Ann Otol Rhinal LaryngollOO:1991
MAGNETIC RESONANCE IMAGING OF PEDIATRIC HEAD AND NECK CYSTIC HYGROMAS WILLIAM T. C. YUH, MD, MSEE
LINDA S. BUEHNER, MD
SIMON C. S. KAO, MD
IOWA CITY, IOWA
IOWA CITY, IOWA
IOWA CITY, IOWA
ROBERT A. ROBINSON, MD, PHD
KENNETH D. DOLAN, MD
JEFFREY J. PHILLIPS, MD
IOWA CITY, IOWA
IOWA CITY, IOWA
TORRANCE, CALIFORNIA
We retrospectively reviewed themagnetic resonance imaging (MRI) findings ofeight pathologically proved cystic hygromas inseven pediatric patients. All lesions showed multiple cysts, best depicted onT2-weighted images (T2WI). Six oftheeight lesions hadwell-defined borders. Fluid-fluid levels were visualized in seven ofeight lesions, with very high signal intensity of the upper fluid onT2WI. On TIweighted images, alllesions showed a mean signal intensity greater than that of muscle (1.6 times) and cerebrospinal fluid (CSF; 4.04 times) and less than that of fat (0.5 times). On T2WI, the mean signal intensity was greater than that of CSF (1.8 times), muscle (9.45 times), and fat (2.54 times). Chemical analysis ofthecystic fluid from one lesion showed high lipid content and hemorrhage, consistent with thepreoperative and invitro MRI findings onthefluid from thesame patient. Lesion anatomic distribution showed frequent posteriortriangle involvement; however, theepicenter of 75% ofthelesions was outside theposterior triangle. Only one lesion hadinvolvement limited totheposterior triangle. There was equal distribution ofright and left sides and nomidline lesion. Seven lesions displaced thesternocleidomastoid muscle laterally, whereas one displaced it posteriorly, with no evidence ofmuscle infiltration. Only those patients with submucosal involvement (two ofseven) hadrespiratory symptoms. Gadolinium provided no additional information with regard todiagnosis or extent of involvement. Ourexperience indicates that MRI is useful in the diagnosis and treatment planning of cystic hygromas. KEY WORDS - cystic hygroma, magnetic resonance imaging. Cystic hygromas are developmental tumors of lymphatic origin, most common in the neck region. Radiologic findings of these lesions by plain film, sonography, and computed tomography (CT) have been well established.t ? Recently, Siegel et al" reported magnetic resonance imaging (MRI) findings of lymphangiomas in children. We retrospectively studied the MRI characteristics of cystic hygroma, a subset of lymphangiomas, with specific attention to anatomic distribution and both quantitative and qualitative analyses.
in two patients. Informed parental consent required by our institutional review board was obtained before the intravenous injection of Gd-DTPA (0.1 mmol/kg). Images were obtained immediately after contrast administration by using the same parameters as those of the precontrast Tl WI. Three radiologists reviewed the lesions with attention to signal intensity, fluid-fluid levels, anatomic distribution, definition of margins, contrast enhancement, and postoperative follow-up. Signal intensities were determined by direct measurement from the console of each patient (reload patient's storage tape into the computer) at various areas of interest including upper and lower fluid within various cysts of all lesions. To minimize the variation of signal intensity at various locations, the signal measurements of the other normal structures including fat, muscle, and cerebrospinal fluid (CSF) were chosen at locations nearest to the lesion. The ratios of signal intensity between the cystic content and subcutaneous fat, muscle, and CSF were tabulated in both TIWI and T2WI pulse sequences. The extent of involvement in various anatomic compartments of the lesion was recorded.
MATERIALS AND METHODS
We retrospectively reviewed the MRI findings of eight pathologically proved cystic hygromas in seven pediatric patients. There were three boys and four girls, ranging in age from 1 week to 5 1/ 1 years (mean age, 25 months). One patient had two lesions. Two patients also had postoperative followup with MRI. Cystic contents were chemically analyzed and imaged in vitro by MRI in only one patient. All MRI examinations were performed with either a 0.5-T (Picker International, Highland Heights, Ohio) or 1.5-T (GE, Milwaukee, Wis) superconductive unit. At least one TI-weighted image (TIWI) (TR 300-600, TE 20-26) and one T2-weighted image (T2WI) (TR 2,000-2,350, TE 80-100) were ob.. tained in the same plane. Images were also obtained in at least two orthogonal planes. The slice thickness ranged from 0.3 to 1.0 em (10% to 50% slice gap in the 1.5-T unit). Gadopentetate dimeglumine (Gd-DTPA)-enhanced MRI studies were performed
RESULTS
All lesions showed multiple cysts (Figs I and 2) that were much better depicted by T2WI than TIWI. Septa or walls between two adjacent cysts were shown in all lesions and were best depicted by T2WI. Six of eight lesions showed well-defined bor-
From the Departments of Radiology (Yuh, Buehner, Kao, Dolan) and Pathology (Robinson), The University of Iowa College of Medicine, Iowa City, Iowa, and the Department of Radiology, Harbor-UCLA Medical Center, Torrance, California (Phillips). REPRINTS - William T. C. Yuh, MD, MSEE, Dept of Radiology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242.
