Measuring supratentorial and infratentorial area in Chiari I malformation using MRI

Objective To probe pathogenesis of Chiari I malformation by measuring supratentorial and infratentorial area with MRI. Methods 114 patients with tonsillar hernia underwent MRI along midsagittal T1WI, and another 100 patients without diseases in central nervous system underwent the same procedures as control. Results Measured values varied from group to group. As for (hindbrain width × hindbrain length)/(posterior cranial width × posterior cranial depth), the two groups measured 1.42 ±0.60 and 0.95 ±0.20 respectively, the mal- formation group was significantly higher than the control group (P 0.01), and as for(posterior cranial width ×posterior cranial depth), the two groups measured 2027.96 ±584.84 mm2 and 2740.00±565.54 mm2, respectively, and the malformation group was significantly smaller than the control group(P 0.01). Conclusion Patients with Chiari I malformation suffer retardation of occipital bone due to undeveloped mesoderm while development of cerebellum and brainstem remains, causing an over crowded posterior cranial fossa. Thus disorder in bony structure is responsible for Chiari I malformation, having no business with nervous structure.