Vascular anomalies, sutures and small canals of the temporal bone on axial CT

PURPOSE: Subtle bony structures, small canals and fine sutures cause sometimes problems in the analysis of CTs of the temporal bone. The aim of this study was: to analyze the visibility of subtle structures and to estimate the incidence of vascular anomalies. PATIENTS AND METHOD: We retrospectively analyzed axial scans of 223 high-resolution CTs of the temporal bone obtained as single slice or spiral CT with 1mm slice thickness. All CTs had clinical indications. Two experienced radiologists studied CTs regarding the visibility of the fine sutures, fissures and small canals and the occurrence of vascular anomalies. RESULTS: The following structures were seen commonly: sphenosquamosal suture (76%), arcuate artery canal (93%), vestibular aqueduct (89%), mastoid emissary vein (82%), singular canal (56%). Not so commonly were observed: tympanosquamosal suture (31%), mastoid canaliculus (28%), lateral sigmoid sinus (28%), petrotympanic fissure (24%), tympanomastoid suture (10%). Seldom we identified: the inferior tympanic canaliculus (6%), high jugular bulb (6%), anterior sigmoid sinus (5%), dehiscent internal carotid artery canal (2%), persistent petrosquamosal sinus (1%), dehiscent jugular bulb (1%). Persistent stapedial artery, aberrant internal carotid artery, dehiscent jugular bulb, high jugular bulb with diverticulum, anterior and dehiscent sigmoid sinus were detected in below 1% of the analyzed temporal bones. The frequency of asymmetry of the jugular foramen, which varied between 3% and 42%, depended on different criterions of size. CONCLUSION: A profound knowledge of normal anatomy and anomalies of the temporal bone avoids misinterpretation as pathological lesions and iatrogenic bleedings.     

Computed tomographic evaluation of surgically significant vascular variations related with the temporal bone

Variations of the vascular structures related with the temporal bone may cause important problems in diagnosis, treatment planning and surgery. High resolution computed tomography (CT) scans of 700 temporal bones of 350 patients were retrospectively examined for the incidence of dehiscent jugular bulb, high jugular bulb, diverticulum of jugular bulb, anteriorly located sigmoid sinus and dehiscent internal carotid artery. Dehiscent jugular bulb was seen in 27 (3.9%), high jugular bulb was seen in 142 (20.3%), jugular bulb diverticulum was seen in 55 cases (7.9%). The average distance between external acoustic canal and sigmoid sinus was found to be 13.3 mm and in 12.4% of the cases this distance was < 10 mm. Of 700 temporal bones, 10 (1.4%) showed dehiscent carotid canal. To aid diagnosis, treatment planning and surgery, CT scanning is currently a very reliable tool in determining these conditions. Special attention should be paid to the position of the vascular structures in the preoperative temporal bone CT scans.     

Endovascular Treatment of Symptomatic Vestibular Aqueduct Dehiscence as a Result of Jugular Bulb Abnormalities

A new endovascular treatment consisting of stent-assisted coil implantation is described for jugular bulb abnormalities causing symptomatic vestibular aqueduct dehiscence. Three patients presenting with vertigo associated with pulsatile tinnitus or hearing loss were treated. This technique cured the vertigo and pulsatile tinnitus in all patients and preserved normal cerebral venous drainage with no side effects.     

Effects of a high jugular fossa and jugular bulb diverticulum on the inner ear. A clinical and radiologic investigation

From a series of patients undergoing routine radiographic examination, 112 temporal bones with a high jugular fossa were selected. Among these, 43 jugular bulb diverticula were found. The structures affected by a high fossa or diverticulum were recorded and correlated to the clinical symptoms of the patient. The vestibule was suspected to be affected in five patients. Two of these patients had tinnitus and vertigo, and three had hearing loss. In one of the latter the hearing loss was most marked in the supine position. The cochlea was close to the fossa in three patients, all of whom had tinnitus. Four patients had a defect of the posterior semicircular canal. One of them lost his hearing after a severe fit of coughing, became unsteady and showed signs of a fistula. The internal acoustic meatus and the mastoid portion of the facial canal were affected in two and four patients, respectively, who had no recorded symptoms. Twelve of 34 patients with Menière's disease and a high jugular fossa on the side of the diseased ear had a dehiscence of the vestibular aqueduct caused by the fossa or diverticulum, compared with nine of 58 patients in the unselected material. For comparison and demonstration of topographic relationships, 58 casts of unselected radiographed temporal bone specimens with high jugular fossae or diverticula were investigated. In patients with a high jugular fossa or jugular bulb diverticulum, tomographic assessment may be of value.     

