Evaluation of variations in sinonasal region with computed tomography

AIM: To investigate the frequency of anatomical variations in sinonasal region and association of these variations with mucosal diseases.METHODS: The study included 400 cases (191 female and 209 male) who were considered to have preliminary diagnoses of sinonasal pathology and who had paranasal sinus computed tomography (CT) examination in axial plane. Reformatted CT images were studied in all planes.RESULTS: Age range of the patients was 20-83 (mean 40.26 ± 14.85). Most commonly detected anatomical variation was Agger nasi cell (74.8%). There was a significant association between clinoid process pneumatization and protrusion of internal carotid arteries and optic nerves into sphenoid sinus (P < 0.001). Besides, the relationships between pterygoid process pneumatization and protrusion of vidian nerve into sphenoid sinus, and between pneumatization of large sphenoid wing and protrusion of maxillary nerves into sphenoid sinus were also significant (P < 0.001). Uncinate bulla and giant ethmoid bulla were found to be significantly associated with sinonasal mucosal diseases (P = 0.004 and P = 0.002, respectively).CONCLUSION: Sinonasal region has a great number of variations, and some of them have been determined to be associated with sinonasal mucosal disease. It is necessary to know that some of these variations are associated with protrusion of significant structures such as carotid artery or optic nerve into the sinus and care should be observed in surgeries on patients carrying these variations.     

The CT Prevalence of Arrested Pneumatization of the Sphenoid Sinus in Patients with Sickle Cell Disease

BACKGROUND AND PURPOSE:Arrested sphenoid pneumatization is an incidental radiologic finding on CT and MR imaging that may be confused with more aggressive pathologic conditions. No definite etiology for arrested sphenoid pneumatization has been established, though changes in regional blood flow during childhood, as is seen with sickle cell disease, have been proposed. The purpose of our study was to compare the prevalence of arrested pneumatization of the sphenoid sinus in patients with and without sickle cell disease.MATERIALS AND METHODS:We retrospectively identified 146 patients with sickle cell disease who had undergone CT scans of the skull base between January 1990 and May 2015. We identified 292 control patients without sickle cell disease matched for age and sex in a 1:2 ratio. We tabulated the prevalence of arrested pneumatization as well as the location and size of the lesions. We used the Fisher exact test to correlate sickle cell disease with arrested pneumatization of the sphenoid sinus and the t test to correlate sickle cell disease with lesion size.RESULTS:Of the 146 patients with sickle cell disease, 14 (9.6%) had arrested pneumatization of the sphenoid sinus. In the 292 control patients, 6 (2.1%) had arrested pneumatization. Patients with sickle cell disease had a statistically significant higher rate of arrested pneumatization compared with patients without sickle cell disease (P < .001). There was no statistically significant correlation between lesion size and diagnosis of sickle cell disease.CONCLUSIONS:Patients with sickle cell disease have a greater prevalence of arrested pneumatization of the sphenoid sinus than patients without sickle cell disease. This supports the theory that either regional blood flow anomalies or increased serum erythropoietin causes arrested sinus pneumatization.

The normal development of the sphenoid sinus is preceded by a phase of fatty transformation and fat involution in the bone marrow, followed by aeration of the marrow that then results in full pneumatization.^1,2 This process begins at 4 months of age and usually ends at 10–14 years of age.^3,4 This process may be interrupted, leaving atypical fatty marrow that persists into adulthood.Change in regional blood flow has been suggested as a potential stimulus for fatty marrow conversion.⁵ If this theory is correct, then diseases that produce aberrant regional blood flow might predispose a person to arrested sinus pneumatization. Sickle cell disease (SCD) is an example of a disorder that produces regional blood flow changes in childhood, but no study has investigated the correlation between arrested sphenoid pneumatization and SCD.We hypothesized that there is an increased prevalence of arrested pneumatization of the sphenoid sinus in patients with SCD compared with those without SCD.     

