Spinal subdural haematoma mimicking tethered cord after posterior fossa open surgery

We report the MRI findings in a girl aged 3 years and 10 months who developed a spinal subdural haematoma after posterior fossa open surgery for cerebellar malignant rhabdoid tumour. Emergency surgery was performed immediately because of increased intracranial pressure. Control MRI 48 h after surgery showed a spinal subdural haematoma without clinical signs of paresis or bladder dysfunction. Spinal subdural haematoma is rare, and only few cases have been reported, especially in children. This report suggests that "silent" (without clinical symptoms) postoperative spinal acute subdural haemorrhage can occur after posterior fossa surgery.     

Medulloblastoma in children: CT and MRI findings

Our purpose was to determine whether medulloblastoma (MB) shows specific neuroradiological features which may be employed in differential diagnosis from other common posterior cranial fossa tumours in childhood. Preoperative MRI was performed on 20 children with MB, and preoperative CT in 17 of them. All underwent surgery and histopathological diagnosis. There was a constant relationship between high density on CT and low signal on T1-weighted images. Signal behaviour on T2-weighted images and the degree of contrast enhancement were more variable. Most tumours arose in the midline, from the cerebellar vermis, involving the fourth ventricle, but hemisphere and extra-axial neoplasms were also seen. The combination of high density on CT and low signal on T1-weighted images is highly suggestive of MB and may assist preoperative differential diagnosis from other posterior cranial fossa tumours.     

Spinal subdural enhancement after suboccipital craniectomy.

PURPOSETo characterize transient intraspinal subdural enhancement (potentially mimicking the subarachnoid spread of tumor) seen on MR images in some children after suboccipital craniectomy for posterior fossa tumor resection.METHODSRadiologic and medical records of 10 consecutive children who had MR imaging for spinal staging after resection of posterior fossa tumor during a 9-month period were reviewed retrospectively. In addition, one case with similar findings of intraspinal enhancement on spinal staging MR images obtained at another institution was included in the review.RESULTSIntraspinal enhancement thought to be subdural was seen in four of 10 patients undergoing spinal staging MR imaging 6 to 12 days after surgery. In these four patients, MR studies 50 to 18 days later, without intervening treatment, showed resolution of the abnormal enhancement. A fifth patient (from another institution) with similar intraspinal enhancement underwent CT myelography 4 days later, which showed no subarachnoid lesions. No metastases have developed in any of these five patients during the 2.5- to 3.5-year follow-up period. conclusions: From analysis of the MR appearance and on the basis of prior myelographic experience, we suggest an extraarachnoid, probably subdural, location of this enhancement. Awareness of this phenomenon will reduce the rate of false-positive diagnoses of metastatic disease. Preoperative spinal staging should be considered for patients undergoing suboccipital craniectomy.     

Atypical aesthesioneuroblastoma: CT and MRI findings

Aesthesioneuroblastoma is an uncommon tumour of the superior nasal cavity, originating from the olfactory mucosa. Usually no specific radiological features indicate the diagnosis; normally these tumours are seen on CT as homogeneous, enhacing, soft tissue masses causing bone remodelling. Typical but quite nonspecific MRI findings include high signal on T2-weighted images and strong enhancement after gadolinium. The extent of tumour in the paranasal sinuses and anterior cranial fossa is best assessed with MRI after intravenous gadolinium, and this is considered as the most accurate method for assessing preoperative resectability. We report an aesthesioneuroblastoma in an atypical location, with extensive calcification.     

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.     

