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Syringomyelia: Myelography, computed tomography, and magnetic resonance imaging
CT: THE JOlJRNAL
SYRINGOMYELIA: TOMOGRAPHY, RESONANCE
OF COMPUTED
MYELOGRAPHY,
TOMOGRAPHY
1
COMPUTED
AND MAGNETIC
IMAGING
ZIAD L. DEEB, MD, RICHARD H. DAFFNER, MD, WILLIAM E. ROTHFUS, MD, ANDREW L. GOLDBERG, JANET H. TABAS, MD, AND JACK E. WILBERGER, MD
Seventeen patients with cervical spinal cord cavities were studied with rnyelography, postmyelographic computed tomography scanning, and magnetic resonance imaging. The three diagnostic. techniques were compared for accuracy, patient comfort, and ease of procedure. Magnetic resonance imaging was the best diagnostic and most comfortable procedure. There is no need for myelography or postmyelographic computed tomography scanning for the evaluation of cervical syringomyelia. KEY WOKDS:
Syringomyelia; Magnetic resonance imaging of cervical spine; Intrathecal enhanced computed tomography
Previous reports have emphasized magnetic resonance imaging (MRI) as a diagnostic tool for evaluating syringomyelia (l-4). We performed a comparative study of syringomyelia patients using MRI, myelography, and postmyelographic computed tomography (CT), ie, intrathecally enhanced CT scan, to determine whether MRI was superior to the other two imaging procedures. We will use the term “syr-
From the Departments of Diagnostic Radiology and Neurosurgery, Allegheny-General Hospital, Pittsburgh, P&nsylvania. Address requests for reprints to: Ziad L. Deeb, MD, Department of Diagnostic Radiology, Allegheny General Hospital- 320 East North Avenue, Pittsburgh, Pennsylvania 15212-9986. Received May 1987. 0 1988 by Elsevier Science Publishing Co., Inc. 52 Vanderbilt Avenue, New York, NY 10017 0149-936X188/$3.50
1988;12:1-8
MD,
inx” or “syringomyelia” to refer to all conditions in which a cavity is present within the spinal cord (5, 6)
SUBJECTS
AND METHODS
Seventeen patients with a surgically proven syringomyelia were reviewed retrospectively. The MRI, myelograms, and postmyelographic CT scans were studied and tabulated (Table 1). The MRI studies were performed on a 0.5 Tesla Siemens superconductive magnet using spin echo techniques of repetition time (TR) 500 msec and echo time (TE) 17 to 35 msec for a Tl-weighted image and TZweighted image of TR 1500 to 2100 msec and TE of 90 to 105 msec. CT scans were performed on a Siemens DR3 immediately following myelography or intrathecal injection of contrast material and also 4 to 6 hours after injection. Metrizamide (Amipaque) was used for all myelograms via lumbar puncture.
RESULTS Two patients had spinal cord tumors (an astrocytoma and a hemangioblastoma) plus the syringomyelia. MRI accurately identified tumor in both patients, while CT was diagnostic in only one patient. Cord atrophy associated with syringomyelia was observed in three patients; it was easily demonstrated by MRI but could not be shown on either CT or myelography. Six out of twelve myelograms performed were negative. Differentiation between syrinx and spinal cord tumor was not achieved by the positive myelograms. Intrathecal enhanced CT was performed following the myelograms in twelve pa-
2
CT: THE JOURNAL
DEEB ET AL.
