Modified subtotal lothrop procedure for extended frontal sinus and anterior skull base access: a cadaveric feasibility study with clinical correlates

Abstract

Objective The endoscopic modified Lothrop procedure (EMLP) is an established approach for recalcitrant frontal sinus disease and anterior skull base exposure. However, in select cases, this technique may involve unnecessary resection of sinonasal structures. In this study, we propose a modification of the EMLP, termed the modified subtotal-Lothrop procedure (MSLP), to access the anterior skull base and complex frontal sinus disease for which access to the bilateral frontal sinus posterior table is required. Methods A cadaveric dissection with photo documentation was performed at an academic medical center on four cadaver heads using standard endoscopic techniques to demonstrate the MSLP and its feasibility. Results The endoscopic MSLP allowed ample access for instrumentation in each of the dissections using a 30- or 70-degree endoscope. Adequate bilateral access to the posterior table of the frontal sinus was gained in all cases without the need for dissection of the contralateral frontal sinus recess (FSR). Conclusion The MSLP appears to be a feasible technique for exposure of the anterior skull base and accessing complex frontal sinus pathology. This modification provides similar anterior skull base exposure and surgical maneuverability as the EMLP while limiting surgical dissection to one FSR, thereby preserving as much of the natural mucociliary drainage pathways as possible.

Keywords: Lothrop procedure; cadaveric technique; endoscopic modified Lothrop procedure; extended Draf IIB; modified hemi-Lothrop procedure; modified mini-Lothrop procedure; modified subtotal-Lothrop procedure.

Fig. 1

Endonasal view of cadaveric modified subtotal-Lothrop procedure in cadaver 1. (A) Using a 30-degree endoscope, a right Draf IIB is performed. (B) A superior septectomy is performed and the medial contralateral frontal sinus floor is resected. (C) The intersinus septectomy is subsequently started. (D) View from the contralateral (left) nasal cavity after completion of right Draf II B, superior septectomy, and intersinus septectomy.

Fig. 2

(A) Axial and (B) coronal paranasal sinus computed tomography scans of a patient with a large right frontal sinus encephalocele. The patient underwent endoscopic resection of the encephalocele through an endoscopic modified subtotal-Lothrop procedure (MSLP). (C) Intraoperative 30-degree endoscopic view of the encephalocele after intrathecal fluorescein injection. (D) Seventy-degree endoscopic view of the base of the encephalocele after resection through the MSLP approach.

Fig. 3

(A) Coronal paranasal sinus computed tomography scan and (B) gadolinium enhanced T1-weighted magnetic resonance (MR) imaging of a patient with a large left anterior skull base lesion abutting the midline. This patient underwent endoscopic resection of the lesion using the modified subtotal-Lothrop procedure for anterior skull base exposure with preservation of the right frontal sinus recess. (C) Intraoperative endoscopic view of the modified subtotal-Lothrop procedure using a 30-degree endoscope. (D) Five-months postoperative MR showed enhancement of the nasoseptal flap at the skull base without evidence of recurrence.

Fig. 4

(A) Axial T1-weighted and (B) coronal T2-weighted magnetic resonance imaging (MRI) of a patient with recurrent right cribriform osteoblastoma. (C) Thirty-degree endoscopic view after endoscopic endonasal right hemi-skull base resection using the modified subtotal-Lothrop procedure for exposure. (D) Immediate axial and (E) coronal postoperative computed tomography scans revealed adequate resection with undissected left frontal sinus recess. (F) Four-months postoperative MRI shows no recurrent disease and a patent undissected left frontal sinus recess.