Postoperative Intraspinal Subdural Collections after Pediatric Posterior Fossa Tumor Resection: Incidence,Imaging, and Clinical Features

BACKGROUND AND PURPOSE:Postoperative intraspinal subdural collections in children after posterior fossa tumor resection may temporarily hinder metastasis detection by MR imaging or CSF analysis, potentially impacting therapy. We investigated the incidence, imaging and clinical features, predisposing factors, and time course of these collections after posterior fossa tumor resection.MATERIALS AND METHODS:Retrospective review of postoperative spine MRI in 243 children (5.5 ± 4.6 years of age) from our clinical data base postresection of posterior fossa tumors from October 1994 to August 2010 yielded 37 (6.0 ± 4.8 years of age) subjects positive for postoperative intraspinal subdural collections. Their extent and signal properties were recorded for postoperative (37/37), preoperative (15/37), and follow-up spine (35/37) MRI. Risk factors were compared with age-matched internal controls (n = 37, 5.9 ± 4.5 years of age). Associations of histology, hydrocephalus and cerebellar tonsillar herniation, and postoperative intracranial subdural collections with postoperative intraspinal subdural collections were assessed by the Fisher exact test or χ² test. The association between preoperative tumor volume and postoperative intraspinal subdural collections was assessed by the Wilcoxon rank sum test.RESULTS:The overall incidence of postoperative intraspinal subdural collections was 37/243 (15.2%), greatest ≤7 days postoperatively (36%); 97% were seen 0–41 days postoperatively (12.9 ± 11.0 days). They were T2 hyperintense and isointense to CSF on T1WI, homogeneously enhanced, and resolved on follow-up MR imaging (35/35). None were symptomatic. They were associated with intracranial subdural collections (P = .0011) and preoperative tonsillar herniation (P = .0228).CONCLUSIONS:Postoperative intraspinal subdural collections are infrequent and clinically silent, resolve spontaneously, and have a distinctive appearance. Preoperative tonsillar herniation appears to be a predisposing factor. In this series, repeat MR imaging by 4 weeks documented improvement or resolution of these collections in 88%.

The importance of MR imaging for the diagnosis of leptomeningeal metastasis in children with posterior fossa tumors, critical for risk stratification and treatment,¹ is well-recognized. MR imaging detects leptomeningeal metastasis in up to 50% of those with false-negative CSF examination findings, which may occur in up to 45% of initial lumbar punctures,² and findings on MR imaging correlate better with survival than CSF results.^2–4 Although preoperative brain and spine MR imaging are optimal, neurosurgical urgency may dictate deferral until the postoperative period, or repeat spine imaging may be necessary to exclude leptomeningeal metastasis postoperatively. A few case reports and small series have described spinal subdural collections and enhancement on postoperative myelography and MR imaging.^5–8 These findings were further investigated in a larger series by Warmuth-Metz et al,⁹ who described such findings in children after posterior fossa (7/45) but not supratentorial (0/8) tumor resection. However, due to the limited availability of follow-up imaging, the natural history could not be established.At St. Jude Children''s Research Hospital, enrollment of patients with posterior fossa tumors on long-term therapeutic protocols confers the advantage of follow-up imaging availability. Because most arrive postoperatively and undergo subsequent metastasis-screening MR imaging according to our imaging protocols before enrollment, we see a number of postoperative intraspinal subdural collections (PISC). While these collections do not indicate metastasis,^6,7,9 they may be misinterpreted by radiologists unfamiliar with their appearance, prompt neurosurgical consult, or hinder metastasis detection in the critical postoperative staging period. We therefore investigated the incidence, imaging and clinical features and course, and associated potentially predisposing factors in patients with PISC after suboccipital tumor resection in a large pediatric cohort.     

Metastases to the pituitary-hypothalamic axis

Summary Seven patients with metastatic tumour in the pituitary-hypothalamic axis were investigated by MRI. The main clinical problems were diabetes insipidus (5 cases) and general pituitary dysfunction (2 cases). No patient had visual or oculomotor symptoms. In 6 of the 7 patients the primary malignant tumour was known, but no patient had symptoms from the primary tumour; 1 had symptoms from metastases in locations other than the pituitary gland. In one patient no primary tumour was known. MR detection of a second, clinically silent, 5 mm lesion in the posterior cranial fossa initiated the search for primary tumour. MRI showed purely suprasellar tumours in 3 patients and intra- and suprasellar tumours in 4. The latter were dumbbell lesions with only a small bridge of tissue connecting the intra- und suprasellar portions. Six of the 7 suprasellar tumours seemed to be in the infundibular recess of the third ventricle; in 5 the infundibulum was visible as an enhancing linear structure at the postero-inferior border of the tumour. The pituitary fossa was normal in all cases.     

