Posterior cranial fossa dural arteriovenous malformation with a varix mimicking a thrombosed aneurysm: case report

Summary Dural arteriovenous malformations (AVMs) in the posterior cranial fossa are relatively infrequent. Intradural haemorrhage is one of their specific complications. Angiographic demonstration of varices or aneurysmal structures is one of the hallmarks of severe cases. We report a patient with posterior cranial fossa dural AVM associated with a varix mimicking a thrombosed aneurysm on CT and MRI. Internal carotid and vertebral angiography failed to demonstrate an aneurysm, but external carotid injection revealed a dural AVM affecting the sigmoid sinus, and a varix. The AVM was completely eliminated by embolization. When a dural AVM is suspected clinically selctive angiography should be performed to confirm the diagnosis even when CT or MRI do not show dilated vessels.     

Gliosarcoma of the posterior cranial fossa: MRI findings

We report the MR findings of a biopsyproven gliosarcoma of the posterior cranial fossa. Multiple homogeneously enhancing lesions had shaggy margins and broad-based dural attachments, which may reflect the gliomatous and sarcomatous element of this tumour.     

Imaging in neurenteric cysts of the posterior cranial fossa

Neurenteric cysts are cystic masses lined by a columnar epithelium of endodermal origin. They are rare in the central nervous system. We report two neurenteric cysts in the posterior cranial fossa and describe their neuroradiological features. The lesions were of low density on CT and more accurately delineated on MRI. They gave the same signal as cerebrospinal fluid on all sequences. There was no contrast enhancement. Received: 26 June 1997 Accepted: 13 November 1997     

Arteriovenous malformation with middle cranial fossa expansion a previously unrecorded association

Summary A large temporal arteriovenous malformation with expansion of the middle fossa is described. This previously unreported association is discussed in relation to the possible aetiology.     

Primary germinoma of the posterior cranial fossa: a case report

We describe a primary germinoma arising in an unusual site, in multiple areas on the cerebellar convexity, in an adult man. Received: 26 October 1995 Accepted: 2 July 1996     

Uncommon posterior cranial fossa anomalies: MRI with clinical correlation

The clinical and MRI findings in two cases of rhombencephalosynapsis (RS) and two of tectocerebellar dysraphia (TCD) with an associated occipital encephalocele were studied to elucidate the clinical picture and embryogenesis of these rare anomalies. To our knowledge, only one case of TCD [1] and four of RS [2, 3] examined by MRI during life have been reported. The clinical picture in the cases of RS was rather constant and there were similarities with TCD. Consideration of the embryogenesis of the neural tube suggests a temporal proximity of the abnormalities, with TCD arising at a slightly earlier time.     

Chiari Ⅰ型畸形并发脊髓空洞症的MRI颅脑测量及临床意义

目的运用MRI对ChiariI型畸形患者进行颅脑形态学测量,探讨ChiariI型畸形患者脊髓空洞症的发病机制。方法在颅脑正中矢状面上分别对50例正常国人和24例合并脊髓空洞症及26例不合并脊髓空洞症的ChiariI型畸形患者的后颅窝骨性和神经结构进行测量,测量结果用t检验进行统计分析。结果畸形组与正常组枕大孔平面延前池前后径分别为(4.2±1.8)mm和(6.6±1.4)mm,前者明显小于后者（t=7.30,P<0.01）,畸形组脑颅比明显大于正常组（t=7.33,P<0.01）,后脑大小两组间无显著性差异（t=0.28,P>0.05）。ChiariI型畸形脊髓空洞组和无空洞组枕大孔平面的延前池前后径分别为(2.9±1.4)mm和(5.5±1.1)mm,前者明显小于后者（t=7.26,P<0.01）,脊髓空洞组枕大孔平面延髓前后径大于无空洞组（t=2.16,P<0.05）,小脑扁桃体前后径大于无空洞组（t=3.97,P<0.01）,小脑扁桃体后脑脊液间隙的前后径小于无空洞组（t=5.77,P<0.01）;脊髓空洞组的脑颅比大于无空洞组（t=2.68,P<0.05）,延髓下移程度大于无空洞组（t=3.25,P<0.01）;后颅窝颅腔形态两组间无显著性差异。结论ChiariI型畸形患者的后颅窝及枕大孔区过度拥挤导致第4脑室出口受阻,以及因颈延髓联合部受压,影响脊髓中央管的通畅性,使搏动性的脑脊液不断冲击具有活瓣效应的脊髓中央管,进而引发脊髓中央管扩张,这可能是ChiariI型畸形并发脊髓空洞症的主要原因。后颅窝MRI测量对ChiariI型畸形的治疗及预后有重要价值。     