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Yuh et al, Magnetic Resonance Imaging oj Cystic Hygroma
Fig 1. Images from 5-year-old girl with respiratory symptoms and painful swelling of left side of neck. A) Parasagittal T1weighted image (T1WI; 550/20) and B,C) axial T2~weighted images (T2WI; 2,016/100) show large soft tissue mass with multiple cysts (C) and fluid-fluid levels (B). Fluid-fluid level is more obvious on T2WI (B) than T1WI (A, arrows). Lesion extends into prevertebral region and parapharyngeal space, ineluding submucosal area of hypopharynx (C). Airway (large arrow) is compressed by adenoid tissue anteriorly and lesion posteriorly and laterally (C). Sternocleidomastoid muscle is displaced laterally and wraps around lesion (C, small arrows).
ders, whereas the other two lesions showed ill-defined borders. All lesions were located within the fascia without apparent evidence of muscle infiltration. In seven of eight lesions, the sternocleidomastoid (SCM) muscle was displaced laterally, tending to wrap around the lesions. One patient had posterior and lateral displacement of the SCM muscle (Fig IC). Fluid-fluid levels within the cysts were visualized in seven of eight lesions. The one lesion without a demonstrable fluid-fluid level consisted of numerous small cysts. The upper-level fluid usually had a much higher signal intensity on both Tl WI (87.50/0 of all cysts) and T2WI (100 % of all cysts) as compared with the lower-level fluid. In vitro MRI examination (1.5-T GE) of the fluid specimen from only one patient (Fig 3) showed similar findings with high signal intensity of the upper-level fluid on both Tl WI and T2WI compared with that of the in
vivo study (Fig 2). Chemical analysis of this upperlevel fluid showed high lipid content (cholesterol 550, normal 120 to 220; triglycerides 229, normal 10 to 180) and methemoglobin from subacute bleeding. In vitro MRI findings of the lower layer showed lower signal intensity on both Tl WI and T2WI. Chemical analysis of this lower-level fluid revealed fresh intact blood cells and debris, which accounted for the low signal intensity (deoxyhemoglobin), especially on the T2WI (Fig 3B). Although lipid content was demonstrated in the upper-level fluid, no solid adipose tissue was identified within the lesion in the pathologic specimen or by MRI of all lesions. Signal intensity of cysts within a lesion usually showed a range of variation among various cysts and between fluid-fluid levels of each cyst. On T1WI, all lesions showed an average signal intensity greater than that of muscle and CSF and less than that of fat (Table 1). The overall average signal of
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Fig 2. Images from 24-month-old boy with acute progressive swelling of neck without chills or fever. A) Axial Tl-weighted image (TI WI; 583/20) and B) T2-weighted image (T2WI; 2,000/100) show multicystic mass with fluid-fluid levels. Upperlevel fluid has much higher signal intensity than does lower-level fluid on both TlWI and T2WI. Sternocleidomastoid muscle (large arrow) is displaced posteriorly and laterally between mass and enlarged lymph nodes (small arrow). Note relatively lower signal intensity without fluid-fluid level of lymph nodes on T2WI.
all cysts from all lesions was greater than that of muscle (1.6 times) and much greater than that of CSF (4.04 times) but only half that of fat (0.5 times). On T2WI, the overall average signal intensity of all cysts from all lesions showed a signal ratio greater than that of CSF (1.8), muscle (9.45), and fat (2.54; Table 2). Lesion anatomic distribution in the cervical region showed frequent posterior triangle involvement in our series. However, only one lesion had involvement limited to the posterior triangle. Seventy-five percent of our cases showed predominant in-
volvement (the epicenter of the mass) outside the posterior triangle. Two lesions showed involvement of the superior mediastinum, one of which recurred postoperatively and was proved surgically. Two patients presenting with signs of airway obstruction had involvement of the submucosal space adjacent to airway and prevertebral spaces (Fig 1C). Lesions were equally distributed to the right and left sides of the neck in our series. Contrast MRI showed enhancement of the solid portion (cyst walls or septa) of the lesion with clearer definition of the capsule and septa than on noo-
Fig 3. Surgical aspiration of cyst fluid from lesion in Fig 2 was collected in two tubes, both within water container. A) Tl-weighted image (TIWI; 600/20) and B) T2-weighted image (T2WI; 2,000/90) show upper-level fluid has higher signal intensity. Chemical analysis of upper-level fluid showed high lipid content (cholesterol and triglycerides). Signal of lower fluid is lower than that of upper fluid on both TlWI and T2WI. These magnetic resonance imaging findings are consistent with laboratory results of intact red blood cells (deoxyhemoglobin) and cell debris.
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Yuh et al, Magnetic Resonance Imaging of Cystic Hygroma TABLE 1. Tl SIGNAL RATIO Lesion/Muscle
Lesion/CSF
Lesion/Fat
Lesion
Range
Mean
Range
Mean
Range
Mean
1 2 3 4 5 6 7 8 Average
3.3-5.2 2.2-4.0 1.5-2.7 1.9-3.0 5.0-8.0 3.3-4.4 4.0-6.4 3.8-6.0
4.75 3.1 2.1 2.45 6.5 3.85 5.2 4.7 4.04
1.4-2.2 0.9-1. 7 0.8·1.5 1.0-1.6 1.1-1.8 1.3-1.8 1.5-2.4 1.6-2.6
1.8 1.4 1.15 1.3 1.45 1.65 1.95 2.1 1.6
0.5-0.8 0.3-0.5 0.3-0.5 0.4-0.6 0.4-0.6 0.4-0.5 0.5-0.8 0.5-0.8
0.65 0.4 0.4 0.5 0.5 0.45 0.65 0.65 0.52
CSF - cerebrospinal fluid.