Glomus tumours of the ear: an imaging regime

Jugulotympanic glomus tumours usually present in the middle ear either primarily or as a result of extension upwards from the jugular fossa. Usually they are the initial responsibility of the otologist. If the jugular fossa is involved, special head and neck surgical expertise is required in treatment and spread into the cranial cavity will involve the neurosurgeon. Previously, angiography was used for diagnosis and assessment of the extent of the tumour but it possesses disadvantages. A new protocol has been evolved using high resolution CT combined with MRI including sequences before and after gadolinium-DTPA enhancement. This regimen has been applied successfully in 25 glomus tumours (14 tympanicum and 11 jugulare).     

Unusual localization of a recurrent benign parotid tumor in the infratemporal fossa]

Recurrences of parotid tumours are frequent (10 to 20% of cases) and require regular follow-up of these patients, especially when primary surgery was only partial and the initial tumour was multinodular. Malignant degeneration is reported in 1% of these tumours. The site of a parotid tumour in the infratemporal fossa is exceptional and usually indicates a malignant tumour metastasising along the internal maxillary artery and auriculotemporal nerve, as the inter-pterygoid aponeurosis is very resistant. However, this is no longer true following primary surgery in which damage to this aponeurosis is responsible for dissemination or localisation of the recurrence in the infratemporal fossa. The infiltrated appearance of the skin, muscles or fat is not suggestive of a malignant tumour and this dissemination can be explained by the multinodular and invasive potential of this tumour.     

Supratentorial primitive neuroectodermal tumours: diffusion-weighted MRI

We report the clinical and pathological findings of supratentorial primitive neuroectodermal tumours (PNETs). These are rare, poorly differentiated, highly malignant neoplasms occurring primarily in young individuals. They frequently show dissemination to the spinal cord and sometimes also beyond neuraxis. Preoperative radiological diagnosis is difficult, due to the nonspecific CT and MRI characteristics. Our findings indicate that diffusion-weighted imaging (DWI) can be used to show the solid portion of the tumour preoperatively and to monitor postsurgical recovery. We describe the MRI findings in three patients with histologically confirmed supratentorial PNET, focussing on the role of DWI for improving the specificity of radiological diagnosis. Received: 27 January 1999/Accepted: 3 September 1999     

Rare tumors of the cerebellopontine angle]

Tumours of the cerebellopontine angle are essentially benign in adults, are generally treated surgically and require a preoperative assessment as precise as possible. MRI simplifies the diagnostic assessment; it is indicated as the first-line investigation and is usually sufficient whenever a tumour of the posterior cranial fossa is suspected. Acoustic neuromas represent 75% of all tumours of the cerebellopontine angle. Other tumours are rare and essentially consist of meningioma, detected in 10 to 14% of cases and cholesteatoma in 1 to 5% of cases. Cholesteatoma, with a pathognomonic appearance, must be distinguished from arachnoid cyst. Other tumours are exceptional. The authors define the diagnostic criteria based on their experience and present a recent review of the literature.     

Spread of blood in cerebrospinal fluid following craniotomy simulates spinal metastases

Postoperative myelography with water-soluble contrast media was performed in 36 children with a diagnosis of posterior cranial fossa tumour. The myelograms were normal in 15. In 5 an intramedullary tumour was present and 3 of these had in addition subarachnoid changes as evidence of tumour spread. The remaining 16 patient had subarachnoid changes of a different character, mainly located in the posterior thoracic region and similar to those seen after subarachnoid haemorrhage. It is suggested that they represent adhesions caused by blood from the operation. The blood is assumed to be distributed by the large cerebrospinal fluid pulsations to the cervical and thoracic regions. It is important to recognise and differentiate subarachnoid changes due to tumour and to postoperative adhesions to avoid unnecessary radiotherapy to the spinal cord.     

