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Vertex epidural hematomas: imaging findings and diagnostic pitfalls
European Journal of Radiology 36 (2000) 150 – 157 www.elsevier.nl/locate/ejrad
Vertex epidural hematomas: imaging findings and diagnostic pitfalls Olin L. Harbury a, James M. Provenzale b,*, Daniel P. Barboriak a b
a Metrolina Imaging Group, Mercy Hospital, Charlotte, NC 28207, USA Department of Radiology, Duke Uni6ersity Medical Center, Box 3803, Durham, NC 27710, USA
Received 19 August 1999; received in revised form 1 February 2000; accepted 1 February 2000
Abstract Purpose: Our purpose was to show the computed tomography (CT) and magnetic resonance (MR) imaging features of vertex epidural hematomas (EDHs) and emphasize pitfalls in the diagnosis of this entity. Subjects and methods: The neuroradiologic studies of four patients (CT in four, MR imaging and MR venography in one) were evaluated for EDH shape, size and appearance. Results: EDHs were biconvex in three patients and crescentic in one patient. CT appearances included a collection that was hyperdense (two patients), generally isodense with a few regions of hyperdensity (one patient) and mixed hyperdense and hypodense (one patient). MR imaging findings in one patient consisted of hyperintense signal on T1-weighted images and hypointense signal on T2-weighted images. Inferior displacement of the superior sagittal sinus was seen in two patients. Diagnosis of a small vertex EDH was difficult on routine axial CT in one patient, but apparent on MR imaging and MR venography. Conclusions: Small vertex EDHs can be difficult to diagnose on routine CT. MR imaging or thin section CT should be performed to exclude the diagnosis in patients with trauma to the skull vertex. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Computed tomography; Epidural hematomas; Magnetic resonance
1. Introduction The skull vertex is an uncommon site for epidural hematoma (EDH) formation, accounting for only 1– 8% of EDHs [1–4]. EDHs at this site typically occur after a traumatic injury of sufficient force to produce a fracture or diastasis of the sagittal suture [1]. Vertex EDHs often cause rapid neurologic deterioration and death. The mortality associated with vertex EDHs is high, reported to be between 18 and 50% in some series [2,3] and rapid diagnosis is important to limit morbidity and mortality. Many authors have noted the difficulty of diagnosing vertex EDHs by computed tomography (CT) [2,3,5,6]. The difficulty arises because lesion conspicuity can be low due to (1) near-isodensity of the EDH and adjacent bone; (2) alignment of the EDH along the scan plane; and (3) volume averaging effects in instances when CT * Corresponding author. Tel.: +1-919-6847409; fax: + 1-9196847138. E-mail address: [email protected] (J.M. Provenzale).
slices are relatively thick compared with the thickness of the EDH. These facts have led some investigators to regard the vertex as a potential ‘blind spot’ on CT imaging [6]. With these facts in mind, we analyzed four cases of vertex EDH to assess imaging features of the lesions further, define difficulties in diagnosis and suggest optimal imaging protocols.
2. Subjects and methods The radiologic files of three hospitals (two community-based hospitals and one tertiary care-teaching hospital) were reviewed for patients with the diagnosis of vertex EDH. Four patients (three men, average age, 33 years) were identified (Table 1). The medical records were reviewed for history of trauma and operative findings at the time of EDH evacuation. Imaging studies were reviewed for the presence of skull fracture and EDH shape, size and appearance. Imaging examinations included CT (four patients), magnetic resonance (MR) imaging (one patient) and
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MR venography (one patient). CT imaging was performed in the axial plane using 10-mm slice thickness at the level of the vertex (three patients) and in the coronal plane using 5-mm slice thickness (one patient). Coronal CT images reconstructed from 10-mm thick axial images were available in two patients, one of which also had reconstructed sagittal images. MR imaging and MR venography was performed in one individual (patient 1). T1-weighted MR images were obtained in the axial plane using a TR of 400 ms, TE of 19 ms and one excitation. T2-weighted images were performed in the sagittal plane using a TR of 2500 ms, TEs of 30 and 90 ms and 0.75 excitations. Coronal MR images were reconstructed from a sagittal 3D-volume acquisition obtained using gradient echo technique using a dedicated independent workstation (General Electric Medical Systems, Milwaukee, WI). MR venography was performed using 2D-phase contrast technique, TR of 25 ms, TE of 10 ms, two excitations and an encoding velocity (Venc) of 20 cm/s.
