Caudal agenesis and associated caudal spinal cord malformations.

Caudal agenesis is a rare congenital anomaly resulting from an insult to the structures of the caudal eminence. It may be associated with anomalies of other structures derived from the caudal eminence: the hindgut and the urogenital system. Patients are more likely to present first to the pediatric surgeon (for evaluation of gastrointestinal anomalies), the urologist (for urogenital malformation or dysfunction), or the orthopedic surgeon (for lower extremity abnormalities), than to the neurosurgeon. Characteristic external features of the buttocks, hips, and lower extremities may suggest the diagnosis. MR imaging is the diagnostic modality of choice and should be used in all patients with suggestive external features or other caudal anomalies. The level of bone anomaly corresponds well to the level of weakness but not sensory loss. Sensation is usually relatively preserved. The caudal spinal cord is often truncated in cases of high bone lesions and tethered, with occasional association with a dysraphic lesion, in cases of low bone lesions. Early neurosurgical intervention is preferred in all cases of recognized occult spinal dysraphism. Progressive neurologic deficits may develop later in life in patients with unrecognized tethered cord or dural stenosis and require neurosurgical repair on diagnosis. A better understanding of the embryology of the caudal region and investigation of the teratogens that may interfere with this stage of development should lead to more effective treatment and prevention of caudal agenesis and the associated caudal anomalies.