MR imaging of optic pathways in patients with neurofibromatosis

Twenty-one patients with documented neurofibromatosis had MR examinations to evaluate possible intracranial disease. In five cases the indication was a known or suspected optic glioma. Two patients were examined because of a history of seizures; the rest were examined as part of a baseline evaluation. Eighteen patients showed evidence of signal hyperintensity on T2-weighted images. Lesions involved the optic nerves, optic chiasm, optic tracts, lateral geniculate body, optic radiations, basal ganglia, periventricular white matter, cerebellar white matter, and dentate nucleus of the cerebellum. Comparison between MR and concurrent CT scans showed MR to be superior in demonstrating the posterior extent of optic-pathway gliomas. In addition, MR showed focal areas of hyperintensity in the basal ganglia, internal capsule, cerebellum, and/or white matter that were not detected on CT. Although we found MR to be superior to CT in detecting intracranial tumors in patients with neurofibromatosis, and in evaluating the extensive involvement of known lesions, the full clinical implications of our findings remain to be determined.     

视力下降患者MRI分析

目的：探讨引起视力下降的病变发生特点及最佳MRI扫描方案。方法：搜集2080例因视力下降行MRI检查患者的病例资料,计算MRI显示病变的阳性率和各种病变的构成比,应用Fisher精确检验法比较不同MRI序列对视神经炎的显示能力。结果：MRI检出病变的总阳性率为76.5%（1591/2080例）,视路病变最常见,共1520例（95.54%）,其中视路本身病变1157例,视路外压性病变363例;眼球病变21例,占1.32%;其它病变50例,占3.14%。对视神经炎,冠状面STIR显示率优于其它常规序列（P=0.001）。结论：MRI可发现引起视力下降的视路病变和其它病变,视神经病变和颅内占位性病变是引起视力下降的常见视路病变,冠状面STIR显示视神经炎最佳。     

Usefulness of contrast material in MR of patients with neurofibromatosis type 1.

PURPOSEOur objective was to determine the usefulness of routine administration of contrast material in brain MR imaging for the evaluation of areas of probable myelin vacuolization and neoplasms in patients with neurofibromatosis type 1 (NF-1).METHODSWe retrospectively reviewed 112 consecutive contrast-enhanced brain MR studies obtained over a period of 7 years in 109 symptomatic and asymptomatic patients compiled from two institutional NF-1 data bases. MR studies were analyzed for areas of probable myelin vacuolization, with attention to degree of enhancement and its impact on lesion detection and characterization. Usefulness of contrast material was graded as 0 = not useful, 1+ = somewhat useful, and 2+ = useful.RESULTSOf 112 studies, 45% (n = 49) were normal. In the remaining 63 studies, 88 regions of probable myelin vacuolization and 52 tumors were identified. Enhancement was not observed in any regions of probable myelin vacuolization. Enhancement was present in 31% of tumors, and, of these, was found to be useful in 44%, somewhat useful in 12%, and not useful in 44%. For enhancing tumors, contrast agent was useful for lesion detection in 19% and for lesion characterization in 25%.CONCLUSIONContrast administration is useful in baseline MR studies to maximize tumor detection and characterization, to add confidence to the diagnosis of benign probable myelin vacuolization, and to document stability of neoplasms on follow-up examinations.     

MR imaging of the corpus callosum in pediatric patients with neurofibromatosis type 1