Overlapping thin-section fast spin-echo MR of the large vestibular aqueduct syndrome.

PURPOSETo evaluate a high-resolution, thin-section fast spin-echo MR imaging technique of the inner ear to identify the large vestibular aqueduct syndrome seen on temporal bone CT scans.METHODSWe retrospectively reviewed the temporal bone CT scans of 21 patients with hearing loss and enlarged bony vestibular aqueducts by CT criteria. High-resolution fast spin-echo MR imaging was then performed on these patients using dual 3-inch phased-array receiver coils fixed in a temporomandibular joint holder and centered over the temporal bones. MR imaging included axial and oblique sagittal fast spin-echo sequences. The diameter of the midvestibular aqueduct on CT scans and the signal at the level of the midaqueduct on MR images were measured on axial sequences, then compared. High-resolution MR imaging with the same protocol was performed in 44 control subjects with normal ears, and similar measurements were taken.RESULTSThe average size of the enlarged bony vestibular aqueduct on CT scans was 3.7 mm, and the average width of the signal from within the enlarged aqueduct on MR images was 3.8 mm. Statistical analysis showed excellent correlation. MR images alone displayed the enlarged extraosseous endolymphatic sac, which accompanies the enlarged aqueduct in this syndrome. Five ears in three patients with enlarged bony vestibular aqueducts on CT scans showed no evidence of an enlarged endolymphatic duct or sac on MR images. An enlarged endolymphatic sac was seen on MR images in one patient with a bony vestibular aqueduct, which had normal measurements on CT scans. MR imaging alone identified a single case of mild cochlear dysplasia (Mondini malformation). In the 88 normal ears studied, the average size of the endolymphatic sac at its midpoint between the common crus and the external aperture measured on MR images was 0.8 mm (range, 0.5 to 1.4 mm). In 25% of the normal ears, no signal was seen from within the vestibular aqueduct.CONCLUSIONThin-section, high-resolution fast spin-echo MR imaging of the inner ear is complementary to CT in studying patients with the large vestibular aqueduct syndrome, as MR imaging better displays the soft tissue and fluid of the membranous labyrinth.     

Pulsatile tinnitus and imaging diagnosis. A case report

Tinnitus is the perception of sound in one or both ears when no external noise exists to cause that perception. It can be otological, neurological, drug-related, traumatic, due to exposure to high decibel levels, or associated with a vascular abnormality—the latter usually causing pulsatile tinnitus. We present the diagnostic image of a patient with pulsatile tinnitus with terminal plate dehiscence of the jugular bulb and review the diagnostic workup. Jugular bulb dehiscence is a venous variant that consists of an upper and lateral extension of the jugular bulb into the middle ear through a dehiscent sigmoid plate. It is the most common vascular anatomical variant of the petrous portion of the temporal bone. Imaging studies are essential for establishing a diagnosis and defining possible anatomical variants.     

MRI of enlarged endolymphatic sacs in the large vestibular aqueduct syndrome

We studied ten inner ears of five patients with a bilateral large vestibular aqueduct syndrome, using CT and MRI. Although the large vestibular aqueduct varied in size, a markedly dilated endolymphatic sac extending to the sigmoid sinus was demonstrated bilaterally on MRI in all patients. The cause of hearing loss in this syndrome is unclear. However, it is suggested that reflux of the protein-rich, hyperosmolar endolymph from the enlarged endolymphatic sac (EES) into the cochlea through a widely patent endolymphatic duct may damage the neuroepithelium. CT density and spin-echo MRI signal intensity of the endolymph in EES were markedly higher than those of CSF in eight inner ears of four patients. Increased density and high signal may indicate protein-rich, hyperosmolar endolymph. In some patients with sensorineural hearing loss and EES, the vestibular aqueduct may not appear dilated on CT. MRI is therefore necessary for correct diagnosis of this syndrome, which should more correctly be termed “large endolymphatic duct and sac syndrome”. Prominent EES may predict poor prognosis in this syndrome. Received: 28 March 1997 Accepted: 18 July 1997     

The jugular bulb diverticulum. A radioanatomic investigation

Two hundred and forty-five temporal bone specimens were examined radiographically. Subsequently the topographic relationship between the jugular fossa and surrounding structures was evaluated in plastic casts of the specimens. Fifty-eight casts showed a high jugular fossa and in 17 a jugular bulb diverticulum was found. A diverticulum is regarded as an anomaly of the high jugular bulb and presumably has a potential for expansion. Most frequently a diverticulum was directed medially into the space between the internal acoustic meatus, the vestibular aqueduct and the posterior cranial fossa. Seven diverticula reached the level of the internal acoustic meatus. Encroachment upon the vestibular aqueduct was seen in 4 casts and both the internal acoustic meatus and the cochlear aqueduct were very close to the diverticulum. A few diverticula were directed postero-laterally close to the facial canal and the stapedius muscle. The investigation was supplemented with a selected clinical material of radiographs of temporal bones with high fossae. The results corresponded to those of the experimental investigation. The jugular bulb diverticulum is a relatively common feature and should be regarded as an anomaly with a potential to give rise to clinical symptoms consequent to its intrusion upon surrounding structures.     