CT characterization of developmental variations of the paranasal sinuses in cystic fibrosis

Purpose: To describe variations of paranasal sinus development in patients with cystic fibrosis (CF) and in non-CF patients examined for inflammatory sinonasal disease. We focused on anatomic variants that predispose to orbital and cerebral penetration during functional endoscopic sinus surgery (FESS), e.g. hypoplasia of the maxillary sinus and low ethmoid roof.Material and Methods: One hundred and sixteen CF patients (3-54 years, median 18) and 136 control patients (7-51 years, median 31) were examined with coronal CT of the paranasal sinuses. CF patients were grouped according to number of confirmed mutations: CF-2 (n=70), CF-1 (n=32), CF-0 (n=14). CT images were evaluated with respect to paranasal sinus development, pneumatization variants and bony variants.Results: Frontal sinus aplasia and maxillary, ethmoid, and sphenoid sinus hypoplasia were markedly more frequent in CF-2 than in control patients. No CF-2 patient had pneumatization variants such as Haller cells or concha bullosa. Low ethmoid roof was seen in 30% of CF-2 children, but in no control children. CF-1 and CF-0 groups had prevalences of aplasia and hypoplasia intermediate to that of CF-2 and control patients.Conclusion: Genetically verified CF patients had less developed sinuses, lacked pneumatization variants, and more often had anatomic variants that predispose to complications during FESS. Normally developed sinuses and pneumatization variants in some genetically unverified CF patients (CF-1, CF-0) suggest that these patients may be erroneously diagnosed.     

Remarkable anatomic variations in paranasal sinus region and their clinical importance

With the advent of functional endoscopic sinus surgery (FESS) and coronal computed tomography (CT) imaging, considerable attention has been directed toward paranasal region anatomy. Detailed knowledge of anatomic variations in paranasal sinus region is critical for surgeons performing endoscopic sinus surgery as well as for the radiologist involved in the preoperative work-up. To be in the known anatomical variants with some accompanying pathologies, directly influence the success of diagnostic and therapeutic management of paranasal sinus diseases. A review of 512 (1024 sides) paranasal sinus tomographic scans was carried out to expose remarkable anatomic variations of this region. We used only coronal sections, but for some cases to clear exact diagnosis, additional axial CT scan, magnetic resonance imaging (MRI) and nasal endoscopy were also performed. In this pictorial essay, rates of remarkable anatomic variations in paranasal region were displayed. The images of some interesting cases were illustrated, such as the Onodi cell in which isolated mucocele caused loss of visual acuity, agger nasi cell, Haller's cell, uncinate bulla, giant superior concha bullosa, inferior concha bullosa, bilateral carotid artery protrusion into sphenoid sinus, maxillary sinus agenesis, bilateral secondary middle turbinate (SMT) and sphenomaxillary plate. The clinical importance of all these variations were discussed under the light of the literature. It was suggested that remarkable anatomic variations of paranasal region and their possible pathologic consequences should be well defined in order to improve success of management strategies, and to avoid potential complications of endoscopic sinus surgery. The radiologist must pay close attention to anatomical variations in the preoperative evaluation.     

Variability in sphenoid sinus pneumatization and its impact upon reduction of complications following sellar region surgeries

BackgroundThe rapid evolution of transsphenoidal endoscopic surgical intervention and surgeries of skull base and sellar regions is accompanied by multiple complications.ObjectiveTo determine different types of extension of sphenoid sinus pneumatization detected by CT and MRI and their impact upon different approaches and complications of sellar region surgeries.Subjects and methodsThe pre-operative CT and MRI images of 182 patients with surgical intervention for peri-sellar region pathologies were retrospectively evaluated for patterns of sphenoid pneumatization. Post surgical complications were recorded and analyzed.ResultsThe overall rate of complications was 88 affecting 62 patients (34%), and 120 patients (66%) were free of complications. Different types of pneumatization were detected on CT and MRI images, conchal in 3 cases (1.6%), presellar 23 cases (12.6%) and 156 cases (85.7%) showing sellar pneumatization. Sellar pattern was reclassified into 6 types. Single inter sphenoid septum was seen in 109 patients, accessory septum was found in 13 patients and 10 patients have multiple sphenoid septation. 24 patients (13.2%) show absent septum.ConclusionPre-intervention assessment of sphenoid sinus pneumatization is mandatory in approaching the sella and skull base structures either via the nose or open skull base surgery to avoid injury of the nearby structures and reduce the possibility of CSF leakage.     

