3-D CT for cranial facial and laryngeal surgery

Three-dimensional imaging is a new digital technology which interpolates two-dimensional computer tomography information to render a "life-like" anatomic display of the diagnostic information. We have found that this new methodology significantly improves the assessment and therapy of patients undergoing surgical procedures of the head and neck. The technique has been used in cranial-facial and laryngeal pathology, and in preoperative planning of tumor resection, particularly skull-base neoplasms. The use of three-dimensional computer tomography improves the display of the location and volume of pathology and affords accurate therapeutic and surgical planning. The choice and extent of surgery is better defined, and precise bone removal can be performed. In reconstructive surgery, an accurate prefabricated model of the bony defect can be made to aid reconstruction. Representative cases demonstrating the use of three-dimensional computer tomography in head and neck surgery, and its benefits in saving operative time and improving the postoperative result, will be discussed.     

3D技术在鼻内镜手术精准治疗鼻前颅底恶性肿瘤中的应用

目的 探讨3D技术在鼻内镜手术精准治疗鼻前颅底恶性肿瘤及颅底功能重建手术中的作用。 方法 对21例鼻颅底恶性肿瘤患者术前行鼻窦冠状位CT或MRI扫描,并行3D影像重建及模型打印,根据3D成像及模型了解鼻颅底恶性肿瘤侵及范围、颅底及眶壁骨质的缺损大小形状,制定鼻内镜手术术式、肿瘤精准切除范围及颅底功能精准重建方法。 结果 患者肿瘤均一次手术全切除,其中6例行颅底功能精准重建术,无脑脊液鼻漏及颅内感染并发症。术后病理示鳞癌9例,嗅母细胞瘤5例,腺样囊腺癌3例,横纹肌肉瘤4例。术后行正规放疗,横纹肌肉瘤患者加化疗。经平均随访36个月,未发现肿瘤复发及与本肿瘤相关的死亡。 结论 3D成像及打印模型能清楚显示鼻颅底恶性肿瘤范围、颅底及眶壁骨质缺损的大小及形状,并有助于术者选择最佳内镜手术入路及手术方案,有重要临床指导作用。     

Innovations in neuroimaging of skull base pathology

Recent advances in CT and MR technology have allowed detailed imaging of the skull base with greater diagnostic accuracy. Innovations such as multidetector volumetric CT scanners with 3-D reconstructions provide soft tissue and bony detail with very high resolution for small structures such as the neural foramina. CT angiography can assess vascular structures noninvasively, and CT perfusion can help differentiate between malignant and benign tumors. MR technology has provided high-resolution, rapid volumetric sequences that are useful in skull base imaging. MR angiography and MR venography can also assess vascular structures noninvasively. PET scanning and CT/PET scanning will increasingly become a mainstay of head and neck tumor imaging for initial staging, monitoring response to therapy,and detecting recurrent disease or metastases. Many more diagnostic imaging options are available to the head and neck surgeon today than ever before.     

颅底脊索瘤的CT诊断

目的探讨颅底脊索瘤的CT诊断及临床应用价值。方法回顾性分析15例经手术、病理证实确诊为颅底脊索瘤的CT表现。结果15例颅底脊索瘤中经手术和CT扫描证实,发生于斜坡5例,发生于鞍区及鞍旁7例,发生于鼻咽部1例,发生于蝶窦2例。病灶有钙化11例,颅底骨质破坏12例。结论CT扫描能够显示颅底脊索瘤部位、大小及侵犯范围,有助于确定手术方案及对术后进行评估。     

How best to present the radiological picture of the temporal bone today?

The detailed evaluation of anatomy and pathology of the temporal bone requires imaging modalities that are superior to plain x-ray films. Conventional polytomography has today largely been replaced by high-resolution CT. High-resolution CT provides excellent demonstration of the delicate bony structures and provides superior information about the soft tissues. The axial 1 mm scans of a complete temporal bone examination can be reformated in any number of planes. These reconstructions display the temporal bone in various projections. This theoretically well-founded procedure of individual processing has proven to be highly practical in more than 1000 examinations of the skull base. High-resolution CT with image reconstruction is the diagnostic method of choice for the evaluation of the skull base and especially the temporal bone, as the complex anatomy is best demonstrated by this technique. Six axial computed tomographic scans are demonstrated in detail. The special value of multiplanar reconstructions is illustrated by reconstructions in the coronal, sagittal and longitudinal plane.     