The vestibular aqueduct syndrome: computed tomographic appearance

We have recently examined three young patients with congenital unilateral profound sensorineural hearing loss. On computed tomography the only abnormality discovered was a remarkably enlarged vestibular aqueduct on the abnormal side. The vestibular aqueduct syndrome is an important cause of congenital hearing loss. Although this finding has been well illustrated with conventional multidirectional tomography, there has been little emphasis on the computed tomographic appearance.     

CT evaluation of bone dehiscence of the superior semicircular canal as a cause of sound- and/or pressure-induced vertigo

PURPOSE: To describe the computed tomographic (CT) findings at different collimation widths associated with superior semicircular canal (SSC) dehiscence syndrome and to determine the frequency of these findings in a control population. MATERIALS AND METHODS: Temporal bone CT scans with 1.0-mm and/or 0.5-mm collimation were obtained in 50 patients with sound- and/or pressure-induced vestibular symptoms. The control population consisted of 50 patients undergoing CT at 1.0-mm collimation and 57 patients undergoing CT at 0.5-mm collimation for other reasons. RESULTS: SSC dehiscence was documented on CT scans in all 36 patients with the clinical syndrome, with bilateral findings in six patients. Six other patients without specific clinical signs appeared to have dehiscence on 1.0-mm-collimated scans. Intact bone overlaying the SSC was subsequently identified with 0.5-mm-collimated CT in each case. On the 1.0-mm-collimated scans in 50 control patients, an area judged as possible or definite dehiscence was identified in 18 of 100 ears. The bone overlaying the SSC was intact in each of the 114 control ears evaluated with 0.5-mm-collimated CT. CT findings from the patients with vestibular symptoms combined with those in the control population indicated that the positive predictive value of an apparent dehiscence in the diagnosis of SSC dehiscence syndrome improved from 50% with 1.0-mm-collimated CT with transverse and coronal images to 93% with 0.5-mm-collimated CT with reformation in the plane of the SSC. CONCLUSION: The positive predictive value of CT in identification of SSC dehiscence syndrome improves with 0.5-mm-collimated helical CT and reformation in the SSC plane.     

The topographic relations of the high jugular fossa to the inner ear. A radioanatomic investigation

The radioanatomy of high jugular fossae and their topographic relations to the inner ear structures were investigated in 245 unselected temporal bones. One hundred and fifty specimens were submitted to multidirectional and 10 to computed tomography. After careful chemical and fermentative maceration plastic casts were made, using polyester resin and silicone rubber. With the use of vacuum, even minute structures became filled with the casting material. The specimens offered a three-dimensional view of the jugular fossae and surrounding structures. Fifty-eight (24%) of the total 245 specimens had high jugular fossae at a level above the lower border of the round window. Five casts showed a dehiscence of the peripheral portion of the vestibular aqueduct caused by the high jugular fossa. In 2 casts the proximal portion of the cochlear aqueduct was affected. In some casts the posterior semicircular canal, the facial canal, the stapedial muscle and the round window lay so close to the fossa that a dehiscence could not be excluded. In a clinical material of 102 high fossae the radiographic findings were in accordance with the experimental results. High jugular fossae were predominantly found in pyramids with low-grade mastoid bone pneumatization and sparse or no perilabyrinthine air cells.     

