MRI of intradural-extramedullary spinal neurinomas and meningiomas

Combined radiomics nomogram of different machine learning models for preoperative distinguishing intraspinal schwannomas and meningiomas: a multicenter and comparative study

AIMS

The objective of our study was to establish and verify a novel combined model based on multiparameter magnetic resonance imaging (MRI) radiomics and clinical features to distinguish intraspinal schwannomas from meningiomas.

MATERIALS AND METHODS

This research analyzed the preoperative magnetic resonance (MR) images and clinical characteristics of 209 patients with intraspinal tumors who received tumor resection at three institutions. 159 individuals from institutions 1 and 2 were randomly assigned into a training group (n=111) and a test group (n=48) in a 7-3 ratio. A nomogram was constructed using the training cohort and was internally and externally verified in the test cohort and an independent validation cohort (n=50). Model performance was assessed utilizing the area under the curve (AUC) of receiver operating characteristics (ROC), decision curve analysis (DCA), and calibration curves.

RESULTS

The nomogram exhibited superior predictive efficacy in distinguishing between spinal schwannomas and meningiomas when compared to both the radiomics model and the clinical model. The nomogram yielded AUCs of 0.994, 0.962, and 0.949 in the training, test, and external validation cohorts, respectively, indicating its exceptional differentiating ability. The DCAs demonstrated that the nomogram yielded the best net benefit. The calibration curves indicated that the nomogram got good agreement between the predicted and the actual observation.

CONCLUSION

This research suggests that the nomogram incorporating clinical and radiomic features may be an effective auxiliary tool for distinguishing between intraspinal schwannomas and meningiomas, and has important clinical significance for clinical decision-making and prognosis prediction.

Immunoglobulin G4-Related Spinal Intramedullary Inflammatory Pseudotumor: A Case Report and Literature Review

Immunoglobulin G4-related disease (IgG4-RD) is an autoimmune disease that affects several organs. An inflammatory pseudotumor is a histologically proven benign tumor-like lesion that most commonly involves the lung and orbit. It is rare in the central nervous system, but rarest in the spinal canal. In this report, we present a case of IgG4-related intramedullary spinal inflammatory pseudotumor, along with a literature review. A 29-year-old male was transferred to the Department of Neurosurgery of Lanzhou University Second Hospital with progressive quadriparesis after numbness and weakness in both lower limbs for 50 days. Enhanced magnetic resonance imaging (MRI) of the spine revealed an isointense signal on T1-weighted images and a hyperintense signal on T2-weighted images from an enhanced mass located at the thoracic vertebrae region, for which a schwannoma was highly suspected. Then, a posterior median approach was adopted. The lesion was resected. The patient received further glucocorticoid after the diagnosis of an IgG4-related inflammatory pseudotumor was established, and the patient's symptoms improved, such as quadriparesis and lower limb weakness. This case highlights the importance of considering IgG4-related inflammatory pseudotumor as a differential diagnosis in patients with lesions involving the spinal intramedullary compartment and lower limb weakness when other more threatening causes have been excluded. IgG4-related inflammatory pseudotumor is etiologically unclear and prognostically unpredictable, and imaging may not help establish the diagnosis of IgG4-related inflammatory pseudotumor due to its resemblance to malignant tumors, and total resection might not be warranted. Glucocorticoid and surgery are usually the first-line treatments used.

Cervical intra-extradural meningioma with en-plaque, dumbbell-shaped, and an unusual calcified pattern in a young patient

Background:

Most spinal meningiomas primarily grow in the intradural extramedullary location. Epidural meningiomas are uncommon; if detected, they usually coexist with intradural lesions. They inhere more aggressive and invasive characteristics compared with their counterparts inside the dura.

Case Description:

We report a 22-year-old female who was admitted to the hospital with weakness and numbness in both lower limbs. Her cervical magnetic resonance imaging revealed an en-plaque and dumbbell-shaped lesion located from C5 to C8. After gadolinium injection, the whole mass was enhanced and unveiled two portions: intradural and extradural. The bone window of the computed tomography scan revealed calcification inside the lesion. The patient underwent tumor removal surgery. The pathology findings showed a psammomatous meningioma. After 6 months of surgery, the patient has been able to walk with walkers.

Conclusion:

We should consider spinal meningioma as a differential diagnosis when encountering an extradural lesion in the cervical region. The optimal surgical treatment for young patient with epidural meningiomas is radical surgery with dura attachment removal.

