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Platybasia; Specialty: Neurosurgical, orthopedic: Symptoms: Platybasia is characterised by abnormal flattening of the skull base as defined as a base of skull angle over 143º.In the absence of neural compression, pain at the back of the skull and upper part of the neck is the most common symptom.
Basilar invagination is invagination (infolding) of the base of the skull that occurs when the top of the C2 vertebra migrates upward. It can cause narrowing of the foramen magnum (the opening in the skull where the spinal cord passes through to the brain). It also may press on the lower brainstem. [1]
Potentially life-threatening complications, all of which become more common in more severe OI, include: tearing of the major arteries, such as the aorta; [1]: 333 [11] pulmonary valve insufficiency secondary to distortion of the ribcage; [1]: 335–341 [12] and basilar invagination. [13]: 106–107
Craniocervical instability is more common in people with a connective tissue disease, including Ehlers-Danlos syndromes, [1] osteogenesis imperfecta, and rheumatoid arthritis. [2] It is frequently co-morbid with atlanto-axial joint instability, Chiari malformation , [ 3 ] or tethered spinal cord syndrome .
Several indirect measurements on CT can be used to assess ligamentous integrity at the craniocervical junction. The Wackenheim line, a straight line extending along the posterior margin of the clivus through the dens, should not intersect the dens on plain film, with violation of this relationship raising concern for basilar invagination.
In tunicates, invagination is the first mechanism that takes place during gastrulation. The four largest endoderm cells induce the invagination process in the tunicates. Invagination consists of the internal movements of a sheet of cells (the endoderm) based on changes in their shape.
The neural tube develops in two ways: primary neurulation and secondary neurulation. Primary neurulation divides the ectoderm into three cell types: The internally located neural tube; The externally located epidermis; The neural crest cells, which develop in the region between the neural tube and epidermis but then migrate to new locations
Different portions of the neural tube form by two different processes, called primary and secondary neurulation, in different species. [4] In primary neurulation, the neural plate creases inward until the edges come in contact and fuse. In secondary neurulation, the tube forms by hollowing out of the interior of a solid precursor.