BACKGROUND AND PURPOSE: Many pediatric patients with neurofibromatosis type 1 (NF-1) have an apparent increased thickness of the corpus callosum (CC) on sagittal T1-weighted images compared with patients not affected by NF-1. In this study, we compared the surface area of the CC in children with NF-1 with that of healthy pediatric control subjects to determine if this was another common intracranial manifestation of NF-1. METHODS: Midsagittal T1-weighted MR images of 43 consecutive children with NF-1 and 43 age- and gender-matched healthy control subjects were reviewed retrospectively. The surface area of the CC and the midsagittal intracranial skull surface (MISS) area were measured five times each on all midsagittal images. A mean CC to mean midline intracranial surface area ratio (CC/MISS) was calculated for each. RESULTS: There is a statistically significant increase in the mean CC surface area in pediatric patients with NF-1 (680 mm2 +/- 98, range 509-974 mm2) compared with control subjects (573 mm2 +/- 83, range 404-797 mm2). The mean MISS is significantly increased in patients with NF-1 (16568 mm2 +/- 1161, range 14107-19394 mm2 vs 15402 mm2 +/- 1133, range 12951-17905 mm2 for control subjects). CC/MISS was also significantly increased in the patients with NF-1 relative to the control subjects (.0410 +/- .0043, range .0330-.0530 vs .0372 +/- .0043, range .0270-.0470 for control subjects). CONCLUSION: A larger midsagittal surface area of the CC is another intracranial manifestation of NF-1 that can be demonstrated by sagittal MR imaging. The etiology is unclear, but could be related to abnormal neurofibromin and Ras protein activity. Potential clinical relevance is discussed herein.     

Cranial MR imaging in neurofibromatosis

Cranial MR images of 53 patients with neurofibromatosis were reviewed to determine the nature, extent, and number of intracranial abnormalities present. All patients studied met tentative definitions established for the diagnosis of neurofibromatosis. Twenty-three were scanned for evaluation of known CNS of cranial nerve involvement; the remainder were neurologically asymptomatic patients without suspected lesions referred for screening. Single lesions were noted in 32 patients. Multiple lesions were identified in 14 patients. Seven had normal scans. In 23 patients small focal areas of increased signal on T2-weighted scans within the brain were though to represent heterotopias. Eight patients had chiasmal gliomas and two had optic nerve gliomas. Nine patients had parenchymal gliomas, two had ischemic changes, and one had a colloid cyst. Extraaxial lesions included acoustic neuromas (five patients), meningiomas (four), trigeminal neurofibromas (one), and dysplasia of a sphenoid wing (two). Of the 30 asymptomatic patients referred for screening, lesions were found in 23. MR was found to be an excellent method of imaging known disease and of detecting lesions in asymptomatic patients. Because of the large number of asymptomatic lesions detected in this population, a screening MR study is recommended in patients with neurofibromatosis.     

神经纤维瘤病中枢神经系统的MRI表现

目的 探讨神经纤维瘤病(NF)的中枢神经系统(CNS)MR表现。方法 回顾性分析10例神经纤维瘤病患的临床资料并对其中枢神经系统MR表现进行分析，所有病例均行常规MR平扫及增强扫描。结果 10例病例中，NF—1型6例，表现为脑内胶质瘤、椎管内神经纤维瘤，4例合并皮肤损害，其中一例有家族史，NF—2型4例，表现为双侧听神经瘤、多发脑膜瘤或神经纤维瘤，皮肤损害少见。所有病例中增强扫描均发现平扫未发现之病灶。结论 MR能很好显示病变的大小、形态及信号特点，对检出神经纤维瘤病中枢神经系统的损害方面有优势，增强扫描可帮助发现平扫未见病灶。     

MR imaging of spinal neurofibromatosis

The MR findings in 7 patients with neurofibromatosis involving the spine were evaluated. Six patients had paraspinal tumors at multiple levels. In 4 they were bilateral. Five patients had multiple intraspinal lesions, frequently with growth through the neural foramen. In one patient paraspinal tumors were found in the lumbar sacral plexus and in another bony dysplasia and meningoceles but no tumors were disclosed. In 2 patients the lesions were associated with bilateral acoustic neuromas and multiple intracranial meningeomas. In one of these a spinal meningeoma with signal characteristics close to spinal cord was found. The other tumors had a signal that was equal to or slightly lower than the spinal cord and slightly higher than muscle on T1-weighted images. On T2-weighted images the tumors had a markedly increased signal compared to surrounding tissue. In 3 patients with tumors larger than 4 cm the signal intensity was inhomogeneous with decreased signal in the center on T2-weighted images, indicating the presence of increased fibrous tissue. Gadolinium-DTPA was given to one patient with marked increase in intensity of small tumors on T1-weighted images. The study shows that MR imaging is the modality of choice for evaluating most aspects of spinal and paraspinal neurofibromatosis.     