Magnetic resonance imaging spectrum of spinal meningioma

PURPOSE

To evaluate magnetic resonance (MR) imaging findings of spinal meningioma and to determine the radiological subtypes based on the MR imaging findings and their respective clinical features.

MATERIAL AND METHODS

Data for 105 patients with surgically treated and histopathologically diagnosed spinal meningiomas at our hospital between May 1, 2003 and May 1, 2017 were evaluated in this study. Two radiologists reviewed the characteristics of spinal meningiomas on MR images and categorized the spinal meningiomas into subtypes based on MR imaging findings.

RESULTS

Most spinal meningiomas showed higher signal intensity than that of the spinal cord but lower than that of the subcutaneous fat on T2-weighted images (WI). 56 cases (54%) showed adjacent spinal cord signal changes. Meningiomas could be categorized according to MR imaging findings into type A: dural-based tumors with a homogeneous signal intensity and intense contrast enhancement (81 cases, 77%); type B: round or oval-shaped tumors with an internal hypointense portion on T2-weighted images (18 cases, 17%); type C: en plaque tumors (three cases, 3%); and type D: tumors with unusual findings and a heterogeneous appearance (three cases, 3%). All type C patients showed spinal cord signal changes.

CONCLUSIONS

Spinal meningioma showed slightly high signal intensity rather than high signal intensity on T2-weighted images. Spinal cord signal changes were present in more than half of the cases. Clinical differences were observed among the different MR imaging types.

Differentiation between intraspinal schwannoma and meningioma by MR characteristics and clinic features

OBJECTIVES

To retrospectively review the MRI characteristics and clinic features and evaluate the effectiveness of MR imaging in differentiating intraspinal schwannomas and meningiomas, with the excised histopathologic findings as the reference standard.

MATERIALS AND METHODS

One hundred and four schwannomas (M/F, 57:47) and 53 meningiomas (M/F, 13:40) underwent MR examinations before surgical treatment. Simple clinic data and imaging findings were considered:(a) location (craniocaudal and axial), (b) size, (c) morphology, (d) dural contact, (e) signal characteristics, (f) enhancement degree and patterns. The usefulness of the algorithm for differential diagnosis was examined between the two tumors.

RESULTS

Interobserver agreement was good (κ = 0.7-0.9). Ten cases meningiomas demonstrated multiple lesions. There was a female predominance in the meningiomas (P < 0.001). Meningiomas predominantly were located in the ventral or anterolateral areas of thoracic regions, while schwannomas in the posterolateral areas of the thoracic and the lumbar regions (P < 0.001). Mean size of the lesions was 1.47 ± 0.36 cm for meningioma, and 2.02 ± 1.13 cm for schwannoma (P < 0.001). A dumbbell shape with intervertebral foramen widening could detect schwannomas, while the "dural tail sign" did meningiomas (P < 0.001). Hypointense and miscellaneous signal implied meningioma on T₁WIs (P < 0.001). Isointense was more frequently observed in the meningiomas, while the fluid signal intensity and miscellaneous signal in the schwannomas on T₂WIs (P < 0.001). Schwannomas usually manifested rim enhancement, while meningiomas diffuse enhancement (P = 0.005). There were six variables including the logistic equation (age, size, dural tail sign, morphology, T₂WI, and axial location). The accuracy of the algorithm in diagnosis of schwannomas was 87.1%.

CONCLUSIONS

Combination of clinic data and MRI performs significantly for differentiating between intraspinal meningiomas and schwannomas.

Fulminant spinal cord compression caused by postradiation inflammatory pseudotumor with rapid response to steroids: case report

Radiation therapy continues to play an extremely valuable role in the treatment of malignancy. The effects of radiation therapy on normal tissue can present in a delayed fashion, resulting in localized damage with pseudomalignant transformation, producing a compressive effect on the spinal cord or exiting nerve roots. Infiltration of inflammatory cells and the subsequent fibrotic response can result in the development of an inflammatory pseudotumor (benign tumor-like lesion) with subsequent mass effect. Herein, the authors present a rare case of inflammatory pseudotumor with fulminant cervicothoracic cord compression, developing 7 years after radiation therapy for breast cancer. The lesion recurred following resection but subsequently displayed complete and rapid resolution following steroid therapy. To the best of the authors' knowledge, no previous studies have reported such an incident.

