Книги по МРТ КТ на английском языке / MRI for Orthopaedic Surgeons Khanna ed 2010

A

Fig. 12.18 Cervical meningioma. (A) A coronal postgadolinium T1weighted image showing a widely dural-based lesion (arrow) that enhances and is hyperintense compared with the cord. (B) On a sagittal

B

T2-weighted image, the lesion is slightly hyperintense compared with the cord, showing cord displacement and widening of the ipsilateral CSF space, characteristic of intradural–extramedullary lesions.

A

Fig. 12.19 A sagittal image of a schwannoma at the cervicothoracic junction. The dural-based lesion is slightly hyperintense compared with the cord on T2-weighted images (A) and shows strong homo-

B

geneous contrast enhancement with gadolinium on T1-weighted images (arrows) (B).

Fig. 12.20 An axial T2-weighted image of a cervical neurofibroma showing a dumbbell-shaped lesion that resides in both the intradural and extradural compartments. Note the neuroforaminal widening where the tumor exits the spinal canal (arrows).

■ Intramedullary Tumors

These lesions of the spinal cord itself account for 5% to 10% of all central nervous system tumors, 20% of intraspinal neoplasms in adults, and 30% to 35% of intraspinal neoplasms in children.9 More than 90% of these lesions are gliomas.57 Of spinal cord gliomas, more than 95% are ependymomas and low-grade astrocytomas, with ependymomas being more common (60%) than astrocytomas (30%).9,58 In children, however, astrocytomas are more common.59 The remaining lesions include hemangioblastomas and metastases, but these lesions are very rare.

MRI is the diagnostic procedure of choice in evaluating possible spinal cord tumors and myelopathy in general. Classic MRI findings show a di use, multisegmental smoothly enlarged cord or filum terminale mass with gradual surrounding subarachnoid e acement. Many lesions are associated with syringomyelia, or cyst-like cavities within the cord, extending within the central canal of the cord or eccentric to the canal in a longitudinal orientation (Fig. 12.22).

locally aggressive, and more prone to metastasis. They often erode and replace adjacent bone and exhibit large soft-tissue components. MRI reveals multilobular masses hypointense on T1-weighted images and hyperintense on T2-weighted images.56 T1-weighted images with contrast and fat suppression show robust, homogeneous enhancement. Malignant meningiomas may look similar to hemangiopericytomas,

Ependymoma and Low-Grade Astrocytoma

Ependymomas and low-grade astrocytomas appear nearly identical on MRI. Widening of the cord secondary to infiltration and syringomyelia are most obvious on T2-weighted images, in which the hyperintense CSF signal is contrasted against the less intense cord signal. Additionally, such lesions typically possess high signal intensity on T2-weighted images. T1-weighted images usually reveal lesions that are isoor hypointense relative to the surrounding spinal cord (Fig. 12.23).60,61

Mixed signal lesions are seen if hemorrhage (more typical of ependymomas), tumor necrosis, or cyst formation has occurred. With the administration of contrast, intramedullary tumors generally show robust enhancement, often in a nodular, peripheral, or heterogeneous pattern (Fig. 12.24). Such lesions usually are located in the cervical and/or thoracic spinal cord.62 Ependymomas more commonly have a “cap sign,” referring to a focal hypointensity on T2-weighted images that appears in areas of hemosiderin at the cranial or caudal margin of the tumor. A helpful tool for learning to identify intramedullary spinal cord tumors, most specifically ependymomas, is recalling the five C’s:

•Central within the cord

•Cervical in location

•Contrast-enhancing

•(Associated with) cysts

•Cap sign

Unlike cellular or mixed ependymomas, which most commonly occur in the cervical spine, myxopapillary ependymomas most often occur in the conus medullaris and filum terminale.63 Because these lesions typically are slow growing, vertebral body scalloping is common with a large conus lesion that fills the entire lumbosacral thecal sac; the neural foramina also may be enlarged. Interestingly, although these lesions grow from ependymal cells of the conus and filum, making them intramedullary in origin, they most commonly appear like intradural–extramedullary masses because there is no widening of the cord at the level of the cauda equina. Thus, CSF signal on T2-weighted images creates a meniscuslike sign around the lesion (Fig. 12.25).

Paragangliomas are rare tumors that most commonly present in the cauda equina, where they often are indistinguishable from myxopapillary ependymomas. On MRI, these lesions are typically seen as well-defined areas of intense enhancement after contrast administration. Because of their high degree of vascularity, paragangliomas often show prominent foci of high-velocity signal loss (“flow voids”), corresponding to enlarged feeding arteries and/or draining veins.

