Relationship of the optic nerve to the posterior paranasal sinuses: a CT anatomic study

PURPOSE

To delineate the relationship between the optic nerves and the posterior paranasal sinuses using CT data.

METHODS

Direct coronal sinus CT scans of 150 consecutive patients with chronic inflammatory sinus disease were reviewed by two radiologists. Axial oblique reconstructions along the course of the optic nerve were obtained for the first 100 patients. The direct relationship between the optic nerve and the posterior ethmoid and sphenoidal sinuses was recorded, as were identations into the sinus wall, course of the nerve through the sinus region, pneumatization of the anterior clinoid process, and bone dehiscence.

RESULTS

The relationship of the optic nerve to the posterior paranasal sinus fell into one of four discrete categories, type 1 through type 4. All 300 nerves were intimately related to the sphenoidal sinus. A small minority (3%) were in contact with the posterior ethmoidal sinus. Only type 4 nerves had contact with the posterior ethmoid air cell. Type 1 nerves course adjacent to the sphenoid sinus without indentation of the wall (228 nerves, 76%). Type 2 nerves course adjacent to the sphenoidal sinus, causing indentation of the sinus wall (44 nerves, 15%). Type 3 nerves course through the sphenoid sinus (19 nerves, 6%). Type 4 nerves course immediately adjacent to the sphenoidal sinus and the posterior ethmoidal air cell (9 nerves, 3%). Bone dehiscence over the optic nerve was found in 24% of the nerves; 4% of the optic nerves in our study had an associated pneumatized anterior clinoid process and 77% of these had an associated dehiscence over the optic canal.

CONCLUSIONS

In all our cases the course of the optic nerve was adjacent to the sphenoidal sinus. Only 3% were in contact with the posterior ethmoidal sinus. Anatomic configurations that predispose the optic nerve to injury include type 2 or 3 optic nerves, bone dehiscence over the nerve, and pneumatization of the anterior clinoid process. These configurations are common and should be routinely sought out so that devastating complications from sinus surgery can be avoided.

Primary craniosynostosis: imaging features

In 1851, Virchow introduced the term craniosynostosis to describe a variety of abnormalities in calvarial growth. These skull deformities are usually apparent in infancy. When an abnormal calvarial configuration is detected, a radiologic evaluation is necessary to characterize the deformity and to guide the corrective surgical procedure. Affected children are believed to have an improved outcome when diagnosis and surgical intervention occur at an early age. CT with three-dimensional reconstruction optimally evaluates the presence and degree of sutural involvement and assesses associated facial and intracranial abnormalities. This pictorial essay illustrates the imaging findings, nomenclature, and associated abnormalities of the various types of primary craniosynostosis.

Optimal CT evaluation for functional endoscopic sinus surgery

PURPOSE

To evaluate the optimal parameters for the CT examination of patients who are having functional endoscopic sinus surgery.

METHODS

CT scanning was performed on two fresh cadaveric heads in the direct coronal plane, varying the section thickness, intersection gap, scanner gantry angle, and amperage. The nasal cavity and paranasal sinuses were examined independently in a blinded fashion by four staff neuroradiologists and a staff otolaryngologist with special attention to 10 anatomic landmarks within the ostiomeatal unit that are considered important for preoperative planning. A score of 0 (nonvisualization/incomplete visualization) or 1 (clear/complete visualization) was assigned to each of these 10 landmarks. Analysis of variance was used in which reader, subject, and side were simultaneously controlled by "blocking." Multiple comparison methods (ie, Bonferroni) were used to compare the different protocols.

RESULTS

We found a significant reduction in the delineation, and therefore the perception, of the ostiomeatal unit structures when the section thickness was greater than 5mm, any intersection gap was used, and the gantry angle was greater than 10 degrees from the plane perpendicular to the hard palate. However, a reduction in the radiation exposure from 200 mA to 80 mA did not affect the display of the anatomic landmarks.

CONCLUSION

We found the optimal screening CT protocol for the paranasal sinuses to be a section thickness of 3 mm, no intersection gap, and a section angle within 10 degrees from the plane perpendicular to the palate. Also, owing to inherent contrast between air, soft tissue, and bone in the paranasal sinuses, a reduction in the radiation exposure parameter to 80 mA did not affect image quality.