Ginkgo leaf sign: a highly predictive imaging feature of spinal meningioma

OBJECT

Spinal meningioma and schwannoma are the most common spinal intradural extramedullary tumors, and the differentiation of these 2 tumors by CT and MRI has been a matter of debate. The purpose of this article is to present a case series of spinal meningiomas showing unique imaging features: a combination of a fan-shaped spinal cord and a streak in the tumor. The authors termed the former imaging feature “ginkgo leaf sign” and evaluated its diagnostic value.

METHODS

The authors present 7 cases of spinal meningioma having the ginkgo leaf sign. Thirty spinal extramedullary tumors arising lateral or ventrolateral to the spinal cord were studied to evaluate the diagnostic value of the ginkgo leaf sign for spinal meningiomas. Among 30 cases, 12 tumors were spinal meningiomas and 18 tumors from the control group were all schwannomas.

RESULTS

Seven of the 12 spinal meningiomas were positive for the ginkgo leaf sign. The sign was not present in the control group tumors. The overall ability to use the ginkgo leaf sign to detect meningioma indicated a sensitivity of 58%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 78%.

CONCLUSIONS

The ginkgo leaf sign is highly specific to spinal meningiomas arising lateral or ventrolateral to the spinal cord. In the present series, the ginkgo leaf sign was perfectly predictive for spinal meningioma.

MR Imaging of the Lumbosacral Plexus: A Review of Techniques and Pathologies

The lumbosacral plexus is a complex anatomic area that serves as the conduit of innervation and sensory information to and from the lower extremities. It is formed by the ventral rami of the lumbar and sacral spine which then combine into larger nerves serving the pelvis and lower extremities. It can be a source of severe disability and morbidity for patients when afflicted with pathology. Patients may experience motor weakness, sensory loss, and/or debilitating pain. Primary neurologic processes can affect the lumbosacral plexus in both genetic and acquired conditions and typically affect the plexus and nerves symmetrically. Additionally, its unique relationship to the pelvic musculature and viscera render it vulnerable to trauma, infection, and malignancy. Such conditions are typically proceeded by a known history of trauma or established pelvic malignancy or infection. Magnetic resonance imaging is an invaluable tool for evaluation of the lumbosacral plexus due to its anatomic detail and sensitivity to pathologic changes. It can identify the cause for disability, indicate prognosis for improvement, and be a tool for delivery of interventions. Knowledge of proper MR protocols and imaging features is key for appropriate and timely diagnosis. Here we discuss the relevant anatomy of the lumbosacral plexus, appropriate imaging techniques for its evaluation, and discuss the variety of pathologies that may afflict it.

A dumbbell-shaped meningioma mimicking a schwannoma in the thoracic spine

A 50-year-old man presented bilateral hypesthesia on and below the T6 dermatome and paresthesia. Magnetic resonance imaging (MRI) showed an intraspinal extradural tumor, which located from the 6th thoracic vertebral body to the upper margin of the 7th vertebral body, continuing dumbbell-like through the intervertebral foramen into the right middle thorax suggesting a neurogenic tumor (neurofibroma or neurilemmoma). With the patient in a prone position, we exposed and excised the tumor via a one stage posterior approach through a hemi-laminictomy of T6. Histologic examination showed a grade 1 meningothelial meningioma, according to the World Health Organization classification. Initially, we assumed the mass was a schwannoma because of its location and dumbbell shape. However, the tumor was actually a meningioma. Postoperatively, hypesthesia resolved completely and motor power of the leg gradually full recovered. A postoperative MRI revealed no evidence of residual tumor.

Concurrent spinal nerve root schwannoma and meningioma mimicking single-component schwannoma

We present a first case of concurrent tumors consisting of schwannoma and meningioma arising at the same spinal level in a patient without neurofibromatosis. A 49-year-old man without clinical evidence of neurofibromatosis presented with a 5-month history of right neck pain. MRI demonstrated an extradural tumor involving the right-sided C2 nerve root with a small intradural component. T1- and T2-weighted and contrast-enhanced MRI could not differentiate the intradural tumor as different from the extradural tumor. Total removal of the tumors was performed. No contiguity of the extradural tumor with the intradural tumor was seen. The intradural tumor attached strongly to the dura mater around the C2 nerve root exits. Intraoperative pathological diagnosis confirmed the extradural tumor as schwannoma and the intradural tumor as meningioma. We therefore thoroughly coagulated the dura mater adjacent to the intradural tumor and resected the dura mater around the nerve root exits together with the tumor. Pathological examination revealed that the resection edge of the extradural component consisted of a spinal nerve with thickened epineurium and was free of neoplastic cells. No schwannoma component was evident in the intradural tumor. No obvious transition thus existed between the extra- and intradural tumors. Distinguishing these tumors prior to surgery is critical for determining an optimal surgical plan, as schwannoma and meningioma require different surgical procedures. We therefore recommend a careful review of preoperative imaging with the possibility of concurrent tumors in mind.