contrast TIWI and T2WI. However, no additional information was provided with regard to diagnosis or extent of involvement in those two patients who received the contrast agent. Postoperative examinations were obtained in two patients, and MRI findings were consistent with residual tumor in one patient and complete resection in the other. DISCUSSION
Generally, cystic hygromas, a cystic subtype of lymphangiomas, are considered rare lesions,"" accounting for 5 % to 6 % of benign tumors and O. 7 % to 4.5 % of mediastinal tumors of infants and children. Most lesions are seen in younger age groups: 65 % to 75 % are diagnosed during the first year of life and 80 % to 90 % by the second to third year. There appears to be a small increase again after the age of 20 years, occurring even into the fifth and sixth decades.?" The male to female incidence rate appears to be equal in most reports, except in the groin area, in which the male incidence is five times greater. 6 The cervical region is the most common site for cystic hygromas, with a predilection for the left posterior triangle region." This finding correlates well anatomically, because the lymphatic system is more complex and extensive in the cervical region as compared with other areas of the body. Interestingly, our limited number of cases showed equal distribution on both sides. Cystic hygromas derive from the lymphatic tissue in areas in which expansion can occur, and large multiloculated cystic spaces can therefore develop. OUf lesions were located predominantly in the fascia planes between the muscles. Most of our lesions expanded anteriorly with the epicenter outside the posterior triangle. Twenty percent occur in the axilla and 5 % in other locations such as the mediastinum, retroperitoneum, pelvis, groin, liver, and spleen.vv" The most frequent sign of cystic hygroma is the presence of a mass that typically feels like a lipoma or fluid-filled cyst." Difficulties with breathing and swallowing are usually the second and third most common symptoms, caused by lesions extending in-
to the floor of the mouth and tongue, displacing the soft tissues posteriorly into the oropharynx. Small cysts may also occur internally in and around the larynx and hypopharynx, resulting in airway obstruction." In our series, only the two patients with submucosal involvement of the airway had respiratory symptoms (Fig 1C). Therefore, identification of submucosal lesions may be essential in the management of the patient. On sonography, cystic hygromas show multilocular, predominantly cystic masses with linear septa of various thicknesses, depending on the amount of connective tissue, muscle, and fat between the cysts.' All have some solid components related to the cyst walls or septa. Some have echogenic material representing focal hemorrhage or calcification. Sonography is useful in the evaluation of superficial lesions, but not for those lesions involving deep structures. The CT findings of cystic hygroma include thinwalled, nonenhancing cystic masses filled with near-water density material. 2,3 The cyst wall may enhance with intravenous contrast material. Isodense areas have been described with hemorrhage or infection. Computed tomography more clearly defines anatomic location than plain film or sonography. Bony artifact from the skull base, vertebrae, and shoulder and the isodensity of some cysts may prevent accurate evaluation by CT of the extent of involvement. Similar to previous reports," our study showed cystic hygroma had signal intensity greater than or equal to that of muscle on TI WI and greater than that of fat on T2WI. All cysts also had signal higher than that of CSF on both TI WI and T2WI, suggesting cyst fluid is very proteinaceous and may contain subacute blood or lipid components. The fluid-fluid level reported by Siegel et al" was seen in our cases. However, we also found that the upper-level fluid frequently had a higher signal than did lower-level fluid on TIWI (87.5%) and always had a higher signal than did lower-level fluid on T2WI. Chemical analysis of the upper-level fluid in only one patient showed lower-molecular weight lipid content (cholesterol and triglycerides) consistent with the in
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Yuh et al, Magnetic Resonance Imaging of Cystic Hygroma TABLE 2. T2 SIGNAL RATIO Lesion/CSF
Lesion/Muscle
Lesion/Fat
Lesion
Range
Mean
Range
Mean
Range
Mean
1 2 3
2.1-3.0 1.4-1.7 1.0-1.3 1.2-1.4 1.7-3.2 1.6-2.4 1.5-2.7 1.5-2.5
2.55 1.55 1.15 1.3 2.45 2.0 2.1 2.0 1.8
7.0-10.0 7.0-9.0 10.0-13.0 12.0-14.0 5.7-10.0 8.0-12.0 5.0-9.0 7.5-12.5
8.5 8.0 11.5 13.0 7.85 10.0 7.0 10.0 9.45
2.6-3.7 1.7-2.1 2.0-2.6 2.4-2.8 1.9-3.6 2.0-3.0 1.9-3.4 1.9-3.1
3.15 1.9 2.3 2.6 2.75 2.5 2.15 2.5 2.54
4
5 6 7 8 Average
CSF - cerebrospinal fluid.
