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Localization of intracranial lesions utilizing the coronal suture as a landmark on axial computed tomography
Localization of Intracranial Lesions Utilizing the Coronal Suture as a Landmark on Axial Computed Tomography Jamshid Ahmadi, M.D., Jong S. Han, M.D., James S. Teal, M.D., Fong ¥. Tsai, M.D., Chi-Shing Zee, M.D., and Hervey D. Segall, M.D.
The superior portion of the coronal suture is often easily identified by appropriately setting the window width and level of the CT scanner's display system. It provides a valuable and practical reference point for the localization of intracranial lesions, particularly those above the level of the lateral ventricles, where fewer anatomical land. marks are available when using computed tomography. AhmadiJ, Han JS, Teal JS, Tsai FY, Zee C-S, SegaUHD: Localizationof intracraniallesions utilizing the coronalsuture as a landmarkon axial computedtomography.SurgNeurol 17:209-212, 1982 Accurate anatomical localization of intracranial lesions seen on computed tomography (CT) is often difficult due to the varying angles at which the scans may be performed. Several methods of precise localization of intracranial lesions have been described [1-6, 8-10]; these are quite accurate and useful. The recent generation of scanners is capable of providing such information directly. Many CT scanners are still in use, however, that are not equipped with the necessary software for precise anatomical localization. Therefore, we would like to present a simple, practical method that could be useful in many situations. With this method, the coronal suture is used as a reference point for anteroposterior localization of high intracranial lesions.
Materials and Methods The superior portion of the coronal suture is often easily identified by appropriately setting the window width and level of the scanner's display system. When the window width is set at 400 Hounsfield units (HU), the coronal suture appears as a small dense area (higher in density than the adjacent osseous structures). At a certain window level in Fromthe DepartmentofRadiology,SectionofNeuroradiology,University of Southern CaliforniaSchoolof Medicine, Los Angeles, CA. Addressreprint requeststo Dr. JamshidAhmadi,3804Via La Selva, Palos Verdes Estates, CA 90274. Keywords:computedtomography;vertex;anatomiclocalization;coronal suture.
the range of 800 to 1500 HU, the coronal suture is best visualized as an oval or fusiform high-density area (Fig. 1). The accuracy of the identification of the coronal suture by this technique was verified by placing a marker wire over the coronal suture of a dry skull as well as in several patients prior to routine CT scanning. We also randomly selected and subsequently reviewed 600 C'I" scans to evaluate the frequency with which the coronal suture could be identified. The superior portion of the coronal suture (above the level of the lateral ventricle), was identified in 92% of patients; this percentage did not vary significantly with patient age or sex (Fig. 2). The suture could be vi. sualized in 42% at the level of the lateral ventricle, and in only 8% at its lowest portion. The distance between the coronal suture and any particular part of a lesion is measured directly with most CT scanners by placing one cursor over the lesion and another over the coronal suture in the axial plane. The height of the lesion relative to the orbitomeatal line (also an important neurosurgical landmark) is determined directly from the tomogram or is calculated by superimposing the plane of CT sections on a standard skull radiograph using prominent bony landmarks seen on lower CT sections. The location of the lesion then can be calculated, given the thickness of the intervening CT sections and the CT image-skull film enlargement ratio [9]. For accurate localization of a small lesion prior to biopsy, the lesion is outlined on the scalp as described above and a marker is placed over any particular part of the lesion. A few additional axial and coronal CT sections are then obtained, using the scanner's gantry light. The precise site and depth of the biopsy is thus verified. It will also become apparent at this point if the original localization was imprecise.
Discussion The tightly interlocked margins of the superior portion of the coronal suture are denser than the adjacent portions of the frontal and parietal bones. This is mainly due to sutural sclerosis and an absent or less-developed middle table (diploe) in the suture. The superior portion of the coronal
0090-3019/82/030209-04501.25 © 1981 by Little, Brown and Company (Inc.)
209
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SurgicalNeurology Vol 17 No 3 March 1982
A
B
Fig. I. (A) A tumor is present in the left cerebral hemisphere. (B) The image has been altered; it is presented at a high window level and width and is reversed so that the coronal suture appears in dark tones (arrows). This is done to allow the superimposition of images as shown in 1C. (C) A composite image in which 1B has been superimposed on IA. This demonstrates the relationship of the tumor to the coronal suture.