Giant thoracic schwannoma presenting with abrupt onset of abdominal pain: a case report

Introduction

Giant intradural extramedullary schwannomas of the thoracic spine are not common. Schwannomas, that is, tumors derived from neoplastic Schwann cells, and neurofibromas represent the most common intradural extramedullary spinal lesions. We report the case of a patient with a giant thoracic schwannoma presenting unusually with acute abdominal pain and with delayed neurological impairment.

Case presentation

A 26-year-old Hispanic man with no previous medical problems presented with acute periumbilical pain. After extensive work-up including an exploratory laparotomy for appendectomy, magnetic resonance imaging scans of the lumbar and thoracic spine revealed a giant intradural extramedullary thoracic schwannoma within the spinal canal posterior to the T9, T10, and T11 vertebral bodies. Magnetic resonance imaging signal prolongation was noted in the spinal cord both rostral and caudal to the schwannoma. The patient underwent an urgent laminectomy from T8 to L1. After sacrificing the T10 root, the tumor was removed en bloc. Postoperatively, the patient improved significantly gaining antigravity strength in both lower extremities.

Conclusion

The T10 dermatome is represented by the umbilical region. This referred pain may represent a mechanism by which a giant thoracic schwannoma may present as acute abdominal pain. Acute, intense abdominal pain with delayed neurologic deficit is a rare presentation of a thoracic schwannoma but should be considered as a possible cause of abdominal pain presenting without clear etiology. Although these lesions may be delayed in their diagnosis, early diagnosis and treatment may lead to an improved clinical outcome.

Radiological findings of spinal schwannomas and meningiomas: focus on discrimination of two disease entities

This study evaluates the effectiveness of CT and MR imaging in differentiating intradural extramedullary spinal schwannomas and meningiomas in a large group of patients. In addition, the study correlates tumour location, morphologic characteristics and enhancement pattern. From January 2000 to June 2007, we retrospectively reviewed 128 consecutive patients (51 male, 77 female; mean age at admission 53.8 years; range 17-83 years) with spinal intradural extramedullary tumours (92 schwannomas, 36 meningiomas) at our institution. Fifty-one of ninety-two schwannomas (55.4%) showed fluid signal intensity on T2-weighted MR images. Twenty-two of thirty-six meningiomas (61.1%) showed hyperintense signal intensity and thirteen of thirty-six meningiomas (36.1%) showed isointense signal on T2-weighted MR images. Fifty-four schwannomas (58.7%) showed rim enhancement and thirty-three meningiomas (91.7%) showed diffuse enhancement on contrast-enhanced T1-weighted MR imaging. Twenty-one meningiomas (58.3%) showed dural tail sign in contrast-enhanced T1-weighted MR imaging. Twenty-one meningiomas (58.3%) showed calcification on CT images. MR and CT imaging results are therefore useful for the differentiation of schwannomas from meningiomas of the spine.

Cervical spinal meningioma mimicking intramedullary spinal tumor

STUDY DESIGN

Case report.

OBJECTIVE

To report a very unusual spinal meningioma, mimicking an intramedullary spinal tumor.

SUMMARY OF BACKGROUND DATA

Spinal meningiomas, usually associated with signs and symptoms of cord or nerve root compression, are generally encountered in women aged over 40. Radiologic diagnosis is often established by their intradural extramedullary location on magnetic resonance images.

METHODS

A 60-year-old woman had a 6-month history of progressive weakness in her upper extremities, difficulty in walking, and cervical pain radiating through both arms. Neurologic examination revealed motor strength deficiency in all her extremities, with extensor reflexes, clonus, and bilateral hyper-reflexiveness. A sensory deficit was present all over her body. Magnetic resonance images revealed that the spinal cord appeared expanded with an ill-defined, homogeneously contrast-enhanced, lobulated, eccentric mass at the C1-C3 level. The patient was operated with a preliminary diagnosis of an intramedullary tumor.