Eosinophilia in chronic childhood sinusitis

OBJECTIVES

To quantify eosinophilia in sinus tissues obtained from children with chronic sinusitis and to correlate the degree of eosinophilia with history of asthma, allergy, cystic fibrosis, and preoperative computed tomographic (CT) scans.

DESIGN

Examination of surgical specimens from children who underwent functional endoscopic sinus surgery and controls.

SETTING

Tertiary care medical center.

PATIENTS

Thirty-four children who underwent functional endoscopic sinus surgery for chronic sinusitis refractory to medical treatment were divided into three groups: 13 with asthma, 11 without asthma, and 10 with cystic fibrosis. Normal sphenoid sinus mucosa was also obtained from six adults undergoing transsphenoidal hypophysectomies.

MAIN OUTCOME MEASURES

Number of lamina propria and intraepithelial eosinophils in surgical specimens, allergic status, presence or absence of asthma, and CT scans obtained preoperatively.

RESULTS

There were significantly more lamina propria and intraepithelial eosinophils in the tissue of children with chronic sinusitis compared with normal sphenoid sinus mucosa. More eosinophils were counted in the tissues of patients with asthma and cystic fibrosis compared with patients without concomitant disease, but this did not reach statistical significance. Allergy status did not affect the degree of tissue eosinophilia. Eosinophilia did not correlate with severity of mucosal disease as assessed by CT scans.

CONCLUSIONS

Tissue eosinophilia is a characteristic histologic feature of chronic sinusitis in children, especially those with asthma. The presence of allergy does not predict tissue eosinophilia. Furthermore, the degree of tissue eosinophilia does not correlate with the severity of mucosal thickening seen on CT scans.

Update on imaging for functional endoscopic sinus surgery

This article details the imaging modalities available for patients being considered for functional endoscopic sinus surgery. The pertinent radiologic anatomy is reviewed with an emphasis on normal variations. Imaging appearances of inflammatory sinus disease as well as postoperative appearances, including complications, are presented.

Three-dimensional reconstruction of the feline larynx with serial histologic sections

This paper reviews a new technique to develop high-resolution three-dimensional (3-D) images of the larynx using histological sections. Three-dimensional computer-reconstructed histological sections of the cat are used in this study to evaluate the recurrent laryngeal nerve (RLN) in its true anatomic course, with emphasis on its relationship to surrounding structures (laryngeal framework). A cat model was used because of specimen availability and technical ease of tissue preparation. Computer-reconstructed serial histologic sections add a new dimension to the study of laryngeal anatomy, laryngeal trauma, and growth patterns of laryngeal cancer. The technical aspects of three-dimensional reconstruction and future applications are discussed.

In vitro evaluation of MR hypointensity in Aspergillus colonies

PURPOSE

To demonstrate that paramagnetic elements in fungal colonies can cause hypointensity in MR images.

METHODS

Aspergillus fumigatus grown in vitro was imaged with CT and MR at the time of initial inoculation and 5 days later. CT and MR images, T2 values, scanning electron microscopy, energy-dispersive analysis, and furnace atomic absorption spectrometry were performed.

RESULTS

After 5 days of growth, MR images of A fumigatus revealed curvilinear hypointensities on T2-weighted images corresponding to the fungal growth. Gradient-echo images revealed two distinct components of hypointensity with different calculated T2 values. Phase-angle-difference images revealed a phase shift characteristic of magnetic-susceptibility paramagnetic effects, which corresponded to the hypointense regions on gradient-echo images. Energy-dispersive analysis and furnace atomic absorption spectrometry confirmed the presence of paramagnetic elements.

CONCLUSION

It was shown that in vitro A fumigatus concentrates metal elements contained within the nutrient broth. These focal collections of calculated T2 values are caused at least partly by magnetic susceptibility effects.

Three-dimensional models for head and neck tumor treatment planning

The authors have evaluated two types of practical maxillofacial model systems useful to the head and neck surgeon:1. plastic mandibular model generated by three-dimensional computerized tomography (CT) reconstruction, and 2. dental impression model of the maxilla. The first model is expensive and technology intensive; the second is simple but limited. Both three-dimensional models offer several advantages: 1. they provide segmental mandibular relationships that are not known because of oncologic restrictions or previous surgery; 2. they allow preoperative reconstructive planning including prosthesis fabrication and visualization of tumor extent not obvious by two dimensional imaging; and 3. they provide a permanent record for future needs or reconstructions. The disadvantages include cost, time, and possible inaccuracies secondary to image artifacts. We find both models to be of significant practical value in selected head and neck tumor patients.