vitro MRI of these fluids. In addition, methemoglobin due to subacute bleeding in the upper cyst fluid can also show similar MRI findings. The surrounding fatty septa in those lesions containing smaller cysts with signal equal to that of fat on TI WI reported by Siegel et al" were not demonstrable in any of our cases by pathologic examination or MRI. The reason for this is unknown, and it may suggest a subtype of lymphangioma other than the pure cystic hygroma. Previous reports of spontaneous regression warrant close observation in selected asymptomatic cases.v'? Magnetic resonance imaging may play an important role in providing a noninvasive way to follow this group of patients, especially those whose lesions are deep in location. Preoperative MRI demonstrating the exact extent of involvement and the relationship to vital structures, such as mediastinal involvement, is important for surgical planning for complete resection and reduction of recurrences. Because of the characteristic extremely high signal intensity of most cysts as compared with that of the surrounding fat and muscle on T2WI, multiplanar ability, and lack of bony artifact, MRI is an excellent method to outline the extent of involvement. From our limited experience, coronal T2WI is the best image to outline the craniocaudal extension, whereas axial T2WI best defines the involvement of various compartments. Both axial T2WI and coronal T2WI are essential for preoperative planning. Septation is best demonstrated by both T2WI and contrast MRI. The radiologic differential diagnosis includes hemangioma, lipoma, and other congenital cysts such as branchial cleft cyst and thyroglossal duct cyst.":":" Hemangiomas typically show serpiginous high signal intensity rather than multiple dilated cystic structures with fluid-fluid level on T2WI.12 Hemangiomas frequently infiltrate muscle and contain adipose tissue. None of our cases showed typical adipose tissue within the lesion on either Tl WI or T2WI. All of our lesions showed displacement rather than infiltration of muscle. Both untreated thyro~KNOWLEDGMENTS -
glossal duct cysts and branchial cleft cysts tend to be unilocular. In addition, branchial cleft cysts may have a much thicker cyst wall. Neither lesion may exhibit fluid-fluid levels with higher signal in the upper-level fluid on T2WI. Branchial cleft cysts are found anterolateral to the carotid sheath and may cause posterior medial displacement of the SCM muscle. Most cystic hygromas arise from the posterior triangle and therefore tend to displace laterally and wrap around the SCM muscle, as seen in seven of our eight cases. Although cystic hygromas may occur in the anterior compartment, involving the submandibular area, this is not a typical location for branchial cleft cysts. Thyroglossal duct cysts typically are located anteriorly in the midline, embedded in the strap muscles. None of our lesions occurred in this location. Lipoma is probably the most difficult to differentiate clinically and the most common misdiagnosis made by the primary physician." However, lipoma has characteristic MRI findings and therefore is easily differentiated from cystic hygroma. In conclusion, although cystic hygroma has characteristic findings on sonography and CT, both modalities have some limitations. Recognizing the MRI signal and anatomic characteristics of cystic hygroma may be essential to diagnosis. These include multiple cysts with relatively well-demarcated margins and extremely high signal on T2WI, wide range of cyst signal on both TIWI and T2WI, fluidfluid levels with higher signal in the upper layer, displacement rather than infiltration of muscle, lateral displacement and wrapping around of the SCM muscle, and absence of adipose tissue. Magnetic resonance imaging is also useful (especially the coronal image) in preoperative evaluation of extent of involvement for complete resection and/or conservative evaluation for follow-up of lesions. Submucosal involvement in those patients with airway symptoms can be readily demonstrated. Finally, similar to the contrast agent in CT, Gd-DTPA demonstrated the cyst capsule and septa but offered no information other than that obtained in the noncontrast study.
The authors thank Drs Y. Sato, W. L. Smith, and S. D. Gray for their assistance in the preparation of this manuscript.
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REFERENCES 1. Sheth S, Nussbaum A, Hutchins GM, Sanders Re. Cystic
hygromas in children: sonographic-pathologic correlation. Radiology 1987;162:821-4. 2. Silverman PM, Korobldn M, Moore AV. CT diagnosis of cystic hygroma of the neck. J Comput AssistTomogr 1983;7:51920. 3. Shin MS, Berland LL, Ho KJ. Mediastinal cystic hygromas: CT characteristics and pathogenetic consideration. J Comput Assist Tomogr 1985;9:297-301. 4. Siegel MJ, Glazer HS, St Amour TE, Rosenthal DD. Lymph angiomas in children: MR imaging. Radiology 1989;170:467-70. 5. Sabin FR. The lymphatic system in human embryos with consideration of the morphology of the system as a whole. Am J Anat 1909;9:43-91. 6. Kennedy TL. Cystic hygroma-lymphangioma: a rare and
still unclear entity. Laryngoscope 1989;99(suppl 49). 7. Stal S, Hamilton S, Spira M. Hemangiomas, lymphangiomas, and vascular malformations of the head and neck. Otolaryngol CUn North Am 1986;19:769-96. 8. Emery PJ, Bailey CM, Evans JNG. Cystic hygroma of the head and neck. A review of 37 cases. J Laryngol Otol 1984;98: 613-9. 9. Schefter RP, Olsen KD, Gaffey TA. Cervicallymphangiorna in the adult. Otolaryngol Head Neck Surg 1985;93:65-9. 10. Broomhead IW. Cystic hygroma of the neck. Br J Plast Surg 1964;17:225-44. 11. Mancuso AA, Dillon WP. MRI of the head and neck: the neck. Radiol Clin North Am 1989;27:407-34. 12. Yuh WTC, Kathol M, Sein M, Ehara S, Chiu L. Hemangiomas of skeletal muscle: MR findings in five patients. AJR 1987; 149:765-8.
EXTRACRANIAL OPTIC NERVE DECOMPRESSION MEETING An Extracranial Optic Nerve Decompression Meeting will be held Nov 2-3, 1991, in Boston. For further information, contact Michael P. Joseph, MD, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114; (617) 573-3192.
SEVENTH INTERNATIONAL SYMPOSIUM ON THE FACIAL NERVE The Seventh International Symposium on the Facial Nerve will take place June 9-14,1992, in Cologne, Germany. For further information, please contact the Congress Secretary, Klinik und Poliklinik Fur HNO, Universitat zu Koln, Kongressburo, Joseph-StelzmannStrasse 9, D-5000 Koln, Germany; 49-221-478-6190.