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
TABLE 1. Results of MRI, Myelogram, and Myelography Study Name KT
DA FF BL NM
sJ
CK DK
CH RG vc WD MM
JS ER AP RB
MyelogramiCT 1984 CT+ 1985 CT? Follow-up CT syrinx vs. tumor Large cord CT - myelogram CT - myelogram CT head hydrocephalus CT + / myelogram + CT - / myelogram CT - / myelogram CTimyelogram + Large cord Syrinx vs. tumor Delayed CT + Myelo + ? syrinx CT + / myelogram Delayed CT+ CT tumor vs. syrinx CT, tumor vs. syrinx CT / myelogram Tumor vs. syrinx Myelogram i CT Myelogram / CT? Nonenhanced CT Myelogram, tumor vs. syrinx
MR MR+
Diagnosis
for syrinx
Syrinx and hemangioblastoma cord, and medulla
MR syrinx
Syrinx
MR+ MR+
Syrinx Syrinx
+ cord atrophy + cord atrophy
MR+ MR+ MR+ MR+ Syrinx
Syrinx Syrinx Syrinx Syrinx
+ tumor of cord
+ tumor
MR+
Syrinx
MR+
Syrinx
MR+ MR+ MR+ MR+
Syrinx Syrinx Syrinx Syrinx
MR+ MR+ MR+
Syrinx
tients and following injection of 5 mL of 190 mg/mL metrizamide in five patients. Twelve intrathecally enhanced CT scans were positive; three atrophic cords due to syringomyelia were missed, and five CT scans were negative. In summary, MRI correctly showed the abnormalities in all patients. The results are shown in Table 1. DISCUSSION Syrinx cavities were visualized in all patients on the MRI. Sagittal Tl-weighted images were the most diagnostic and also provided a view of the cord from the thoracic region into the cranial compartment. These images were more optimal than the axial images proposed previously (5). Changing the spin-echo parameters between Tlweighting and T2-weighting confirmed the CSFcontaining nature of the cavities and also suggested the presence of tumors in two of our patients, which was later confirmed at surgery (Figure 1). This was important because the spinal cord was enlarged or normal in size in all but three patients. The tumor, however, had a different signal intensity than the syrinx on both the Tl-weighted and the
of cerebellum,
+ small cord
Syrinx
T&weighted images, thus differentiating it from the areas of gliosis observed with cord-expanding syringomyelia (1, 3, 7). When a tumor is associated with syringomyelia, two different signal intensities are often observed: CSF and tumor. These intensities varied differently as we altered the Tl- and the T2weighted parameters. Myelography was the previous definitive radiographic procedure for the diagnosis of syringomyelia (8). Oily contrast was replaced by air contrast, and lately, water-soluble products are used for myelography. A swollen and enlarged spinal cord with a “collapsing sign” was diagnostic, An enlarged or swollen cervical spinal cord was found in only 50% of our cases (Figure 2). Differentiating a syrinx from a tumor was not feasible, and the “collapsing sign” was not pursued due to the severe discomfort for the patient and associated complications of high doses of myelographic contrast agent entering the neurocranium (9-11). Computed tomography, especially when performed following intrathecal contrast enhancement, has been the diagnostic method of choice for syringomyelia for the last few years (12). The diagnostic accuracy in our series was 12 out of 17, although a
JANUARY
SYRINGOMYELIA
1988
3
C
FIGURE 1. (A) Preoperative water-soluble myelogram reveals a large spinal cord from the cervicomedullary junction to the upper thoracic area. Differentiation between a simple syrinx and a multicavitary syrinx, with or without a tumor, cannot be achieved on this exam. (B,C) Postmyelographic CT scans demonstrated the enlarged spinal cord as seen on the myelogram within the cervical region (B) and the thoracic region (C). Continued.
4
DEEB ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
F
FIGURE 1. (continued). (D,E) MR images obtained at our institution following surgery demonstrate on the Tlweighted images (TR = 0.3, TE = 35) multiple, separate cystic cavities within the spinal cord from the foramen magnum to the mid-thoracic region (D). The suspicion that a large septum was actually a tumor was confirmed on the T2-weighted MR images (TR = 2.1, TE = 120), where it had a different signal intensity than the syrinx cavities, septae, or the spinal cord (E). At surgery this proved to be an ependymoma, which was removed. (F) A postoperative MR reveals the small spinal cord without tumor or syrinx. MR imaging is superior to other modalities for patient follow-up after surgery.
JANUARY
1988
SYRINGOMYELIA
5
FIGURE 2. Syrinx was overlooked on both myelography and postmyelographic CT due to its location within the cervicomedullary junction (TR = 0.3, TE = 35).
FIGURE 3. (A) A postintrathecal enhanced CT scan revealed the atrophic cord, but no definite filling of a cavity is noted on these delayed scans. (B) The MR images demonstrate an extensive syrinx from the foramen magnum to
the thoracic region. Atrophy of the spinal cord is also present with widening of the subarachnoid space (TR = 0.5, TE = 35).