Lipomyeloschisis associated with thoracic syringomyelia and Chiari I malformation

Co-existence of Chiari I malformation and myelomeningocele is uncommon. Syringomyelia, when associated with a Chiari I malformation, classically involves the cervical spinal cord. Intramedullary extension of lipoma is unusual in lipomyeloschisis. A patient with lumbar lipomyelomeningocele with tethered cord, lower thoracic syringomyelia and Chiari I malformation, shown by MRI is reported.     

Ependymomas of the posterior cranial fossa: CT and MRI findings

We studied nine children with posterior cranial fossa ependymomas to identify specific neuroradiological features. Patients were studied preoperatively with CT and MRI; T1-, T2-and proton-density (PD)-weighted images were obtained. All children underwent surgery and a definite histopathological diagnosis was made. All the tumours grew into the fourth ventricle and caused dilatation of its upper part, which resembled a cap. All but one were separated from the vermis by a cleavage plane. In eight cases there was desmoplastic development through the foramina of the fourth ventricle, and five were heterogeneous due to necrosis and cystic change; one had a haemorrhagic area. In most cases the solid portion was isointense with grey matter on T1-weighted images, hyperintense on PD weighting, and isointense on T2-weighted images. On CT the tumour was isodense in six cases and calcification was detected in four. The presence of both desmoplastic development and a tumour/vermis cleavage plane in a posterior cranial fossa tumour isodense on CT is highly suggestive of ependymoma.     

Cholesterol granuloma in the middle cranial fossa: report of two cases

We report two cases of cholesterol granuloma in the middle cranial fossa. On CT the lesions appeared as a nonspecific, nonenhancing soft-tissue mass with bone erosion. On MRI they were seen as areas of high signal intensity surrounded by a low-intensity peripheral zone on both T1- and T2-weighted images. Cholesterol granuloma is thought to occur when pneumatised cellsin the temporal bone become obstructed. Although this lesion usually occurs in the petrous bone, it can extend to the middle cranial fossa. The diagnosis and surgical management are discussed.     

MRI demonstration of midbrain deformity in association with Chiari malformation

Summary The differentiation of Chiari malformation from intrinsic brainstem neoplasm in adults can be difficult. We report three patients presenting with brainstem signs, in whom midbrain abnormality was detected on computed tomography and interpreted as evidence of intrinsic tumour. Subsequent investigation by magnetic resonance imaging revealed evidence of Chiari I malformation in all three cases and a syrinx in two. The association of Chiari I with deformity of the midbrain or pons has not been described previously.     

Increased pulsatile movement of the hindbrain in syringomyelia associated with the Chiari malformation: cine-MRI with presaturation bolus tracking

Cine-MRI with presaturation bolus tracking was used in patients with syringomyelia associated with a Chiari malformation to study pulsatile movement of the hindbrain, cervical spinal cord, cerebrospinal fluid and the fluid within the syrinx. Nine patients had 13 examinations, 6 preoperative, 3 after syringosubarachnoid shunting and 4 after posterior fossa decompression. Five controls were also examined. Dynamic display of the acquired images demonstrated downward displacement of the presaturation bolus on the cerebellar tonsils and medulla oblongata (or upper cervical cord) at the C1 level in all preoperative examinations and in two patients after syringo-subarachnoid shunting but with residual foramen magnum obstruction. Downward displacement of the bolus on the cervical spinal cord was also demonstrated in 7 examintions, but not observed in the controls. Thus, the hind-brain-spinal cord axis showed larger pulsatile movements in patients with foramen magnum obstruction. Based on these observations and a review of the literature, a new theory on the mode of extension of syringomyelia, emphasising the role of increased pulsatile movement of the hind-brain-spinal cord axis is proposed: that the pulsatile movements, together with a one-way valve mechanism in the syrinx cavity act as a vacuum-pump to enlarge the syrinx.     