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MAGNETIC RESONANCE IMAGING OF PEDIATRIC HEAD AND NECK CYSTIC HYGROMAS WILLIAM T. C. YUH, MD, MSEE
LINDA S. BUEHNER, MD
SIMON C. S. KAO, MD
IOWA CITY, IOWA
IOWA CITY, IOWA
IOWA CITY, IOWA
ROBERT A. ROBINSON, MD, PHD
KENNETH D. DOLAN, MD
JEFFREY J. PHILLIPS, MD
IOWA CITY, IOWA
IOWA CITY, IOWA
TORRANCE, CALIFORNIA
We retrospectively reviewed themagnetic resonance imaging (MRI) findings ofeight pathologically proved cystic hygromas inseven pediatric patients. All lesions showed multiple cysts, best depicted onT2-weighted images (T2WI). Six oftheeight lesions hadwell-defined borders. Fluid-fluid levels were visualized in seven ofeight lesions, with very high signal intensity of the upper fluid onT2WI. On TIweighted images, alllesions showed a mean signal intensity greater than that of muscle (1.6 times) and cerebrospinal fluid (CSF; 4.04 times) and less than that of fat (0.5 times). On T2WI, the mean signal intensity was greater than that of CSF (1.8 times), muscle (9.45 times), and fat (2.54 times). Chemical analysis ofthecystic fluid from one lesion showed high lipid content and hemorrhage, consistent with thepreoperative and invitro MRI findings onthefluid from thesame patient. Lesion anatomic distribution showed frequent posteriortriangle involvement; however, theepicenter of 75% ofthelesions was outside theposterior triangle. Only one lesion hadinvolvement limited totheposterior triangle. There was equal distribution ofright and left sides and nomidline lesion. Seven lesions displaced thesternocleidomastoid muscle laterally, whereas one displaced it posteriorly, with no evidence ofmuscle infiltration. Only those patients with submucosal involvement (two ofseven) hadrespiratory symptoms. Gadolinium provided no additional information with regard todiagnosis or extent of involvement. Ourexperience indicates that MRI is useful in the diagnosis and treatment planning of cystic hygromas. KEY WORDS - cystic hygroma, magnetic resonance imaging. Cystic hygromas are developmental tumors of lymphatic origin, most common in the neck region. Radiologic findings of these lesions by plain film, sonography, and computed tomography (CT) have been well established.t ? Recently, Siegel et al" reported magnetic resonance imaging (MRI) findings of lymphangiomas in children. We retrospectively studied the MRI characteristics of cystic hygroma, a subset of lymphangiomas, with specific attention to anatomic distribution and both quantitative and qualitative analyses.
in two patients. Informed parental consent required by our institutional review board was obtained before the intravenous injection of Gd-DTPA (0.1 mmol/kg). Images were obtained immediately after contrast administration by using the same parameters as those of the precontrast Tl WI. Three radiologists reviewed the lesions with attention to signal intensity, fluid-fluid levels, anatomic distribution, definition of margins, contrast enhancement, and postoperative follow-up. Signal intensities were determined by direct measurement from the console of each patient (reload patient's storage tape into the computer) at various areas of interest including upper and lower fluid within various cysts of all lesions. To minimize the variation of signal intensity at various locations, the signal measurements of the other normal structures including fat, muscle, and cerebrospinal fluid (CSF) were chosen at locations nearest to the lesion. The ratios of signal intensity between the cystic content and subcutaneous fat, muscle, and CSF were tabulated in both TIWI and T2WI pulse sequences. The extent of involvement in various anatomic compartments of the lesion was recorded.
MATERIALS AND METHODS
We retrospectively reviewed the MRI findings of eight pathologically proved cystic hygromas in seven pediatric patients. There were three boys and four girls, ranging in age from 1 week to 5 1/ 1 years (mean age, 25 months). One patient had two lesions. Two patients also had postoperative followup with MRI. Cystic contents were chemically analyzed and imaged in vitro by MRI in only one patient. All MRI examinations were performed with either a 0.5-T (Picker International, Highland Heights, Ohio) or 1.5-T (GE, Milwaukee, Wis) superconductive unit. At least one TI-weighted image (TIWI) (TR 300-600, TE 20-26) and one T2-weighted image (T2WI) (TR 2,000-2,350, TE 80-100) were ob.. tained in the same plane. Images were also obtained in at least two orthogonal planes. The slice thickness ranged from 0.3 to 1.0 em (10% to 50% slice gap in the 1.5-T unit). Gadopentetate dimeglumine (Gd-DTPA)-enhanced MRI studies were performed
RESULTS
All lesions showed multiple cysts (Figs I and 2) that were much better depicted by T2WI than TIWI. Septa or walls between two adjacent cysts were shown in all lesions and were best depicted by T2WI. Six of eight lesions showed well-defined bor-
From the Departments of Radiology (Yuh, Buehner, Kao, Dolan) and Pathology (Robinson), The University of Iowa College of Medicine, Iowa City, Iowa, and the Department of Radiology, Harbor-UCLA Medical Center, Torrance, California (Phillips). REPRINTS - William T. C. Yuh, MD, MSEE, Dept of Radiology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242.
