The base of the skull: a comparison of computed and conventional tomography

Large scan field, high spatial resolution flat-panel detector based volumetric CT of the whole human skull base and for maxillofacial imaging

OBJECTIVES

To assess the feasibility of flat-panel detector based volumetric CT (fpVCT) scanning of the whole human skull base and maxillofacial region, which has thus far only been demonstrated on small, excised specimens. Flat-panel detectors offer more favourable imaging properties than image intensifiers. It is therefore likely that they will replace them in cone-beam CT scanners that are currently used to scan parts of the skull base and maxillofacial region. Furthermore, the resolution of current CT imaging limits diagnosis, surgical planning and intraoperative navigation within these regions. fpVCT might overcome these limitations because it offers higher resolution of high contrast structures than current CT.

METHODS

Three embalmed cadaver heads were scanned in two scanners: an experimental fpVCT that offers a scan field large enough for a whole human head, and in a current multislice CT (MSCT). 28 structures were compared.

RESULTS

Both scanners produced bone images of diagnostic quality. Small high contrast structures such as parts of the ossicular chain and thin bony laminas were better delineated in fpVCT than in MSCT. fpVCT of maxillofacial region and skull base was rated superior to MSCT (P=0.002) as found in this limited, experimental study.

CONCLUSIONS

High spatial resolution fpVCT scanning of both regions in a whole human head is feasible and might be slightly superior to MSCT. fpVCT could improve diagnostic accuracy in selected cases, as well as surgical planning and intraoperative navigation accuracy.

Prognosis, incidence and management of acute traumatic intracranial pneumocephalus. A retrospective analysis of 49 cases

CT scanning was carried out in 508 patients with acute head injuries. Retrospective analysis of the findings revealed intracranial air in 49 cases (9.7%). Air may be situated in the extradural, subdural or subarachnoid spaces or intracerebrally. A pneumocephalus was detected in 40 out of 49 (82%) of head injury patients within 6 hours of the accident. Injuries associated with a pneumatocele or a single intracranial air bubble have a good prognosis, as do frontobasal lesions. Injuries associated with multiple air bubbles have a bad prognosis. Intracranial air was a sign of a frontobasal or laterobasal fracture. In cases with a depressed skull fracture, extracerebral haematoma or pneumocephalus acting as a space occupying lesion, an operation should be performed as soon as possible. If associated with a persistent rhinorrhea the CSF-fistula should be operated according to the generally accepted rules. In other post-traumatic cases intracranial air may be disregarded, although its presence may influence the choice of treatment.

Sphenotemporal buttress fracture

A new fracture type visible on CT images of the base of the skull is described. In this fracture the sphenoidal connection to the zygomatic and temporal bone breaks off all its three extensions. It was recognized in five patients with severe head injuries. In three surviving patients it was associated with ipsilateral persistent amaurosis. This fracture should alert the investigator to the possible sequelae of the head injury.

[Computed tomography in craniocerebral injuries in childhood]

In accident diagnosis, the computed tomogram (CT) is nowadays decisive for the determination of craniocerebral traumas. This is true for children as well as for adult patients. Besides the rapid handling and the non-invasiveness, the exact diagnosis with direct imaging of the traumatic cranial lesions is a special advantage of computed tomography. The authors present the characteristic CT modifications of the epidural hematoma, the subdural hematoma and traumatic subdural hygroma, the brain contusion, traumatic subarachnoidal hemorrhage and ventricular hemorrhage. Furthermore the injuries to the osseous skull which can be represented by CT and the late consequences of the accident are mentioned. The special aspects of craniocerebral traumas in children are taken into consideration.

Treatment of recurrent carcinoma at the base of the skull with carbon dioxide laser

The extension of carcinoma to the cribriform plate is a poor prognostic finding. Two extremes of treatment approach have been advocated. On the one hand, patients may be abandoned to palliative chemotherapy. On the other hand, heroic and aggressive resections may be advocated including combined neurosurgical transdural and otolaryngologic facial-orbital resection. Armed with the surgical microscope and the CO2 laser there may be a place for a middle ground of therapy. We present our experience with recurrent tumor after full course radiation therapy and maxilloethmoidectomy. The biopsy proven recurrences were found at the cribriform plate but could not be shown to have crossed into the anterior cranial fossa by polytomography or high resolution CT scanning. The CO2 surgical laser delivered through the surgical microscope was used with repeated applications. Recurrent epidermoid carcinoma found to be confined to the nasal side of the cribriform plate can be controlled by careful microscopic stripping of soft tissue from the cribriform plate with a surgical laser.