C
Ahmadi et al: Localization of Intracranial Lesions 211
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Age Fig. 2. The coronal suture was identified at the level above the lateral ventricles in 92 % of 600 randomly selected scans. This percentage did not vary significantly with patient age or sex.
A
suture, therefore, has a higher x-ray attenuation value than does the adjacent calvarium. At a proper window setting on the scanner'ss display unit, it appears as a small, fusiform or oval, high-density area. It is often difficult to identify the lower portion of the coronal suture due to an absent or less-developed middle table in the supraorbital portion of the frontal bone and temporal squama [7]. Occasionally, the entire calvarium is thin and compact with little or no diploe (compact skull). This may explain why the coronal suture cannot be demonstrated with CT in some individuals. Identification of the coronal suture is a valuable and practical reference point for the localization of intracranial lesions, particularly above the level of the lateral ventricle where fewer anatomical landmarks are available for CT scanning purposes (Fig. 3).
B Fig. 3. (A) Bifrontal and ( B ) right bilocular epidural hematomas. Cursors (+) are placed over the coronal sutures, with wide-window setting of the scanner's display unit. The window is then adjusted to routine setting for demonstrating the relationship of the hematomas to the coronal suture. This simple technique helps in accurate placement of a skull incision or a burr hole.
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Surgical Neurology Vol 17 No 3 March 1982
This paper was presented in part at the 1980 Annual Meeting of The We.stem Neuroradiological Society, October 9-12, 1980, at the Hotel Del Coronado, Coronado, CA.
References 1. Cail WS, Morris JL: Localization of intracranial lesions from CT scans. Surg Neurol 11:35-37, 1979 2. Field JR, Lawrence JA, White TJ III, Lee LH, Lankford WA, Kersey J: Scalp localization of supratentorial lesions demonstrated by computerized tomography. Neurosurgery 6:164-175, 1980 3. Gleason CA, Wise BL, Feinstein B: Stereotactic localization (with computerized tomographic scanning), biopsy, and radiofrequency treatment of deep brain lesions. Neurosurgery 2:217-222, 1978 4. Kido DK, LeMay M, Levinson AW, Benson WE: Computed tomo-
graphic localization of the precentral gyms. Radiology 135:373-377, 1980
5. Levinthal R, Winter J, Bentson JR: Technique for accurate localization with the CT scanner. Bull Los Angeles Neurol Soc 41:6-8, 1976 6. Moseley JI, Giannotta SL, Renaudin JW: A simple inexpensive technique for accurate mass localization by computerized tomography: a technical note. J Neurosurg 52:733-735, 1980 7. Newton TH, Potts I7)(3 (eds): Radiology of the Skull and Brain. St. Louis: Mosby, 1971, Vol 1, Book 1 8. Norman D, Newton TH: Localization with the EMI scanner. Am J Roentgenol Radium Ther Nucl Med 125:961-964, 1975 9. O'Leary DH, Lavyne MH: Localization of vertex lesions seen on CT scan. J Neurosurg 49:71-74, 1978 10. Rosenbaum HE: Localization of vertex lesions seen on CT scans, three-dimensional computerized tomographic scans of brain: a new approach to intracranial diagnosis. Arch Neurol 34:386-387, 1977
Editorial Note: Trauma of the Brain and Spinal Cord Until now the actual incidence of injury to the brain and spinal cord has been little more than an intelligent guess based upon inadequate information. Now the Office of Biometry and Field Studies of the National Institute of Neurological and Communicative Disorders and Stroke has made a more accurate and comprehensive survey of this problem. As a result we now have available definite information rather than informed guesses. This survey revealed that in the United States between 1970 and 1974 there were 439 cases of head injury and 13 cases of spinal cord injury per 100,000 people. Stated differently, this indicates that there are 965,800 cases of head
injuries and 28,600 cases of spinal cord injuries in the United States in this five-year period. The problem is nationwide. The importance of these figures is emphasized by the fact that the majority of those injured in this manner are young people and that the results of these injuries are so disabling. These patients are for the most part vigorous young people on the threshold of their most productive years. This is a problem that concerns neurological surgeons more than any other segment of the medical profession. Paul C. Bucy, M.D., Editor
The superior portion of the coronal suture is often easily identified by appropriately setting the window width and level of the CT scanner's display system. It provides a valuable and practical reference point for the localization of intracranial lesions, particularly those above the level of the lateral ventricles, where fewer anatomical land. marks are available when using computed tomography. AhmadiJ, Han JS, Teal JS, Tsai FY, Zee C-S, SegaUHD: Localizationof intracraniallesions utilizing the coronalsuture as a landmarkon axial computedtomography.SurgNeurol 17:209-212, 1982 Accurate anatomical localization of intracranial lesions seen on computed tomography (CT) is often difficult due to the varying angles at which the scans may be performed. Several methods of precise localization of intracranial lesions have been described [1-6, 8-10]; these are quite accurate and useful. The recent generation of scanners is capable of providing such information directly. Many CT scanners are still in use, however, that are not equipped with the necessary software for precise anatomical localization. Therefore, we would like to present a simple, practical method that could be useful in many situations. With this method, the coronal suture is used as a reference point for anteroposterior localization of high intracranial lesions.