Arachnoid cysts associated with post-traumatic and spontaneous rupture into the subdural space

Post-traumatic or spontaneous rupture of an arachnoid cyst resulting in a subdural haematoma is rare. Much more rarely, a ruptured arachnoid cyst may be present with a subdural CSF collection without evidence of haemorrhage. These are most commonly seen in the middle cranial fossa, where arachnoid cysts occur most frequently. In this paper, five teenage patients (four male, one female) are reported with post-traumatic or spontaneous arachnoid cyst ruptures, resulting in subdural haematomas in four patients and a subdural CSF collection without haemorrhage in one patient. Possible pathogenesis of the condition is discussed.     

Spontaneous intracranial hypotension

Spontaneous intracranial hypotension is a rare benign and usually self-limited condition of unknown aetiology. Four cases are presented that illustrate how the MRI features may support a diagnosis suggested on clinical grounds. The MRI findings include diffuse symmetric smooth dural thickening and enhancement, not only at the cranial level, but also involving the cervical spinal dura, subdural effusions and downward displacement of the cerebellar tonsils.     

Staging of Klatskin tumours (hilar cholangiocarcinomas): comparison of MR cholangiography, MR imaging, and endoscopic retrograde cholangiography

The aim of the study was to compare prospectively magnetic resonance cholangiography (MRC) and magnetic resonance imaging (MRI) with endoscopic retrograde cholangiography (ERC) in the diagnosis and staging of Klatskin tumours of the biliary tree (hilar cholangiocarcinomas). Forty-six patients with suspected Klatskin tumours of the biliary tract underwent MRI and heavily T2-weighted, non-breathhold, respiratory-triggered fast spin-echo MRC. Forty-two patients underwent ERC within 24 h; in four patients, ERC was not feasible, and percutaneous trans-hepatic cholangiography (PTC) was carried out instead. Two independent investigators evaluated imaging results for the presence of tumour, bile duct dilatation, and stenosis. Clinical and histopathological correlation revealed Klatskin tumours in 33 patients. MRI revealed a slightly hyperintense signal of infiltrated bile ducts in T2-weighted fast spin-echo sequences. The malignant lesion was regularly visualized as a hypointense area in T1-weighted gradient-echo sequences with substantial contrast enhancement along the involved bile duct walls. MRC revealed the location and extension of the tumour in 31 of 33 cases correctly (sensitivity 94%, specificity 100%, diagnostic accuracy 95%). In 27 of 31 cases, ERC enabled accurate staging and diagnosis of Klatskin tumours with a sensitivity of 87%. ERC and PTC combined yielded a sensitivity of 84% and a specificity of 97%. Tumours were grouped according to the Bismuth classification, with MRC allowing correct identification of type I tumour in seven patients, type II tumour in four patients, type III tumour in 12 patients, and type IV tumour in ten patients. MRC provided superior visualization of completely obstructed peripheral systems. MRC in combination with MRI is a reliable non-invasive diagnostic method for the pre-therapeutic staging of Klatskin tumours.     

三叉神经瘤的CT及MRI诊断(附27例分析)

目的提高三叉神经瘤的CT、MRI的诊断水平.材料与方法对经手术病理证实的27例三叉神经瘤行CT及MRI检查.结果颅后窝型12例,颅中窝型6例,跨颅窝型5例.位于颅中窝、颅后窝的肿瘤呈椭圆形;跨颅窝生长者呈哑铃形或不规则形.CT扫描显示稍高密度区、混合密度区、囊性低密度区,不均匀增强或环形增强.MRIT1WI呈不均匀低信号,T2WI呈不均匀高信号,肿瘤边缘清楚,有显著占位效应.结论CT、MRI定性诊断困难时,应结合临床三叉神经受损表现诊断.     

