The Meniscus Sign: An Endoscopic Finding of Cerebrospinal Fluid Rhinorrhea

Introduction: Cerebrospinal fluid (CSF) rhinorrhea is typically diagnosed with biochemical assays and imaging studies. Other than direct visualization of a cranial base defect, no specific endoscopic findings have been described to support the diagnosis of a CSF fistula. We describe a series of cases with confirmed CSF rhinorrhea presenting with a focus of clear fluid in a nondependent location resembling a meniscus on nasal endoscopy. This unique endoscopic finding may assist with the evaluation and diagnosis of patients with suspected CSF rhinorrhea.

Methods: Retrospective case series of five adult patient (age ≥ 18 years) who were evaluated in a tertiary rhinology practice for an anterior cranial base CSF fistula confirmed by β-2 transferrin assay. Images from endoscopic nasal examinations were evaluated for the presence of a meniscus sign, defined as an isolated focus of nonpurulent fluid between two mucosal surfaces at an atypical, nondependent location within the nasal cavity

Results: Five patients were identified with endoscopic findings consistent with a meniscus sign. All patients had documented skull base defects (cribiform plate, ethmoid roof, or sphenoid sinus) confirmed either through imaging or at the time of surgical exploration and intervention. The meniscus sign was localized to the side of the skull base defect in all patients.

Conclusion: This case series describes a potentially useful finding to support the diagnosis of CSF rhinorrhea. The finding of fluid suspended between two mucosal surfaces is rarely seen on nasal endoscopy and suggests the presence of fluid with surface tension that differs from nasal mucus.

Fig. 1 (A) Nasal endoscopy of left nasal cavity demonstrating a fluid meniscus between the nasal septum and middle turbinate. (B) Nasal endoscopy of left nasal cavity demonstrating a fluid meniscus at the axilla of the middle turbinate.

Publication History

Article published online:
12 February 2021