FIGURE 4. (A) AP and lateral water-soluble myelogram demonstrates a large spinal cord extending from the C-l level through the upper thoracic region. (B) Delayed CT scan following the myelogram reveals the contrast agent within the syrinx cavity and surrounding the spinal cord within the subarachnoid space. (C) MR demonstrates a large syrinx without septations or tumor from the foramen magnum through the thoracic region (TR = 2.1 msec, TE = 35 msec). On a long T&weighted series (TR = 2.1 msec, TE = 120 msec), the syrinx is of high intensity secondary to the stasis of CSF within its cystic compartment.
‘KJARY
SYRINCOMYELIA
1988
7
tumor within the syrinx was not detected. In five cases, in which the cord was atrophic or normal in size and configuration, the syrinx was overlooked although a CT was performed 4 to 6 hours after intrathecal enhancement (Figure 3). The presence of contrast within the spinal cord is not always diagnostic of syringomyelia (13). All of our patients had postexamination headaches, seven of them developed nausea, and one had vomiting. No seizures were observed. MR images obtained even with only Tl-weighted spin-echo parameters are more diagnostic than myelography and intrathecally enhanced CT. The time it takes to perform a Tl-weighted sagittal study with no known complications is about 3 to 5 minutes. A T2weighted examination adds about 15 minutes and is needed mainly when a tumor is also suspected on the Tl-weighted parameters (Figure 4). Septations within the syrinx were best demonstrated by MRI (Figure 5). The discomfort to the patient is almost nonexistent as compared to CT scanning, and the complications and morbidity of myelography and lumbar punctures can be obviated completely. We propose sagittal Tl-weighted MR imaging for diagnosis of syringomyelia as an initial exam. T2weighted images can be performed if a tumor is sus-
5. MR images reveal the septum within an exThe tonsils are low within the foramen magnum. The surgical procedure was modified to shunt both compartments (TR = 0.3 msec, TE = 35 msec). FIGURE
tended syrinx.
8
DEEB ET AL.
CT: THE JOURNAL
petted with a syrinx. Plain CT scanning, intrathecal enhanced CT scanning, and myelography should not be needed in cervical syringomyelia diagnosis. Axial cuts obtained by MRI or plain CT scanning through the suspected intervertebral disk herniations may be sought if clinically deemed necessary to rule out disk herniations suspected from the sagittal MRI images.
REFERENCES 1. Sherman JL, Barkovich of syringomyelia:
AJ, Citrin CM: The MRI appearance new observations. AJNR 1986;7:985-95.
2. Pojunas K, Williams AL, Daniels DL, Haughton gomyelia and hydromyelia: magnetic resonance Radiology 1984;153:679-83. 3. Lee BCP, Zimmerman aging of syringomyelia 8.
VM: Syrinevaluation.
RD, Manning JJ, Deck MDF: MR imand hydromyelia. AJNR 1985;6:221-
4. Kokmen E, Marsh WR, Baker HI: Magnetic resonance ing in syringomyelia. Neurosurgery 1985;17:267-70.
imag-
5. Yeates A, Brant-Zawadski M, Norman D, et al.: Nuclear magnetic resonance imaging of syringomyelia. AJNR 1983;4:2347.
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
6. Peerless SJ, Durward QJ: Management of syringomyelia: a pathophysiological approach. Clin Neurosurg 1983;30:53176. 7. DiChiro G, Doppman JL, Dwyer AJ, et al.: Tumors and arteriovenous malformations of the spinal cord: assessment using MR. Radiology 1985;156:689-97. 8. Batnitzky S, Price HI, Gaughan MJ, Hall PV, Rosenthal SJ: The radiology of syringohydromyelia. Radiographics 1983;3:585-611. changes of the brain following in9. Schober R: Morphological trathecal application of contrast media. Acta Radiologica [Diagnostica] 1961;5:509-16. 10. Haughton VM, Williams AL, Cusick JF, Meyer GA: A myelographic technique for cysts in the spinal canal and spinal cord. Radiology 1978;129:717-9. 11. Killebrew trizamide
K, Wholey RA, Hayward JN: Complication myelography. Arch Neurol 1983;40:78-80.
of me-
12. Bonafe A, Manelfe C, Espagno J, Guiraud B, Rascal A: Evaluation of syringomyelia with metrizamide computed tomographic myelography. J Comput Assist Tomogr 1980;4:797802. 13. Dubois EJ, Drayer BP, Sage M, Osborne D, Heinz ER: Intramedullary penetrance of metrizamide in the dog spinal cord. AJNR 1981;2:313-7.