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Fig 1. Images from 5-year-old girl with respiratory symptoms and painful swelling of left side of neck. A) Parasagittal T1weighted image (T1WI; 550/20) and B,C) axial T2~weighted images (T2WI; 2,016/100) show large soft tissue mass with multiple cysts (C) and fluid-fluid levels (B). Fluid-fluid level is more obvious on T2WI (B) than T1WI (A, arrows). Lesion extends into prevertebral region and parapharyngeal space, ineluding submucosal area of hypopharynx (C). Airway (large arrow) is compressed by adenoid tissue anteriorly and lesion posteriorly and laterally (C). Sternocleidomastoid muscle is displaced laterally and wraps around lesion (C, small arrows).
ders, whereas the other two lesions showed ill-defined borders. All lesions were located within the fascia without apparent evidence of muscle infiltration. In seven of eight lesions, the sternocleidomastoid (SCM) muscle was displaced laterally, tending to wrap around the lesions. One patient had posterior and lateral displacement of the SCM muscle (Fig IC). Fluid-fluid levels within the cysts were visualized in seven of eight lesions. The one lesion without a demonstrable fluid-fluid level consisted of numerous small cysts. The upper-level fluid usually had a much higher signal intensity on both Tl WI (87.50/0 of all cysts) and T2WI (100 % of all cysts) as compared with the lower-level fluid. In vitro MRI examination (1.5-T GE) of the fluid specimen from only one patient (Fig 3) showed similar findings with high signal intensity of the upper-level fluid on both Tl WI and T2WI compared with that of the in
vivo study (Fig 2). Chemical analysis of this upperlevel fluid showed high lipid content (cholesterol 550, normal 120 to 220; triglycerides 229, normal 10 to 180) and methemoglobin from subacute bleeding. In vitro MRI findings of the lower layer showed lower signal intensity on both Tl WI and T2WI. Chemical analysis of this lower-level fluid revealed fresh intact blood cells and debris, which accounted for the low signal intensity (deoxyhemoglobin), especially on the T2WI (Fig 3B). Although lipid content was demonstrated in the upper-level fluid, no solid adipose tissue was identified within the lesion in the pathologic specimen or by MRI of all lesions. Signal intensity of cysts within a lesion usually showed a range of variation among various cysts and between fluid-fluid levels of each cyst. On T1WI, all lesions showed an average signal intensity greater than that of muscle and CSF and less than that of fat (Table 1). The overall average signal of
Downloaded from aor.sagepub.com at Harvard Libraries on July 9, 2015
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Fig 2. Images from 24-month-old boy with acute progressive swelling of neck without chills or fever. A) Axial Tl-weighted image (TI WI; 583/20) and B) T2-weighted image (T2WI; 2,000/100) show multicystic mass with fluid-fluid levels. Upperlevel fluid has much higher signal intensity than does lower-level fluid on both TlWI and T2WI. Sternocleidomastoid muscle (large arrow) is displaced posteriorly and laterally between mass and enlarged lymph nodes (small arrow). Note relatively lower signal intensity without fluid-fluid level of lymph nodes on T2WI.
all cysts from all lesions was greater than that of muscle (1.6 times) and much greater than that of CSF (4.04 times) but only half that of fat (0.5 times). On T2WI, the overall average signal intensity of all cysts from all lesions showed a signal ratio greater than that of CSF (1.8), muscle (9.45), and fat (2.54; Table 2). Lesion anatomic distribution in the cervical region showed frequent posterior triangle involvement in our series. However, only one lesion had involvement limited to the posterior triangle. Seventy-five percent of our cases showed predominant in-
volvement (the epicenter of the mass) outside the posterior triangle. Two lesions showed involvement of the superior mediastinum, one of which recurred postoperatively and was proved surgically. Two patients presenting with signs of airway obstruction had involvement of the submucosal space adjacent to airway and prevertebral spaces (Fig 1C). Lesions were equally distributed to the right and left sides of the neck in our series. Contrast MRI showed enhancement of the solid portion (cyst walls or septa) of the lesion with clearer definition of the capsule and septa than on noo-
Fig 3. Surgical aspiration of cyst fluid from lesion in Fig 2 was collected in two tubes, both within water container. A) Tl-weighted image (TIWI; 600/20) and B) T2-weighted image (T2WI; 2,000/90) show upper-level fluid has higher signal intensity. Chemical analysis of upper-level fluid showed high lipid content (cholesterol and triglycerides). Signal of lower fluid is lower than that of upper fluid on both TlWI and T2WI. These magnetic resonance imaging findings are consistent with laboratory results of intact red blood cells (deoxyhemoglobin) and cell debris.
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Yuh et al, Magnetic Resonance Imaging of Cystic Hygroma TABLE 1. Tl SIGNAL RATIO Lesion/Muscle
Lesion/CSF
Lesion/Fat
Lesion
Range
Mean
Range
Mean
Range
Mean
1 2 3 4 5 6 7 8 Average
3.3-5.2 2.2-4.0 1.5-2.7 1.9-3.0 5.0-8.0 3.3-4.4 4.0-6.4 3.8-6.0
4.75 3.1 2.1 2.45 6.5 3.85 5.2 4.7 4.04
1.4-2.2 0.9-1. 7 0.8·1.5 1.0-1.6 1.1-1.8 1.3-1.8 1.5-2.4 1.6-2.6
1.8 1.4 1.15 1.3 1.45 1.65 1.95 2.1 1.6
0.5-0.8 0.3-0.5 0.3-0.5 0.4-0.6 0.4-0.6 0.4-0.5 0.5-0.8 0.5-0.8
0.65 0.4 0.4 0.5 0.5 0.45 0.65 0.65 0.52
CSF - cerebrospinal fluid.