Hemangioblastoma

Hemangioblastomas typically appear as highly vascular nodules within the subpial compartment; thus, they lie closer to the surface of the cord than do ependymomas and astrocytomas. They are associated with extensive cyst formation that di usely enlarges the cord in up to 70% of patients.64 Because of the highly vascular nature of such lesions, robust homogeneous contrast enhancement within the tumor nodule is the rule, and MRI almost always shows prominent flow voids (Fig. 12.26). Multiple lesions can occur in the presence of von Hippel–Lindau syndrome, with rare extensive involvement of the leptomeninges, referred to as leptomeningeal

Spinal cord

Exiting nerve root

Tumor

Dura

Fig. 12.22 Artist’s sketch (dorsal view) depicting the characteristics of an intramedullary mass. The mass di usely enlarges the cord over multiple spinal segments.

hemangioblastomatosis.65 When a spinal hemangioblastoma is suspected on MRI, it is advisable to image the entire central nervous system to exclude multiple lesions.

Intramedullary Metastases

Intramedullary metastases are rare, representing only 4% to 8.5% of all central nervous system metastases.9 Most spinal cord metastases are localized to the pia mater in which they appear as a thin rim of enhancement along the cord surface on postcontrast T1-weighted images. In addition, edema out of proportion to a focal, small cord lesion suggests metastasis, even if isolated.66 Primary malignancies accounting for such lesions are most commonly lung and breast carcinomas, lymphoma, leukemia, and melanoma.67 In 20% of

Fig. 12.23 Cervical ependymoma. (A) A sagittal T2-weighted image showing a large cervical ependymoma centered at C4-C5 but with cord signal change extending from C2 to C7. (B) A postgadolinium T1-weighted image showing that the tumor is located at C4-C5 and that the signal change extended from C2 to C7 shown in A represents edema proximal and distal to the lesion. (C) An axial T2-weighted im-

age showing that the lesion (between arrowheads) is located within the spinal cord, which is seen as a thin sliver of low signal intensity surrounding the lesion (arrow). (D) A postgadolinium T1-weighted image showing similar findings with enhancement of the tumor (between arrowheads).

References

1.Masaryk TJ. Neoplastic disease of the spine. Radiol Clin North Am 1991;29:829–845

2.Sevick RJ, Wallace CJ. MR imaging of neoplasms of the lumbar spine. Magn Reson Imaging Clin N Am 1999;7:539–553

3.Williams RS, Williams JP. Tumors. In: Rao KCVG, Williams JP, Lee BCP, Sherman JL, eds. MRI and CT of the Spine. Baltimore: Williams & Wilkins; 1994:347–426

4.Khanna AJ, Shindle MK, Wasserman BA, et al. Use of magnetic resonance imaging in di erentiating compartmental location of spinal tumors. Am J Orthop 2005;34:472–476

5.Osborn AG. Cysts, tumors, and tumorlike lesions of the spine and spinal cord. In: Osborn AG, ed. Diagnostic Neuroradiology. St. Louis: Mosby; 1994:876–918

6.Gebauer GP, Farjoodi P, Sciubba DM, et al. Magnetic resonance imaging of spine tumors: classification, di erential diagnosis, and spectrum of disease. J Bone Joint Surg Am 2008;90(Suppl 4):146–162

7.Perrin RG, Laxton AW. Metastatic spine disease: epidemiology, pathophysiology, and evaluation of patients. Neurosurg Clin N Am 2004;15:365–373

8.Kamholtz R, Sze G. Current imaging in spinal metastatic disease. Semin Oncol 1991;18:158–169

9.Ross JS. Neoplasms, pathways of spread. In: Ross JS, Brant-Zawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-2–IV-1-5

10.Balériaux DLF. Spinal cord tumors. Eur Radiol 1999;9:1252–1258

11.Van Goethem JWM, van den Hauwe L, Ozsarlak O, De Schepper AMA, Parizel PM. Spinal tumors. Eur J Radiol 2004;50:159–176

12.Algra PR, Bloem JL, Tissing H, Falke TH, Arndt JW, Verboom LJ. Detection of vertebral metastases: comparison between MR imaging and bone scintigraphy. Radiographics 1991;11:219–232

13.Avrahami E, Tadmor R, Dally O, Hadar H. Early MR demonstration of spinal metastases in patients with normal radiographs and CT and radionuclide bone scans. J Comput Assist Tomogr 1989;13: 598–602