儿童后颅窝肿瘤的MRI诊断与鉴别诊断

目的：探讨磁共振成像（MRI）对儿童后颅窝肿瘤的诊断与鉴别诊断价值。方法：回顾性分析33例经手术病理证实的儿童后颅窝肿瘤的MRI和临床资料,其中星形细胞瘤13例、髓母细胞瘤11例、室管膜瘤5例、血管母细胞瘤1例、胚胎发育不良性神经上皮瘤2例、弥漫性大B细胞淋巴瘤1例。结果：肿瘤位于小脑半球7例,小脑蚓部16例,第四脑室4例,脑干6例。所有病灶均引起梗阻性脑积水。MRI能显示肿瘤的位置、大小、形态及信号特点,增强扫描对肿瘤的定性诊断有帮助。结论：儿童后颅窝肿瘤的MRI表现具有一定的特征性,MRI多参数、多平面成像,对儿童后颅窝肿瘤的定位和定性诊断具有重要的临床应用价值。     

四脑室顶位置磁共振成像的临床定量研究

目的：用ＭＲＩ测量正常国人各性别、年龄组及Ｃｈｉａｒｉ畸形患者的第四脑室顶高距与水平距,以探讨其正常值范围及四脑室顶位置的发育规律。材料与方法：在颅脑（旁）正中矢状面ＳＥＴ１ＷＩ上测量３１７例正常国人和４２例Ｃｈｉａｒｉ畸形及可疑病人的第四脑室顶高距及水平距。正常组按性别、年龄分为１６组,每组２０例（７０岁以上女性组１７例）。ＭＲＩ应用１．０Ｔ全身ＭＲ机,用ｔ检验作统计分析。结果：四脑室顶高距女性为３０．０ｍｍ±１．９ｍｍ,男性为２９．６ｍｍ±２．９ｍｍ～３２．２ｍｍ±３．５ｍｍ;仅部分男性有显著年龄差异,但无显著性别差异。四脑室顶水平距男性为１１．０ｍｍ±１．５ｍｍ,女性为１０．６ｍｍ±１．３ｍｍ,无显著性别、年龄差异。Ｃｈｉａｒｉ畸形的四脑室高距明显低于正常人（Ｐ＜０．０１）,可疑组也明显低于部分年龄组正常男性（Ｐ＜０．０５）,而其水平距与正常各性别、年龄组的无显著差异（Ｐ＞０．０５）。结论：第四脑室顶位置有一定的生长发育规律,Ｃｈｉａｒｉ畸形常伴四脑室顶下移。     

Subdural enhancement on postoperative spinal MRI after resection of posterior cranial fossa tumours

In malignant brain tumours which may disseminate staging, usually by cranial and spinal MRI is necessary. If MRI is performed in the postoperative period pitfalls should be considered. Nonspecific subdural contrast enhancement on spinal staging MRI is rarely reported after resection of posterior fossa tumours, which may be mistaken for dissemination of malignancy. We investigated the frequency of spinal subdural enhancement after posterior cranial fossa neurosurgery in children. We reviewed 53 postoperative spinal MRI studies performed for staging of paediatric malignant brain tumours, mainly infratentorial primitive neuroectodermal tumours 2–40 days after surgery. There was contrast enhancement in the spinal subdural space in seven cases. This was not seen in any of eight patients who had been operated upon for a supratentorial tumour. After resection of 45 posterior cranial fossa tumours the frequency of subdural enhancement was 15.5%. MRI showing subdural enhancement was obtained up to 25 days postoperatively. No patient with subdural enhancement had cerebrospinal fluid (CSF) examinations positive for tumour cells or developed dissemination of disease in the CSF. Because the characteristic appearances of subdural contrast enhancement, appropriate interpretation is possible; diagnosis of neoplastic meningitis should rarely be impeded. Because of the striking similarity to that in patients with a low CSF-pressure syndrome and in view of the fact that only resection of tumours of the posterior cranial fossa, usually associated with obstructive hydrocephalus, was followed by this type of enhancement one might suggest that rapid changes in CSF pressure are implicated, rather the effects of blood introduced into the spinal canal at surgery.     

