Intra-operative MRI facilitates tumour resection during trans-sphenoidal surgery for pituitary adenomas

Abstract

Background: During trans-sphenoidal microsurgical resection of pituitary adenomas, the extent of resection may be difficult to assess, especially when extensive suprasellar and parasellar growth has occurred. In this prospective study, we investigated whether intra-operative magnetic resonance imaging (iMRI) can facilitate tumour resection.

Methods: Twenty patients with macroadenomas, (16 non-functioning, three growth-hormone secreting and one pharmaco-resistant prolactinoma) were selected for surgery in the iMRI. The mean tumour diameter was 27 mm (range 11-41). The mean parasellar grade, according to the Knosp classification, was 2.3. Pre-operative coronal and sagittal T1-weighted and T2-weighted images were obtained. The trans-sphenoidal tumour resection was performed at the edge of the tunnel of a Signa SP 0.5-Tesla MRI. The surgeon aimed at a radical tumour resection that was followed by a peri-operative MRI scan. When a residual tumour was visualised and deemed resectable, an extended resection was performed, followed by another MRI scan. This procedure was repeated until the imaging results were satisfactory. In all patients, we were able to obtain images to assess the extent of resection and to classify the resection as either total or subtotal.

Results: After primary resection, eight out of 20 cases were classified as total resections. A second resection was performed in 11 of 12 cases classified as subtotal resections, and in four of these, total resection was achieved. A third resection was performed in three of the remaining seven cases with subtotal resections, but we did not achieve total resection in any of these cases. Therefore, the use of iMRI increased the number of patients with total resection from 8/20 (40%) to 12/20 (60%). The only observed complication was a transient spinal fluid leakage.

Conclusion: Intra-operative MRI during trans-sphenoidal microsurgery is useful in selected patients for a safe and more complete resection.

Fig. 1

The surgical set-up with the patient in the supine position. The patient’s head was slightly elevated and rotated and was positioned just outside the MRI scanner. All the instruments were MRI-compatible, including the microscope. During imaging, the speculum was left in place, the resection cavity was filled with saline, and the patient was moved approximately 50 cm into the scanning position

Fig. 2

MRI pictures from the surgery of patient 4, who had bilateral visual field deficits and was normopit pre-operative. At 3 months follow-up, the visual fields were normalised, and the patient was still normopit. a Pre-operative T1 without contrast in the Signa SP 0.5-Tesla scanner. b Intra-operative T2 after primary resection. c Intra-operative T1 with contrast enhancement after extended resection showing a suspect remnant in the right side of the sella. d Three months post-operative follow-up showing subtotal resection with a remnant in the right side of the sella