Frameless stereotaxic integration of CT imaging data: accuracy and initial applications

To evaluate the spatial accuracy of a rapid interactive method of transferring computed tomographic (CT) information between its display on a computer screen to its source (test object, operating field), a multidimensional computer combined with a six-jointed position-sensing mechanical arm was tested with a Plexiglas model consisting of 50 rods of varied height and known location, a plastic replica of the skull, and, subsequently, three patients. The median error value between image and real location was 1-2 mm (P > .95), regardless of the registration target sites. The accuracy, however, increased with the selection of widespread registration points, and 95% of all errors were below 3.70 mm (P > .95). The results compare favorably with the four most commonly used stereotaxic framed units. A misregistration error of 0.3-2.2 mm was found during intraoperative correlation between anatomy on the CT display and actual anatomic location in the operative field.

Coronal CT scan abnormalities in children with chronic sinusitis

Coronal computed tomography (CT) scans are currently the optimal study to display the normal and abnormal anatomy in children with chronic and recurrent acute sinusitis after failure of medical therapy. To assess the extent and distribution of disease as well as associated anatomic abnormalities in this pediatric population, 74 coronal CT scans of children with continued symptoms of sinusitis after failure of extensive medical therapy were reviewed retrospectively. Twelve children with cystic fibrosis showed the characteristic features of medial displacement of the lateral nasal wall in the middle meatus and uncinate process demineralization, creating the appearance of a maxillary sinus mucocele. Nine of these 12 children had increased attenuation in the maxillary sinus on soft-tissue windows. In the remaining 62 children, a significantly greater frequency of disease, when compared with that reported for adults, was seen in the maxillary, anterior ethmoid, posterior ethmoid, and frontal sinuses. Children with asthma (n = 33) had more extensive disease. Bony anatomic abnormalities were similar to those reported for adults, except for a lower incidence of septal deformity.

Radiographic imaging of sinusitis in HIV infection

Magnetic resonance images (MRI) of the brain from 75 homosexual men were reviewed to evaluate the frequency and severity of incidental sinus disease associated with human immunodeficiency virus (HIV). All scans had been performed for reasons other than a history of sinus disease. The opacification of each sinus cavity was scored such that 0 = normal, 1 = < 25%, 2 = 25% to 75%, and 3 = > 75% opacification. Subjects were then stratified by clinical status into four groups: HIV-, HIV+ without HIV-related symptoms, AIDS-related complex (ARC), or AIDS. Grade 1 mucosal thickening was present in 52% to 55% of HIV- and HIV+ subjects alike. Moderate disease (grade 2 or 3) was seen in seven of 52 HIV+ subjects, but none of the 23 HIV- controls. The incidence of maxillary sinus thickening was 69% in men with AIDS, compared to 30% in HIV- men (chi 2 = 4.1, p < 0.05). Mean maxillary sinus scores were 1.25 +/- 0.29 in those with AIDS compared to 0.43 +/- 0.15 in HIV- men (f = 5.11, p < 0.05). Our results suggest that maxillary sinus disease is more common and more severe in patients who have AIDS.

The influence of finasteride on the volume of the peripheral and periurethral zones of the prostate in men with benign prostatic hyperplasia

To determine the influence of androgen deprivation induced by the potent 5 alpha-reductase inhibitor finasteride on the volume of the zones of the prostate, 20 symptomatic men with established BPH were randomized to one of three groups: placebo, finasteride 1 mg, and finasteride 5 mg/day. The volume of the entire prostate gland, periurethral zone, and peripheral zone and the seminal vesicles were determined by three dimensional reconstructions of magnetic resonance contoured images of the prostate. There was no significant difference between the results achieved with 1 and 5 mg of finasteride per day; thus the results in these two groups were combined. In the placebo group there was no significant change in the volume of any structure. Following treatment for 1 year with finasteride there was a significant (P < 0.02) 17% decrease in total gland size (11.5 +/- 3.2 cc). Similarly, there was a significant (P < 0.02) 17% decrease in total gland size (11.5 +/- 3.2 cc). Similarly, there was a significant (P < 0.03) decrease in the size of the periurethral zone of the prostate (6.2 +/- 3 cc). Although there was also a decrease in the size of the peripheral zone of the prostate (2.8 +/- 1.2 cc) this did not reach statistical significance. There was no significant change in the volume of the seminal vesicles. These findings indicate for the first time that androgen deprivation induces a significant decrease in the size of the periurethral zone of the prostate in men with established BPH.

