Dr Imelda McGonnell has sent the following report summary, dated May 2009.

Investigation of the presence of Chiari-like malformation and syringomyelia in stillborn Cavalier King Charles Spaniel Foetuses
Chiari-like malformation (CLM) is described as an occipital bone hypoplasia and is a condition that is prevalent in Cavalier King Charles Spaniels (CKCS). It is thought to be an inherited condition that affects growth of the skull. The characteristics of the condition are a compression of the cerebellum which is pushed out of the foramen magnum. Many affected individuals also have syringomyelia (SM) which causes significant pain.

CLM is sometimes described as a condition that is due to altered development before birth, however no investigations have ever taken place to assess if changes in the skull are present at birth. Equally, it is not known if SM is a condition that can be identified in the spinal cord at birth. We have studied the development of the occipital bone and cerebellum in stillborn CKCS foetuses with the aim to discover if CLM/SM can be seen at birth and to begin to define what changes we see in the cells of these tissues. This work will also define the earliest stages at which CM and/or SM could be detected and diagnosed in CKCS.


Anatomical investigations have shown that the occipital bone overlying the cerebellum has an abnormal bulge in the centre. These investigations also show that the cerebellum is compressed in CKCS foetuses at birth. However this compression is not yet sufficient to cause descent of the brain into the foramen magnum. The region of the compression in the brain corresponds to the region where we see the bulge in the bone. It suggests that the abnormal skull is compressing the brain. When we looked at the occipital bone in more detail, using sectioning, we saw that there was a region where there were more cells than normal – this was the region of the bulge. These cells were also immature - they had not formed proper bone. We looked at the part of the spinal cord nearest the brain but did not see SM. We will continue to examine the remainder of the spinal cord.

When we looked at the cerebellum, we also found that there were more cells in parts of the cerebellum. When we counted the numbers of cells that were dividing, they were statistically significantly increased. Usually if there are too many cells being produced, we see lots of cells dying. However we found there were fewer cells dying. Both the increased cell division and reduced cell death make the cerebellum bigger. We also saw that some cells in the cerebellum that control co-ordination of movement were also not properly formed. This all tells us that both the brain and the bone are growing too much and that as a result, some of the cells are more immature at birth than they should be.

This all points to this condition being caused by abnormal cell division. Importantly, it tells us that the brain and bone are not able to communicate with each other. In the normal situation, if the brain was growing too much, the bone should keep up with it. In the CKCS this relationship is lost.

We will follow up these findings by investigating what is controlling the cell division in the brain and bone. We will also investigate why these two tissues are unable to communicate with each other.

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