Background: The endoscopic modified Lothrop procedure (EMLP) has become a frequently utilized procedure in rhinologic surgery. One of the most serious complications of the procedure is cerebrospinal fluid leak, which may occur due to lack of recognition of the anterior skull base in the region of the first olfactory filum (FOF), or direct injury to the FOF itself.
Objectives: To evaluate the position of the head of the middle turbinate (MT) relative to the FOF, which is an important landmark in the EMLP.
Methods: A series of previously obtained patient computed tomography scans of the sinus were reviewed. A reproducible process was implemented to obtain the measurements. First, the FOF was identified on an axial series. Using a localization feature of the radiographic software, this anteroposterior (AP) position could be visualized in a coronal plane. Subsequently, the MT was viewed in a sagittal plane, where a measurement between the head of the MT and the AP position of the FOF could be performed.
Results: The AP distance between the head of the MT and the FOF was measured in 92 patients. The head of the MT was either at or anterior to the FOF in all measured subjects. The mean anterior distance of the head of the MT to FOF was 3.6 mm (±2.4 mm) on the right, and 3.8 mm (±2.2 mm) on the left. The range in AP distance was 0 to 12 mm. There was no significant difference in AP distance between the head of the MT and FOF based on gender (P = .413) or diagnosis (P = .254).
Conclusions: In our study, the head of the MT was reliably at or anterior to the FOF in all subjects, suggesting its utility as a fixed landmark in endoscopic sinus surgery, particularly in the EMLP.
Level of evidence: N/A.
Keywords: Draf III; anterior skull base; cerebrospinal fluid leak; endoscopic modified Lothrop; first olfactory filum; frontal sinus; middle turbinate; revision sinus surgery; rhinology; sinus anatomy.