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A unifying hypothesis for hydrocephalus, Chiari malformation, syringomyelia, anencephaly and spina bifida.

Williams H - Cerebrospinal Fluid Res (2008)

Bottom Line: This occurs because veins are compressible and a CNS volume increase may result in reduced venous blood flow.The flow of CSF has a beneficial effect on venous drainage.Conversely, obstruction to CSF flow causes localised pressure increases, which have an adverse effect on venous drainage.The Chiari malformation is associated with hindbrain herniation, which may be caused by low spinal pressure relative to cranial pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: 19 Elibank Road, Eltham, London, SE9 1QQ, UK. hfw@dircon.co.uk.

ABSTRACT
This work is a modified version of the Casey Holter Memorial prize essay presented to the Society for Research into Hydrocephalus and Spina Bifida, June 29th 2007, Heidelberg, Germany. It describes the origin and consequences of the Chiari malformation, and proposes that hydrocephalus is caused by inadequate central nervous system (CNS) venous drainage. A new hypothesis regarding the pathogenesis, anencephaly and spina bifida is described.Any volume increase in the central nervous system can increase venous pressure. This occurs because veins are compressible and a CNS volume increase may result in reduced venous blood flow. This has the potential to cause progressive increase in cerebrospinal fluid (CSF) volume. Venous insufficiency may be caused by any disease that reduces space for venous volume. The flow of CSF has a beneficial effect on venous drainage. In health it moderates central nervous system pressure by moving between the head and spine. Conversely, obstruction to CSF flow causes localised pressure increases, which have an adverse effect on venous drainage.The Chiari malformation is associated with hindbrain herniation, which may be caused by low spinal pressure relative to cranial pressure. In these instances, there are hindbrain-related symptoms caused by cerebellar and brainstem compression. When spinal injury occurs as a result of a Chiari malformation, the primary pathology is posterior fossa hypoplasia, resulting in raised spinal pressure. The small posterior fossa prevents the flow of CSF from the spine to the head as blood enters the central nervous system during movement. Consequently, intermittent increases in spinal pressure caused by movement, result in injury to the spinal cord. It is proposed that posterior fossa hypoplasia, which has origins in fetal life, causes syringomyelia after birth and leads to damage to the spinal cord in spina bifida. It is proposed that hydrocephalus may occur as a result of posterior fossa hypoplasia, where raised pressure occurs as a result of obstruction to flow of CSF from the head to the spine, and cerebral injury with raised pressure occurs in anencephaly by this mechanism.The current view of dysraphism is that low central nervous system pressure and exposure to amniotic fluid, damage the central nervous system. The hypothesis proposed in this essay supports the view that spina bifida is a manifestation of progressive hydrocephalus in the fetus. It is proposed that that mesodermal growth insufficiency influences both neural tube closure and central nervous system pressure, leading to dysraphism.

No MeSH data available.


Related in: MedlinePlus

Hypothetical graph showing the effect of posterior fossa size on the frequency of dysraphic lesions at different levels in males and females. Higher, more severe, lesions tend to be more frequent in females who have a smaller posterior fossa as illustrated by the curve on the left. Lower, less severe, lesions are more frequent in males with a larger posterior fossa, as illustrated by the curve on the right.
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Figure 6: Hypothetical graph showing the effect of posterior fossa size on the frequency of dysraphic lesions at different levels in males and females. Higher, more severe, lesions tend to be more frequent in females who have a smaller posterior fossa as illustrated by the curve on the left. Lower, less severe, lesions are more frequent in males with a larger posterior fossa, as illustrated by the curve on the right.

Mentions: The proposed hypothesis depends upon restriction of posterior fossa growth as a cause of neural injury with females having a smaller, genetically-determined, average posterior fossa size and cisterna magna CSF space than males. Posterior fossa size will be normally distributed. The genders represented separately will form overlapping curves with males to the right. If genetic or environmental factors that restrict growth of the posterior fossa interact with a normal variation in posterior fossa CSF space, and if the pathogenesis of spina bifida is related to hindbrain compression due to posterior fossa hypoplasia, there will tend to be a difference in severity of lesions between the sexes. Anencephaly will predominate in females, with lower spinal lesions being more common in males. This concept is represented in Fig. 6, and accords with observations on differences between lesion prevalence between the genders [49,67]. This hypothesis allows speculation that smaller CSF spaces in the female are part of a regulatory mechanism leading to smaller head size. With similar fluctuations in spinal venous volume a more spacious posterior fossa in the male may facilitate greater pressure wave transmission into the head resulting in larger fetal head size [68].