前庭导水管扩大畸形的CT诊断

目的评价横轴位高分辨率CT扫描对前庭导水管扩大畸形的诊断价值。方法分析16例前庭导水管畸形横轴位耳部扫描的高分辨率CT图像并与50例正常人进行对比分析。结果正常人前庭导水管表现为岩骨后缘小而浅的模糊骨切迹或者与后半规管平行的略低小细管状影。前庭导水管扩大大多表现为岩骨后缘深大三角形骨缺损影,少数为深长裂隙影,岩骨后缘骨缺损影边缘均清晰锐利,其内侧缘绝大部分与总脚或前庭直接相通,前庭导水管中段最大前后径大于1.5mm。结论CT轴位扫描对前庭导水管扩大畸形的诊断有重要价值。     

前庭导水管扩大的CT和MRI的诊断(附14例报告)

目的本文回顾分析了14例前庭导水管扩大患者的CT、MRI资料,并对两种检查方法作了比较.方法14例患者作了高分辨的颞骨颅底横断位扫描,其中6例作了MRI多方位的扫描.具体测量相关数据.结果在CT图像上,在14位患者中12例双侧和2例单侧扩大的前庭导水管外口均大于1.5mm.MRI图像上,5例双侧,1例单侧内淋巴管和内淋巴囊均有扩大,骨外内淋巴囊扩大尤为明显.倾斜矢状位能清晰显示与前庭相连的扩大的内淋巴管.结论CT和MRI都能准确地判定前庭导水管扩大的存在,MRI更为直观、明显.     

POU3F4基因突变致耳聋的HRCT和MRI表现

目的：探讨POU3F4基因突变致耳聋患儿的颞骨高分辨率CT（high resolution CT ,HRCT）及MRI表现特征,提高对该病的认识。方法结合文献回顾性分析5例（10耳）经临床诊断POU3F4基因突变致耳聋患儿的影像学资料。结果5例（10耳）双侧内听道底“球茎状”扩大,以下壁扩大明显;5例（10耳）内听道底与耳蜗底圈骨性间隔缺失;4例（7耳）蜗神经孔扩大;5例（10耳）蜗轴缺失;2例（2耳）前庭水管扩大;2例（4耳）半规管发育异常;1例（2耳）Mondini畸形;1例（2耳）前庭扩大;4例（4耳）颈静脉窝高位。结论 POU3F4基因突变致耳聋的影像学表现具有特征性,对本病诊断及指导手术有重要价值。     

Contrast enhancement of the cochlear aqueduct in MR imaging: its frequency and clinical significance

There have been no previous reports on contrast enhancement of the cochlear aqueduct in magnetic resonance imaging. The purpose of the present study was to evaluate the frequency and significance of this finding. Thirty-one patients (15 men and 16 women; age range 18–81 years) with otologic symptoms (sudden sensorineural hearing loss, vertigo, or tinnitus) were examined using contrast-enhanced imaging on a 1.5-T MR scanner. The normal ear served as the control. Two radiologists evaluated contrast enhancement in the area of the cochlear aqueduct. Forty-eight of 62 ears (77.4%) showed contrast enhancement of the cochlear aqueduct, but no significant differences in the frequency of contrast enhancement were observed between patients with and patients without vertigo, tinnitus, sensorineural hearing loss, cerebellopontine angle tumors, or a high-riding jugular bulb. In addition, no gender- or age-related differences were noted. Contrast enhancement of the cochlear aqueduct was frequently observed, but the frequency of enhancement in symptomatic ears was not significantly higher than in control ears. The results of this study may prove helpful in avoiding unnecessary examinations and potential diagnostic confusion.     

Semicircular canal dehiscence: Frequency and distribution on temporal bone CT and its relationship with the clinical outcomes

Purpose

In this study, we aimed to investigate the frequency of SCD and its distribution and relationship with clinical outcomes on thin-section CT of the temporal bone.

Materials and methods

Digital temporal bone CT images of 850 consecutive patients (1700 temporal bone CTs, 5100 SCs) who presented with a range of complaints such as vertigo, deafness, ear pain, fullness, and discharge between January 2008 and December 2011 were re-evaluated. Axial and oblique coronal reconstruction images of the temporal bone were made with a reconstruction thickness of 0.5 mm. Additionally, superior SC was evaluated in two perpendicular planes.

Results

Out of 850 patients, 70 had completely normal temporal bone CT. Ninety-three patients had at least one SCD. In the temporal bone-based evaluation, 119 (26 bilateral, 67 unilateral) of 1700 temporal bones (7%) showed dehiscence. The SC-based evaluation revealed 125 SCD (2.5%) in 5100 SCs. The total number and rates of SCD were as follows: superior 103 (82.4%), posterior 13 (10.4%), and lateral nine (7.2%). Twenty of the 93 patients with SCD (21.5%) revealed no other findings on their temporal bone CTs. We determined a significant correlation between vestibular complaints, conductive hearing loss and SCD but there was no correlation between mixed, sensorineural hearing loss and SCD.

Conclusion

We determined the frequency of SCD in 11% of patients and 7% of temporal bones. With regards to the distribution, the superior SC showed the highest dehiscence rate (82.4%). We found a significant correlation between vestibular symptoms, conductive hearing loss and SCD.     