颅中窝海绵状血管瘤的影像及其鉴别诊断

目的:探讨颅底海绵状血管瘤的影像特征及其鉴别诊断,提高影像定性诊断率。方法:总结11例颅底鞍旁海绵状血管瘤(CA)病例,对其影像进行回顾性分析。结果:CT表现呈圆形略高密度均一肿块,增强后强化明显;MRI平扫T1WI、T2WI呈底向外的葫芦状、长T1长T2信号改变,增强后同样明显强化;DSA呈棉絮状染色,MRA不显影。术前影像定性诊断准确率45.5%(5/11)。结论:CT表现与其它实体肿瘤相比无特异性,定性诊断困难;MRI表现呈底向外的葫芦状、长T1长T2信号改变较具特征性;“脑膜尾”征改变并非为脑膜瘤所特有,脑外CA同样常见。     

儿童颅后窝肿瘤的磁共振成像

目的：探讨磁共振成像（MRI）对儿童颅后窝肿瘤的诊断价值。材料和方法：回顾性分析23例经手术病理证实的儿童颅后窝肿瘤的MRI和临床资料，其中髓母细胞瘤13例、室管膜瘤6例、星形细胞瘤2例、血管母细胞瘤2例。结果：肿瘤位于小脑半球8例，小脑蚓部5例，第四脑室10例。所有病灶均引起梗阻性脑积水。MR扫描能显示肿瘤的大小、形态、信号、边缘情况，强化扫描对肿瘤的定性诊断有帮助，结论：儿童颅后窝肿瘤的MRI表现具有一定的特征性，MRI检查多方位、多序列成像，对其诊断有重要作用，是儿童颅后窝肿瘤检查的首选。     

MRI在Chiari畸形颅脑体积测量中的应用价值

目的 :研究MRI在Chiari畸形颅脑体积测量中的临床应用价值与意义 ,为临床开展定量后颅窝扩大成形术治疗Chiari畸形提供依据。方法 :采用象素体积测量法 ,对正常人、Chiari畸形患者分别进行全脑、后颅窝体积测量 ,计算幕下 /幕上体积之比 ,并进行统计学分析。结果 :对照组 3 5例正常人全脑体积平均值为 15 5 4.3 1cm3 ,后颅窝体积平均值为2 0 5 .43cm3 ;幕下 /幕上体积之比平均值为 0 .15 2。Chiari畸形组 2 2例患者全脑体积平均值为 14 5 7.85cm3 ,后颅窝体积平均值为 172 .84cm3 ,幕下 /幕上体积之比平均值为 0 .13 4。病人组与正常对照组的全脑体积、后颅窝体积、幕下 /幕上之比的P值分别为 0 .0 612、0 .0 0 173和 0 .0 0 10 8,差异具有显著性意义。后颅窝扩大成形术后 ,后颅窝体积扩大平均值为 16.7cm3 。结论 :采用MRI对Chiari畸形患者进行颅脑体积、后颅窝体积测量 ,数据准确可靠 ,能为临床开展定量后颅窝扩大成形术治疗Chiari畸形提供准确数据 ,为术后疗效进行科学评价提供可靠依据     

Chiari畸形Ⅰ型颅颈部蛛网膜下腔改变与外科治疗

目的:研究Chiari畸形I型(CMI)患者颅颈部蛛网膜下腔(SS)形态学改变及其在疾病发生和外科治疗中的意义。方法:通过磁共振成象(MRI)技术观测颅颈部蛛网膜下腔形态学指标,结合临床,对病例组与正常对照组、术前与术后,进行对比分析;手术采用后颅窝减压、枕大池成形术。结果:CMI患者颅颈部既有先天性发育异常,又有后天继发性改变,导致其整个颅颈部SS较对照组显著变窄(前池、侧池、枕大池均明显变窄);术后均有不同程度增宽,术后SS狭窄较术前改善明显者,其临床症状恢复和空洞消退也快而明显。结论:颅颈部SS狭窄导致脑脊液循环障碍在CMI疾病发生发展和转归中起重要作用,外科治疗应以解除颅颈部蛛网膜下腔梗阻为目的,减压一定要充分,重建颅颈部蛛网膜下腔。     

后颅窝脑实质出血穿入脑室系统的CT研究

目的：探讨后颅窝出血经脑室系统弥散的CT表现及临床意义。方法：回顾性分析23例后颅窝出血的CT检查资料。结果：后颅窝出血经脑室系统弥散者12例,其中第四脑室积血12例,第三脑室积血9例,侧脑室积血8例。后颅窝出血穿入脑室与血肿体积有明显关系（P＜0．01）,第三脑室扩大在脑室积血与非积血者之间有显著差异（P＜0．01）。结论：后颅窝出血可穿入第四脑室并经脑室系统弥散。CT检查对于发现病因及制定治疗方案具有重要意义。