 
Blunt traumas are
responsable of a large variety of orbital and midfacial fractures :
Lefort’s and tripod fractures, orbital roof’s fractures with possible
CSF leakage, blow-out fracture with entrapment of the orbital fat and
medial or inferior rectus muscles (fig. 20). Apical injuries may be
complicated by impingement of the optic nerve or hematoma of the nerve
sheath as well as by vascular lesions : carotid cavernous fistula (fig.
31), pseudoaneurysm of the internal carotid artery.
Subperiostal hematomas collect
between the periosteum and the bony walls of the orbit, cause painful
proptosis and are either traumatic or spontaneous secondary to blood
dyscrasia, hemophilia or leukemia (fig. 21).
Infections and inflammatory lesions
of the orbit usually occur as a secondary process from the surrounding
structures, such as the paranasal sinuses and the nasopharyngeal
cavity. This processes are divided into pre and postseptal cellulitis.
Preseptal cellulitis are characterized by edema of the eyelids anterior to the orbital septum.
Postseptal cellulitis refer to
elevation of the orbital periosteum with phlegmon or abcess formation.
Surgical drainage and sinus surgery are mandatory. Cavernous sinus
thrombosis must always be searched by CT (fig. 22).
Lots of tumoral processes may develop
in the extraconal and bony para-orbitary space. Dermoids cysts are the
most common congenital lesions of the orbit accounting for 2 % of the
orbital masses. On the CT scan dermoid cysts appear as deep
well-defined nodular lesions, isodense with orbital fat, with a
calcified rim and little mass effect on the globe (fig. 23).
Meningiomas may extend from the
sphenoid wing (fig. 24), simulating metastasis or osteosarcoma or
develop in the optic canal with compression of the optic nerve (fig.
25).
Rhabdomyosarcoma, most common primary
orbital malignancy of childhood, may originate from the orbit or as an
extension of lesions of the naso-ethmoidal sinus, pterygopalatine fossa
or infratemporal fossa (ref. 12). Arising from undifferentiated
mesenchymal cells, they are of various histological types with
different behaviours. Rapidly progressing proptosis in childhood is
highly suggestive. CT is necessary to evaluate bone destruction (fig.
26). MR is the exam of choice to appreciate the tumor and its cranial
extension. Diagnosis can only be established by biopsy. Adequate sample
may be obtained, with minimal risks, by CT or MR-assisted needle
biopsy. Otherwise Langerhans’cell histiocystosis, a destructive
granulomatous disorder of young children may involve the soft tissue of
the orbit with destruction of orbital walls (ref. 13).
Fibrous dysplasia is a common
lesion of the greater wing of the sphenoid. CT scan usually shows
enlarged bone with an intact cortical and a ground of glass texture ;
compression of the optic nerve can be observed.
Paraorbital diseases can expand into
the orbit : benign lesions such as mucoceles, angiofibroma and
malignant tumors such as squamous cell carcinoma,
esthesioneuroblastoma. The integrity of the periorbital layer and fat
preservation have to be evaluate by imaging to provide correct surgical
planning (ref. 14). | |
