MR of visual pathways in patients with neurofibromatosis

MR was performed on six patients clinically diagnosed as having neurofibromatosis. Owing to its multiplanar capability, MR greatly helped determine the extent of visual pathway disease. We attempted to find specific optimal pulse sequences for evaluating the prechiasmatic, chiasmatic, and retrochiasmatic visual system at 0.35 T. Using spin-echo techniques, we evaluated a T1-weighted sequence (TR 300 msec/TE 35 msec), an intermediate T2-weighted sequence (TR 1500 msec/TE 35 msec), and a T2-weighted sequence (TR 1500 msec/TR 70 msec). We found that the orbital and intracanalicular optic nerves were most accurately and easily seen with the T1-weighted sequence axially and coronally; the chiasm was best seen with the intermediate T2-weighted coronal sequence; and the retrochiasmatic visual pathway was optimally evaluated with T2-weighted spin-echo technique.     

MR imaging anatomy of the optic pathways

Imaging in neuro-ophthalmology is a major, developing field. Visual and motor ocular symptoms and signs are of diagnostic and localizing significance, and occur frequently in patients with brain space-occupying lesions. Knowledge of the anatomy of the optic pathways extending from the retina to the calcarine fissure throughout the brain is crucial. Multiplanar high resolution MR imaging permits the physician to depict the visual path with exquisite detail. This article provides a correlative regional anatomic and imaging atlas of the brain following the optic pathways, with reference to the most accurate technical imaging procedures.     

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.     

Contrast-enhanced MR imaging of optic nerve lesions in patients with acute optic neuritis

The purpose of this study was to determine if administration of gadopentetate dimeglumine aids in the MR detection of optic nerve lesions in patients with acute optic neuritis and to establish an efficient MR imaging protocol to effectively demonstrate such lesions. Patients with acutely decreased visual acuity were referred for MR imaging of the brain and orbits. Predominantly, T1-weighted images were obtained in axial and coronal planes with and without contrast administration. Enhancing lesions were observed in the optic nerve (7/14 patients) and optic chiasm (2/14), and associated white matter lesions were seen elsewhere in the brain (5/19). Our results indicate that administration of gadopentetate dimeglumine aids in the MR detection of lesions of the optic nerve and optic chiasm. Applicability of our MR imaging protocol was confirmed by the demonstration of these lesions and by the disseminated white matter lesions seen simultaneously elsewhere in the brain.     

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.     

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.     

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.     

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.     

原发性慢性闭角型青光眼视神经MR扩散张量成像的研究

目的 探讨视神经MR DTI在研究原发性慢性闭角型青光眼所致视神经改变的临床应用价值.方法 对25例原发性慢性闭角型青光眼患者(病变组,4例为单眼发病,其余为双眼发病,共46只眼,其中右眼24只,左眼22只)和20名正常人(对照组)分别行3.0T视神经MRI和DTI检查,对比两组间各向异性(FA)、平行扩散率(λ∥)、垂直扩散率(λ⊥)、平均扩散率(MD)值差别.病变组与对照组同侧视神经比较、病变组内左与右侧视神经间比较,分别采用两独立样本t检验和配对t检验.结果 病变组6例患者8条视神经MRI表现为轻微变细,视神经鞘膜腔轻微增宽.病变组24条右眼视神经DTI的FA、λ∥、λ⊥、MD值分别为(0.27 ±0.09)×10-3、(2.30 ±0.26) ×10-3、(1.55 ±0.35)×10-3、(1.80±0.31) ×10-3mm2/s,22条左眼视神经分别为(0.24 ±0.09)×10-3、(2.25 ±0.41) ×10-3、(1.61 ±0.46) ×10-3、(1.82±0.47)×10-3 mm2/s;对照组20条右眼视神经DTI的FA、λ∥、λ⊥、MD值分别为(0.57±0.04) ×10-3、(1.78 ±0.24) ×10-3、(0.68±0.11) ×10-3、(1.01 ±0.08)×10 -3mm2/s,20条左眼视神经分别为(0.59 ±0.03) ×10-3、(1.76 ±0.13)×10-3、(0.63 ±0.07)×10-3、( 1.04±0.15)×10-3 mm2/s.与对照组比较,病变组FA值降低、λ∥、λ⊥、MD值升高,差异均有统计学意义(P值均＜0.05);病变组内左、右侧视神经相互比较,差异无统计学意义(P＞0.05).结论 DTI可以发现原发性慢性闭角型青光眼视神经扩散异常,并可定量推测视神经病理变化.     

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.     