蝶筛外侧壁HRCT影像解剖学研究

目的：探讨蝶筛外侧壁与颈内动脉(ICA)和视神经(ON)的毗邻关系及其临床意义。资料与方法：回顾性分析80例(160侧)颅底高分辨率CT(HRCT)轴位图像。评价ICA和ON在蝶筛外侧壁上形成隆起的形态特征及视神经管(OC)与蝶筛外侧壁的毗邻关系。结果：ICA隆起型27侧(16．88％)，压迹型68侧(42．50％)，远离型65侧(40．62％)；ON隆起型46侧(28．75％)，压迹型95侧(59．38％)，远离型19侧(11.87％)；OC46侧(28．75％)全程与蝶窦外侧壁毗邻，40侧(25％)全程与后组筛窦毗邻，61侧(38.13％)与两者共邻。结论：颅底轴位HRCT扫描能够很好地评价蝶筛外侧壁毗邻的解剖关系，可以在术前为蝶筛区域手术提供精确的解剖信息，不仅能有效地提高手术的安全性，还有助于手术进路的选择及手术方案的确定。     

CT evaluation of pterygoid process pneumatization and the anatomic variations of related neural structures

Objective

This topic is concerned with the clarification of the radiological findings that should be reported as regard the anatomic variations of the neural structures related to the pterygoid process in patients listed for endoscopic sinus surgery.

颈内动脉海绵窦段创伤性假性动脉瘤破入蝶窦的CT和MRI诊断

目的评价CT和MRI对颈内动脉海绵窦段创伤性假性动脉瘤（TPA）破入蝶窦的诊断价值.方法对经DSA证实的6例海绵窦段TPA破入蝶窦的CT和MRI资料进行回顾性分析.全部患者均行CT检查,5例行MR检查.结果6例颈内动脉海绵窦段TPA中,CT平扫均显示蝶窦侧壁骨折及其密度增高,2例CT增强扫描均可见蝶窦呈明显均匀强化,强化程度与正常血管一致,海绵窦扩大,1例CT血管成像（CTA）明确显示动脉瘤体与瘤颈.5例行MR SE序列平扫,患者均表现为分层状混杂长T1、混杂长T2信号的血栓,4例尚可见瘤腔内的流空现象;3例增强扫描示蝶窦呈明显均匀强化,强化程度与正常血管一致,其中1例在相位编码方向上流动伪影明显;2例MR血管成像均明确显示瘤体与瘤颈.结论CT和MRI是诊断颈内动脉海绵窦段TPA破入蝶窦的有效非创伤性检查,并可作为手术前后长期随访的良好检查方法.     

Pneumatization of the sphenoid sinus

This paper describes a case of pneumatization of the sphenoid sinus in the pterygoid process and greater wing of the sphenoid bone, observed on a panoramic radiograph. Conventional radiographs and computerized tomography in axial and coronal sections confirmed the presence of the pneumatization of these structures.     

X-ray computed tomographic study of the ethmoid and middle meatus. II. Radio-anatomy (axial incidence) and morphological variations

Chronic rhinosinusitis endoscopic surgery needs an accurate evaluation of diseases and paranasal sinus anatomic variations. High resolution CT by thin section (2 mm) allow this pre-operative assessment. An anatomical study of the ethmoid air cell system is always possible in axial plane. The bidimensional CT exploration (axial and coronal plane) displays the anatomic variations of ostiomeatal unit, that have been reported to predispose sinusitis. They are nasal septal deviation, pneumatization and paradoxical curvature of the middle turbinate, pneumatization of unciform process, Haller's cells, prominent agger nasi cell and ethmoid bulla. The endoscopic endonasal surgery landmarks, the individual morphologic variations, the topographic relations to the orbit and to the brain are also well shown by CT.     

Marrow conversion before pneumatization of the sphenoid sinus: assessment with MR imaging

To evaluate the bone marrow change before pneumatization of the sphenoid sinuses in childhood, the authors retrospectively reviewed short repetition time/echo time midsagittal magnetic resonance images in 56 patients younger than 6 years. The signal intensity of the presphenoid bone marrow (anteromedial part of the sphenoid bone) was as low as that of muscle (grade 1) and remained the same as that of the basisphenoid and basiocicput in all infants (n = 6) younger than 6 months. Between 7 months and 2 years, most patients (24 of 27) exhibited fatty conversion of bone marrow limited to the presphenoid (grade 2). After 3 years of age, most patients demonstrated pneumatization (six of 12 at 3-4 years, eight of 11 at 5-6 years) in addition to the grade 2 findings (grade 3). The presphenoid exhibits signal intensity characteristics of fatty marrow before it is invaginated by the developing sphenoid sinus. Fatty change before pneumatization is a normal developmental process and should not be misinterpreted as a pathologic condition.     