Chirurgische Simulation an der Laterobasis

Critical neurovascular structures are confined in a small bony space at the lateral skull base. Thus, high quality of surgical training and planning of minimally invasive procedures is crucial. Simulation of lateral skull base procedures can improve motor skills, anatomical orientation, and complication management in a safe environment. Thus, simulation training can be beneficial for skull base surgeons. Minimally invasive interventions at the lateral skull base are under research, and several authors have presented approaches through single or multiple drilled ports. Precise planning and simulation of such interventions is essential because even submillimeter errors can lead to damage to critical anatomical structures. Therefore, high demands have been set for the accuracy of computer-assisted surgery.     

Radiographic evaluation of the skull base.

The anatomic complexities of the skull base and the variable clinical presentation of skull base tumors often precludes accurate determination of tumor boundaries by history and physical alone. Imaging, employing computed tomography (CT) and magnetic resonance imaging (MR) allows for accurate tumor mapping and planning of appropriate therapeutic intervention. Calvarium floor involvement and extracranial lesions are well delineated by CT. While multiplanar MR is unparalleled in demonstrating tumor boundaries and extension through the skull base. In order to employ these imaging modalities in an efficient way, it is important to understand the limitations and capabilities of these modalities as well as the imaging characteristics of common skull base lesions.     

Osteoradionecrosis of the maxilla and skull base

Osteoradionecrosis of the maxilla and base of skull are rare phenomena, usually seen after combined therapy for malignancies of the maxillary sinus. While the mandible is most commonly affected by osteoradionecrosis, the maxilla and skull base may also be affected when preoperative or postoperative radiotherapy is combined with surgery. Contributing factors may be: high radiation dosage delivered to the treatment volume (greater than 6000 rads), loss of tissue protective effects due to surgery, decreased vascularity caused by surgery and radiation, and proximity of a contaminated field. Onset of symptoms may vary. One patient presented 25 years after postoperative radiotherapy. Major symptoms were pain, trismus, and purulent discharge. The best diagnostic modality remains the history and physical exam, as the area is readily accessible. CT scans may be helpful in diagnosis and treatment planning. Therapy should follow time honored principles of local wound care. Home irrigations and hyperbaric therapy have been helpful in encouraging early sequestration and rapid healing.     

Lesions of the petrous apex: diagnosis and management

Management of petrous apex pathology poses a unique challenge even to the most seasoned skull base surgeons. The central location in the skull base with adjacent critical neurovascular structures makes access to this region more than a trivial matter. Significant advances in diagnostic imaging have greatly facilitated the diagnosis of petrous apex lesions. The introduction of modern skull base surgery techniques also has provided skull base surgeons with numerous avenues to the petrous apex while significantly decreasing morbidity. The latest diagnostic and management strategies are discussed and an update of some of the more common pathologic entities is provided.     

Endoscopic transsphenoidal biopsy of the sphenoid and clival mass

Abnormalities of the clivus/skull base occur most commonly as a result of disease spread from adjacent structures, but can also occur from primary involvement of the clivus. Traditionally, definitive diagnosis was made by CT guided biopsy or craniotomy. However, lesions can occur in this area that are not amenable to CT guided biopsy or craniotomy. Endoscopic transsphenoidal surgery can provide a safe method for obtaining a clival biopsy, debulking of tumor tissue, or definitive treatment without the morbidity and mortality of a craniotomy. This study was designed to describe our experience with the endoscopic approach to the skull base and clivus via the sphenoid sinus. A series of seven patients underwent endoscopic transsphenoidal biopsy of a sphenoid clival lesion. All patients avoided anticipated craniotomy, and definitive pathology was obtained in five of six patients. In two cases, excisional biopsy proved to be therapeutic. There were no deaths, and major complications included one CSF leak and one intraoperative hemorrhage, both of which were controlled immediately. The experience gained with these patients demonstrates the feasibility and safety of this new application of endoscopic sinus surgery for the diagnosis and possible treatment of lesions of the sphenoid and clivus.     