RESULTS

At surgery, the mass was found to be extramedullary, and gross total resection was performed. Histopathological examination revealed a meningioma characterized by the presence of fibrous and meningothelial components. The patient was able to ambulate with a cane, and extremity strength and sensation improved 2 months after surgery.

CONCLUSION

Spinal meningiomas can mimic intramedullary tumors, and should be considered in differential diagnosis of intradural tumors with atypical appearance.

Cervical dumbbell meningioma and thoracic dumbbell schwannoma in a patient with neurofibromatosis

The occurrence of both dumbbell meningioma and dumbbell schwannoma in one patient has not been reported in the literature. We present a 16-year-old female patient, who had progressive bilateral hearing impairment for 5 years and a progressively enlarged, non-tender neck mass for 1.5 years. Mild motor weakness over her right upper limb was noted 1 week before admission. No café-au-lait spot was noted. Magnetic resonance imaging (MRI) revealed bilateral cerebellopontine angle tumors, a C1-2 dumbbell tumor, and a T5-6 dumbbell tumor. Neurofibromatosis type 2 was diagnosed. The cervical spine and thoracic spine tumors were removed via one-staged combined posterior (laminectomy) and antero-lateral (transforaminal or thoracoscopic) approaches during two operations performed 1 month apart. The pathology revealed meningioma and schwannoma, respectively. The patient had good recovery after these two operations and her motor function improved. Six months after the second surgery, radiosurgery was performed for the bilateral acoustic tumors, because of enlarged tumor size on follow-up MRI. To the best of our knowledge, this is the first case reported in the literature of a patient, having both dumbbell meningioma and dumbbell schwannoma. A literature review of the dumbbell tumors was done, and their treatment strategies were discussed.

MR imaging features of spinal schwannomas and meningiomas

Spinal schwannomas and meningiomas are mostly benign, intra-dural extramedullary tumours. We retrospectively reviewed the Magnetic Resonance Imaging (MRI) examinations of 52 spinal schwannomas and meningiomas operated on at our institution since 1998. The series included 28 schwannomas and 24 meningiomas. We compared MRI features of schwannomas and meningiomas and evaluated statistical features that would allow differentiation. Tumours with extraspinal extension were excluded. Concerning the cranio-caudal distribution, half of the cervical tumours were schwannomas, 72% of thoracic lesions were meningiomas and all lumbar tumours were schwannomas. Meningiomas were significantly located at the upper and mid thoracic levels and schwannomas in the lumbar area. On T1-weighted images, MRI signal intensity and heterogeneity were not statistically different between meningiomas and schwannomas. On T2-weighted images, the signal intensity appeared significantly hyperintense and heterogeneous for schwannomas. After Gd-DTPA, we observed a significant difference between meningiomas and schwannomas, the enhancement being intense and heterogeneous in cases of schwannomas, and moderate and homogeneous in cases of meningiomas. The last significant qualitative item was the "dural tail sign", a dural enhancement or thickening near the tumour. It was found in only 16 cases of meningiomas. A simple diagnostic test was built for schwannomas by processing a multiple agreement analysis with the 6 significant items: cranio-caudal location, T2 signal intensity, T2 signal heterogeneity, Gd-DTPA enhancement intensity and heterogeneity, and the "dural tail sign". This test allowed diagnosis of schwannomas with a sensitivity of 96.4%, a specificity of 83.3%, a positive predictive value of 87.1%, and a negative predictive value of 95.7%. In conclusion, we consider that a diagnosis of schwannoma should be made when a spinal intradural extramedullary tumour shows hyperintensity on T2W images or intense enhancement without dural tail sign; otherwise meningioma is more probable.

Imaging of low back pain in children and adolescents

In children with low back pain (LBP), a specific cause is often identified. LBP has a relatively high prevalence during school years. However, only a minority of the children suffering from LBP seek medical attention. Protracted back pain in childhood is a serious condition that should be thoroughly investigated. This article is a systematic review of the intrinsic causes of LBP. Imaging modalities are discussed, with emphasis on magnetic resonance imaging. We have divided the intrinsic causes of LBP into four main groups: mechanical, developmental, infectious/inflammatory, and neoplastic. Disk protrusion is prevalent in young athletes. Spondylolysis and spondylolisthesis are the most common causes of chronic LBP in children. Thoracic or thoracolumbar Scheuermann disease causes kyphosis while a lumbar localization is more painful. Childhood diskitis is associated with fever and leukocytosis. Spinal inflammatory arthritides in children include juvenile rheumatoid arthritis, the juvenile spondyloarthropathies, and SAPHO syndrome, where spine as well as sacroiliac joint changes may be seen. Cysts, tumors, tumor-like lesions, and metastases are infrequent causes of back pain in children. Several of these conditions are described and illustrated in this review of LBP in children and adolescents.

