Coronal and axial high resolution computed tomography of the mandible extends facilities in dentoalveolar surgery. Preoperatively the relationship between the mandibular canal and the roots of deeply displaced third molars can be determined precisely. After surgical removal of lower wisdom teeth iatrogenic defects of the lingual cortical bone can be detected. The additional information obtained when compared with conventional radiographs is demonstrated in case descriptions. Indications for this technique, radiation exposure and implications for surgery are discussed.
The diagnostic utility of imaging techniques in injuries to the intramedullary and subarachnoid portions of the brachial plexus, with possibly complete avulsion of one or more nerve roots from the spinal cord and extramedullary meningocoele was compared in 18 patients studied by unenhanced computed tomography (CT), cervical myelography, myelographic CT (MCT) and magnetic resonance imaging (MRI). Emphasis was placed on the lesions of the subarachnoid roots. CM was the only diagnostic modality to show avulsion of 18 nerve roots and their levels in 8 patients (100% = gold standard), and to verify 2 incomplete avulsions. MCT reliably revealed 8 of 18 (45%) and MRI 1 out of 18 (6%) avulsions. Myelography with MCT showed intact subarachnoid nerve roots in 10 additional patients. MRI and MCT (16 out of 16 = 100%) were superior to myelography (14/16 = 88%) for demonstrating 16 traumatic meningocoeles in 8 patients; follow-up MRI (6-24 months) showed no increase in their size. We recommend a subsequent CT to role out fracture to the spinal column; MRI should provide significant information concerning oedema or haemorrhage in the spinal cord. Myelography with segmental MCT is performed to differentiate pre- from post-ganglionic lesions, data which are essential for deciding whether exploration of the plexus or a motor substitution operation is indicated.
It is therefore necessary to carefully control and sometimes correct diagnosis in cases of sudden deafness and acute vestibular neuritis. Especially additional neurological symptoms indicate the necessity of a MRI-angiogram or CT-(angiography)scan to exclude thrombosis of the basilar artery.
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