Olfactory Groove Schwannomas: A Single-Center Experience of 15 Cases with a Comprehensive Review of Clinical Presentation and Surgical Outcomes

Objective: Schwannomas of the anterior cranial fossa (ACF) are exceedingly rare, and their origin remains controversial, with hypotheses suggesting various structures such as the ACF base, olfactory nerve, and olfactory bulb. This debate extends to the classification of olfactory ensheathing cell tumors, creating challenges in the nomenclature. Due to their rarity and location, olfactory groove schwannomas (OGS) are frequently misdiagnosed preoperatively as meningiomas, which are more common in this region. In this study, we present the largest reported series of OGS cases, examining tumor origin, clinical presentations, and surgical outcomes to provide insights into management strategies.

Methods: This retrospective analysis included all cases of olfactory nerve schwannoma treated at our center from 1991 to 2023. We collected clinical and demographic data and reviewed operative notes with radiological imaging using the hospital PACS system. Follow-up data were also retrieved and analyzed for long-term outcomes. Additionally, a systematic literature review was conducted using PubMed and Scopus to identify and compare previously reported cases of OGS. Data from the literature were matched with our findings to provide a broader understanding of these tumors.

Results: A total of 15 patients were identified with OGS. There were nine males and six females, with a mean age of 33.5 years. All patients underwent surgical resection via a subfrontal approach, (either a bifrontal or lateral subfrontal craniotomy). Gross total resection (GTR) was achieved in 14 cases, as confirmed by postoperative MRI, while 1 patient had a subtotal resection. No adjuvant therapy was administered. Postoperatively, five patients experienced olfactory dysfunction, and two patients developed CSF rhinorrhea, which was managed conservatively. One patient required reoperation due to tumor recurrence. The mean follow-up was 9.3 years.

Our literature review identified 82 cases of OGS. The average patient age was 36.8 years, with a male-to-female ratio of 1.2. Headache was the most common presenting symptom (68 cases, 82.9%), followed by preoperative anosmia (48 cases, 58.5%). On imaging, the tumors were predominantly hyperintense on T2-weighted MRI and uniformly showed contrast enhancement. Nasal or paranasal sinus involvement was observed in 28 cases (34.1%). GTR was achieved in 71 out of 77 cases with reported outcomes. Olfactory dysfunction occurred in 31 patients (37.8%) postoperatively. CSF rhinorrhea was seen in 9 patients, with 2 cases progressing to meningitis. Adjuvant radiotherapy was reported in 2 cases, with 1 patient undergoing Gamma Knife radiosurgery and another receiving conformal radiotherapy.

Conclusion: Schwannomas of the ACF base are rare, and patients often present with anosmia or develop olfactory dysfunction following surgery. Approximately 30% of lesions exhibit nasal or paranasal extension, heightening the risk of CSF rhinorrhea or meningitis postoperatively. Although minimally invasive approaches such as endoscopic or supraorbital craniotomies are viable options, GTR remains achievable in most cases with careful planning. Long-term follow-up is essential for detecting early recurrence, where radiosurgery may offer a feasible treatment option. Further research is needed to establish the pathological origins of these tumors.

Publikationsverlauf

Artikel online veröffentlicht:
07. Februar 2025