A retrospective analysis of spontaneous sphenoid sinus fistula: MR and CT findings

BACKGROUND AND PURPOSE: The sphenoid sinus is rarely implicated as a site of spontaneous CSF fistula. We undertook this study to evaluate the potential etiopathogenesis of spontaneous CSF fistula involving the sphenoid sinus and to review the imaging findings. METHODS: We retrospectively reviewed the imaging findings of 145 cases of CSF fistula from our departmental archives (August 1995 through August 1998). Fifteen (10%) patients had CSF fistulas involving the sphenoid sinus. Eleven (7%) patients had spontaneous CSF fistulas, whereas in four patients, the CSF fistulas in the sphenoid sinus were related to trauma. Of the 11 patients, nine underwent only plain high-resolution CT and MR cisternography. One patient additionally underwent contrast-enhanced CT cisternography, and one other patient underwent MR cisternography only. For each patient, the CSF fistula site was surgically confirmed. The MR imaging technique included T1-weighted and fast spin-echo T2-weighted 3-mm-thick coronal sequences obtained with the patient in the supine position. The plain high-resolution CT study included 3-mm-thick, and sometimes 1- to 1.5-mm-thick, coronal sections obtained with the patient in the prone position. Similar sections were obtained after injecting nonionic contrast material intrathecally via lumbar puncture for the CT cisternographic study. We evaluated each of the 11 patients for the exact site of CSF leak in the sphenoid sinus. We also determined the presence of pneumatization of lateral recess of the sphenoid sinus, orientation of the lateral wall of the sphenoid sinus, presence of arachnoid pits, presence of brain tissue herniation, and presence of empty sella in each of these patients. RESULTS: The exact sites of the CSF fistulas were documented for all 11 patients by using plain high-resolution CT, MR cisternography, or CT cisternography. In nine (82%) patients, the sites of the CSF fistulas were at the junction of the anterior portion of the lateral wall of the sphenoid sinus and the floor of the middle cranial fossa. In the remaining two (18%) patients, the sites of the CSF fistulas were along the midportion of the lateral wall of the sphenoid sinus. Of these 11 patients, one had bilateral sites of the CSF fistula at the junction of the anterior portion of the lateral wall of the sphenoid sinus with the floor of the middle cranial fossa. In nine (82%) patients, the presence of brain tissue herniation was revealed, and this finding was best shown by MR cisternography. Ten (91%) patients had extensive pneumatization of the lateral recess of the sphenoid sinus, with an equal number having outward concave orientation of the inferior portion of the lateral wall of the sphenoid sinus. In seven (63%) patients, the presence of arachnoid pits, predominantly along the anteromedial aspect of the middle cranial fossa, was shown. In seven (63%) patients, empty sella was shown. For comparison, we reviewed the CT studies of the paranasal sinuses in 100 age-matched control subjects from a normal population. Twenty-three had extensive lateral pneumatization of the sphenoid sinus along with outward concavity of the inferior portion of the lateral wall. None of these 23 patients had arachnoid pits. CONCLUSION: The sphenoid sinus, when implicated as a site of spontaneous CSF leak, yields a multitude of imaging findings. These are extensive pneumatization of the lateral recess of the sphenoid sinus, outward concave orientation of the inferior portion of the lateral wall of the sphenoid sinus, arachnoid pits, and empty sella. Considering the normative data, we speculate that this constellation of findings could play a role in the etiopathogenesis of spontaneous sphenoid sinus fistulas. Our findings also show the efficacy of noninvasive imaging techniques, such as plain high-resolution CT and MR cisternography, in the evaluation of sphenoid sinus CSF leak. Our data also suggest that spontaneous sphenoid sinus CSF leak is not an uncommon occurrenc     

Benign expansile lesions of the sphenoid sinus: differentiation from normal asymmetry of the lateral recesses

