Comparison of intraoperative and post-operative 3-T MRI performed at 24-72 h following brain tumour resection in children.

PURPOSE: Intraoperative MRI (ioMRI) is a valuable tool aiding paediatric brain tumour resection. There is no published evidence comparing the effectiveness of the final intraoperative MRI and early post-operative (24-72 h) MRI as baseline scans following brain tumour resection. We aimed to evaluate whether the final ioMRI scan could serve as the post-operative baseline scan after paediatric brain tumour resections. METHODS: This prospective study compared the final ioMRI scan with the immediate post-operative MRI scan performed 24-72 h post-surgery. We included 20 patients aged 6.6-21 years undergoing brain tumour resection using ioMRI and were suitable for MRI scan without general anaesthesia. The scans were independently evaluated by experienced local and external paediatric neuroradiologists. Identical sequences in the final ioMRI and the 24-72-h MRI were compared to assess the extent of resection, imaging characteristics of residual tumour, the surgical field, extent of surgically induced contrast enhancement, and diffusion abnormalities. RESULTS: In 20 patients undergoing intraoperative and early post-operative MRI, there was no difference between ioMRI and 24-72-h post-op scans in identifying residual tumour. Surgically induced contrast enhancement was similar in both groups. There were more abnormalities on diffusion imaging and a greater degree of oedema around the surgical cavity on the 24-72-h scan. CONCLUSION: The final 3-T ioMRI scan may be used as a baseline post-operative scan provided standard imaging guidelines are followed and is evaluated jointly by the operating neurosurgeon and neuroradiologist. Advantages of final ioMRI as a baseline scan are identified.

Diffusion abnormalities on intraoperative magnetic resonance imaging as an early predictor for the risk of posterior fossa syndrome.

BACKGROUND: Posterior fossa syndrome (PFS) is an important complication of posterior fossa surgery in children. The pathophysiology of this condition remains unclear, but there is evidence implicating surgical injury of the proximal efferent cerebellar pathway (pECP) and the cerebellar vermis to PFS. We aimed to evaluate if diffusion abnormalities involving these structures on the final intraoperative MRI can predict the development of PFS. METHODS: Diffusion-weighted imaging from 31 posterior fossa resections were anonymized and evaluated for abnormalities involving the dentate nucleus, superior cerebellar peduncle, and the mesencephalic tegmentum forming the pECP, vermis, and middle cerebellar peduncle. The case notes were independently evaluated for evidence of PFS. RESULTS: The diffusion imaging in 28 cases was of optimal quality for evaluation. Diffusion abnormalities were identified in 10 cases, 7 of which involved the pECP. Retrospective evaluation revealed evidence of PFS in 6 cases. There was a significant association between abnormalities involving pECP structures (P = .001) and development of PFS. Bilateral involvement of pECP (P = .006) was a highly specific risk factor for predicting the development of PFS. Diffusion abnormality of the inferior vermis was significantly associated with PFS (P = .001) but may not represent a risk factor in isolation. CONCLUSION: This study demonstrates the feasibility of identifying children at risk for developing PFS at the earliest stage post tumor resection and thus adds to the growing evidence base on its pathophysiology.

Intraoperative 3-Tesla MRI in the management of paediatric cranial tumours--initial experience.

BACKGROUND: Intraoperative MRI (ioMRI) has been gaining recognition because of its value in the neurosurgical management of cranial tumours. There is limited documentation of its value in children. OBJECTIVES: To review the initial experience of a paediatric 3-Tesla ioMRI unit in the management of cranial tumours. MATERIALS AND METHODS: Thirty-eight children underwent ioMRI during 40 cranial tumour resections using a 3-Tesla MR scanner co-located with the neurosurgical operating theatre. IoMRI was performed to assess the extent of tumour resection and/or to update neuronavigation. The intraoperative and follow-up scans, and the clinical records were reviewed. RESULTS: In 27/40 operations, complete resection was intended. IoMRI confirmed complete resection in 15/27 (56%). As a consequence, surgical resection was extended in 5/27 (19%). In 6/27 (22%), ioMRI was equivocal for residual tumour. In 13/40 (33%) operations, the surgical aim was to partially resect the tumour. In 7 of the 13 (54%), surgical resection was extended following ioMRI. CONCLUSION: In our initial experience, ioMRI has increased the rate of complete resection, with intraoperative surgical strategy being modified in 30% of procedures. Collaborative analysis of ioMRI by the radiologist and neurosurgeon is vital to avoid errors in interpretation.