Results: 5 types (after Natsis) of SSN were observed: type I, without a discret notch, 63 (32.8%); type II, a notch that was longer in its transverse diameter, 92 (47.9%); type III, a notch that was longer in its vertical diameter, 33 (17.2%); type IV, a bony foramen, 4 (2, 1%); type V, a notch and a bony foramen, zero.