视交叉的MRI解剖

目的　研究成人正常视交叉的MRI解剖及其毗邻结构。方法　 6 5例受检者 ,男 31例 ,女 34例 ;年龄 18～ 72岁 ,平均 4 2 3岁。均行横断、冠状和矢状面T1W扫描和矢状T2 W扫描 ,2 0例行横断面T2 W扫描 ,2 0例行冠状面T2 W扫描。分别测量视交叉的横径、高度、前后径、视交叉 -鞍结节间距、视交叉与枕骨大孔前后径夹角及颅内段视神经的夹角 ,并观察视交叉的层面形态及其毗邻结构。结果　 (1)横断面上视交叉的横径为 (13 0± 1 7)mm ,冠状面上横径为 (13 5± 1 7)mm。视交叉高度为 (3 1± 0 5 5 )mm。视交叉前后径为 (8 6± 0 93)mm。视交叉 -鞍结节间距为 (3 1± 1 7)mm。视交叉与枕大孔前后径的夹角为 (38 3± 8 4 )°。两侧颅内段视神经夹角为 (6 5 6± 8 5 )°。所有测量结果按男女分组进行统计学分析 ,男女之间没有显著统计学差异。 (2 )视交叉的毗邻 :视交叉上方为第 3脑室 ;两侧为颈内动脉 ;前上方为大脑前动脉 ;前方为额叶直回 ;后方为漏斗、灰结节和乳头体 ;下方为垂体和蝶窦。结论　MR能很好地显示视交叉的形态及其毗邻 ,并能准确地测量视交叉的大小。     

MR imaging study of edema-like change along the optic tract in patients with pituitary region tumors

BACKGROUND AND PURPOSE: Edema-like change along the optic tract commonly occurs in association with craniopharyngiomas. The aim of this study was to clarify whether it occurs in association with other common pituitary region tumors and to elucidate its mechanism as seen on MR images. METHODS: Fifty patients with pituitary region tumors that were touching or compressing the optic pathway underwent heavily T2-weighted MR imaging before and after treatment. RESULTS: Edema-like change along the optic tract was visible on the images of four of 25 pituitary adenomas, eight of 11 craniopharyngiomas, one germ cell tumor, and one malignant lymphoma and was not visible on the images of seven meningiomas and five Rathke's cleft cysts. After therapeutic decompression of the optic pathway, the edema-like change disappeared and large Virchow-Robin spaces, present under normal conditions, became visible along the optic tract. Comparison of pre- and post-treatment coronal and axial view MR images revealed that the edema-like change had been located at, along, and/or around the large Virchow-Robin spaces along the optic tract. CONCLUSION: Edema-like change occurs in association with pituitary region tumors other than craniopharyngiomas. It is related with distension of normally present large Virchow-Robin spaces adjacent to the optic tract. Because Virchow-Robin spaces are speculated to be a drainage route of interstitial fluid into the subarachnoid space, their distension may be related to the fluid retention in and along the Virchow-Robin spaces, the outlet of which into the subpial and/or subarachnoid space(s) is blocked by pituitary region tumors.     

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.     

MR imaging of compact white matter pathways

A prominent decreased signal intensity can be seen in many of the heavily myelinated, compact fiber pathways of the brain on T2-weighted spin-echo MR images (TR = 2500 msec, TE = 80 msec). These areas include the anterior commissure, internal capsule, optic tract and radiations, fornix, mammillothalamic tract, superior frontooccipital fasciculus, cingulum, corpus callosum, uncinate fasciculus, and superior longitudinal fasciculus. All these pathways could be identified in normal subjects 3 years old and older when 1.5-T axial and coronal images of 50 adults and 17 children were reviewed. Correlation of the in vivo and postmortem MR appearance of two human brains with Perls and Luxol fast blue stains indicates that the short T2 reflects heavy myelination and fiber density, not iron deposition. This is in contrast to the short T2 signal seen in the subcortical U fibers and deep nuclei of the brain that result from iron deposition. These pathways also differ from areas of brain iron accumulation in that (1) they may appear as areas of short T1 on partial-saturation or inversion-recovery pulse sequences and (2) they can be seen with regularity in all patients over 3 years of age. It is important to distinguish between the effect of the myelin sheath and the effect of brain iron on the T2 relaxation values seen in the normal brain since both result in shortened T2 relaxation. The importance of the role of these fiber tracts in disease processes and in modifying the spread of vasogenic edema and tumor needs further investigation.     

MR imaging of patients with carotidynia

BACKGROUND AND PURPOSE: Carotidynia is an idiopathic neck pain syndrome associated with tenderness to palpation over the carotid bifurcation. Although well known in the otolaryngology and neurology literature, the validity of the entity has recently been questioned, in part because of the almost uniform absence of radiologic or pathologic findings. We report the MR findings in five patients with carotidynia. METHODS: During a period of 44 months, five patients with clinical signs and symptoms consistent with carotidynia were referred for imaging from the otolaryngology service. Each patient underwent MR imaging of the neck on a 1.5-T system. The studies included, as a minimum, pre- and postcontrast axial and postcontrast coronal T1-weighted images. Two patients also had axial T2-weighted imaging and another two patients underwent duplex sonography of the carotids. RESULTS: All five patients had abnormal enhancing tissue surrounding the symptomatic carotid artery centered at the level of the distal common carotid and carotid bifurcation. This tissue had intermediate signal intensity on T1-weighted images and showed marked enhancement. In all patients, the remaining visualized portions of the carotid artery were normal. Normal flow voids were present throughout the vessel, and the caliber of the vessels was always within normal limits. There was no evidence of intramural hematoma, cervical lymphadenopathy, or atherosclerotic disease of the vessel. In one patient, repeat imaging after resolution of symptoms showed an absence of the previous abnormality. CONCLUSION: The MR findings in these patients, along with the lack of any findings to suggest alternative diagnoses, support the existence of carotidynia as a distinct clinical entity.     

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。