contrast TIWI and T2WI. However, no additional information was provided with regard to diagnosis or extent of involvement in those two patients who received the contrast agent. Postoperative examinations were obtained in two patients, and MRI findings were consistent with residual tumor in one patient and complete resection in the other. DISCUSSION
Generally, cystic hygromas, a cystic subtype of lymphangiomas, are considered rare lesions,"" accounting for 5 % to 6 % of benign tumors and O. 7 % to 4.5 % of mediastinal tumors of infants and children. Most lesions are seen in younger age groups: 65 % to 75 % are diagnosed during the first year of life and 80 % to 90 % by the second to third year. There appears to be a small increase again after the age of 20 years, occurring even into the fifth and sixth decades.?" The male to female incidence rate appears to be equal in most reports, except in the groin area, in which the male incidence is five times greater. 6 The cervical region is the most common site for cystic hygromas, with a predilection for the left posterior triangle region." This finding correlates well anatomically, because the lymphatic system is more complex and extensive in the cervical region as compared with other areas of the body. Interestingly, our limited number of cases showed equal distribution on both sides. Cystic hygromas derive from the lymphatic tissue in areas in which expansion can occur, and large multiloculated cystic spaces can therefore develop. OUf lesions were located predominantly in the fascia planes between the muscles. Most of our lesions expanded anteriorly with the epicenter outside the posterior triangle. Twenty percent occur in the axilla and 5 % in other locations such as the mediastinum, retroperitoneum, pelvis, groin, liver, and spleen.vv" The most frequent sign of cystic hygroma is the presence of a mass that typically feels like a lipoma or fluid-filled cyst." Difficulties with breathing and swallowing are usually the second and third most common symptoms, caused by lesions extending in-
to the floor of the mouth and tongue, displacing the soft tissues posteriorly into the oropharynx. Small cysts may also occur internally in and around the larynx and hypopharynx, resulting in airway obstruction." In our series, only the two patients with submucosal involvement of the airway had respiratory symptoms (Fig 1C). Therefore, identification of submucosal lesions may be essential in the management of the patient. On sonography, cystic hygromas show multilocular, predominantly cystic masses with linear septa of various thicknesses, depending on the amount of connective tissue, muscle, and fat between the cysts.' All have some solid components related to the cyst walls or septa. Some have echogenic material representing focal hemorrhage or calcification. Sonography is useful in the evaluation of superficial lesions, but not for those lesions involving deep structures. The CT findings of cystic hygroma include thinwalled, nonenhancing cystic masses filled with near-water density material. 2,3 The cyst wall may enhance with intravenous contrast material. Isodense areas have been described with hemorrhage or infection. Computed tomography more clearly defines anatomic location than plain film or sonography. Bony artifact from the skull base, vertebrae, and shoulder and the isodensity of some cysts may prevent accurate evaluation by CT of the extent of involvement. Similar to previous reports," our study showed cystic hygroma had signal intensity greater than or equal to that of muscle on TI WI and greater than that of fat on T2WI. All cysts also had signal higher than that of CSF on both TI WI and T2WI, suggesting cyst fluid is very proteinaceous and may contain subacute blood or lipid components. The fluid-fluid level reported by Siegel et al" was seen in our cases. However, we also found that the upper-level fluid frequently had a higher signal than did lower-level fluid on TIWI (87.5%) and always had a higher signal than did lower-level fluid on T2WI. Chemical analysis of the upper-level fluid in only one patient showed lower-molecular weight lipid content (cholesterol and triglycerides) consistent with the in
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Yuh et al, Magnetic Resonance Imaging of Cystic Hygroma TABLE 2. T2 SIGNAL RATIO Lesion/CSF
Lesion/Muscle
Lesion/Fat
Lesion
Range
Mean
Range
Mean
Range
Mean
1 2 3
2.1-3.0 1.4-1.7 1.0-1.3 1.2-1.4 1.7-3.2 1.6-2.4 1.5-2.7 1.5-2.5
2.55 1.55 1.15 1.3 2.45 2.0 2.1 2.0 1.8
7.0-10.0 7.0-9.0 10.0-13.0 12.0-14.0 5.7-10.0 8.0-12.0 5.0-9.0 7.5-12.5
8.5 8.0 11.5 13.0 7.85 10.0 7.0 10.0 9.45
2.6-3.7 1.7-2.1 2.0-2.6 2.4-2.8 1.9-3.6 2.0-3.0 1.9-3.4 1.9-3.1
3.15 1.9 2.3 2.6 2.75 2.5 2.15 2.5 2.54
4
5 6 7 8 Average
CSF - cerebrospinal fluid.