Multifocal intracranial MR abnormalities in neurofibromatosis

MR imaging of four children with neurofibromatosis demonstrated areas of increased T2 signal involving widespread multifocal regions of basal ganglia and brainstem. Such abnormalities have not been previously reported. No corresponding CT abnormalities were present. These regions may represent hamartomatous or low-grade gliomatous change, and appear to be characteristic of neurofibromatosis in children.     

MR imaging of spinal tumors in children with neurofibromatosis 1

OBJECTIVE: The need for radiologic surveillance of spinal tumors in children with neurofibromatosis 1 is controversial and unresolved. We aimed to determine the incidence of spinal tumors in asymptomatic patients, describe the imaging findings, and evaluate the clinical usefulness of a prospective MR imaging surveillance program of the spine in children with neurofibromatosis 1. SUBJECTS AND METHODS: Of 62 children consecutively seen in a neurofibromatosis 1 clinic, 53 (85.5%) were recruited for MR imaging of the whole spine. All children satisfied the clinical criteria for diagnosis of neurofibromatosis 1. Imaging findings, clinical signs and symptoms, and subsequent clinical management were reviewed. RESULTS: The patients were 35 boys and 18 girls (age range, 11 months-18 years; mean age, 9.6 years), all of whom were asymptomatic, with no remarkable neurologic signs. Seven children (13.2%) had spinal neurofibromas: four had solitary neurofibromas (two dumbbell, one intradural, and one paraspinal tumor) and three had plexiform neurofibromas of the sacral plexus and thoracic and lumbar nerve sheaths. The incidences of scoliosis, localized cutaneous neurofibromas, and massive soft-tissue neurofibromas were 71.4%, 71.4%, and 28.6%, respectively, in the group with spinal neurofibromas (n = 7), and 30.4%, 39.1%, and 8.7%, respectively, in the group without spinal neurofibromas (n = 46). Patient clinical outcome was affected in only one patient (1.9%) in whom a solitary neurofibroma was resected. Follow-up imaging in 10 patients (mean period, 29 months) showed no evidence of tumor occurrence, progression, or recurrence. CONCLUSION: Although benign spinal neurofibromas are not uncommon in asymptomatic children with neurofibromatosis 1, the clinical usefulness of spine surveillance with MR imaging is limited in these children, making its effectiveness questionable.     

MR in neurofibromatosis of the larynx.

We report the MR results of four patients with plexiform neurofibromas of the larynx. Three had irregular margins and were circumferential around the airway. The distinction between regularly and irregularly shaped neurofibromas may have implications for symptom onset.     

MR of uncommon congenital and vascular lesions of the intracranial visual pathways

Summary The MR findings of two patients with rare congenital abnormalities of the optic pathways are reported and illustrated, including one case of unilateral aplasia of the optic chiasm, tract, and visual radiations and another patient with anophthalmos. In three other patients with unusual vascular causes of visual disturbance, MR was important in early establishment of an accurate diagnosis and had consequent implications for decisions regarding further patient management.     

Proton MR spectroscopy in patients with neurofibromatosis type 1: evaluation of hamartomas and clinical correlation.

PURPOSETo use proton MR spectroscopy in patients with neurofibromatosis type 1 to determine: (a) the spectroscopic characteristics of hamartomas and compare them with that of gliomas; (b) whether differences exist between patients with and without learning disabilities; and (c) spectroscopic patterns in normal-appearing brain (by MR imaging) in patients with and without focal lesions.METHODSSeventeen proton MR spectroscopy volumes were obtained in 10 patients with neurofibromatosis type 1 (including hamartomas, N = 7; normal-appearing brain, N = 10). Seven patients had learning disorders, and 3 were mentally normal. Ten healthy volunteers and 10 patients with pathologically proved gliomas (all grades) were also examined. N-Acetyl aspartate/creatine, creatine/choline, and N-acetyl aspartate/choline ratios were calculated for all samples.RESULTS(a) Hamartomas showed higher N-acetyl aspartate/creatine, creatine/choline, and N-acetyl aspartate/choline ratios than gliomas. Hamartomas showed N-acetyl aspartate/creatine, creatine/choline, and N-acetyl aspartate/choline ratios similar to those of healthy volunteers. (b) No significant differences in N-acetyl aspartate/creatine, creatine/choline, and N-acetyl aspartate/choline ratios were found in patients who had neurofibromatosis type 1 with and without learning disabilities. (c) N-acetyl aspartate/creatine, creatine/choline, and N-acetyl aspartate/choline ratios were similar for patients who had neurofibromatosis type 1 with and without focal hamartomas and in healthy volunteers.CONCLUSIONS(a) Hamartomas have a proton MR spectroscopy pattern different from that of glioma and similar to that of normal brain. (b) As performed in this study, proton MR spectroscopy did not show significant differences in patients who had neurofibromatosis type 1 with and without learning disabilities. (c) Patients who have neurofibromatosis type 1 with and without hamartomas seem to have normal intervening brain by proton MR spectroscopy when compared with healthy volunteers.     