the sagittal suture (Fig. 2) and another had a recent bifrontal craniotomy. In three individuals (patients 2, 3 and 4), the EDH had a convex shape at the interface with brain and in patient 1, a concave shape was seen. Vertex EDH was difficult to diagnose by CT in one patient (Fig. 1) but was much more apparent by MR imaging, which showed a hematoma which was slightly hyperintense relative to gray matter on T1-weighted images and hypointense on T2-weighted images (Fig. 1C and D). A fluid collection was seen within the postoperative bed, which at surgery was found to be only slightly blood-tinged cerebrospinal fluid (Fig. 1D and E). The patient’s neurologic signs resolved following evacuation of the EDH, even though the fluid collection within the tumor resection bed was not evacuated. This suggests that the EDH (and not the fluid collection within the postoperative bed) was the source of the neurologic deterioration. MR venography in patient 1 showed inferior displacement of the superior sagittal sinus (Fig. 1F).
3. Results
4. Discussion
Two patients developed vertex EDHs following head trauma and two other patients had vertex EDH after cranial surgery (resection of a falx meningioma in patient 1 and following resection of a high cervical arachnoid cyst in patient 4) (Table 1). Fractures were seen in both the patients with a history of trauma, at the vertex in one patient and high parietal bone in the other patient. At surgery, venous bleeding sites were identified in all four patients (Table 1). On CT imaging, EDHs were relatively isodense relative to gray matter in one patient with a few regions of hyperdensity (Fig. 1), hyperdense in two patients (Fig. 2) and inhomogeneous with both hypodense and hyperdense components in one patient (Fig. 3). In three patients, the EDH extended across the sagittal suture (Table 1). One of these patients had a fracture involving
Vertex EDHs are usually post-traumatic in origin and often follow fracture at the level of the vertex or diastasis of the sagittal suture. In one series, 92% of patients with vertex fractures were found to have EDHs [2]. Signs and symptoms due to vertex EDHs are variable and appear to depend on the source of hemorrhage, size of hematoma, and rapidity of hematoma formation [1,2]. Most patients with vertex EDH due to laceration of the superior sagittal sinus become comatose within a few hours (Table 2) [1,2]. Less commonly, a slow and steady neurologic decline over the course of many hours is seen, sometimes after a symptom-free interval of many hours or days [3,5,7,8]. Acute worsening manifested as headache, encephalopathy and decreased level of consciousness can occur due to venous obstruction and thrombosis caused by the mas-
Table 1 Vertex epidural hematomas: imaging and operative findings Case
Age/gender
Precipitating event
Fracture site
CT appearance
MR appearance
Hemorrhage site
1
26, F
Meningioma resection
None (craniotomy)
Isodense to gray matter
T1-slightly hyperintense
Dural vein
2
45, M
Struck on head
Vertex
Hyperdense
T2-mixed hyper and hypointense signal –a
3
23, M
Struck on head
High parietal
Hyperdense
–a
4
37, M
Drainage of cervical spine arachnoid cyst
None
Inhomogeneous predominantly hypodense
–a
a
–, Not performed.
Diploic space and dural veins Margin of superior sagittal sinus Emissary veins
152
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Fig. 1.
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Fig. 1. (Continued) Twenty-seven year-old woman (patient 1) with somnolence and paraparesis after complete resection of a falx meningioma. Following CT and MR imaging, she underwent evacuation of a vertex EDH with resolution of neurologic signs over the next few days. (A) Unenhanced 10-mm thick axial CT image shows an extra-axial hematoma (arrows) which is relatively isodense compared with gray matter. (B) Magnified view of Fig. 1A shows the EDH (arrows) is slightly hyperintense to normal brain tissue. The EDH was difficult to see on coronal images (not shown) reconstructed from the 10-mm thick axial images. (C) Axial T2-weighted (2500/90, 0.75 [TR/TE/excitations]) MR image shows the EDH (arrows) as a collection which has an anterior hyperintense component and a hypointense posterior component. (D) Coronal MR images reconstructed from a sagittal 3D volume acquisition using gradient echo technique show the hematoma (solid arrows) extending over both hemispheres, displacing brain tissue inferiorly. On this image, the EDH has a convex surface at the interface with brain. The postoperative surgical bed (open arrows) is seen as a cavity flanked by brain tissue, which is still deformed due to the previous compressive effect of the resected falcine meningioma. At the time of re-operation for evacuation of the EDH, solely blood-tinged cerebrospinal fluid without an active bleeding source was seen within the postsurgical cavity. Neurologic symptoms resolved following evacuation of the EDH. (E) Unenhanced sagittal T1-weighted (400/19/1) MR image shows the EDH (arrowheads) as an inhomogeneous collection, which is predominantly isointense relative to gray matter and separated from brain tissue by a hypointense rim. It is difficult to distinguish the flow void of the superior sagittal sinus from the hypointense signal of the dura. On this image, the EDH appears to have a biconvex shape. The hemorrhagic cerebrospinal fluid collection (arrows) is predominantly hyperintense. Note the residual deformity of the brain adjacent to the surgical resection bed following removal of the large meningioma. (F) Sagittal image from a 2D-phase contrast MR venogram (25/10/2, Venc 20 cm/s) shows inferior displacement of the superior sagittal sinus (arrowheads).
