COVID-19 test caused man's 9-month-long brain fluid leak

A man's persistently runny nose following a COVID-19 test wasn't caused by allergies as he suspected, but rather cerebrospinal fluid leaking from his brain, according to a new report.

The man, who lives in the Czech Republic, received a COVID-19 nasal swab test in March 2020 after he had contact with a person infected with COVID-19, according to the report, published Thursday (Sept. 9) in the journal JAMA Otolaryngology–Head & Neck Surgery. The man's test was negative, but afterward he experienced a runny nose from just his right nostril. This symptom, which the patient mistakenly thought was due to allergies, lasted for months before he went to see a doctor in December 2020.

A CT scan of his skull showed that the man had an injury to the cribriform plate, a spongy bone that separates the nose and the brain. He was diagnosed with a cerebrospinal fluid (CSF) leak, a rare but serious condition in which the clear fluid that surrounds the brain and spinal cord leaks through a defect in the skull and out through the nose, according to Johns Hopkins University. Typically, the leakage happens from just one side of the nose, according to the Cleveland Clinic.

CSF leaks are dangerous because they can increase the risk of meningitis, which is an infection of the membranes that surround the brain and spinal cord. Still, patients can have a CSF leak for years before they develop serious problems, Live Science previously reported. 

Related: 10 things you didn't know about the brain

CSF leaks can have a number of causes, including head injury or brain or sinus surgery. In this case, the man's CSF leak was likely an extremely rare complication caused by his March 2020 COVID-19 test. The man had received a nasopharyngeal COVID-19 test, in which a healthcare provider takes a sample from deep inside the nose, where the nasal cavity meets the upper part of the throat, according to the Food and Drug Administration. Such tests are known to be uncomfortable, and they have been referred to as "brain scrapers." However, although these tests may feel strange and result in symptoms such as watery eyes,  they shouldn't be painful, according to the Virginia Department of Health.

What's more, although the nasopharyngeal test was the main testing method used early in the pandemic, such tests have become less common following the development of other tests that can detect COVID-19 using samples collected from the front part of the nose, according to The Conversation.

It's also important to note that only a handful of CSF leak cases linked with COVID-19 tests have been reported worldwide since the pandemic began, out of the hundreds of millions of COVID-19 tests conducted. In the Czech Republic, 25 million COVID-19 tests were conducted between March 2020 and May 2021, according to the JAMA report. (In the U.S., more than 539 million tests have been conducted since the pandemic began, according to data from the Centers for Disease Control and Prevention.)

Two previously reported cases of CSF leaks tied to COVID-19 testing were in people who had existing defects in their skull base, which increased their risk of this complication, the report said. In one of those cases, described in the April 2021 issue of the Journal of Clinical Neuroscience, the authors believe that the nasal swab was also "inserted at an incorrect angle." 

The new report appears to be the first case of a CSF leak following COVID-19 testing in which the patient didn't have a preexisting skull defect. A CT scan performed on the man in 2011 showed no defects, the JAMA report said.

The man needed surgery to close the cribriform plate injury, along with a prescription for antibiotics to prevent infection. The man recovered well without complications from his surgery, but at a follow-up appointment three weeks later, he reported that he could not smell out of his right nostril, the report said.

Originally published on Live Science.