Platybasia (from the Greek. platys - flat and basis - the base) is the change in the ratio between the bones of the skull base and upper cervical vertebrae, which is characterized by an increase basilar corner of the skull, i.e. the angle between planum sphenoideum (JNA) and blumenbaum slope (clivus). The value of this angle normal ranges 135-143 degrees. To judge availability of platibai possible by side review x-ray of the skull, and tomograms. The increase of this angle (more 143 degrees) indicates platibas.
The second diagnostic sign is a change of position of the upper point of the odontoid process II cervical vertebra (apostrofa), located on level lines Chamberlain, connecting the rear edge of the hard palate with the rear edge of the great occipital foramen.
Platybasia flows neurologically asymptomatic. Often mistakenly equated with basilar impression of the skull in which the upper point of the odontoid process of epistrophe is above the line of the Chamberlain. In addition, unlike P., basilar impression skull occurs with symptoms of basal nerves, most of the IX-XII pair.