Materials and Methods The superior portion of the coronal suture is often easily identified by appropriately setting the window width and level of the scanner's display system. When the window width is set at 400 Hounsfield units (HU), the coronal suture appears as a small dense area (higher in density than the adjacent osseous structures). At a certain window level in Fromthe DepartmentofRadiology,SectionofNeuroradiology,University of Southern CaliforniaSchoolof Medicine, Los Angeles, CA. Addressreprint requeststo Dr. JamshidAhmadi,3804Via La Selva, Palos Verdes Estates, CA 90274. Keywords:computedtomography;vertex;anatomiclocalization;coronal suture.
the range of 800 to 1500 HU, the coronal suture is best visualized as an oval or fusiform high-density area (Fig. 1). The accuracy of the identification of the coronal suture by this technique was verified by placing a marker wire over the coronal suture of a dry skull as well as in several patients prior to routine CT scanning. We also randomly selected and subsequently reviewed 600 C'I" scans to evaluate the frequency with which the coronal suture could be identified. The superior portion of the coronal suture (above the level of the lateral ventricle), was identified in 92% of patients; this percentage did not vary significantly with patient age or sex (Fig. 2). The suture could be vi. sualized in 42% at the level of the lateral ventricle, and in only 8% at its lowest portion. The distance between the coronal suture and any particular part of a lesion is measured directly with most CT scanners by placing one cursor over the lesion and another over the coronal suture in the axial plane. The height of the lesion relative to the orbitomeatal line (also an important neurosurgical landmark) is determined directly from the tomogram or is calculated by superimposing the plane of CT sections on a standard skull radiograph using prominent bony landmarks seen on lower CT sections. The location of the lesion then can be calculated, given the thickness of the intervening CT sections and the CT image-skull film enlargement ratio [9]. For accurate localization of a small lesion prior to biopsy, the lesion is outlined on the scalp as described above and a marker is placed over any particular part of the lesion. A few additional axial and coronal CT sections are then obtained, using the scanner's gantry light. The precise site and depth of the biopsy is thus verified. It will also become apparent at this point if the original localization was imprecise.
Discussion The tightly interlocked margins of the superior portion of the coronal suture are denser than the adjacent portions of the frontal and parietal bones. This is mainly due to sutural sclerosis and an absent or less-developed middle table (diploe) in the suture. The superior portion of the coronal
0090-3019/82/030209-04501.25 © 1981 by Little, Brown and Company (Inc.)
209
210
SurgicalNeurology Vol 17 No 3 March 1982
A
B
Fig. I. (A) A tumor is present in the left cerebral hemisphere. (B) The image has been altered; it is presented at a high window level and width and is reversed so that the coronal suture appears in dark tones (arrows). This is done to allow the superimposition of images as shown in 1C. (C) A composite image in which 1B has been superimposed on IA. This demonstrates the relationship of the tumor to the coronal suture.