BACKGROUND AND PURPOSE: There is a wide range of normal variation is sphenoid sinus development, especially in the size of the lateral recesses. The purpose of this study was to determine imaging characteristics that may help differentiate between opacification of a developmentally asymmetric lateral recess and a true expansile lesion of the sphenoid sinus. METHODS: Coronal CT was performed in seven patients with expansile or erosive benign lesions of the sphenoid sinus, and results were compared to a control population of 72 subjects with unopacified sphenoid sinuses. The degree of asymmetry of lateral recess development was assessed with particular attention to the separation of vidian's canal and the foramen rotundum (vidian-rotundum distance). The images were also examined for evidence of: erosion, defined as loss of the normal thin bony margin on at least two contiguous sections; apparent thinning of the sinus wall, defined as a focal apparent decrease in thickness again on at least two contiguous sections; and for vidian's canal or foramen rotundum rim erosion or flattening. RESULTS: Of the seven patients with expansile lesions, vidian's canal margin erosion was present in seven, unequivocal sinus expansion in three, wall erosion in three, wall thinning in three, erosion of the foramen rotundum in two, and flattening in the foramen rotundum in four. Forty-one of the 72 controls had lateral recess formation, 28 of which were asymmetric. The distance between vidian's canal and the foramen rotundum (vidian-rotundum distance) relied on the presence or absence of pneumatization, with a significantly larger distance in the presence of greater wing pneumatization. Examination of 24 controls revealed apparent thinning of the sinus wall, typically at the carotid groove, but no flattening, thinning, or erosion of the vidian canal or of the foramen rotundum. CONCLUSION: Examination of controls and patients with expansile or erosive lesions of the sphenoid sinus revealed side-to-side asymmetry in the development of the sinus and lateral recess, making subtle expansion difficult to assess. Furthermore, variability in the vidian-rotundum distance correlated with degree of pneumatization, and did not necessarily reflect expansion. Thus, in the absence of gross sinus wall erosion, flattening or erosion of the rims of vidian's canal or the foramen rotundum provides the most specific evidence of an expansile or erosive process within the sinus.     

CT血管成像诊断破入蝶窦的颈内动脉创伤性假性动脉瘤

目的 评价颅脑CTA在海绵窦段颈内动脉创伤性假性动脉瘤中的诊断价值.方法 对7例经DSA证实的颈内动脉海绵窦段创伤性假性动脉瘤患者的CTA联合应用VR、MIP、MPR、CPR后处理技术及临床资料进行回顾性分析.结果 7例CTA均表现为蝶窦内不规则软组织影与海绵窦段颈内动脉同步均匀强化并与其沟通,边界清晰,边缘不规则,病变大小自3 mm×2 mm×1 mm～33 mm×30 mm×27 mm.周边为动脉期不强化的软组织影,邻近蝶窦壁骨折、缺损.6例病变位于海绵窦段颈内动脉前突段,1例位于游离段.7例破口均位于颈内动脉内壁或前内壁.多种后处理技术联合应用可明确显示病变与蝶窦腔、蝶窦骨质及邻近血管的空间关系.结论 颅脑CTA检查对破入蝶窦的海绵窦段颈内动脉创伤性假性动脉瘤可明确诊断;VR、MIP、MPR、CPR后处理技术联合应用可明确蝶窦壁骨折和颈内动脉破口的位置、范围及其二者的关系.

Abstract：

Objective To investigate diagnostic value of CTA for traumatic pseudoaneurysms (TPA) in the cavernous segment of the internal carotid artery (ICA) when they rupture into the sphenoid sinus. Methods CTA of 7 patients with TPA in the cavernous segments of ICA verified by DSA were retrospectively analyzed. All the patients were performed CTA scanning. The post-processing techniques included VR,MIP,MPR, and CPR. Results All the CTA images of 7 patients showed irregular mass in the sphenoid sinus with obviously enhancement in the same phase to ICA, which communicating with ICA in wide base. The peripheral area of the mass showed no enhancement. The size varied from 3 mm × 2 mm × 1 mm to 33 mm × 30 mm × 27 mm. The adjacent lateral wall of sphenoid sinus showed fractures in all cases. TPA located at anterior-knee segments of cavernous ICA in 6 cases, and cavernous free segment in 1 case. All the disruptions were found at medial or anterior medial wall of ICA. Conclusions Cranial CTA is the effective non-invasive method for diagnosing TPA in the cavernous segment of ICA when they rupture into sphenoid sinus. Combined using of VR, MIP, MPR, and CPR can delineate the location and size of the sphenoid wall fracture and the ICA rupture, which help to clarify the anatomical relationship between them.     