Granular cell tumor presenting as an intradural extramedullary tumor

Granular cell tumor (GCT) is an uncommon benign tumor, which is thought to originate from a Schwann cell. GCT may involve any part of the body, but in our knowledge, there has been only one previous report of GCT, which arose in the intradural extramedullary space of the spine. We report a case of GCT, which occurred in the intradural extramedullary space.

Les méningiomes rachidiens extraduraux : Données IRM à propos de deux observations

Spinal extradural meningiomas are rare and may be easily confused with malignant neoplasms. We report two unusual cases of epidural spinal meningioma one within the left C6-C7 foramen and the other within the left posterolateral epidural space at the T3-T4 level. Low signal intensity of the tumor on T2-wi, thickening and enhancement of the dura with only the possibility of bone erosion are the most characteristic MR findings.

Spinal cord schwannomas mimicking drop metastases in a patient with intramedullary ependymoma and neurofibromatosis 2

The authors describe a 9-year-old boy with a large spinal cord ependymoma whose apparent drop metastases on imaging studies were later demonstrated to be schwannomas. This finding led to the discovery of small bilateral acoustic neuromas and an intracranial meningioma, establishing the diagnosis of neurofibromatosis 2. The presence of additional radiographic abnormalities in a patient with a spinal cord tumor should prompt careful consideration of the diagnosis of neurofibromatosis 2, as early identification of this disorder may significantly affect patient management.

Giant ventral intradural extramedullary neuroma: case report

OBJECTIVE AND IMPORTANCE: We report an extremely rare, giant, ventrally located, intradural extramedullary neuroma in a 32-year-old woman. It extended from the foramen magnum to the level of the 10th thoracic vertebra. To our knowledge, this is the largest reported intraspinal neuroma. CLINICAL PRESENTATION: A mixed polyradicular and medullary lesion with symptoms and signs of raised intracranial pressure was observed on clinical presentation. Magnetic resonance imaging of the entire neuraxis was suggestive of a neuroma. Histological findings revealed characteristics of a classic neuroma. INTERVENTION: A complete surgical excision of the tumor was accomplished through an osteoplastic laminotomy from C1 to T10 with monitoring of the somatosensory evoked potentials. CONCLUSION: Even such a huge, ventrally located, intradural extramedullary tumor, as in this patient, can be completely removed with good results when a preoperative radiological and histological diagnosis is considered. With the help of new-generation magnetic resonance imaging scans, the intradural neural, vascular, and other structures can be clearly outlined. These tests also obviate the need for invasive diagnostic procedures such as myelography. We recommend an osteoplastic laminotomy instead of laminectomy to reduce the risk of postoperative spinal instability.

PET-methionine of skull base neuromas and meningiomas

Eighteen patients with intracranial skull base tumours diagnosed at CT or MR as neuromas or meningiomas were studied with positron emission tomography (PET) using L-(methyl-11C) methionine. Compared with normal cerebellar tissue, the uptake of methionine in the tumours increased more rapidly and reached a higher level, and showed a slow decline after a peak occurring about 5 min after the injection. All the meningiomas exhibited considerably higher accumulation of the tracer compared with the surrounding cerebellar tissue, which made the tumour easy to identify and to demarcate from the surrounding cerebellar tissue, which made the tumour easy to identify and to demarcate from the surrounding structures (tumour to cerebellum ratios 2.62-5.37, mean 3.63). The uptake was homogeneous in all meningiomas, which were all of the syncytial type. The neuromas showed lower contrast against the cerebellum (tumour to cerebellum ratios 1.1-1.87, mean 1.48). Some neuromas displayed an irregular pattern with regions of decreased tracer uptake corresponding to small cystic areas within the neuroma. There was no overlap in methionine uptake between the two tumour groups. The results indicate that PET-methionine may contribute to the evaluation, treatment planning and follow-up of patients with skull base meningiomas and neuromas.