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Nasal swabbing to test for COVID-19 may have caused a patient to begin leaking cerebrospinal fluid (CSF), researchers reported.

The woman in her 40s underwent testing prior to an elective hernia repair, and shortly thereafter developed a variety of symptoms, including unilateral rhinorrhea, headache, and vomiting, but her nasal drainage tested positive for β2-transferrin, reported Jarrett Walsh, MD, PhD, of University of Iowa Hospitals and Clinics in Iowa City, and colleagues.

"To our knowledge, this is the first report of an iatrogenic CSF leak after a nasal swab for COVID-19," they wrote in a letter in .

Key to the patient's case was that she had a history of removal of nasal polyps for 20 years, and when the authors performed a CT scan and MRI, they found a 1.8-cm encephalocele, or a sac-like formation consisting of CSF, brain tissue, and membranes, which dated back to 2017. However, the patient's 2017 CT diagnosis was para-nasal sinus disease, not an encephalocele.

The patient also had idiopathic intracranial hypertension, a disorder related to high pressure in the brain where CSF can build up, mimicking signs of a brain tumor. She also had an "undiagnosed skull base defect," but the swab did not break through there. Instead, it "caused trauma to the patient's preexisting encephalocele," Walsh and colleagues explained.

The case illustrates how "prior surgical intervention, or pathology that distorts normal nasal anatomy, may increase the risk of adverse events associated with nasal testing for respiratory pathogens, including COVID-19," the researchers wrote.

Symptoms at presentation included unilateral rhinorrhea, metallic taste, headache, neck stiffness, and photophobia. After imaging identified the encephalocele, the patient was admitted for endoscopic surgical repair. The encephalocele was reduced, the skull base defect was repaired, and the patient was admitted postoperatively for "neurological monitoring and lumbar drain management."

As COVID-19 testing continues to increase, Walsh's group stressed the importance of properly training clinicians, and even the general public, to safely perform nasal and nasopharyngeal swab testing, though they warned that "adverse events may still occur owing to complex and delicate anatomy," which have not been well described in the existing literature.

Clinicians should be mindful of patients with prior surgical intervention when testing for COVID-19, the researchers concluded: "One should consider alternative methods to nasal screening in patients with known prior skull base defects, history of sinus or skull base surgery, or predisposing conditions to skull base erosion."

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