14.Li KC, Poon PY. Sensitivity and specificity of MRI in detecting malignant spinal cord compression and in distinguishing malignant from benign compression fractures of vertebrae. Magn Reson Imaging 1988;6:547–556

Spinal metastases with neurological manifestations. Review of 600 cases. J Neurosurg 1983;59:111–118

16.Tatsui H, Onomura T, Morishita S, Oketa M, Inoue T. Survival rates of patients with metastatic spinal cancer after scintigraphic detection of abnormal radioactive accumulation. Spine (Phila Pa 1976) 1996;21:2143–2148

17.Byrne TN. Spinal cord compression from epidural metastases. N Engl J Med 1992;327:614–619

18.Klein SL, Sanford RA, Muhlbauer MS. Pediatric spinal epidural metastases. J Neurosurg 1991;74:70–75

19.Algra PR, Heimans JJ, Valk J, Nauta JJ, Lachniet M, Van Kooten B. Do metastases in vertebrae begin in the body or the pedicles? Imaging study in 45 patients. AJR Am J Roentgenol 1992;158:1275– 1279

20.Baker LL, Goodman SB, Perkash I, Lane B, Enzmann DR. Benign versus pathologic compression fractures of vertebral bodies: assessment with conventional spin-echo, chemical-shift, and STIR MR imaging. Radiology 1990;174:495–502

21.Yochum TR, Lile RL, Schultz GD, Mick TJ, Brown CW. Acquired spinal stenosis secondary to an expanding thoracic vertebral hemangioma. Spine (Phila Pa 1976) 1993;18:299–305

22.Bandiera S, Gasbarrini A, De Iure F, Cappuccio M, Picci P, Boriani S. Symptomatic vertebral hemangioma: the treatment of 23 cases and a review of the literature. Chir Organi Mov 2002;87:1–15

23.Baudrez V, Galant C, Vande Berg BC. Benign vertebral hemangioma: MR-histological correlation. Skeletal Radiol 2001;30:442–446

24.Djindjian M, Nguyen JP, Gaston A, Pavlovitch JM, Poirier J, Awad IA. Multiple vertebral hemangiomas with neurological signs. Case report. J Neurosurg 1992;76:1025–1028

25.Liu PT, Chivers FS, Roberts CC, Schultz CJ, Beauchamp CP. Imaging of osteoid osteoma with dynamic gadolinium-enhanced MR imaging. Radiology 2003;227:691–700

26.Dorwart RH, LaMasters DL, Watanabe TJ. Tumors. In: Newton T, Potts D, eds. Computed Tomography of the Spine and Spinal Cord. San Anselmo, CA: Clavadel Press; 1983:115–147

27.Boriani S, Capanna R, Donati D, Levine A, Picci P, Savini R. Osteoblastoma of the spine. Clin Orthop Relat Res 1992;278:37– 45

28.Murphey MD, Nomikos GC, Flemming DJ, Gannon FH, Temple HT, Kransdorf MJ. From the archives of AFIP. Imaging of giant cell tumor and giant cell reparative granuloma of bone: radiologic-pathologic correlation. Radiographics 2001;21:1283–1309

29.Luther N, Bilsky MH, Härtl R. Giant cell tumor of the spine. Neurosurg Clin N Am 2008;19:49–55

30.Sharma MC, Arora R, Deol PS, Mahapatra AK, Mehta VS, Sarkar C. Osteochondroma of the spine: an enigmatic tumor of the spinal cord. A series of 10 cases. J Neurosurg Sci 2002;46:66–70, discussion 70

31.Manaster BJ. Skeletal Radiology. Chicago: Year Book Medical Publishers; 1989

32.Boriani S, De Iure F, Campanacci L, et al. Aneurysmal bone cyst of the mobile spine: report on 41 cases. Spine (Phila Pa 1976) 2001;26: 27–35

33.Moulopoulos LA, Dimopoulos MA, Alexanian R, Leeds NE, Libshitz HI. Multiple myeloma: MR patterns of response to treatment. Radiology 1994;193:441–446

34.Ota K, Tsuda T, Katayama N, et al. A therapeutic strategy for isolated plasmacytoma of bone. J Int Med Res 2001;29:366–373

plasmacytoma. Clin Radiol 2000;55:439–445

36.Boriani S, Weinstein JN, Biagini R. Primary bone tumors of the spine. Terminology and surgical staging. Spine (Phila Pa 1976) 1997;22:1036–1044