The utility of magnetic resonance imaging in the diagnosis of intranasal meningoencephaloceles

We present three patients in whom the diagnosis of intranasal meningoencephalocele was made by magnetic resonance imaging. The initial clinical evaluation and computed tomographic examinations of these patients failed to distinguish between chronic inflammation and intranasal meningoencephalocele. Although both computed tomography and magnetic resonance imaging are used to distinguish between normal, inflammatory, and neoplastic tissue in the nasal cavity and paranasal sinuses, limitations do exist and these are the focus of our communication. A clear understanding of the efficacy of these radiographic modalities will enhance surgical planning and can preclude severe complications.

Inverted papilloma: evaluation with MR imaging

The authors examined the magnetic resonance (MR) appearance of inverted papillomas to determine if this histologically benign lesion could be distinguished from malignancies of the sinonasal cavity. MR images in 10 patients with histologically proved inverted papilloma were retrospectively reviewed. The signal intensity of inverted papillomas on short repetition time (TR) images was iso- to slightly hypertintense to muscle in all 10 patients. Inverted papillomas had intermediate signal intensity on the long TR/echo time (TE) images. The tumors were iso- or slightly hypointense to fat on long TR/short TE images. In the seven patients who received gadopentetate dimeglumine, all inverted papillomas showed solid inhomogeneous enhancement. A review of eight sinonasal malignancies showed no distinctive signal intensity or enhancement characteristics to help differentiate inverted papillomas from various malignant tumors. The authors conclude that there is no signature MR appearance for the benign inverted papilloma. The main utility of MR imaging is in defining the extent of the lesion.

Human papillomavirus in sinonasal papillomas and squamous cell carcinoma

The diagnostic and prognostic relevance of human papillomavirus (HPV) types 6, 11, 16, and 18 in squamous papilloma, inverted papilloma, and squamous carcinoma of the sinonasal epithelium was examined using the polymerase chain reaction (PCR) technique. Four (15%) of 26 squamous papillomas, 7 (24%) of 29 inverted papillomas, and 1 (4%) of 24 squamous carcinomas were positive for HPV when examined using the PCR amplification technique. Human papillomavirus 6 was present in 5 specimens (3 squamous and 2 inverted papillomas); HPV-11 was present in 6 specimens (1 squamous and 5 inverted papillomas); and HPV-18 was present in 1 of 24 squamous carcinomas. HPV-16 was not identified in any specimen. The proportion of tissue samples showing HPV presence, and the association of HPV types 6 and 11 with benign lesions and HPV-18 with malignant lesions, are both in accord with findings from prior investigations. Two major questions regarding nasal papilloma are the probability for lesion recurrence after surgical excision and the risk for malignant transformation. There is no unanimity of opinion regarding the prognostic value of histopathologic dysplasia to forecast these outcomes. HPV is etiologically related to a subset of sinonasal papillomas and squamous carcinoma, and those with benign and malignant clinical course are separable on basis of HPV type. Because of the paucity of these nasal lesions, a multi-institutional prospective collaborative study is the ideal way to address these questions.

Imaging of the nasal cavity and paranasal sinuses

The CT examination in the coronal plane is the optimal imaging modality to evaluate the nasal cavity and the paranasal sinuses, especially for evaluating chronic inflammatory disease. This modality affords optimal display of the osteomeatal channels and best defines the extent of mucoperiosteal disease. Updated parameters for scanning afford a significant reduction of radiation. MR imaging supersedes CT in its ability to distinguish between inflammatory and neoplastic pathology and appears to be the optimal imaging modality for diagnosis of fungal sinusitis.

Iohexol cervical myelography in adult outpatients

The incidence of adverse reactions following standard film or screen cervical myelography with iohexol in 32 adult outpatients was reported. Iohexol at a dose of 1,080-3,000 mg of iodine was administered via a lateral C1-C2 approach in 26 patients and via a lumbar route in 6 patients. All 32 patients underwent postmyelographic cervical spine computed tomography and were discharged after the procedure was completed. No adverse reactions occurred in 53.1% of patients. The most common adverse reaction was headache (31.3%); other minor adverse reactions included exacerbation of pre-existing pain (12.5%), neck stiffness (9.4%), and vomiting (6.3%). Good to excellent technical quality was seen on all myelograms and computed tomographic scans. Outpatient cervical myelography with iohexol appears to be a safe and cost-effective alternative to inpatient examination.

