4 month old with achondroplasia. There is malformation of the skull base with associated frontal bossing in keeping with achondroplasia. In particular, there is narrowing of the foramen magnum and perhaps the jugular foramina. There is an enlarged suprasellar cistern, effacement of the cisterna magna, and a relatively vertical orientation of the straight sinus. The third and lateral ventricles are enlarged, while the fourth ventricle is not enlarged. There is no evidence of intracranial hemorrhage, mass, or acute infarct. The brain parenchyma otherwise appears unremarkable, with a normal degree of myelination. There is prominence of the cerebrospinal fluid spaces overlying the cerebral convexities. There is no midline shift or herniation. There is nonspecific fluid signal within the bilateral mastoid air cells and middle ears.
Malformation of the skull base with associated frontal bossing in keeping with achondroplasia with associated narrowing of the foramen magnum and perhaps the jugular foramina, which may be associated with communicating hydrocephalus.