Foramen Magnum Decompression for Chiari Malformation Type 1: Is There a Superior Surgical Technique?

BACKGROUND: Foramen magnum decompression is a common operation used to treat Chiari malformation. There are different surgical techniques; however, some are anecdotally more effective than others. Our aim was to determine whether there is a superior technique in relation to revision rates, presence of persistent postoperative headache and nausea, and syrinx reduction. METHODS: This was a retrospective analysis of foramen magnum decompressions performed between 2012 and 2017 for Chiari 1 in a single institution. Three types of operations were performed: 1) bony decompression alone; 2) bony decompression with durotomy and dura left open; 3) bony decompression with opening of dura and duraplasty. We compared postoperative symptoms and revision rates between these 3 operations. RESULTS: In 168 patients, 185 foramen magnum decompressions were performed. Among the 168 primary operations, in 66 the dura was not opened, in 86 the dura was opened without a duraplasty, and in 16 a duraplasty was performed. Of 185 operations, 17 were revision surgery. For primary procedures, the revision rates were 12 (18%) where the dura was not opened, 4 (5%) where the dura was left open, and 1 (6%) when duraplasty was performed. Severe postoperative headache and nausea occurred in 2 (3%) patients where the dura was not opened, 4 (25%) patients after primary duraplasty, and 64 (74%) patients after primary durotomy. CONCLUSIONS: In this study, rate of revision surgery was highest in patients who had bony decompression without dural opening. Rate of postoperative headache and nausea was highest in the durotomy group. Overall duraplasty had the best results.

Solid Component Volume as a Proxy to Identify Distinct Hemangioblastoma Populations.

BACKGROUND: Posterior fossa hemangioblastomas usually consist of a small solid nodule with a large cyst, while more rarely they present as a large solid mass with a small or absent cyst, which can be surgically challenging. We sought to investigate the potential existence of multiple distinct hemangioblastoma populations using tumor volumetric data as an indicator. METHODS: We conducted a retrospective review of surgically treated hemangioblastomas between 2005 and 2019 in our unit, including clinical notes, preoperative magnetic resonance imaging volumetric analysis of the solid component of the tumor, and pathology. Finite Gaussian mixture modeling was applied on the solid component volume dataset to identify potential underlying Gaussian distributions with their associated characteristics. Nonparametric Mann-Whitney U tests were used to investigate significance of differences (P < 0.05) in solid component volume and different variables (Von Hippel-Lindau disease, extent of resection, outcome). RESULTS: A total of 68 consecutive patients were included. Solid component volumes followed a multimodal distribution (median = 1287 mm3, interquartile range of 3428 mm3). The best-fit finite Gaussian mixture modeling model identified 3 statistically significant different (P = 0.001) potential mixture components: X1 (219 ± 187 mm3), X2 (2686 ± 1299 mm3), and X3 (10,800 ± 5514 mm3). The second-best model detected 2 significantly different (P = 9.99e-08) mixture components Y1 (222 ± 189 mm3) and Y2 (5391 ± 5094 mm3). A significant difference in solid component volume was found between patients with favorable and unfavorable outcome (P = 0.002). CONCLUSIONS: This study has shown preliminary evidence that large solid hemangioblastomas may constitute a completely distinct population, rather than a variant of one large group of hemangioblastomas.