Abnormal and ectopic spinal neural tubes may be regarded as variant forms of NTDs as it may be possible that the neural tube reopens after closure due to various reasons. Ectopic neural tube may take on many different variations apart from the expected second or multiple neural tubes. Among them are a neural tube positioned above another neural tube as well as a wavy neural tube phenotype that is observed in many knockout mice with NTDs. The wavy region in these knockout mice has not had its spinal neural tube sectioned; thus it remains unknown whether the neural tube remains adhered. Spina bifida occulta in humans is usually accompanied by various physical abnormalities such as lipoma, rachischisis, hair tufts, ectodermal sinuses, skin pigmentation, or diastematomyelia. These associated defects occur in either syndromic or nonsyndromic NTDs. However, they may be missed and not categorized properly in cases of transgenic mice with possible NTDs. There is only one example of a null mouse in which these abnormalities have been well described which is the Gcm1 mouse mutant that exhibits both open (meningomyelocele) and close (lipoma and diastematomyelia) spina bifida in its litters .