High-resolution computerized tomographic scans of the normal and abnormal ear

Possible applications of high-resolution computerized tomographic scans to otology are discussed. On the basis of examples, the authors illustrate the normal structure of the ear as well as possible pathologic conditions such as congenital abnormalities, cholesteatoma, neoplasms, trauma, and systemic diseases. The advantages of the current generation of computerized tomographic scanners are reviewed, notably contrast potentialities, radiation load, reconstitution of images at a later time, and storage of imaging data. Drawbacks include the high acquisition price of the equipment and the limited mobility of the scanning gantry.

CT for trauma to the base of the skull and spine in children

Five patients have been selected to demonstrate the diagnostic accuracy of CT in cases of traumatic damage to the base of the skull and spine in infants and children. Ct is superior to any other diagnostic radiological technique as bone and soft tissues are usually equally well demonstrated during one visit to the Radiology Department. Thus, CT is considered to be the primary investigative procedure of choice to evaluate trauma of the base of the skull and spine in infants and children.

The diagnosis and surgical management of olfactory neuroblastoma: the role of craniofacial resection

The diagnosis and clinical management of olfactory neuroblastoma are discussed. Computerized tomography is a valuable means of assessing the pre-operative extent of disease and the efficacy of subsequent major surgery. The tissue diagnosis is facilitated by electron microscopy, demonstrating the presence of dense core vesicles and cytoplasmic filaments. Radiotherapy followed by craniofacial resection is the treatment of choice for olfactory neuroblastomas that are locally extensive at presentation.

Computed tomography and hypocycloid tomography in lesions of the nose, paranasal sinuses and nasopharynx

In 31 patients with lesions mainly arising from the nose, paranasal sinuses and nasopharynx comparative evaluation of the results of CT and hypocycloid tomography indicated that CT generally gave a better representation of both the bony structures and the soft parts and alone has the capacity to evaluate intracranial extension. CT should first be performed in the transverse axial plane. If abnormalities in relation to horizontal bony structures are demonstrated, the examination should be supplemented by CT in the coronal plane or, if CT scanning in this plane is not possible, by conventional tomography. Enhancement after intravenous injection of contrast medium does not as a rule seem to add information of diagnostic importance.

CT in trauma of the base of the skull and its complications

Diagnosis and accurate delineation of fractures involving the base of the skull can easily be done with newer generation computed tomography (CT) scanner. CT also demonstrates associated complications, such as hemorrhage, brain injury, and leakage of cerebrospinal fluid (CSF), not seen in plain skull radiography or tomography.

Computed tomography: a three-dimensional study of the nasal airway

1. Accurate volume measurement of the nasal airway based upon computed tomography images sequentially generated along the length of the airway is possible. 2. The cross-sectional area of the airway at any position along its length can be determined. 3. The most constricted part of the airway is not necessarily at the location of the turbinates. 4. Details of hard- and soft-tissue anatomy not otherwise discernible can be detected with computed tomography imaging.

Computerized tomography scanning of the temporal bone

Computerized tomography (CT) scanning has reached a degree of sophistication that requires alteration of technical factors to demonstrate different parameters of temporal bone pathology. The techniques for pontocerebellar angle display, eustachian tube, middle ear pathology, and overall temporal bone display are quite different. Close cooperation between the radiologist and otologic surgeon are required for optimal use of CT scanning advances.

Orbital syndromes--CT analysis of 100 cases

100 cases of orbital syndromes, primary or secondary, are reviewed after CT analysis and compared with the results of plain and angiographic conventional examinations. First, the technique and normal results are described. Primary orbital syndromes (45 cases) originating in the orbit form three subgroups--tumors of the eyeball, tumors limited to the orbit and tumors of the orbit with bone lesions, with or without extra-orbital extension. Secondary orbital syndromes (55 cases) spreading to the orbit contain malignant tumors (36 cases) of which 25 are epitheliomas and benign tumors, the most frequent being meningiomas. For ocular and orbital tumors, CT allows the diagnosis of a mass and sometimes the pathological diagnosis (endocrine exophtalmos, inflammatory pseudotumors, varicose ophthalmic veins). For all other orbital tumors CT is important in determining the volume, relationships and extension, and does so better than carotid angiography or orbital phlebography. In secondary orbital syndromes, and particularly in facial malignant tumors and in meningiomas, CT is of great interest in the pretherapeutic evaluation of a tumor. It shows its volume and extension toward the face and orbital cavities, the pterygo-maxillary fossa (so important in determining the operability), the infra-temporal fossa and the endocranium, often without resorting to complementary investigational procedures which are much more aggressive. After histological diagnosis, CT allows the establishment of a therapeutic program.

CT of the base of the skull

A systematic study of the structures of the base of the skull was performed with CT. The findings in 141 pathological cases are described. The value and some limitations of this kind of investigation are described and discussed. A comparison with conventional tomography is made.