Objective: To describe tonsillar blackout sign (TBS) on three-dimensional (3D)-SPACE, evaluate its performance in identifying Chiari malformation (CM1) as diagnostic marker, and investigate its role in differentiation of symptomatic and asymptomatic CM1.
Methods: One-hundred fifty-six patients were divided into two groups based on caudal displacement of cerebellar tonsils: CM1 (Group I) and non-CM1 (Group II). Group I was subclassified as symptomatic and asymptomatic by a neurosurgeon. Two radiologists evaluated TBS and cerebrospinal fluid flow abnormality.
Results: All subjects presenting TBS had CM1. Difference in presence of TBS between Group I and Group II was highly significant (P<.001).Grading of TBS in symptomatic patients was significantly higher than that in asymptomatic patients (P<.001).
Conclusion: TBS is highly suggestive of CM1 and potentially useful in differentiation of symptomatic and asymptomatic CM1.
Keywords: 3D T2-weighted high-sampling-efficiency technique (SPACE); CSF flow MR imaging; Chiari I malformation; Tonsillar motion.
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