The use of gated cine phase contrast and MR venography in achondroplasia

Objects: Foramen magnum and jugular foramen stenosis, well-known problems i n achondroplasia, may result in brain stem compression and venous outflow o bstruction, respectively. We studied a series of children with achondroplas ia using gated cine phase contrast (PC) CSF flow studies to evaluate CSF dy namics across the foramen magnum and MR venography (MRV) to depict obstruct ed venous drainage. Methods: Ten patients (9 months to 11 years, mean 2.85 years) were referred for possible brain stem compression. MRI included rout ine sequences, cine PC with velocity encoding (VENC) = 5 cm/s, and MRV. Six patients, including the asymptomatic patient, had brain stem compression w ithout tonsillar herniation; two had tonsillar herniation; and two had neit her brain stem compression nor tonsillar herniation. Abnormal tonsillar mov ement was seen only with tonsillar herniation. MRV showed steno-occlusive d isease of the internal jugular vein (IJV) in nine patients, sigmoid sinus i n four, and absent or hypoplastic transverse sinus in seven. Veno-occlusive disease was not progressive. No patient had massive hydrocephalus, althoug h larger ventricles were associated with more profuse venous collateral for mation and more severe degrees of IJV stenosis. Three patients have undergo ne CSF diversion. Conclusions: MR imaging may be useful in defining the pat hophysiology of brain stem compression and hydrocephalus in achondroplasia.