Anatomic-radiographic study of ossified pterygospinous and “innominate” ligaments

On the basis of our anatomico-radiographic studies and a review of the literature, we have reported a series of macroscopic and radiologic findings of typical and significant anomalies which involve the ossification of the group of aponeuroses and ligaments in the interpterygoid region corresponding to the exocranial opening of the foramen ovale. These anatomic variations refer to the osseous bars of Civinini, formed by the ossification of the pterygospinous ligament (pterygospinous foramen), and to the osseous bridge of Hyrtl, caused by the ossification of Hyrtl-Calori's “innominate” or pterygoalar ligament (porus crotaphiticobuccinatorius of Hyrtl). The anatomic and radiologic peculiarities of these delicate anomalous structures are demonstrated by means of typical photographs and radiographs. It has been shown that, besides their anatomic and anthropologic significance these osseous variations are of greater clinical interest with respect to the transoval injection technique of the trigeminal cistern at the level of the Gasserian ganglion. It is important to point out that only the ossified “innominate” or pterygoalar ligament of Hyrtl-Calori (porus crotaphiticobuccinatorius) has true clinical significance, and this only when supramandibular or transzygomatic punctures are used to reach the retrogasserian trigeminal cistern. On the contrary, no difficulty arises when the semilunar ganglion is injected by means of the inframandibular approach, since in this case neither Civinini's pterygospinous nor Hyrtl's pterygoalar bar is ever a barrier to the passage of the needle through the foramen ovale. Under this condition, however, an intracisternal injection of the Gasserian ganglion is questionable. Finally, it should be emphasized that exploratory radiologic examination is required before this kind of therapeutic procedure is performed at the base of the skull. Likewise, it is of the utmost importance to use highly specialized techniques, equipment, and personnel in a department of block anesthesia expressly created for this purpose.