A unifying hypothesis for hydrocephalus, Chiari malformation, syringomyelia, anencephaly and spina bifida.

Williams H - Cerebrospinal Fluid Res (2008)

Hypothetical graph showing the effect of posterior fossa size on the frequency of dysraphic lesions at different levels in males and females. Higher, more severe, lesions tend to be more frequent in females who have a smaller posterior fossa as illustrated by the curve on the left. Lower, less severe, lesions are more frequent in males with a larger posterior fossa, as illustrated by the curve on the right.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2365936&req=5

Figure 6: Hypothetical graph showing the effect of posterior fossa size on the frequency of dysraphic lesions at different levels in males and females. Higher, more severe, lesions tend to be more frequent in females who have a smaller posterior fossa as illustrated by the curve on the left. Lower, less severe, lesions are more frequent in males with a larger posterior fossa, as illustrated by the curve on the right.
Mentions: The proposed hypothesis depends upon restriction of posterior fossa growth as a cause of neural injury with females having a smaller, genetically-determined, average posterior fossa size and cisterna magna CSF space than males. Posterior fossa size will be normally distributed. The genders represented separately will form overlapping curves with males to the right. If genetic or environmental factors that restrict growth of the posterior fossa interact with a normal variation in posterior fossa CSF space, and if the pathogenesis of spina bifida is related to hindbrain compression due to posterior fossa hypoplasia, there will tend to be a difference in severity of lesions between the sexes. Anencephaly will predominate in females, with lower spinal lesions being more common in males. This concept is represented in Fig. 6, and accords with observations on differences between lesion prevalence between the genders [49,67]. This hypothesis allows speculation that smaller CSF spaces in the female are part of a regulatory mechanism leading to smaller head size. With similar fluctuations in spinal venous volume a more spacious posterior fossa in the male may facilitate greater pressure wave transmission into the head resulting in larger fetal head size [68].

Bottom Line: This occurs because veins are compressible and a CNS volume increase may result in reduced venous blood flow.The flow of CSF has a beneficial effect on venous drainage.Conversely, obstruction to CSF flow causes localised pressure increases, which have an adverse effect on venous drainage.The Chiari malformation is associated with hindbrain herniation, which may be caused by low spinal pressure relative to cranial pressure.

View Article: PubMed Central - HTML - PubMed

Affiliation: 19 Elibank Road, Eltham, London, SE9 1QQ, UK. hfw@dircon.co.uk.

ABSTRACT
This work is a modified version of the Casey Holter Memorial prize essay presented to the Society for Research into Hydrocephalus and Spina Bifida, June 29th 2007, Heidelberg, Germany. It describes the origin and consequences of the Chiari malformation, and proposes that hydrocephalus is caused by inadequate central nervous system (CNS) venous drainage. A new hypothesis regarding the pathogenesis, anencephaly and spina bifida is described.Any volume increase in the central nervous system can increase venous pressure. This occurs because veins are compressible and a CNS volume increase may result in reduced venous blood flow. This has the potential to cause progressive increase in cerebrospinal fluid (CSF) volume. Venous insufficiency may be caused by any disease that reduces space for venous volume. The flow of CSF has a beneficial effect on venous drainage. In health it moderates central nervous system pressure by moving between the head and spine. Conversely, obstruction to CSF flow causes localised pressure increases, which have an adverse effect on venous drainage.The Chiari malformation is associated with hindbrain herniation, which may be caused by low spinal pressure relative to cranial pressure. In these instances, there are hindbrain-related symptoms caused by cerebellar and brainstem compression. When spinal injury occurs as a result of a Chiari malformation, the primary pathology is posterior fossa hypoplasia, resulting in raised spinal pressure. The small posterior fossa prevents the flow of CSF from the spine to the head as blood enters the central nervous system during movement. Consequently, intermittent increases in spinal pressure caused by movement, result in injury to the spinal cord. It is proposed that posterior fossa hypoplasia, which has origins in fetal life, causes syringomyelia after birth and leads to damage to the spinal cord in spina bifida. It is proposed that hydrocephalus may occur as a result of posterior fossa hypoplasia, where raised pressure occurs as a result of obstruction to flow of CSF from the head to the spine, and cerebral injury with raised pressure occurs in anencephaly by this mechanism.The current view of dysraphism is that low central nervous system pressure and exposure to amniotic fluid, damage the central nervous system. The hypothesis proposed in this essay supports the view that spina bifida is a manifestation of progressive hydrocephalus in the fetus. It is proposed that that mesodermal growth insufficiency influences both neural tube closure and central nervous system pressure, leading to dysraphism.

No MeSH data available.


Related in: MedlinePlus