37.Soo MYS. Chordoma: review of clinicoradiological features and factors a ecting survival. Australas Radiol 2001;45:427–434

38.Dorfman HD, Czerniak B. Bone Tumors. St. Louis: Mosby; 1998

39.Ross JS. Chondrosarcoma. In: Ross JS, Brant-Zawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-38–IV-1-41

40.Aoki J, Sone S, Fujioka F, et al. MR of enchondroma and chondrosarcoma: rings and arcs of Gd-DTPA enhancement. J Comput Assist Tomogr 1991;15:1011–1016

41.Crim J. Osteosarcoma. In: Ross JS, Brant-Zawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-42–IV-1-45

42.Bramwell VHC. Osteosarcomas and other cancers of bone. Curr Opin Oncol 2000;12:330–336

43.Crim J. Ewing sarcoma. In: Ross JS, Brant-Zawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-50–IV-1-53

44.Boyko OB, Cory DA, Cohen MD, Provisor A, Mirkin D, DeRosa GP. MR imaging of osteogenic and Ewing’s sarcoma. AJR Am J Roentgenol 1987;148:317–322

45.Lonergan GJ, Schwab CM, Suarez ES, Carlson CL. From the archives of the AFIP. Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma: radiologic-pathologic correlation. Radiographics 2002;22:911–934

46.Sofka CM, Semelka RC, Kelekis NL, et al. Magnetic resonance imaging of neuroblastoma using current techniques. Magn Reson Imaging 1999;17:193–198

47.Oge HK, Söylemezoglu F, Rousan N, Ozcan OE. Spinal angiolipoma: case report and review of literature. J Spinal Disord 1999;12:353–356

48.Katzman GL. Lymphoma. In: Ross JS, Brant-Zawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-54–IV-1-57

49.Koeller KK, Rosenblum RS, Morrison AL. Neoplasms of the spinal cord and filum terminale: radiologic-pathologic correlation. Radiographics 2000;20:1721–1749

50.Li MH, Holtås S, Larsson EM. MR imaging of intradural extramedullary tumors. Acta Radiol 1992;33:207–212

51.Burger PC, Shcheithauer BW, Vogel FS. Surgical Pathology of the Nervous System and Its Coverings. Philadelphia: Churchill Livingstone; 2002

52.Cohen-Gadol AA, Zikel OM, Koch CA, Scheithauer BW, Krauss WE. Spinal meningiomas in patients younger than 50 years of age: a 21year experience. J Neurosurg 2003;98(Spine 3)258–263

53.Naderi S. Spinal meningiomas. Surg Neurol 2000;54:95

54.Conti P, Pansini G, Mouchaty H, Capuano C, Conti R. Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of the literature. Surg Neurol 2004;61:34–43, discussion 44

55.Murphey MD, Smith WS, Smith SE, Kransdorf MJ, Temple HT. From the archives of the AFIP. Imaging of musculoskeletal neurogenic tumors: radiologic-pathologic correlation. Radiographics 1999;19:1253–1280

56.Akhaddar A, Chakir N, Amarti A, et al. Thoracic epidural hemangiopericytoma. Case report. J Neurosurg Sci 2002;46:89–92, discussion 92

57.Brant-Zawadzki M. Astrocytoma, spinal cord. In: Ross JS, BrantZawadzki M, Moore KR, Crim J, Chen MZ, Katzman GL, eds. Diagnostic Imaging: Spine. Salt Lake City: Amirsys; 2004:IV-1-102–IV-1-105

58.Houten JK, Cooper PR. Spinal cord astrocytomas: presentation, management and outcome. J Neurooncol 2000;47:219–224

59.Houten JK, Weiner HL. Pediatric intramedullary spinal cord tumors: special considerations. J Neurooncol 2000;47:225–230

60.Lowe GM. Magnetic resonance imaging of intramedullary spinal cord tumors. J Neurooncol 2000;47:195–210

61.Sun B, Wang C, Wang J, Liu A. MRI features of intramedullary spinal cord ependymomas. J Neuroimaging 2003;13:346–351

62.McCormick PC, Torres R, Post KD, Stein BM. Intramedullary ependymoma of the spinal cord. J Neurosurg 1990;72:523–532

63.Bagley CA, Kothbauer KF, Wilson S, Bookland MJ, Epstein FJ, Jallo GI. Resection of myxopapillary ependymomas in children. J Neurosurg 2007;106(4, Suppl Pediatrics)261–267