Long-term endonasal endoscopic review of successful duraplasty after endonasal endoscopic skull base surgery

BACKGROUND: This study was performed to examine the long-term endonasal endoscopic morphological appearance of successful duraplasty after endoscopic skull base surgery for different pathology. METHODS: This study included 65 patients who underwent endonasal endoscopic surgery for different skull base lesions with successful duraplasty. Forty patients had pituitary adenomas, 25 with macroadenomas and 15 with microadenomas. Twenty patients with cerebrospinal fluid rhinorrhea of different etiologies and three patients with meningoencephalocele were included. There were two patients with skull base meningiomas, 1 with an extensive greater wing meningioma reaching the nasal cavity and the 1 with recurrent olfactory groove meningioma. Different types of autologous materials were used in reconstructing the skull base defect. Clinical follow-up with endoscopic nasal examination was done routinely 1, 3, 6, and 12 months after surgery. CT and MRI were performed when indicated. The follow-up period ranged from 6 months to 8 years. RESULTS: Starting from 3 months after surgery to the rest of the follow-up period, endonasal endoscopic view of the site of duraplasty showed that with small skull base defect (<5 mm), there was neither dural pulsation nor prolapse. With moderate-size defect (5-10 mm) there was dural pulsation without prolapse. With larger defect (>10 mm) there was dural pulsation and prolapse. These findings were constant regardless of the etiology of the lesion and the reconstruction material used. CONCLUSION: This long-term study showed that dural pulsation and prolapse at the site of the successful duraplasty is a function of the size of the bony defect and does not depend on the pathology of the lesion or the autologous material used for reconstruction. For any future endonasal procedure for these patients, the surgeons should be fully aware of the state of duraplasty to avoid any complication.     

Experience with various 3-dimensional navigation systems in head and neck surgery

OBJECTIVE: To evaluate the benefits and difficulties encountered when using various 3-dimensional (3-D) navigation systems in head and neck procedures. DESIGN: Five different navigation systems were used for preoperative planning and intraoperative 3-D navigation in procedures at the paranasal sinuses, the frontal and lateral skull bases, and the petrous bone. INTERVENTION: Intraoperative 3-D localizing systems (position-sensitive mechanical arms, infrared cameras, etc) demand reliable patient fixation on the operating table. We achieved this by developing a noninvasive head holder. Other systems allow patient movements by using magnetic digitizing technology (ARTMA System) and sophisticated programming. RESULT: Having surpassed an initial learning curve, we now achieve an accuracy of 1 to 2 mm regularly. Especially in paranasal and frontal basal surgery, all navigation systems used provide valuable positioning information during surgery. In particular for revision or tumor surgery, decisive benefits resulted from use of these systems: shorter overall operation time; safer manipulation near delicate structures; and reliable identification of the skull base even in patients with bleeding, scarring, or missing anatomical landmarks. CONCLUSIONS: We performed approximately 250 operations with different systems and introduced navigation at the lateral skull base and the petrous bone with mechanical, optic, and magnetic digitizers. In these anatomical areas, navigation was used successfully; the technical challenge is greatest at the lateral skull base, however.     

Preoperative evaluation of bone destruction using three-dimensional computed tomography in cholesteatoma

This study investigated the usefulness of three-dimensional computed tomography (3DCT) in the evaluation of bony defects caused by cholesteatoma. Fifteen patients with chronic otitis media with cholesteatoma who showed bony destruction or suspicious destruction in two-dimensional CT were examined using 3DCT. The CT data were transferred to a workstation with a real-time image processor. We used three-dimensional reconstruction software enabling image processing. In all patients, 3DCT clearly delineated the destruction of bony structures by cholesteatoma. The 3DCT-generated images provided spatial relationships, which were not easily appreciated on two-dimensional CT. Intraoperative bony destruction findings correlated with 3DCT findings. From these results, 3DCT could be useful to evaluate the invasiveness of cholesteatoma to the cranial base. It could also be helpful in planning reconstruction during surgery.     

Risk assessment in coronal computed tomography scans of the paranasal sinuses

Computed tomography (CT) is a prerequisite to planning and performing FESS procedures. No standards exist for assessing the risk to the anatomical structures in the proximity of the nose and sinuses associated with surgery. The aim is to assess the agreement of surgeons in identifying key areas related to the anterior skull base and the orbit on coronal CT scans. A cross-sectional study involving five otolaryngologists from three centres related the scans. Two scoring systems were used to rate each film; the Lund-MacKay system and a risk assessment system. The latter system was compiled and agreed upon by the authors. κ analysis was used for measurement of inter-observer agreement. A consecutive series of patients undergoing CT scanning in advance of paranasal sinus surgery formed the study population. Patients who had previous surgery, anterior skull base trauma or were suspected of malignant disease were excluded. Twenty-nine scans were reviewed. There was moderate agreement using the Lund-MacKay system (median value 0.5) values. The risk assessment system showed moderate agreement in two of 11 parameters (pneumatized ethmoid roof 0.58 and uncinate process variations 0.43), poor agreement on the other parameters assessed (range ?0.06–0.21). The difficulties encountered in judging vulnerability or anatomical structures on coronal CT of sinuses may relate to a lack of clear definitions of structures, subtle degree of variation or technical aspects of scanning.     

