Universlty of Manitoba, ln Partîal Fulfiìlment - MSpace at the ...

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flat, exposed plaque of neural tissue (a m'¡,e¡6t"¡¡rts or neuroschlsls).
ln most èases thls open plaque undergoes secondary changes. Accumulation
of fluld (which elevates and disrupts the plaque) leads to formation of a
cyst which ís progressívely covered by squamous epithel îum and scar
tissue, suggesting ên ¡ncorrect diagnosis of ulcerating rmyelomeningocelet
(Cameron, 1956). ln a few cases the exposed neural plaque is still
evident at the tíme of birth.. Some authors, therefore, call any lesion
with cord involvement a myelocele (Cameron, 1!!6; Laurence, 1964).
Roentgenograms of a typical mye I omen i ngoce I e at birth show absence
of spinous processes and reduction of the laminaeuextending from the
upper end of the lesíôn ¡nto the sacrum. The pedicles of affected
vertebrae are splayed out i¡n an oval shape, with the distances between
art¡culãr processes increasíng to a maximum at the centre of the lesion.
The intervertebral disc spaces are reduced, and there may be abnorr,ral
verticaì bars between the lateral masses of involved vertebrae (FiS.. 4).
ln many myelomeningoceles the vertebrôl bodies are well formed,
but some cases may show associated skeletal defects such as:
a) hemivertebrae with congenital scol ìosis
b) anteríor. wedging with congenital kyphosîs
c) partial or complete sacral agenesîs (Sharrard, l97l).
1.5.4 Myeloqlllqqele
A much rarer form of spina bifída cystica (representing another
form of myelocele) is the myelocystocele, ín which the leston contêlns
both meninges and dilated spinal cord, Thís is associated with local
enlargement of the centrai canal of the ¡ntact spìnal cord (hydromyelia),
so thêt the sac is not traversed by spínal nerves.