C
Ahmadi et al: Localization of Intracranial Lesions 211
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jq --
/
30-
/
t/i
/
i
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2~
10"
10
20
30
40
50
60
70
80
90
Age Fig. 2. The coronal suture was identified at the level above the lateral ventricles in 92 % of 600 randomly selected scans. This percentage did not vary significantly with patient age or sex.
A
suture, therefore, has a higher x-ray attenuation value than does the adjacent calvarium. At a proper window setting on the scanner'ss display unit, it appears as a small, fusiform or oval, high-density area. It is often difficult to identify the lower portion of the coronal suture due to an absent or less-developed middle table in the supraorbital portion of the frontal bone and temporal squama [7]. Occasionally, the entire calvarium is thin and compact with little or no diploe (compact skull). This may explain why the coronal suture cannot be demonstrated with CT in some individuals. Identification of the coronal suture is a valuable and practical reference point for the localization of intracranial lesions, particularly above the level of the lateral ventricle where fewer anatomical landmarks are available for CT scanning purposes (Fig. 3).
B Fig. 3. (A) Bifrontal and ( B ) right bilocular epidural hematomas. Cursors (+) are placed over the coronal sutures, with wide-window setting of the scanner's display unit. The window is then adjusted to routine setting for demonstrating the relationship of the hematomas to the coronal suture. This simple technique helps in accurate placement of a skull incision or a burr hole.
212
Surgical Neurology Vol 17 No 3 March 1982
This paper was presented in part at the 1980 Annual Meeting of The We.stem Neuroradiological Society, October 9-12, 1980, at the Hotel Del Coronado, Coronado, CA.
References 1. Cail WS, Morris JL: Localization of intracranial lesions from CT scans. Surg Neurol 11:35-37, 1979 2. Field JR, Lawrence JA, White TJ III, Lee LH, Lankford WA, Kersey J: Scalp localization of supratentorial lesions demonstrated by computerized tomography. Neurosurgery 6:164-175, 1980 3. Gleason CA, Wise BL, Feinstein B: Stereotactic localization (with computerized tomographic scanning), biopsy, and radiofrequency treatment of deep brain lesions. Neurosurgery 2:217-222, 1978 4. Kido DK, LeMay M, Levinson AW, Benson WE: Computed tomo-
graphic localization of the precentral gyms. Radiology 135:373-377, 1980
5. Levinthal R, Winter J, Bentson JR: Technique for accurate localization with the CT scanner. Bull Los Angeles Neurol Soc 41:6-8, 1976 6. Moseley JI, Giannotta SL, Renaudin JW: A simple inexpensive technique for accurate mass localization by computerized tomography: a technical note. J Neurosurg 52:733-735, 1980 7. Newton TH, Potts I7)(3 (eds): Radiology of the Skull and Brain. St. Louis: Mosby, 1971, Vol 1, Book 1 8. Norman D, Newton TH: Localization with the EMI scanner. Am J Roentgenol Radium Ther Nucl Med 125:961-964, 1975 9. O'Leary DH, Lavyne MH: Localization of vertex lesions seen on CT scan. J Neurosurg 49:71-74, 1978 10. Rosenbaum HE: Localization of vertex lesions seen on CT scans, three-dimensional computerized tomographic scans of brain: a new approach to intracranial diagnosis. Arch Neurol 34:386-387, 1977
Editorial Note: Trauma of the Brain and Spinal Cord Until now the actual incidence of injury to the brain and spinal cord has been little more than an intelligent guess based upon inadequate information. Now the Office of Biometry and Field Studies of the National Institute of Neurological and Communicative Disorders and Stroke has made a more accurate and comprehensive survey of this problem. As a result we now have available definite information rather than informed guesses. This survey revealed that in the United States between 1970 and 1974 there were 439 cases of head injury and 13 cases of spinal cord injury per 100,000 people. Stated differently, this indicates that there are 965,800 cases of head
injuries and 28,600 cases of spinal cord injuries in the United States in this five-year period. The problem is nationwide. The importance of these figures is emphasized by the fact that the majority of those injured in this manner are young people and that the results of these injuries are so disabling. These patients are for the most part vigorous young people on the threshold of their most productive years. This is a problem that concerns neurological surgeons more than any other segment of the medical profession. Paul C. Bucy, M.D., Editor