The estimated incidence is at 1:1000-2000 live births 2.
A constellation of features can occur and these depend on the severity of spinal bifida and any associated CNS defects. Common symptoms include:
- back pain
- bladder or bowel incontinence
- spinal or lower limb deformities
The aetiology is often multifactorial with both genetic and environmental factors considered to play a role. Intake of adequate amounts of folic acid plays a protective role.
There are many ways of classifying a spina bifida. One method is according to extent or the defect and is as:
- spina bifida aperta/spina bifida operta: defect can be open or closed, commoner
- spina bifida occulta: mildest form
Another method is based on position as being anterior (ventral) or posterior (dorsal). The vast majority of cases comprise of dorsal spina bifida.
A spina bifida can also be subtyped as:
- open: (80-90%) especially if detected antenatally 4
- closed: if covering skin present
While it can occur anywhere along the spine 14:
- lumbosacral region (90%)
- cervical region (2-3%)
- maternal alpha feto protein (MSAFP): elevated in 80% of open spina bifida (and normal in most fetuses with closed spine bifida) 15.
Associated anomalies can occur in up to 40% of cases (especially if detected antenatally). They include:
- aneuploidic syndromic
- non-aneuploidic syndromic
- CNS anomalies
- limb anomalies
- valproate embryopathy
- neurenteric cysts: particularly with ventral spina bifida
Ultrasound generally has a high detection rate for spina bifida and may show dorsal ossification centers / lateral pedicles as being splayed apart (which can give a V-shaped appearance to the posterior elements).
Ancillary intracranial sonographic findings:
- lemon sign: considered to have a strong association with spina bifida 2
- banana sign: the appearance of the cerebellum wrapped around the medulla as part of a Chiari malformation
Notably, closed and skin covered spinal lesions typically do not have any associated cranial abnormality. A normal cranial ultrasound therefore does not exclude a neural tube defect.
Treatment and prognosis
The overall prognosis is variable depending on the type and extent. For an isolated spina bifida, the recurrence risk range for future pregnancies is thought to be around 0.3-5% 12-13. Maternal intake of folic acid in subsequent pregnancies may again reduce the risk significantly.
- lower limb dysfunction
- development of neurogenic bladder 10
History and etymology
The term spina bifida derives from the Latin words: bifida = split and spina = spine.
Congenital spinal abnormalities
- spinal dysraphism
- 1. Mcconnell JR, Holder JC, Mawk JR et-al. Spina bifida: the radiology of neural tube defects. Curr Probl Diagn Radiol. 15 (4): 241-76. - Pubmed citation
- 2. Thomas M. The lemon sign. Radiology. 2003;228 (1): 206-7. doi:10.1148/radiol.2281020448 - Pubmed citation
- 3. Nakahara T, Uozumi T, Monden S et-al. Prenatal diagnosis of open spina bifida by MRI and ultrasonography. Brain Dev. 15 (1): 75-8. - Pubmed citation
- 4. Ghi T, Pilu G, Falco P et-al. Prenatal diagnosis of open and closed spina bifida. Ultrasound Obstet Gynecol. 2006;28 (7): 899-903. doi:10.1002/uog.3865 - Pubmed citation
- 5. Appasamy M, Roberts D, Pilling D et-al. Antenatal ultrasound and magnetic resonance imaging in localizing the level of lesion in spina bifida and correlation with postnatal outcome. Ultrasound Obstet Gynecol. 2006;27 (5): 530-6. doi:10.1002/uog.2755 - Pubmed citation
- 6. Nicolaides KH, Campbell S, Gabbe SG et-al. Ultrasound screening for spina bifida: cranial and cerebellar signs. Lancet. 1986;2 (8498): 72-4. Lancet (link) - Pubmed citation
- 7. Campbell J, Gilbert WM, Nicolaides KH et-al. Ultrasound screening for spina bifida: cranial and cerebellar signs in a high-risk population. Obstet Gynecol. 1987;70 (2): 247-50. - Pubmed citation
- 8. Rodríguez JI, García M, Morales C et-al. Trisomy 13 syndrome and neural tube defects. Am. J. Med. Genet. 1990;36 (4): 513-6. doi:10.1002/ajmg.1320360429 - Pubmed citation
- 9. Babcook CJ, Ball RH, Feldkamp ML. Prevalence of aneuploidy and additional anatomic abnormalities in fetuses with open spina bifida: population based study in Utah. J Ultrasound Med. 2000;19 (9): 619-23. J Ultrasound Med (abstract) - Pubmed citation
- 10. Aguilera S, Soothill P, Denbow M et-al. Prognosis of spina bifida in the era of prenatal diagnosis and termination of pregnancy. Fetal. Diagn. Ther. 2009;26 (2): 68-74. doi:10.1159/000238116 - Pubmed citation
- 11. Andronikou S, Wieselthaler N, Fieggen AG. Cervical spina bifida cystica: MRI differentiation of the subtypes in children. Childs Nerv Syst. 2006;22 (4): 379-84. doi:10.1007/s00381-005-1165-x - Pubmed citation
- 12. Czeizel A, Métneki J. Recurrence risk after neural tube defects in a genetic counselling clinic. J. Med. Genet. 1984;21 (6): 413-6. J. Med. Genet. (link) - Free text at pubmed - Pubmed citation
- 13. Creasy RK, Resnik R, Iams JD. Maternal-fetal medicine, principles and practice. W B Saunders Co. (2004) ISBN:0721600042. Read it at Google Books - Find it at Amazon
- 14. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 15. Chen CP. Prenatal diagnosis, fetal surgery, recurrence risk and differential diagnosis of neural tube defects. Taiwan J Obstet Gynecol. 2008;47 (3): 283-90. doi:10.1016/S1028-4559(08)60125-4 - Pubmed citation