大前庭导水管综合征内淋巴囊和前庭导水管MRI信号特征及其临床意义

目的 探讨大前庭导水管综合征患者内淋巴囊和前庭导水管MRI信号特征及其与听力损失的关系.方法 搜集大前庭导水管综合征31例共62只内耳的MRI和听力资料.MRI表现分4型:I型的内淋巴囊及前庭导水管裂隙范围内均为低信号区,无高信号区;Ⅱ～Ⅳ型除低信号区外,还可见高信号区;Ⅱ型的高信号区局限于前庭导水管裂隙内;Ⅲ型的高信号区自前庭导水管裂隙向后超出岩骨后缘,但其下界在后半规管下脚平面以上,在平面以下者为Ⅳ型.为避免肉眼观察误差,测量内淋巴囊高信号区、低信号区和前庭的信号强度,并与同层脑脊液信号强度比较.采用配对t检验分析内淋巴囊高信号区与低信号区、前庭之间信号强度的差异,纠正卡方检验,用Spearman分析判断内淋巴囊MRI分型与听力损失程度的相关性.结果 31例共62耳中Ⅰ型10耳(听力下降为中度1耳,重度4耳,极重度5耳);Ⅱ型17耳(听力下降为中度1耳,重度5耳,极重度11耳);Ⅲ型23耳(听力下降为中度3耳,重度5耳,极重度15耳);Ⅳ型12耳(听力下降为轻度1耳,中度1耳,重度3耳,极重度7耳).高信号区与同层脑脊液信号强度的比值为0.95 ±0.12,低信号区为0.49±0.10,前庭为0.99±0.08,高、低信号区分界清楚,信号比值为2.02±0.06.高、低信号区间信号强度差异有统计学意义(t=- 24.966,P＜0.05),高信号区与前庭的信号差异无统计学意义(t=-24.966,P＞0.05).不同MRI分型对应的听力损失差异无统计学意义(似然比值为5.02,P＞0.05),高、低信号区强度比值与听力损失无相关性(r=0.135,P=0.297).结论 大前庭导水管综合征不只是内淋巴囊扩大,也可以伴有外淋巴液疝入前庭导水管骨性裂隙中;内淋巴囊MRI信号特征与听力损失程度之间未见相关.     

Posterior semicircular canal dehiscence: a morphologic cause of vertigo similar to superior semicircular canal dehiscence

The aim of this study was to assess imaging findings of posterior semicircular dehiscence on computed tomography and to evaluate incidence of posterior and superior semicircular canal dehiscence in patients presenting with vertigo, sensorineuronal hearing loss or in a control group without symptoms related to the inner ear. Computed tomography was performed in 507 patients presenting either with vertigo (n=128; 23 of these patients suffered also from sensorineuronal hearing loss), other symptoms related to the inner ear, such as hearing loss or tinnitus (n=183) or symptoms unrelated to the labyrinth (n=196). All images were reviewed for presence of dehiscence of the bone, overlying the semicircular canals. Twenty-nine patients had superior semicircular canal dehiscence. Of these patients, 83% presented with vertigo, 10% with hearing loss or tinnitus and the remaining 7% with symptoms unrelated to the inner ear. In 23 patients dehiscence of the posterior semicircular canal was encountered. Of these patients, 86% presented with vertigo, 9% with hearing loss or tinnitus and 5% with symptoms unrelated to the inner ear. Defects of the bony overly are found at the posterior semicircular canal, in addition to the recently introduced superior canal dehiscence syndrome. Significant prevalence of vertigo in these patients suggests that posterior semicircular canal dehiscence can cause vertigo, similar to superior semicircular canal dehiscence. Electronic Publication     

颞骨气化与颈静脉球高位关系的CT分析

目的探讨乳突及岩尖气化与颈静脉球高位间的相关性。方法回顾性分析477例(954侧)颞骨CT片,统计乳突和岩尖的气化分型及各型颈静脉球高位的发生率,并对其作统计学分析。结果477例中颈静脉球高位的出现率右侧为40.67%(194例),左侧为21.38%(102例);女性出现率为35.37%,男性28.75%,差别均有统计学意义。岩尖气化I型与III型颈静脉球高位的发生率分别为31.25%及30.58%,乳突气化型与其它型颈静脉球高位的出现率分别为31.64%及29.02%,差别均不存在统计学意义。结论颈静脉球高位的发生率在两侧及性别间存在差异;颞骨气化与颈静脉球高位没有相关性。