MR imaging of nonmalignant polyps and masses of the nasopharynx and sphenoid sinus after radiotherapy for nasopharyngeal carcinoma

BACKGROUND AND PURPOSE: The development of a new polyp or mass in the radiation field of a previously treated carcinoma is usually an ominous sign of a recurrent cancer, but rarely may it be caused instead by a nonmalignant process. The purpose of this study was to document the MR appearance of unusual nonmalignant polyps or masses (NMPMs) in the nasopharynx and sphenoid sinus arising after radiation treatment of nasopharyngeal carcinoma.MATERIALS AND METHODS: The MR imaging reports of patients undergoing imaging after radiation therapy for nasopharyngeal carcinoma were reviewed retrospectively to identify patients with unusual polyps and masses in the nasopharynx. The MR images of those patients with no evidence of malignancy on biopsy or follow-up were reviewed.RESULTS: The MR imaging reports of 1282 patients were reviewed, and 11 patients (1%) with NMPMs in the nasopharynx or sphenoid sinus were identified. Two patterns were identified: contrast enhancing nasopharyngeal polyps ranging in size from 1 to 5 cm (n = 5) and sphenoid sinus masses consisting of a nonenhancing mass filling a nonexpanded sinus (n = 4) and a heterogeneous enhancing mass expanding the sinus (n = 2). Osteoradionecrosis produced a large defect in the roof of the nasopharynx causing direct communication with the sphenoid sinus (n = 6). Histology revealed granulation tissue in all of the patients with variable amounts of fibrin and inflammatory cells. A direct infective etiology was not proved in any patient.CONCLUSION: NMPMs in the nasopharynx and sphenoid sinus are rare complications after radiation therapy to the skull base, but the radiologist needs to be aware of their appearance so that they can be considered in the differential diagnosis of suspected tumor recurrence.

The rapidly dividing cells in the mucosal membranes of the pharynx and paranasal sinuses are very sensitive to the effects of radiation. The severity of radiation damage after treatment of head and neck cancers is related to radiation dose and potentially is increased by the use of chemotherapy and altered fractionation schedules of radiation therapy.¹ The naso-pharynx and sphenoid sinus are especially vulnerable to the effects of radiation treatment of nasopharyngeal carcinoma, because they receive the full radiation dose. Acute mucositis is a consistent clinically visible adverse effect during the standard course of radiation therapy for head and neck cancers. It starts around the second to third week of treatment and usually subsides several weeks after the end of treatment.² Likewise, acute radiation change can be seen on MR imaging. In the pharynx, these MR abnormalities often resolve, whereas in the paranasal sinuses there is a high incidence of persistent minor abnormalities, including mucosal thickening and fluid levels, months or years after treatment for nasopharyngeal carcinoma.^3–5 Rarely a mucocele may form in the sphenoid sinus.⁶ However, there are some patients who go on to develop severe delayed radiation effects resulting in the formation of unusual nonmalignant polyps and masses (NMPMs) in the nasopharynx and sphenoid sinus. These radiation-induced injuries cause both clinical and radiologic problems with distinction from recurrent cancer, as well as being a cause of serious morbidity and even mortality. The aim of this study was to describe these abnormalities in patients undergoing MR imaging after radiation therapy for nasopharyngeal carcinoma.     

Protrusion of the Infraorbital Nerve into the Maxillary Sinus on CT: Prevalence,Proposed Grading Method,and Suggested Clinical Implications

BACKGROUND AND PURPOSE:The infraorbital nerve arises from the maxillary branch of the trigeminal nerve and normally traverses the orbital floor in the infraorbital canal. Sometimes, however, the infraorbital canal protrudes into the maxillary sinus separate from the orbital floor. We systematically studied the prevalence of this variant.MATERIALS AND METHODS:We performed a retrospective review of 500 consecutive sinus CTs performed at our outpatient centers. The infraorbital nerve protruded into the maxillary sinus if the entire wall of the infraorbital canal was separate from the walls of the sinus. We recorded the length of the bony septum that attached the infraorbital canal to the wall of the maxillary sinus and noted whether the protrusion was bilateral. We also measured the distance from the inferior orbital rim where the infraorbital canal begins to protrude into the sinus.RESULTS:There was a prevalence of 10.8% for infraorbital canal protrusion into the maxillary sinus and 5.6% for bilateral protrusion. The median length of the bony septum attaching the infraorbital canal to a maxillary sinus wall, which was invariably present, was 4 mm. The median distance at which the infraorbital nerve began to protrude into the sinus was 11 mm posterior to the inferior orbital rim.CONCLUSIONS:Although this condition has been reported in only 3 patients previously, infraorbital canal protrusion into the maxillary sinus was present in >10% of our cohort. Identification of this variant on CT could help a surgeon avoid patient injury.

