Fluid draining from the ear sometimes can arise from your brain. You read that right—from your brain! More precisely, from the fluid that bathes the brain and spinal cord known as cerebral spinal fluid (CSF). We call such a weird phenomenon CSF otorrhea (oto- for “ear,” -rhea for “flow”). Rest assured, CSF otorrhea is quite rare; I’ve diagnosed only about a ½ dozen cases in the past 29 years of practice. Most ear drainage is from infection or inflammation, draining from the ear canal or from a hole in the ear drum (tympanic membrane, abbreviated “TM”), or another source such as ear wax mixed with perspiration secreted from the skin of the ear canal.
In the folks I’ve seen, CSF otorrhea occurred for reasons unknown, with no prior history of head trauma or other insult to one’s noggin (with the exception of one patient who had prior brain surgery). In all these cases, CSF was suspected after a tympanostomy tube was placed. Usually the source of fluid draining through a tympanostomy tube (or a perforation in the TM) arises from inflamed mucosa of the middle ear and/or mastoid. In the case of CSF otorrhea, the CSF that naturally bathes the brain leaks through a defect in the bone that separates the middle ear and mastoid air spaces from the brain above (see the lovely drawing in the title picture).
CSF otorrhea will present as a clear, watery fluid that persistently drains from the ear after a tube is placed. Drainage from an ear infection typically is more viscous, is often colored (yellow, green, gray, tan, bloody or mixture of any or all). Medical treatment does not resolve the drainage. In the case of a watery-like drainage, the doctor must then have a high level of suspicion for CSF otorrhea and additional workup is needed. First, the fluid must be collected for testing. At least one milliliter (ml) of fluid* is required to test for Beta2 transferrin, a protein produced only by the brain and found in no other bodily secretions. It is thus a specific marker for CSF. If this is detected, then the patient has CSF otorrhea.
*(It is difficult to obtain one ml or more of fluid in a single office setting. To accomplish this, we usually give the patient 2 or 3 plastic test-tube containers and instruct them to keep a cotton ball in their ear, especially prior to going to bed. Once the cotton is saturated with fluid, the patient places it into the container and keeps it in their refrigerator. Multiple cotton balls can be collected and placed into a single container. The patient later brings the containers to us, whereon we extract the fluid by placing a cotton ball into a syringe, compress the cotton with the syringe’s plunger to squeeze the fluid out, which we then send for testing.)
If the presence of CSF is confirmed, then imaging with a CT of the temporal bones is needed to locate the defect, which typically is somewhere along the tegmen, the bone that separates the middle ear space and mastoid from the brain above. Note: the middle ear space freely communicates with the mastoid air cells. The tegmen is also the floor of the middle cranial fossa, a space in the cranium that holds the lateral part of the brain. The picture below shows a sagittal slice of the right ear of a patient with CSF otorrhea.
This particular patient required surgery via a middle fossa craniotomy, approaching the defect by opening the skull from above the ear, retracting the brain away from the defect, removing small amount of herniated brain (removing this small amount of devitalized gray matter does not cause mental or cognitive deficiencies), and the defect is repaired, usually using the patient’s own tissue to close and reinforce the defect. This type of surgery is done by a neuro-otology subspecialist and neurosurgeon. Sometimes a lumbar drain is placed to decrease the CSF pressure to allow the surgical site to properly seal and prevent re-leakage.
Another surgical approach is through a mastoidectomy, where an incision is made behind the ear, a drill is used to open the mastoid bone and into the mastoid air spaces to create a single cavity, whereupon the tegmen defect is exposed and repaired from below. At times, abdominal fat (harvested through a small incision from one’s belly) is used to fill the drilled-out mastoid cavity to reinforce the repair.
Again, this is a rare condition, does not happen with an intact TM (in cases with no tube or hole in the TM, the fluid is trapped behind the TM, which necessitates the placement of the tympanostomy tube). Whether it drains from a hole in the TM or stays trapped in the middle ear and mastoid, the defect must be repaired, otherwise the patient is at risk for serious illness such as meningitis (infection of the meninges, the membrane that lines the inside of the skull and spinal canal), a brain abscess, seizures or death.
Don’t freak out if your ear is draining: remember, most do not have CSF otorrhea. Some folks with normal ears and intact TMs can experience ear drainage, feeling it with their fingers or seeing it on their pillow if perchance they slept on their side, ear facing down. Don’t panic and immediately assume you have a CSF leak (I’ve had a number of patients worried about this—too much surfing the internet). Oftentimes, clear ear drainage can occur from perspiration made by the modified sweat glands naturally found in the ear canal that typically produce ear wax (cerumen), or from a process of condensation where moisture created from the skin lining the canal collects in an occluded space if one lies upon that ear.
©Randall S. Fong, M.D.
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