64.Murota T, Symon L. Surgical management of hemangioblastoma of the spinal cord: a report of 18 cases. Neurosurgery 1989;25:699– 707, discussion 708

65.Chu BC, Terae S, Hida K, Furukawa M, Abe S, Miyasaka K. MR findings in spinal hemangioblastoma: correlation with symptoms and with angiographic and surgical findings. AJNR Am J Neuroradiol 2001;22:206–217

66.Reddy P, Sathyanarayana S, Acharya R, Nanda A. Intramedullary spinal cord metastases: case report and review of literature. J La State Med Soc 2003;155:44–45

67.Chamberlain MC, Sandy AD, Press GA. Spinal cord tumors: gadolin- ium-DTPA-enhanced MR imaging. Neuroradiology 1991;33:469–474

68.Brunberg JA, DiPietro MA, Venes JL, et al. Intramedullary lesions of the pediatric spinal cord: correlation of findings from MR imaging, intraoperative sonography, surgery, and histologic study. Radiology 1991;181:573–579

■Specialized Pulse Sequences and Imaging Protocols

Standard pulse sequences for spinal imaging include SE T1weighted and FSE T2-weighted images. The FSE technique allows for the acquisition of T2-weighted images without prolonged imaging times. T1-weighted images allow for the evaluation of anatomic detail, including that of the osseous structures and soft tissues. T2-weighted images are primarily used to evaluate the spinal cord and enhance lesion conspicuity. Because CSF is bright on T2-weighted images and the spinal cord retains its intermediate signal, the T2-weighted images maximize the CSF to neural tissue contrast and therefore allow optimal delineation of the spinal cord and nerve roots. T2-weighted images are very sensitive to pathologic changes in tissue, including any processes in which cells and the extracellular matrix have increased water content. This pathologic change is usually shown as an increase in signal intensity on T2-weighted images, which increases the conspicuity of most pathologic processes a ecting the spine.

Open MRI systems are becoming more frequently used, especially for pediatric imaging. Although these systems often have significantly lower field strengths than closed magnets and thus usually produce studies of inferior overall quality, the open environment provides young patients with access to their parents and makes the experience less intimidating for patients with claustrophobia. Open systems are also helpful for procedures that might benefit from MRI guidance. When possible, however, the authors recommend that MR imaging be performed using closed 1.5-T or 3-T MRI systems.

■ Pediatric Sedation Protocols

Formal sedation is often required for the successful MRI evaluation of the pediatric patient, and multiple studies and reviews have evaluated and recommended specific sedation protocols.1,2 The American Academy of Pediatrics has published guidelines for the elective sedation of pediatric patients,3,4 but compliance with these guidelines is not mandatory. The American Academy of Pediatrics has stated that careful medical screening and patient selection by knowl-

edgeable medical personnel are needed to exclude patients at high risk for life-threatening hypoxia.4 Also, monitoring using their guidelines is necessary for the early detection and management of life-threatening hypoxia.3 The American Academy of Pediatrics recommends that, before examination in which sedation is to be used, children up to 3 years old should ingest nothing by mouth for 4 hours, and children 3 to 6 years old should ingest nothing by mouth for 6 hours.4

Although multiple protocols exist for the specific administration of various mediations for pediatric sedation and practices vary among institutions, a few agents are essential for most sedation protocols. Oral chloral hydrate is recommended for children less than 18 months old. However, the use of oral chloral hydrate is controversial because of its variable absorption, paradoxical e ects, and nonstandardized dosing regimen. Older or larger children usually receive intravenous pentobarbital with or without fentanyl. Although several studies have reported the successful administration of sedation by trained nurses,1,2 patients who may benefit from the expertise of an anesthesiologist include those with substantial comorbidities, such as the following:

•Cardiopulmonary disease

•Skeletal dysplasias

•Neuromuscular disease

•Abnormal airway anatomy

An important consideration after sedation for pediatric MRI is the need for strict adherence to established discharge criteria, including the following5:

•Return to baseline vital signs

•Level of consciousness close to baseline

•Ability to maintain a patent airway

Because of the potential risks associated with anesthesia and sedation in the young patient, there is a trend toward referring pediatric patients who require sedation to hospitals with pediatric anesthesiologists. Alternate techniques include sleep deprivation and rapid, segmental scanning; the latter permits the acquisition of high-quality images without the use of sedation. The surgeon referring pediatric patients for MR images of the spine should be familiar with the sedation protocols and level of expertise at the selected facilities. It is important to note that sedation protocols vary