening condition that causes infection of the meninges, or the membranes that cover the brain. It is usually bacterial in origin. Bacteria can reach the brain through two mechanisms. First is hematogenous, which is the spread of bacteria to the brain's covering through the bloodstream. This is usually the reason behind meningitis cases that occur in clusters, infecting one person to another. The other mechanism of meningitis development is when bacteria reaches the meninges due to an infection in an adjacent structure. Given the proximity of the sinuses, ears, and temporal bone, infections in these areas can potentially spread to the brain and cause meningitis. However, there are patients who develop meningitis without any active infection in the ear or sinuses. These are patients who have an abnormal opening in the meninges, allowing a direct spread of bacteria from the ear or sinuses to the brain. This particularly happens in patients who have cerebrospinal fluid (CSF) leakage.
The brain and the spine are surrounded by CSF. An average human has approximately 150 mL of CSF. One of the functions of the CSF is to clear some of the metabolic byproducts from the brain. Another function is to cushion the brain from being traumatized by movement within the skull. The body continually reabsorbs and makes new CSF. In fact, the body makes approximately 450 milliliters of CSF per day, all of which have to be reabsorbed. The mechanism to reabsorb CSF is located within the lining of the meninges, which recycles the fluid into the bloodstream. Any disturbance in the reabsorption process can lead to an increase in brain fluid pressure, and consequently, to possible CSF leakage (Am J Otolaryngol. 2012;33:556 http://bit.ly/2lBz7EG).
Cerebrospinal fluid appears as a clear or slightly yellow fluid. When present in the middle ear, it can resemble a serous middle ear effusion. A clinician has to be diligent when evaluating a patient with no history of Eustachian tube dysfunction, upper respiratory infection or allergies, or middle ear effusion. Patients with recurrent meningitis caused by one of the respiratory bacteria (e.g., Streptococcus pneumonia, Haemophilus influenzae, or Moraxella catarrhalis) most likely have developed this infection from the ear or sinuses. Fine-cut CT imaging of the ear and sinuses is important to evaluate patients with meningitis. In the presence of infection in the ear or sinuses, a direct extension of the said infection is likely the cause of meningitis. Antibiotic treatment and management of the source of infection are necessary to prevent meningitis from recurring.
In the presence of meningitis, the infected middle ear or mastoid needs to be drained. For the middle ear, a myringotomy and tube placement have to be done immediately if otitis media and meningitis occur concurrently. If a tube could not be placed due to thickened tympanic membrane, a large myringotomy may work to allow continued drainage of the infection from the middle ear.
However, if the middle ear fluid is clear, the patient is most likely suffering from a CSF leakage, which means the bacteria had spread from the nose (nasopharynx) through the Eustachian tube and middle ear into the brain. It is not recommended to place a tube in a patient with meningitis and a serous-like fluid discharge in the ear. This would only create another conduit for the infection to enter the middle ear and the brain in the future. A thorough investigation of the fine-cut CT (0.6 mm cut with window levels of W=4000, L=900) of the temporal bone is necessary to look for any small defect that could allow leakage of the cerebrospinal fluid. Every slice of the CT scan on the axial, coronal, and sagittal directions should be evaluated. Notably, this patient had a previous CT scan of the temporal bone after his second bout of meningitis, but the results were interpreted to show no evidence of defect in the temporal bone.
In a patient who has had previous brain surgery, the most likely site of leakage will be the area of the previous craniotomy. Patients with a history of brain surgery are also at risk of developing an increase in brain fluid pressure because the areas where the CSF is absorbed may get clogged up and damaged by blood during the surgery. This may lead to an increase in brain fluid pressure and cause a breakdown of the temporal bone areas in contact with the dura (covering of the brain).
The patient's imaging shows that the leak is just superior to the external auditory canal, at the site of his previous craniotomy (Figs. 2, 3, 4). The patient's MRI shows herniation of the dura containing cerebrospinal fluid through the site of the craniotomy, sitting in a subcutaneous pocket right above the auricle (Fig. 5). Using a transmastoid approach, we were able to control the CSF leakage using a combination of fascia (covering of muscle) and fat. At the one week post-operative visit, the patient's middle ear was aerated, and his hearing was subjectively normalized.
BONUS VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
* Video 1. Axial CT of the right temporal bone demonstrating the middle ear and mastoid fluid.
* Video 2. Coronal CT of the left temporal bone showing the area of the defect at the lowest aspect of the craniotomy site.
* Video 3. Sagittal CT of the right temporal bone (looking from the outside of the ear inward) showing the leakage site above and anterior to the ear canal.
* Video 4. Coronal T1-weighted post-gadolinium MRI showing no mass present and mildly inflamed meninges.
* Video 5. Axial T2-weighted MRI showing the fluid (white) in the middle ear and mastoid. The MRI cannot distinguish infectious from non-infectious fluid in the mastoid.
* Video 6. Coronal T2-weighted MRI showing the location of the meningocele and its proximity to the temporal bone.
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