SYRINGOMYELIA: TOMOGRAPHY, RESONANCE
OF COMPUTED
MYELOGRAPHY,
TOMOGRAPHY
1
COMPUTED
AND MAGNETIC
IMAGING
ZIAD L. DEEB, MD, RICHARD H. DAFFNER, MD, WILLIAM E. ROTHFUS, MD, ANDREW L. GOLDBERG, JANET H. TABAS, MD, AND JACK E. WILBERGER, MD
Seventeen patients with cervical spinal cord cavities were studied with rnyelography, postmyelographic computed tomography scanning, and magnetic resonance imaging. The three diagnostic. techniques were compared for accuracy, patient comfort, and ease of procedure. Magnetic resonance imaging was the best diagnostic and most comfortable procedure. There is no need for myelography or postmyelographic computed tomography scanning for the evaluation of cervical syringomyelia. KEY WOKDS:
Syringomyelia; Magnetic resonance imaging of cervical spine; Intrathecal enhanced computed tomography
Previous reports have emphasized magnetic resonance imaging (MRI) as a diagnostic tool for evaluating syringomyelia (l-4). We performed a comparative study of syringomyelia patients using MRI, myelography, and postmyelographic computed tomography (CT), ie, intrathecally enhanced CT scan, to determine whether MRI was superior to the other two imaging procedures. We will use the term “syr-
From the Departments of Diagnostic Radiology and Neurosurgery, Allegheny-General Hospital, Pittsburgh, P&nsylvania. Address requests for reprints to: Ziad L. Deeb, MD, Department of Diagnostic Radiology, Allegheny General Hospital- 320 East North Avenue, Pittsburgh, Pennsylvania 15212-9986. Received May 1987. 0 1988 by Elsevier Science Publishing Co., Inc. 52 Vanderbilt Avenue, New York, NY 10017 0149-936X188/$3.50
1988;12:1-8
MD,
inx” or “syringomyelia” to refer to all conditions in which a cavity is present within the spinal cord (5, 6)
SUBJECTS
AND METHODS
Seventeen patients with a surgically proven syringomyelia were reviewed retrospectively. The MRI, myelograms, and postmyelographic CT scans were studied and tabulated (Table 1). The MRI studies were performed on a 0.5 Tesla Siemens superconductive magnet using spin echo techniques of repetition time (TR) 500 msec and echo time (TE) 17 to 35 msec for a Tl-weighted image and TZweighted image of TR 1500 to 2100 msec and TE of 90 to 105 msec. CT scans were performed on a Siemens DR3 immediately following myelography or intrathecal injection of contrast material and also 4 to 6 hours after injection. Metrizamide (Amipaque) was used for all myelograms via lumbar puncture.
RESULTS Two patients had spinal cord tumors (an astrocytoma and a hemangioblastoma) plus the syringomyelia. MRI accurately identified tumor in both patients, while CT was diagnostic in only one patient. Cord atrophy associated with syringomyelia was observed in three patients; it was easily demonstrated by MRI but could not be shown on either CT or myelography. Six out of twelve myelograms performed were negative. Differentiation between syrinx and spinal cord tumor was not achieved by the positive myelograms. Intrathecal enhanced CT was performed following the myelograms in twelve pa-
2
CT: THE JOURNAL
DEEB ET AL.