CT of the paranasal sinuses is an important diagnostic technique in the work-up of patients with known or suspected disease of the nasal cavity and paranasal sinuses. CT gives the surgeon a roadmap for surgery and alerts the surgeon to the presence of potentially clinically relevant anatomic variants. Many sinonasal variants are important to identify since their presence may increase the risk of surgical error.¹ With the advent of endoscopic techniques, surgery of the paranasal sinuses has expanded to involve complex procedures that were once reserved for open approaches. Thus, it is extremely important to identify such variations from the normal sinus anatomy, especially in patients who are likely to require extended endoscopic sinus surgery for etiologies such as inverted papilloma, mucocele, trauma, or malignant tumor.The infraorbital nerve is the distal portion of the maxillary nerve (V2), which originates as the second division of the trigeminal nerve (fifth cranial nerve). After the maxillary nerve traverses the foramen rotundum, it enters the pterygopalatine fossa and gives off nasal and palatine branches before exiting through the inferior orbital fissure and terminating as the infraorbital nerve (ION). The ION then enters the infraorbital canal (IOC) through the infraorbital groove. The IOC is a bony canal typically within the orbital process of the maxilla, synonymous with the floor of the orbit. The ION exits the IOC through the infraorbital foramen of the anterior maxilla. Variably, the IOC can protrude into the maxillary sinus separate from the floor of the orbit. This may leave the ION susceptible to injury during endoscopic or open sinus surgery. To date, just 3 case reports exist in the literature describing this variant,^2,3 with no large studies describing the frequency with which it occurs. The aim of this study was to establish the prevalence of infraorbital nerve protrusion into the maxillary sinus and define its common characteristics. This variation is of clinical importance in sinus surgery, and we suggest an accompanying grading scale to relay the degree of protrusion to the surgeon.     

Magnetic resonance imaging of carotid artery abnormalities in patients with sphenoid sinusitis

Sphenoid sinusitis is unusual in children, but when it occurs, it can lead to serious intracranial complications. We show the value of MRI in demonstrating intracranial abnormalities due to sphenoid sinus infection, particularly those involving the internal carotid arteries and cavernous sinuses. We reviewed our imaging experience of sphenoid sinusitis and found four patients with ICA narrowing who had undergone MR evaluation including conventional and diffusion imaging. MR angiography was also performed in three patients to determine the extent of ICA narrowing. Narrowing of ICA was found in the cavernous segment in all patients and in the supraclinoid segment in three. Cerebral infarction was found in two patients. In one patient the cavernous sinus showed hyperintensity on diffusion-weighted images and hypointensity on apparent diffusion coefficient map, suggesting reduced diffusion. Although infrequent in children, sphenoid sinus infection should be considered as a possible cause of intracranial infection, particularly in teenagers. Early recognition of cavernous sinus involvement and ICA narrowing may lead to prompt treatment and hence a more favorable outcome.     

