The Role Of High Resolution C.t. In Diagnosis And Assessment Of The Sinonasal Pathological Lesions:

Mostafa M.m. Sinna

The radiological examination ofthe sinonasal cavity is difficultbecause of the complicated surrounding bony structures .Conventional radiographic techniques are important in the evaluationof sinus disease, as a general survey of the bony and soft tissuechanges.However, the details of soft tissue involvement and the finedetails of the bony changes are poorly seen on plain radiographs .Conventional radiography has been largely replaced by CT .Computed tomographic sections are clear of overlying structures andcan demonstrate the bony framework and the normal soft tissuestructures .CT is useful in a wide spectrum of sinonasal lesions :Congenital anomalies, trauma, inflammations and neoplasms . In caseof congenital anomalies, coronal CT reveals in detail the sinusconfiguration . In addition, it also shows the associated changes in theorbit, skull and the brain as for example, in encephalo-menigoc des.CT is the primary diagnostic imaging modality used in theevaluation of complex facial trauma after routine screening films areobtained, due to its superior contrast resolution which also allowsdirect visualization of soft tissue .Different sinonasal lesions often simulate each other both intheir clinical and radiographic presentation. The early symptoms ofchronic rhinosinusitis (nasal obstruction or discharge) are identical tothose caused by neoplasms or infections confined to the sinonasalcavity . CT scan should be performed ~hen a patient with knownrhinosinusitis develops ominous new symptoms such as epistaxis,facial swelling, persistent facial pain, facial numbness, oculardysfunction or proptosis .CT is preferably perfonned after the acute excerbations ofrecurrent sinusitis have been optimally treated medically in order tobetter demonstrate the underlying cause of recurrent or persistantinflammation.CT is also valuable, in visualization of tumonr extension toimportant areas such as the infratemporalfossa, orbit, pterygopalatinefossa, nasopharynx and intracranialcavity .Coronal CT cuts demonstrate the anatomical details in anorientation more or less similar to and very helpful in endoscopicassessment and management. Accordingly,coronal CT has a greaterimportance for the preoperative assessment of patients for endonasalendoscopic surgery and follow up of surgicalnasal diseases .CT is of particular value in the assessment of patients withpersistant complaints after sinus surgery . The most common cause offailure in therapy directed at the major sinuses has been persistantetlnnoid diseases . In these cases, CTis mandatory becauseinflannnatory changes in the middle meatus are poorly seen on plainradiographs .CT is also indicated when a conventionalsinus series showsinonasal opacification with bone destruction . The informationobtained in these cases prove essential in surgical planning bydemonstrating early involvement of adjacent structures such as theorbits or cranial cavity . With CT, it is possible to identify osseousinvolvement of the orbital wall and extension of the tumour into the extraocular muscles.