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
TABLE 1. Results of MRI, Myelogram, and Myelography Study Name KT
DA FF BL NM
sJ
CK DK
CH RG vc WD MM
JS ER AP RB
MyelogramiCT 1984 CT+ 1985 CT? Follow-up CT syrinx vs. tumor Large cord CT - myelogram CT - myelogram CT head hydrocephalus CT + / myelogram + CT - / myelogram CT - / myelogram CTimyelogram + Large cord Syrinx vs. tumor Delayed CT + Myelo + ? syrinx CT + / myelogram Delayed CT+ CT tumor vs. syrinx CT, tumor vs. syrinx CT / myelogram Tumor vs. syrinx Myelogram i CT Myelogram / CT? Nonenhanced CT Myelogram, tumor vs. syrinx
MR MR+
Diagnosis
for syrinx
Syrinx and hemangioblastoma cord, and medulla
MR syrinx
Syrinx
MR+ MR+
Syrinx Syrinx
+ cord atrophy + cord atrophy
MR+ MR+ MR+ MR+ Syrinx
Syrinx Syrinx Syrinx Syrinx
+ tumor of cord
+ tumor
MR+
Syrinx
MR+
Syrinx
MR+ MR+ MR+ MR+
Syrinx Syrinx Syrinx Syrinx
MR+ MR+ MR+
Syrinx
tients and following injection of 5 mL of 190 mg/mL metrizamide in five patients. Twelve intrathecally enhanced CT scans were positive; three atrophic cords due to syringomyelia were missed, and five CT scans were negative. In summary, MRI correctly showed the abnormalities in all patients. The results are shown in Table 1. DISCUSSION Syrinx cavities were visualized in all patients on the MRI. Sagittal Tl-weighted images were the most diagnostic and also provided a view of the cord from the thoracic region into the cranial compartment. These images were more optimal than the axial images proposed previously (5). Changing the spin-echo parameters between Tlweighting and T2-weighting confirmed the CSFcontaining nature of the cavities and also suggested the presence of tumors in two of our patients, which was later confirmed at surgery (Figure 1). This was important because the spinal cord was enlarged or normal in size in all but three patients. The tumor, however, had a different signal intensity than the syrinx on both the Tl-weighted and the
of cerebellum,
+ small cord
Syrinx
T&weighted images, thus differentiating it from the areas of gliosis observed with cord-expanding syringomyelia (1, 3, 7). When a tumor is associated with syringomyelia, two different signal intensities are often observed: CSF and tumor. These intensities varied differently as we altered the Tl- and the T2weighted parameters. Myelography was the previous definitive radiographic procedure for the diagnosis of syringomyelia (8). Oily contrast was replaced by air contrast, and lately, water-soluble products are used for myelography. A swollen and enlarged spinal cord with a “collapsing sign” was diagnostic, An enlarged or swollen cervical spinal cord was found in only 50% of our cases (Figure 2). Differentiating a syrinx from a tumor was not feasible, and the “collapsing sign” was not pursued due to the severe discomfort for the patient and associated complications of high doses of myelographic contrast agent entering the neurocranium (9-11). Computed tomography, especially when performed following intrathecal contrast enhancement, has been the diagnostic method of choice for syringomyelia for the last few years (12). The diagnostic accuracy in our series was 12 out of 17, although a
JANUARY
SYRINGOMYELIA
1988
3
C
FIGURE 1. (A) Preoperative water-soluble myelogram reveals a large spinal cord from the cervicomedullary junction to the upper thoracic area. Differentiation between a simple syrinx and a multicavitary syrinx, with or without a tumor, cannot be achieved on this exam. (B,C) Postmyelographic CT scans demonstrated the enlarged spinal cord as seen on the myelogram within the cervical region (B) and the thoracic region (C). Continued.
4
DEEB ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
F
FIGURE 1. (continued). (D,E) MR images obtained at our institution following surgery demonstrate on the Tlweighted images (TR = 0.3, TE = 35) multiple, separate cystic cavities within the spinal cord from the foramen magnum to the mid-thoracic region (D). The suspicion that a large septum was actually a tumor was confirmed on the T2-weighted MR images (TR = 2.1, TE = 120), where it had a different signal intensity than the syrinx cavities, septae, or the spinal cord (E). At surgery this proved to be an ependymoma, which was removed. (F) A postoperative MR reveals the small spinal cord without tumor or syrinx. MR imaging is superior to other modalities for patient follow-up after surgery.
JANUARY
1988
SYRINGOMYELIA
5
FIGURE 2. Syrinx was overlooked on both myelography and postmyelographic CT due to its location within the cervicomedullary junction (TR = 0.3, TE = 35).
FIGURE 3. (A) A postintrathecal enhanced CT scan revealed the atrophic cord, but no definite filling of a cavity is noted on these delayed scans. (B) The MR images demonstrate an extensive syrinx from the foramen magnum to
the thoracic region. Atrophy of the spinal cord is also present with widening of the subarachnoid space (TR = 0.5, TE = 35).
FIGURE 4. (A) AP and lateral water-soluble myelogram demonstrates a large spinal cord extending from the C-l level through the upper thoracic region. (B) Delayed CT scan following the myelogram reveals the contrast agent within the syrinx cavity and surrounding the spinal cord within the subarachnoid space. (C) MR demonstrates a large syrinx without septations or tumor from the foramen magnum through the thoracic region (TR = 2.1 msec, TE = 35 msec). On a long T&weighted series (TR = 2.1 msec, TE = 120 msec), the syrinx is of high intensity secondary to the stasis of CSF within its cystic compartment.