vitro MRI of these fluids. In addition, methemoglobin due to subacute bleeding in the upper cyst fluid can also show similar MRI findings. The surrounding fatty septa in those lesions containing smaller cysts with signal equal to that of fat on TI WI reported by Siegel et al" were not demonstrable in any of our cases by pathologic examination or MRI. The reason for this is unknown, and it may suggest a subtype of lymphangioma other than the pure cystic hygroma. Previous reports of spontaneous regression warrant close observation in selected asymptomatic cases.v'? Magnetic resonance imaging may play an important role in providing a noninvasive way to follow this group of patients, especially those whose lesions are deep in location. Preoperative MRI demonstrating the exact extent of involvement and the relationship to vital structures, such as mediastinal involvement, is important for surgical planning for complete resection and reduction of recurrences. Because of the characteristic extremely high signal intensity of most cysts as compared with that of the surrounding fat and muscle on T2WI, multiplanar ability, and lack of bony artifact, MRI is an excellent method to outline the extent of involvement. From our limited experience, coronal T2WI is the best image to outline the craniocaudal extension, whereas axial T2WI best defines the involvement of various compartments. Both axial T2WI and coronal T2WI are essential for preoperative planning. Septation is best demonstrated by both T2WI and contrast MRI. The radiologic differential diagnosis includes hemangioma, lipoma, and other congenital cysts such as branchial cleft cyst and thyroglossal duct cyst.":":" Hemangiomas typically show serpiginous high signal intensity rather than multiple dilated cystic structures with fluid-fluid level on T2WI.12 Hemangiomas frequently infiltrate muscle and contain adipose tissue. None of our cases showed typical adipose tissue within the lesion on either Tl WI or T2WI. All of our lesions showed displacement rather than infiltration of muscle. Both untreated thyro~KNOWLEDGMENTS -
glossal duct cysts and branchial cleft cysts tend to be unilocular. In addition, branchial cleft cysts may have a much thicker cyst wall. Neither lesion may exhibit fluid-fluid levels with higher signal in the upper-level fluid on T2WI. Branchial cleft cysts are found anterolateral to the carotid sheath and may cause posterior medial displacement of the SCM muscle. Most cystic hygromas arise from the posterior triangle and therefore tend to displace laterally and wrap around the SCM muscle, as seen in seven of our eight cases. Although cystic hygromas may occur in the anterior compartment, involving the submandibular area, this is not a typical location for branchial cleft cysts. Thyroglossal duct cysts typically are located anteriorly in the midline, embedded in the strap muscles. None of our lesions occurred in this location. Lipoma is probably the most difficult to differentiate clinically and the most common misdiagnosis made by the primary physician." However, lipoma has characteristic MRI findings and therefore is easily differentiated from cystic hygroma. In conclusion, although cystic hygroma has characteristic findings on sonography and CT, both modalities have some limitations. Recognizing the MRI signal and anatomic characteristics of cystic hygroma may be essential to diagnosis. These include multiple cysts with relatively well-demarcated margins and extremely high signal on T2WI, wide range of cyst signal on both TIWI and T2WI, fluidfluid levels with higher signal in the upper layer, displacement rather than infiltration of muscle, lateral displacement and wrapping around of the SCM muscle, and absence of adipose tissue. Magnetic resonance imaging is also useful (especially the coronal image) in preoperative evaluation of extent of involvement for complete resection and/or conservative evaluation for follow-up of lesions. Submucosal involvement in those patients with airway symptoms can be readily demonstrated. Finally, similar to the contrast agent in CT, Gd-DTPA demonstrated the cyst capsule and septa but offered no information other than that obtained in the noncontrast study.
The authors thank Drs Y. Sato, W. L. Smith, and S. D. Gray for their assistance in the preparation of this manuscript.
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Yuh et al, Magnetic Resonance Imaging oj Cystic Hygroma
REFERENCES 1. Sheth S, Nussbaum A, Hutchins GM, Sanders Re. Cystic
hygromas in children: sonographic-pathologic correlation. Radiology 1987;162:821-4. 2. Silverman PM, Korobldn M, Moore AV. CT diagnosis of cystic hygroma of the neck. J Comput AssistTomogr 1983;7:51920. 3. Shin MS, Berland LL, Ho KJ. Mediastinal cystic hygromas: CT characteristics and pathogenetic consideration. J Comput Assist Tomogr 1985;9:297-301. 4. Siegel MJ, Glazer HS, St Amour TE, Rosenthal DD. Lymph angiomas in children: MR imaging. Radiology 1989;170:467-70. 5. Sabin FR. The lymphatic system in human embryos with consideration of the morphology of the system as a whole. Am J Anat 1909;9:43-91. 6. Kennedy TL. Cystic hygroma-lymphangioma: a rare and
still unclear entity. Laryngoscope 1989;99(suppl 49). 7. Stal S, Hamilton S, Spira M. Hemangiomas, lymphangiomas, and vascular malformations of the head and neck. Otolaryngol CUn North Am 1986;19:769-96. 8. Emery PJ, Bailey CM, Evans JNG. Cystic hygroma of the head and neck. A review of 37 cases. J Laryngol Otol 1984;98: 613-9. 9. Schefter RP, Olsen KD, Gaffey TA. Cervicallymphangiorna in the adult. Otolaryngol Head Neck Surg 1985;93:65-9. 10. Broomhead IW. Cystic hygroma of the neck. Br J Plast Surg 1964;17:225-44. 11. Mancuso AA, Dillon WP. MRI of the head and neck: the neck. Radiol Clin North Am 1989;27:407-34. 12. Yuh WTC, Kathol M, Sein M, Ehara S, Chiu L. Hemangiomas of skeletal muscle: MR findings in five patients. AJR 1987; 149:765-8.
EXTRACRANIAL OPTIC NERVE DECOMPRESSION MEETING An Extracranial Optic Nerve Decompression Meeting will be held Nov 2-3, 1991, in Boston. For further information, contact Michael P. Joseph, MD, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114; (617) 573-3192.
SEVENTH INTERNATIONAL SYMPOSIUM ON THE FACIAL NERVE The Seventh International Symposium on the Facial Nerve will take place June 9-14,1992, in Cologne, Germany. For further information, please contact the Congress Secretary, Klinik und Poliklinik Fur HNO, Universitat zu Koln, Kongressburo, Joseph-StelzmannStrasse 9, D-5000 Koln, Germany; 49-221-478-6190.
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