Magnetic Resonance Imaging Evaluation of the Position of the Cerebellar Tonsil before and after Posterior Spinal Fusion in Adolescent Idiopathic Scoliosis
Abstract
Objective: To evaluate variations in cerebellar tonsil position after posterior spinal fusion (PSF) in neurologically intact patients with adolescent idiopathic scoliosis (AIS). Methods: We retrospective evaluated 40 patients with AIS and no neurological symptoms that underwent PSF. Anteroposterior and sagittal standing radiographs, and sagittal hindbrain MRI were performed in all patients before and after spinal surgery. The level of the cerebellar tonsil relative to the magnum foramen was measured according to the method described by Aboulezz (J Comput Assist Tomogr 1985). We evaluate variations in cerebellar tonsil position in relation to spinal correction and spinal elongation after PSF.Results: Mean preoperative magnitude of the curve was 53,15° (SD 10,46°) and thoracic kyphosis was 35,42º (SD 12,38°). Mean postoperative values were 7,45º (SD 7,33°) and 27,87º (SD 9,03°), respectively. This represents 86% correction in the coronal plane (p<0.00001) and 25% of kyphosis variation (p<0.00001). The average length of the spine in the coronal plane was 44,5 cm (SD 5,25 cm) in preoperative x-rays and 48,27 cm (SD 4,40 cm) in postoperative x-rays (p<0.00001). The average length in the sagittal plane was 50,87 cm (SD 4,47 cm) in preoperative x-rays and 55,13cm (SD 3,27 cm) in postoperative x-rays (p<0.00001). There was no significant difference in the position of the Cerebellar Tonsil before and after spinal correction (p=0,6042). In 10 (25%) of the 40 patients, we observed caudal displacement in cerebellar tonsil position after PSF. Average displacement in these patients was 1,22 mm (range 0.1-2.3 mm). In 21 patients we did not observe any variation and in 2 a cephalic displacement was measured.Conclusions: In most AIS patients, position of the cerebellar tonsil does not change with PSF. We were not able to find any correlation between curve correction or spine elongation and variations in cerebellar tonsillar position.Downloads
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