Imaging nervous pathways with MR tractography

This paper describes the state of the art of tractography, a technique which enables the virtual reconstruction of axon bundles of the central nervous system using diffusion-weighted magnetic resonance images. This technique has raised enthusiasm and expectations among specialists because it is the only non-invasive method for studying the three-dimensional architecture of axonal fibres in vivo. Tractography is a new technique used to assess the anatomy of the central nervous system, and it will be available for routine clinical use in the future. Understanding its potential applications and limitations is therefore important.     

Intramedullary and spinal canal tumors in patients with neurofibromatosis 2: MR imaging findings and correlation with genotype

PURPOSE: To determine the appearance of spinal tumors on magnetic resonance (MR) images of patients with neurofibromatosis 2 (NF2), to assess the biologic behavior of these tumors, and to determine the correlation between NF2 germline mutations and these tumors. MATERIALS AND METHODS: Spinal MR images in 49 patients with NF2 were reviewed retrospectively. Intramedullary and intradural extramedullary tumors were counted, and imaging features and growth patterns of intramedullary tumors were determined. Medical records were reviewed for spinal tumor surgery. Data on spinal tumors and NF2 germline mutations in 37 patients from 19 families were analyzed for genotype-phenotype correlation. RESULTS: Thirty-one patients (63%) had spinal tumors: Twenty-six (53%) had intramedullary tumors, 27 (55%) had intradural extramedullary tumors, and 22 (45%) had at least one tumor of each type. Three (12%) patients with intramedullary tumors versus 16 (59%) with extramedullary tumors had undergone surgery for the respective types of tumors. Compared with patients with all other types of mutations, a higher percentage of patients with nonsense and frameshift mutations had intramedullary tumors (P <.025); these patients also had higher mean numbers of all tumors (P <.001), intramedullary tumors (P <.001), and nerve sheath tumors (NSTs) (P <.001). CONCLUSION: In patients with NF2 and spinal tumors, extramedullary tumors (predominantly NSTs) were present in higher numbers and were associated with more surgery than were intramedullary tumors. Our data suggest that the association between nonsense and frameshift mutations and severe NF2 may extend to specific categories of spinal tumors.     

Whole body MR imaging in neurofibromatosis type 1

Objective

To assess the value of whole body MR imaging in patients with neurofibromatosis type 1 (NF1).

Materials and methods

24 patients (15–59 years; mean and median 36 years; 7 males; 17 females) with genetically proven neurofibromatosis type 1 were examined with whole body MR imaging. Axial and coronal T1- and fat-suppressed T2-weighted images (slice thickness 6–12 mm) were acquired on a 1.5 T MR unit (Symphony; Siemens, Erlangen, Germany). The images were reviewed by 2 radiologists: 1 senior, 1 junior. The criterion for a neurofibroma was a mass lesion with low signal intensity on T1 and high signal intensity on T2, along the course of a nerve. The location, size, general morphology and course along plexuses and nerves were evaluated. Cutaneous and subcutaneous neurofibromas were defined as “superficial” neurofibromas. The other neurofibromas were regarded as “deep” neurofibromas.

