MR Venography in Gamma Knife Radiosurgery for Parasagittal Meningiomas: A Technical Note with the Rationale of Venous Protection and a Review of Literature

Radiosurgical Decompression of Trigeminal Nerve and Its Correlation with Functional Outcome in Tumor-Related Trigeminal Neuralgia

BACKGROUND

Target selection during Gamma Knife radiosurgery (GKRS) in cases of tumor-related trigeminal neuralgia is always debatable. We analyzed the correlation of regression of tumor size and degree of release of the nerve with long-term pain control.

METHODS

Between March 2012 and March 2023, 50 cases of tumor-related trigeminal neuralgia were treated with GKRS (tumor was targeted). Radiological findings after GKRS were categorized into 3 types: 1) tumor volume remained same or decreased, additional segment of nerve not seen; 2) tumor volume decreased, additional segment of trigeminal nerve seen, but tumor still adherent to the nerve; 3) tumor volume decreased, adjacent nerve seen completely separated from tumor. Pain score before and after GKRS (Barrow Neurological Institute I-III: good; Barrow Neurological Institute IV and V: poor) was correlated with these subgroups.

RESULTS

At median follow-up of 46.5 months, 18 cases showed type 1 radiological response, 23 showed type 2 response, and 9 showed type 3 response. Good pain control was achieved in 10 (55.5%) patients with type 1, 15 (65.21%) with type 2, and 7 (77.8%) with type 3 responses. The outcome differences among these 3 groups were not statistically significant (P = 0.519). Five patients with type 3 radiological response were off medication, which was statistically better than type 1 and type 2 radiological responses, with 3 patients (P = 0.012) and 2 patients (P = 0.002), respectively, still receiving medication.

CONCLUSIONS

Tumor volume reduction after GKRS may be associated with good pain control in tumor-related trigeminal neuralgia. Further, this allows visualization of additional segment of nerve that can be targeted in a second session for treating recurrent or failed cases.

Morphology of intra tumoral cystic vestibular schwannoma and their response to gammaknife radiosurgery

BACKGROUND

Cystic vestibular schwannoma (CVS) traditionally considered as poor responder to gammaknife radiosurgery (GKRS). Their longterm radiobiological behavior is less known. Here we discuss 38 cases with intra tumoral cyst CVS primarily treated with GKRS. Tumor morphology was assessed to understand their response to GKRS.

METHODS

Total 38 patients(21 male and 17 female with median age of 41.7 years) of CVS treated with GKRS were retrospectively analysed. Tumors were divided as predominantly (greater than50% of total tumor volume) cystic or solid. They were subclassified as type 1 (predominantly cystic CVS, single cyst), type 2 (predominantly solid CVS, single cysts), type 3 (multicystic CVS). The entire cyst was incorporated for radiosurgery. The results were compared with volume matched control of 58 solid tumors(SVS).

RESULT

The median tumor volume of CVS was 5.8 cc. The median tumor volume reduction was 44.5 % at a median follow-up of 68.5 months (30-110 months). Median tumor volume reduction was 68.5 %, 34.0%, 11.0.%, 30.5% at a median follow up of 52.5months, 66 months, 78.6 months, 96.5 months for type 1 CVS, type 2 CVS, type 3 CVS and SVS respectively. One patient with multicystic CVS showed increased tumor volume and expired after 9 months of surgery.The tumor volume reduction in type 1CVS was statistically significant as compared to type 3 CVS and SVS. However the tumor volume reduction among other groups did not differ significantly.

CONCLUSION

Intra tumoral cystic components respond better to gammaknife radiosurgery in CVS. Tumor with single cyst respond better than multicystic vestibular schwannoma.

Utility of MRI in surgical planning for parasagittal meningiomas

BACKGROUND

Surgical resection is the standard treatment for parasagittal meningioma (PSM), but complete resection may be challenging due to superior sagittal sinus (SSS) involvement. The SSS may be partially or completely obstructed, and collateral veins are commonly present. Thus, knowing the status of the SSS in PSM cases prior to treatment is essential to a successful outcome. MRI is utilized prior to surgery in order to determine SSS status and to check for presence of collateral veins. The objective of this study is to evaluate the reliability of MRI in predicting both SSS involvement and presence of collateral veins in subsequent comparison to actual intra-operative findings, and to report on complications and outcomes.

METHODS

27 patients were retrospectively analyzed for this study. A blinded radiologist reviewed all pre-operative images, noting SSS status and collateral vein presence. Intraoperative findings were obtained from hospital records to similarly categorize SSS status and collateral vein presence.

RESULTS

Sensitivity of the MRI to SSS status was found to be 100% and specificity was 93%. However, sensitivity and specificity of MRI to collateral vein presence was only 40% and 78.6%, respectively. Complications were experienced by 22% of patients, the majority neurologic in nature.

CONCLUSION

MRI accurately predicted SSS occlusion status, but was less consistent in identification of collateral veins. These findings suggest MRI should be used with caution prior to PSM resection surgery particularly with regards to the presence of collateral veins which may complicate resection.