Foramen magnum growth curves in achondroplasia and in the general population are presented. The achondroplastic foramen magnum is small at birth, and during the first year it has a severely impaired rate of growth especially in the transverse dimension. This markedly diminished growth results not only from abnormal endochondral bone growth but also because of abnormal placement and premature fusion of the synchondroses. Evaluation of the foramen magnum in achondroplasia should address absolute size of the transverse and sagittal dimensions, shape, and growth centers to determine growth potential of this area. KEYWORDS: foramen magnum stenosis, craniocervical stenosis, foramen magnum normal curves, foramen magnum achondroplasia curves

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Many chromosomal abnormalities have craniofacial manifestations. One such abnormality, partial monosomy of chromosome 11q, is associated with metopic synostosis and resultant trigonocephaly. We reviewed 48 published cases of 11q deletions and translocations. Eighty percent were associated with abnormal head shape. Also commonly found were hypertelorism, ptosis of the eyelids, wide or low nasal bridge, apparently low-set malformed ears, down-turned mouth, micro/retrognathia, digital and cardiac anomalies, and psychomotor retardation. We report on two patients referred for abnormal head shape. The first case had brachycephaly, flat occiput, hypertelorism, and maxillary hypoplasia. Karyotype was 46,XY,del(11)(q24.1-->qter). The second patient had trigonocephaly, hypotelorism, posteriorly angulated ears, horizontal crease below his lower lip, syndactyly, shawl scrotum, cryptorchidism, and inguinal hernias. Karyotype showed partial trisomy of chromosome 4q as well as partial monosomy of 11q [46,XY,11,+der(11)t(4;11) (q31.3;q25)], a combination not previously reported. Deletions of 11q appear to produce a wide spectrum of abnormalities.