Oculomotor nerve schwannoma: case series and literature review
Flores, Christopher Robert
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PURPOSE: To develop an algorithm in order to establish a consensus on how oculomotor nerve schwannomas should be treated by reviewing results from reported cases in the literature. Given the rarity of oculomotor nerve schwannomas, there is no agreed upon criteria for when a surgical or a nonsurgical intervention would be indicated. By reviewing former cases of oculomotor nerve schwannomas, our study proposes a flowchart for physicians to follow for optimal management. METHODS: The review of reported oculomotor nerve schwannoma cases involved 51 cases. From the 51 cases, data was tabulated including age, patient symptoms, symptom duration, tumor size, tumor location, treatment, post operative results, and follow up time. The cases were then divided in to surgical subgroup and a nonsurgical subgroup. Each case was also grouped based on post operative oculomotor function into improved, no change, and worsened groups. Our collaboration with Tufts Medical center also yielded 4 unreported cases of oculomotor nerve schwannoma that are described and compared to the previous 51 cases from the literature review. RESULTS: The review of the 51 reported cases yielded a few statistically significance differences between the surgical and nonsurgical subgroups. The surgical subgroup was older with a mean age of 35 years than the nonsurgical subgroup with a mean age of 15.8 years. The surgical group also had larger tumors with a mean tumor diameter of 29.5 mm versus the nonsurgical subgroup's 4.5 mm mean tumor diameter. The surgical subgroup also experienced shorter symptom durations as well. The mean duration of symptoms in the surgical subgroup was 17.8 months versus the 140 month mean symptom duration for the nonsurgical cases. Finally, the majority of surgically treated cases experienced a worsening of residual oculomotor function (20/38), while the majority of nonsurgically treated cases experienced little to no change in oculomotor function (11/13). CONCLUSION: Given the high likelihood of complete third nerve palsy after surgery, this study advocates a conservative approach to oculomotor nerve schwannomas that do not present with any life threatening symptoms or acutely deteriorating symptoms. The cases that are presented in this study also corroborate previous studies' findings on the efficacy of stereotactic radiosurgery in managing schwannoma size without resorting to more invasive interventions.