Results

There were no major problems to differentiate neurofibromas from lymph nodes, vessels or cysts. The latter three were easily recognised by their typical shape and location, whereas neurofibromas occurred in regions where no mass lesion was anatomically expected. There was no relation between age and total number of neurofibromas throughout the body. Classification according to location and number of neurofibromas: 8 patients had only superficial neurofibromas, 1 only deep and 15 both superficial and deep lesions. Twelve patients had less than 15 neurofibromas and 12 had more. Classification according to course: in 8 patients the neurofibromas occurred along plexuses or proximal part of the intercostal nerves; in 16 patients the lesions were more peripheral. Classification according to morphology: 4 patients had plexiform neurofibromas and 20 patients had multiple solitary lesions. Twelve of these 20 patients had less than 15 lesions, and 8 had more. In 2 patients multiple solitary neurofibromas occurred along the nerve in a chain configuration. In one patient a clinically unsuspected brain tumour was found.

Conclusion

Whole body MR imaging is a reliable method to evaluate the distribution, size and morphology of neurofibromas in patients with NF1.     

Hydrocephalus in patients with neurofibromatosis type 1: MR imaging findings and the outcome of endoscopic third ventriculostomy

Although hydrocephalus associated with NF-1 is not rare, up to now the MR imaging findings in these patients and the role of ETV in the treatment of hydrocephalus associated with NF-1 have not been investigated thoroughly. We present the MR imaging findings of hydrocephalus associated with NF-1 in 7 of 54 patients with NF-1. Although the types of obstruction were various, including aqueductal web, superior velum medullary synechia, periaqueductal/tectal hamartomas, cerebellar and pontine tegmentum hamartomas, brain stem glioma, or a combination, the presence of hamartomas was a consistent finding in patients with NF-1 with hydrocephalus. In 5 cases, 8 ETV procedures were performed and followed for up to 53 months. All children treated with ETV were shunt-free at their most recent examinations. ETV may be the primary procedure for the treatment of hydrocephalus associated with NF-1, regardless of the cause and the level of the obstruction.     

Visual stimulation, 1H MR spectroscopy and fMRI of the human visual pathways

The purpose was to assess changes in lactate content and other brain metabolites under visual stimulation in optical chiasm, optic radiations and occipital cortex using multiple voxel MR spectroscopy (MRS). ¹H chemical shift imaging (CSI) examinations of transverse planes centered to include the above structures were performed in four subjects at an echo time of 135 ms. Functional MRI (fMRI) was used to confirm the presence of activity in the visual cortex during the visual stimulation. Spectral maps of optical chiasm were of poor quality due to field disturbances caused by nearby large blood vessels and/or eye movements. The optic radiations and the occipital lobe did not show any significant MR spectral change upon visual stimulation, i.e., the peak areas of inositol, choline, creatine, glutamate and N-acetylaspartate were not affected. Reproducible lactate signals were not observed. fMRI confirmed the presence of strong activations in stimulated visual cortex. Prolonged visual stimulation did not cause significant changes in MR spectra. Any signal observed near the 1.33 ppm resonance frequency of the lactate methyl-group was artifactual, originating from lipid signals from outside the volume of interest (VOI). Previous claims about changes in lactate levels in the visual cortex upon visual stimulation may have been based on such erroneous observations.     

Anterolateral cervical meningocele in association with neurofibromatosis: MR and CT studies

Cervical anterolateral meningocele is rarer than its counterpart in the thoracic region. All of the previously described patients and the present case had associated neurofibromatosis. The magnetic resonance appearance is diagnostic.     

Fibrosing alveolitis in patients with neurofibromatosis.

Fibrosing alveolitis, or interstitial pulmonary fibrosis, is a common manifestation of neurofibromatosis, and was observed in 7 of 70 patients with the disease. Though neurofibromatosis is congenital, fibrosing alveolitis does not appear until adulthood, and occurs in 20% of patients with the disease who are over 30 years old. Characteristic radiographic findings include linear, interstitial density, and large upper lobe bullae; this combination limits the differential diagnosis. Pathological examination demonstrates alveolar wall thickening progressing to fibrosis and lung destruction. Pulmonary function tests can show obstructive or restrictive lung disease.