Facial nerve imaging

A review of past, present, and potential future imaging of the facial nerve outlines the general technologic advances in radiology. The newer modalities provide more information than before; however, with more sophisticated technology, efficient use should be emphasized. A coordinated approach between the otolaryngologist and the radiologist is needed first to localize the most likely segment and then to perform a tailored radiographic study specifically for that segment. In this way, it is hoped that we can avoid unnecessary studies and achieve earlier diagnoses.

Computerized tomography in the evaluation of penetrating ocular injuries

An evaluation was made of the cases of 80 consecutive patients (82 eyes) who underwent acute surgical intervention for penetrating eye injuries. Of these cases, 46 patients had computerized tomography (CT) of the orbit performed in addition to routine preoperative ophthalmic examination. Eyes with more severe injuries and eyes in which the posterior segment was not visualized on the preoperative ophthalmic examination were more likely to undergo CT evaluation. CT scanning frequently demonstrated posterior segment pathology not observable by ophthalmic examination. The following CT findings were associated with poor visual or anatomic outcome: (1) posterior segment hemorrhage; (2) vitreous space distortion; and (3) lens disruption. This study suggests that CT scanning may provide useful information as to the nature and extent of injury in cases of penetrating ocular trauma.

Surgical resection of intrinsic brain stem lesions: an overview

A major limitation to the effective treatment of intrinsic mass lesions of the brain stem has been the inability to clearly define the pathological anatomy radiographically. The improved soft tissue resolution offered by magnetic resonance imaging, as compared with axial computed tomography, now makes it possible not only to accurately distinguish anatomical relationships, but also to predict the pathological nature of the lesion. Accordingly, we have been encouraged to pursue a more aggressive approach to intrinsic lesions of the brain stem that appear well circumscribed on magnetic resonance imaging scan. The object of this paper is to report the successful treatment of four intrinsic lesions of the brain stem and to present an overview of the relevant published experience.

Paranasal sinus imaging

The inability of plain radiographs to yield conclusive information about the ostiomeatal complex in sinusitis is no longer a significant problem. Computed tomography (CT), magnetic resonance imaging (MRI), and improved endoscopic technology now enable almost complete exploration of the sinus anatomy and the pathophysiology of sinus disease. Nasal endoscopy provides a clear view of the anterior nasal cavity--including the middle meatus--in patients with symptoms of sinusitis. However, the maxillary ostia are still difficult to visualize directly. CT is required for noninvasive evaluation of deep ostiomeatal air passages and posterior ethmoid and sphenoid sinuses. MRI of the nasal cavity and paranasal sinuses, although of limited use for displaying nasal morphology, is even more sensitive than CT in identifying fungal concretions and neoplasms.

Three-dimensional CT imaging in postsurgical "failed back" syndrome

One hundred consecutive patients with postsurgical "failed back" syndrome (PSFBS) without fusion and 100 patients with PSFBS with fusion were evaluated with direct CT, two-dimensional (2D) multiplanar, and three-dimensional (3D) imaging. In the patients with and without fusion, 3D images were found to best display the following: the surgical procedure and its extent, lateral neural foraminal narrowing, and fractures of the posterior elements. The 3D images enabled optimal demonstration of fusion: solidity, pseudarthrosis, incorporation of transverse processes and facet joints, and transitional syndrome. In the patients without fusion, 3D images provided improved appraisal of surgical results in 31%; it showed additional fracture(s) in 9%, better displayed lateral neural foraminal narrowing in 42%, and showed additional posterior element fractures in 11% as compared to axial and 2D multiplanar reconstructed (MPR) scans. Three-dimensional imaging uncovered incomplete fusion in 17%, transitional syndrome in 13%, and pseudarthrosis in 6%. Thus, the 3D imaging provided additional information over the direct axial and MPR images (2D images) in 56 of 100 patients without fusion and 76 of 100 patients with fusion. At our institution, this imaging modality is now routinely performed in this patient population.