‘KJARY
SYRINCOMYELIA
1988
7
tumor within the syrinx was not detected. In five cases, in which the cord was atrophic or normal in size and configuration, the syrinx was overlooked although a CT was performed 4 to 6 hours after intrathecal enhancement (Figure 3). The presence of contrast within the spinal cord is not always diagnostic of syringomyelia (13). All of our patients had postexamination headaches, seven of them developed nausea, and one had vomiting. No seizures were observed. MR images obtained even with only Tl-weighted spin-echo parameters are more diagnostic than myelography and intrathecally enhanced CT. The time it takes to perform a Tl-weighted sagittal study with no known complications is about 3 to 5 minutes. A T2weighted examination adds about 15 minutes and is needed mainly when a tumor is also suspected on the Tl-weighted parameters (Figure 4). Septations within the syrinx were best demonstrated by MRI (Figure 5). The discomfort to the patient is almost nonexistent as compared to CT scanning, and the complications and morbidity of myelography and lumbar punctures can be obviated completely. We propose sagittal Tl-weighted MR imaging for diagnosis of syringomyelia as an initial exam. T2weighted images can be performed if a tumor is sus-
5. MR images reveal the septum within an exThe tonsils are low within the foramen magnum. The surgical procedure was modified to shunt both compartments (TR = 0.3 msec, TE = 35 msec). FIGURE
tended syrinx.
8
DEEB ET AL.
CT: THE JOURNAL
petted with a syrinx. Plain CT scanning, intrathecal enhanced CT scanning, and myelography should not be needed in cervical syringomyelia diagnosis. Axial cuts obtained by MRI or plain CT scanning through the suspected intervertebral disk herniations may be sought if clinically deemed necessary to rule out disk herniations suspected from the sagittal MRI images.
REFERENCES 1. Sherman JL, Barkovich of syringomyelia:
AJ, Citrin CM: The MRI appearance new observations. AJNR 1986;7:985-95.
2. Pojunas K, Williams AL, Daniels DL, Haughton gomyelia and hydromyelia: magnetic resonance Radiology 1984;153:679-83. 3. Lee BCP, Zimmerman aging of syringomyelia 8.
VM: Syrinevaluation.
RD, Manning JJ, Deck MDF: MR imand hydromyelia. AJNR 1985;6:221-
4. Kokmen E, Marsh WR, Baker HI: Magnetic resonance ing in syringomyelia. Neurosurgery 1985;17:267-70.
imag-
5. Yeates A, Brant-Zawadski M, Norman D, et al.: Nuclear magnetic resonance imaging of syringomyelia. AJNR 1983;4:2347.
OF COMPUTED
TOMOGRAPHY
VOL. 12 NO. 1
6. Peerless SJ, Durward QJ: Management of syringomyelia: a pathophysiological approach. Clin Neurosurg 1983;30:53176. 7. DiChiro G, Doppman JL, Dwyer AJ, et al.: Tumors and arteriovenous malformations of the spinal cord: assessment using MR. Radiology 1985;156:689-97. 8. Batnitzky S, Price HI, Gaughan MJ, Hall PV, Rosenthal SJ: The radiology of syringohydromyelia. Radiographics 1983;3:585-611. changes of the brain following in9. Schober R: Morphological trathecal application of contrast media. Acta Radiologica [Diagnostica] 1961;5:509-16. 10. Haughton VM, Williams AL, Cusick JF, Meyer GA: A myelographic technique for cysts in the spinal canal and spinal cord. Radiology 1978;129:717-9. 11. Killebrew trizamide
K, Wholey RA, Hayward JN: Complication myelography. Arch Neurol 1983;40:78-80.
of me-
12. Bonafe A, Manelfe C, Espagno J, Guiraud B, Rascal A: Evaluation of syringomyelia with metrizamide computed tomographic myelography. J Comput Assist Tomogr 1980;4:797802. 13. Dubois EJ, Drayer BP, Sage M, Osborne D, Heinz ER: Intramedullary penetrance of metrizamide in the dog spinal cord. AJNR 1981;2:313-7.