Methods for simulation of surgical interventions in head and neck surgery]

Preoperative evaluation of the operating site is essential in planning surgical procedures. The relationship of pathology to adjacent tissues and vital anatomical structures needs to be analyzed to determine the intraoperative procedures required. For this the surgeon mentally simulates the procedure planned. For complicated conditions or reconstructive surgery in extensive bony defects, surgery can be simulated with three-dimensional reconstruction on either a monitor screen or on an individually manufactured plastic model of the patient. For this purpose different procedures for 3 D representation and manipulation of tomographic image data have been developed in our departments and the technique of stereolithography used experimentally to create custom-made plastic model of patients. A computerized video image manipulator was also developed for simulation of aesthetic plastic surgical procedures.     

CAS-System MKM(R): use and results in lateral skull base surgery

BACKGROUND: Computer assisted surgery has reached an advanced stage of development and offers new possibilities in daily surgical procedures. METHODS: The MKM(R) - is a navigation system fitted with a laser-guided, autofocus-microscope for referencing purposes. The coordinates can be set using various marker systems and a special workstation is used for preoperative planning. It is possible to add landmarks and display them in the surgeon's eyepiece. The clinical integration, the time required for the use of the navigation system and the intraoperative accuracy of the system were evaluated on the basis of 136 lateral skull base procedures. RESULTS: The degree of accuracy is determined by the type, amount and positioning of markers. The adjustment of reference points should be carried out following macrosurgery in order to avoid shifting factors. For an additional increase in accuracy, an improvement in the spatial resolution of the CT scans is required, with a section thickness of 1 mm and a pixel size of 0.5mm. The bone-anchored structures of the temporal bone do not underlie shifting or extensive intraoperative swelling. Skull base surgery is, therefore, ideally suited for the application of CAS. We found that registration was accurate to less than 1 mm (0.68 mm +/- 0.17 mm) and that the MKM(R) system made an additional contribution to surgical safety by identifying important structures. CONCLUSIONS: A practical accuracy found to be approximately one millimetre suggests that the non-invasive referencing system may be effective, accurate and useful for computer assisted identification of vital structures. We expect navigation systems to improve the quality and reduce the risks of surgical intraventions.     

Computer-assisted three-dimensional reconstruction of head and neck tumors

Objective: Because head and neck tumors reside in a complex area, having a three-dimensional (3-D) model of the patient's unique anatomical features may assist in the delineation of pathology. The authors describe a new computer technique of 3-D anatomical reconstruction from two-dimensional computed tomography (CT) and magnetic resonance (MR) data and discuss how it represents a step forward in the continuing evolution of 3-D imaging. Study Design: The authors selected three patients with solitary head and neck tumors and reconstructed their anatomy in a 3-D format for study. The tumors represented locations in the nose and central skull base (patient 1), temporal bone (patient 2), and neck (patient 3). Materials and Methods: MR and CT images from the individual patients were electronically transferred to workstations in the Surgical Planning Laboratory of the authors' institution. Registration (or fusion) was carried out between the MR and CT images. The desired anatomic components underwent segmentation (identification and isolation). Assembly of the segmented images was performed and the resulting structures were integrated to produce a 3-D model. Results: 3-D models of the following were constructed and displayed in an interactive format on high-capacity computer workstations: 1) a skull base sarcoma with extension into the nasopharynx and nose; 2) an acoustic neuroma with internal auditory canal involvement; and 3) a metastatic recurrence of a tongue base squamous cell carcinoma in the posterior triangle of the right side of the neck with extension to the skull base. Conclusion: The authors' Surgical Planning Laboratory has developed a 3-D reconstruction technique that has several new features. The models provided a very good 3-D interactive representation of the tumors and patient anatomy. The need now exists to develop this method of 3-D reconstruction of head and neck tumors for potential applications in treatment, research, and medical education. Laryngoscope, 108:1592–1598, 1998     