The role of MR imaging in the diagnostic characterisation of appendicular bone tumours and tumour-like conditions

MRI has an established role in the local staging of primary bone tumours. However, as the majority of tumours have non-specific appearances on MRI, the diagnosis is usually established on the basis of clinical history, plain film findings and biopsy. This article reviews the value of MRI in the further characterisation of appendicular bone tumours and tumour-like lesions, with particular reference to peri-lesional oedema, fluid-fluid levels, flow voids, fat signal, cartilage signal and dedifferentiation. These features are a useful adjunct for distinguishing between benign and malignant disease, pointing towards a more specific diagnosis, and guiding biopsy.     

儿童后颅凹肿瘤的CT, MRI诊断

目的：分析儿童后颅凹常见肿瘤的ＣＴ和ＭＲＩ影像学表现,提高诊断该病的准确性。材料和方法：收集儿童后颅凹常见肿瘤４０例,其中髓母细胞瘤１８例,星形细胞瘤１３例,室管膜瘤９例。行ＣＴ和ＭＲＩ检查。ＣＴ平扫４０例,增强扫描３２例;ＭＲＩ平扫２８例,增强扫描１６例。将其结果与手术病理对照。结果：４０例儿童后颅凹常见肿瘤ＣＴ显示率为９７５％,ＭＲＩ显示率为１００％。术前ＣＴ定性误诊１１例,准确率为７２５％。术前ＭＲＩ定性误诊４例,准确率为８５７％。ＣＴ和ＭＲＩ联合检查,能对后颅凹多数常见肿瘤作出定位及定性诊断。ＭＲＩ能多方位成像,去除后颅凹颅骨伪影的干扰,对该病的定位定性诊断明显优于ＣＴ。结论：ＣＴ和ＭＲＩ检查相结合,能提高诊断儿童后颅凹常见肿瘤的准确率,为临床提供更准确的诊疗信息。     

椎管内肠源性囊肿的MRI与临床诊断

目的 探讨椎管内肠源性囊肿的MRI与临床表现,旨在提高对该病的认识与诊断水平。资料与方法 回顾性分析经手术病理证实的7例椎管内肠源性囊肿患者的MRI及临床资料,并复习相关文献。结果 7例椎管内肠源性囊肿均发生于髓外硬膜下,4例位于脊髓腹侧,3例位于背侧。脊髓受压变窄。平扫T1WI上类似或稍高于脑脊液信号,T2WI上为脑脊液样信号。增强扫描无明显强化。临床表现以脊髓压迫症状为主,均有短期内症状进行性加重的病程特点。结论 MRI对椎管内肠源性囊肿的诊断和鉴别诊断具有重要价值,对指导治疗及评价预后十分重要。     

Malignant peripheral nerve sheath tumours in neurofibromatosis type 1: MRI supports the diagnosis of malignant plexiform neurofibroma

Plexiform neurofibroma (PNF) is a typical feature of neurofibromatosis 1 (NF1). About 10% of patients with NF1 develop malignant peripheral nerve-sheath tumours (MPNST), usually arising from PNF, and this is the major cause of poor survival. A better prognosis can be achieved if the tumours are diagnosed at an early stage. Our objective was to establish MRI criteria for MPNST and to test their usefulness in detecting early malignant change in PNF. MRI was performed on 50 patients with NF1 and nerve-sheath tumours, of whom seven had atypical pain, tumour growth or neurological deficits indicative of malignancy; the other 43 were asymptomatic. On MRI all seven symptomatic patients had inhomogeneous lesions, due to necrosis and haemorrhage and patchy contrast enhancement. In one patient, the multiplicity of confluent tumours with inhomogeneous areas in addition to central lesions did not allow exclusion of malignancy. Only three of the 43 asymptomatic patients had comparable changes; the other 40 patients had tumours being of relatively homogeneous structure on T1- and T2-weighted images before and after contrast enhancement. All three asymptomatic patients with inhomogeneous lesions were shown to have MPNST.