The sphenoparietal sinus of breschet: does it exist? An anatomic study

BACKGROUND AND PURPOSE: The termination of the superficial middle cerebral vein is classically assimilated to the sphenoid portion of the sphenoparietal sinus. This notion has, however, been challenged in a sometimes confusing literature. The purpose of the present study was to evaluate the actual anatomic relationship existing between the sphenoparietal sinus and the superficial middle cerebral vein. METHODS: The cranial venous system of 15 nonfixed human specimens was evaluated by the corrosion cast technique (12 cases) and by classic anatomic dissection (three cases). Angiographic correlation was provided by use of the digital subtraction technique. RESULTS: The parietal portion of the sphenoparietal sinus was found to correspond to the parietal portion of the anterior branch of the middle meningeal veins. The sphenoid portion of the sphenoparietal sinus was found to be an independent venous sinus coursing under the lesser sphenoid wing, the sinus of the lesser sphenoid wing, which was connected medially to the cavernous sinus and laterally to the anterior middle meningeal veins. The superficial middle cerebral vein drained into a paracavernous sinus, a laterocavernous sinus, or a cavernous sinus but was never connected to the sphenoparietal sinus. All these venous structures were demonstrated angiographically. CONCLUSION: The sphenoparietal sinus corresponds to the artificial combination of two venous structures, the parietal portion of the anterior branch of the middle meningeal veins and a dural channel located under the lesser sphenoid wing, the sinus of the lesser sphenoid wing. The classic notion that the superficial middle cerebral vein drains into or is partially equivalent to the sphenoparietal sinus is erroneous. Our study showed these structures to be independent of each other; we found no instance in which the superficial middle cerebral vein was connected to the anterior branch of the middle meningeal veins or the sinus of the lesser sphenoid wing. The clinical implications of these anatomic findings are discussed in relation to dural arteriovenous fistulas in the region of the lesser sphenoid wing.     

Detectability and detection rate of acute cerebral hemisphere infarcts on CT and diffusion-weighted MRI

Our purpose was to compare the detectability and detection rate of acute ischaemic cerebral hemisphere infarcts on CT and diffusion-weighted MRI (DWI). We investigated 32 consecutive patients with acute hemisphere stroke with unenhanced CT and DWI within 6 h of stroke onset. The interval between CT and DWI ranged from 15 to 180 min (mean 60 min). Infarct detectability on CT and DWI was determined by comparing the initial CT, DWI and later reference images in a consensus reading of five independent examiners. The “true” detection rate was assessed by analysing all single readings. Two patients had intracerebral haematomas on DWI and CT and were excluded. There were 27 patients with ischaemic infarcts; all were visible on DWI and proven by follow-up. DWI was negative in three patients without a final diagnosis of infarct (100 % sensitivity, 100 % specificity, χ² = 30, P < 0.0001). Ischaemic infarcts were visible on 15 and not seen on 12 CT studies (55 % sensitivity, 100 %specificity, χ² = 1.48, P = 0.224). With regard to the single readings (30 examinations × 5 examiners = 150 readings), 63 CT readings were true positive and 72 false negative (sensitivity 47 %, specificity 86 %, χ² = 2.88, P = 0.089). Of the DWI readings 128 were true positive and 7 false negative (sensitivity 95 %, specificity 87 %, χ² = 70.67, P < 0.0001). Interobserver agreement was substantial for CT (ϰ = 0.72, 95 % confidence interval, 0.6–0.84) and DWI (ϰ = 0.82, 95 % confidence interval, 0.46–1). Taken together, detectability and detection rate of acute (< 6 h) hemisphere infarcts are significantly higher with DWI than with CT. Received: 14 December 1999/Accepted: 15 February 2000     

MRI of growth hormone-secreting pituitary adenomas: factors determining pretreatment hormone levels

Preoperative serum growth hormone (GH) level is one of the most important determinants of outcome. Our aim was to assess MRI findings which may correlate with pretreatment GH levels in GH-secreting adenomas. We retrospectively studied 29 patients with acromegaly caused by a pituitary adenoma. Tumor size (height, width, thickness and volume), suprasellar extension, sphenoid or cavernous sinus invasion, signal intensity and contrast enhancement were studied. Linear regression analysis or Fisher's exact probability test was used for statistical analysis. Factors related to high GH levels were the maximum dimension of the tumour (r = 0.496, P < 0.01), its volume (r = 0.439, P < 0.05), spenoid sinus invasion (P < 0.01) and intracavernous carotid artery (encasement (P < 0.01). The other items were not related to serum GH levels. Since we believe surgery is the first choice of treatment and the cavernous sinus is difficult of access with a conventional surgical approach, preoperative assessment of invasion into the cavernous sinus is critical for predicting the surgical outcome. Low GH levels (5–50 ng/ml) were found with tumours medial to the intercarotid line and high levels (more than 101 ng/ml) with invasive tumours with carotid artery encasement. Variable GH levels were noted with tumours extending beyond the intercarotid line. Because functioning adenomas invading the cavernous sinus tend to have markedly high hormone levels, and only patients with carotid artery encasement showed markedly elevated GH levels, we believe carotid artery encasement a reliable MRI indicator of cavernous sinus invasion. Received: 1 January 1998 Accepted: 18 March 1999