How to reliably evaluate middle ear diseases? Comparison of different methods of post-processing based on multislice computed tomography examination

CONCLUSIONS: Multislice computed tomography (MSCT) virtual endoscopy was useful in evaluating mainly post-traumatic and postoperative cases. In other pathological conditions axial images and MPR reformations were most useful. OBJECTIVES: Evaluation of cross-sectional images, multiplanar 2-D reformations, 3-D reconstructions and virtual endoscopy (VE) in assessment of the middle ear in inflammatory diseases, trauma, otosclerosis and tumours. Comparison of each method and correlation with surgical findings. MATERIALS AND METHODS: Investigations were carried out in 80 patients with middle ear pathology. In each case MSCT of the petrous bone was performed. In addition to cross-sectional native scans, frontal and sagittal images were achieved using MPR reconstructions. 3-D volume rendering (VR) and VE images were also generated. The value of native scans information, 2-D, 3-D reconstructions and VE of the tympanic cavity structures was assessed in comparison to intraoperative findings. RESULTS: MPR reconstructions were most useful in the assessment of skull base trauma, skull base tumours and in cases of chronic middle ear inflammation. Highly vascularized tumours, disruption of ossicular chain and stapes prosthesis were best evaluated on 3-D reconstructions. Axial images proved to be the best for otosclerosis interpretation.     

Endoscopic diagnosis and treatment of nasal rhinorrhea

43 patients with nasal liquorrhea (NL) were admitted to and operated on using endonasal endoscopic technique in N. N. Burdenko Research Institute of Neurosurgery from 1999 to 2002. The diagnostic examination included nasal cavity endoscopy, biochemistry of glucose in nasal discharge. CT and MRT-cysternography, plain CT and MRT of the brain. By etiology, liquor fistulas were divided into spontaneous (n = 21), posttraumatic (n = 6) and iatrogenic (n = 16). The source of liquorrhea located in the sphenoidal sinus (n = 20), roof of the ethmoidal labyrinth (n = 10), cribriform plate (n = 12). A total of 47 operations and 4 reoperations were made with application of the biological fibrin-thrombin glue tissucol. The maximal size of the defect in the base of the skull in this series reached 15 mm. Lumbar drainage, removed on postoperative day 5, on the average, was established during endoscopic endonasal plastic repair of the liquor fistula in 34 patients. In maximal follow-up of 3.5 years, a complete recovery was observed in 38 (88.4%) operated on patients. The main causes of unsatisfactory effectiveness of endonasal operations were the following: impossible visualization of the fistula in a deep lateral pocket of the sphenoidal sinus, compound pathology (nasal liquorrhea and tumor of the base of the skull), extensive multiple traumas of the bone structures of the base of the skull.     

Three-dimensional computed tomography of congenital nasal anomalies

OBJECTIVE: To determine the utility of performing three-dimensional (3D) computed tomography (CT) of congenital naso-frontal anomalies for preoperative planning and counseling and compare it with standard two-dimensional (2D) imaging and intraoperative findings. STUDY DESIGN: Prospective case evaluation of imaging studies and medical records in cohort of patients with congenital nasal anomalies. METHODS: We performed 3D CT imaging of three different types of congenital nasal lesions. Additional preoperative imaging consisted of standard 2D CT scans and/or magnetic resonance imaging (MRI). Information obtained from the 3D CTs was compared with other standard imaging and intraoperative findings. RESULTS: 3D CT was most useful in the case of a large encephalocele with a significant bony defect of the anterior cranial fossa. It provided moderate utility when used to evaluate a nasal dermoid with nasal bone and septal abnormalities and was of limited benefit in the case of a bifid nose with significant external soft tissue deformity and relatively normal bony anatomy. CONCLUSION: Congenital midline nasal anomalies are rare lesions with the potential for intracranial extension and anterior skull base abnormalities. The safe surgical treatment of these lesions depends upon accurate preoperative imaging to assist in establishing the diagnosis, to help guide surgical planning, and to assist in communicating the diagnosis and surgical approach for optimal counseling of families. 3D CT was instrumental in providing additional useful information in cases with significant bony abnormalities at little additional cost or time. It is also beneficial for preoperative counseling of patients and families with limited medical knowledge.