sive effect of the hematoma [9]. Increased intracranial pressure, manifested clinically as headache, papilledema and encephalopathy is often present (Table 2), even with a relative small hematoma, due to impairment of venous drainage or diminished cerebrospinal fluid resorption rather than the compressive effect of the hematoma on adjacent brain parenchyma [3,5,7]. Because of these facts, the significance of even a small vertex EDH should not be underestimated. Furthermore, vertex EDH can be the only radiologic manifestation of intracranial trauma [1]. Therefore, physicians treating patients, who are initially asymptomatic and in whom the finding of a vertex EDH has been overlooked on imaging studies, can assume a false sense of security regarding neurologic outcome. In all our patients, a venous bleeding site was identified at surgery. It was shown early in this century that (1) venous laceration alone can produce fatal EDH; and (2) the vascular grooves found along the inner table of the skull (through which fracture associated with EDH often extends) contain the middle meningeal vein rather than the middle meningeal artery [10]. In addition to the superior sagittal sinus, other potential sources of hemorrhage include the meningeal veins,
venous lacunae, meningeal sinuses (which are aligned alongside the superior sagittal sinus and receive drainage from cortical veins), the diploic space and small arteries supplying midline structures [11]. Most series of patients with vertex EDH have been published in the neurosurgical literature [2–7,9], and these lesions have received relatively little attention in the radiologic literature. In one series of 348 patients with EDH studies in the pre-CT era, the prevalence of EDHs occurring at the vertex was 4%, but none of 168 EDH patients studied after the advent of CT were found to have a vertex EDH [3], suggested a limited ability to establish the diagnosis. Similar data in multiple neurosurgical series have led to the conclusion that a normal CT does not rule out vertex EDH. Some authors have proposed that in any case of suspected vertex EDH (especially in the presence of a fracture involving the vertex, or diastasis of the sagittal suture), coronal CT imaging should be performed and that catheter angiography is indicated if the diagnosis is still in doubt [2,5,6]. These reports led us to review our series to determine whether vertex EDHs are, in fact, difficult to diagnose by CT and to examine the role of MR imaging.
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Fig. 2. Forty-five year-old man (patient 2) who was struck on the top of the head and developed right hemiplegia and aphasia within a few hours. (A) Unenhanced axial CT image at the level of the vertex shows a extra-axial hematoma (arrows) crossing the midline. (B) Magnified view of Fig. 2A shows that the hematoma (arrows) is hyperdense compared with normal brain tissue. A small interhemispheric subdural hematoma (arrowheads) is also present. (C) Unenhanced coronal CT image using wide window technique shows a hyperdense epidural collection (solid arrows) crossing the midline subjacent to a fracture, which extended through the sagittal suture (open arrows). At surgery, bleeding from the diploic space and epidural venous hemorrhage were seen.
The diagnosis of vertex EDH should be suspected in any patient with a vertex fracture or sutural diastasis at the vertex on bone window images or the CT scanogram, or in whom disruption of the superior
sagittal sinus is suspected. In our series, vertex EDHs were not difficult to diagnose by CT in three patients because they were thick and/or had attenuation characteristics that differed significantly from adjacent par-
O.L. Harbury et al. / European Journal of Radiology 36 (2000) 150–157
enchyma and bone. However, diagnosis was difficult in patient 1 because the hematoma was thin and relatively isodense to gray matter. Because the short axis is usually perpendicular to the CT imaging plane, diagnosis of thin vertex EDHs by CT can be difficult. This is
155
due, in part, to the fact that CT imaging is often performed in the axial plane using thick (10 mm) slices through this region of the brain (as was the case in our patient). Coronal imaging could have alleviated the problem of diagnosis in patient 1 but the patient’s poor
Fig. 3. Thirty-seven year-old man (patient 4) with a history of hydrocephalus and ventriculoperitoneal shunt that developed syringomyelia and a high cervical arachnoid cyst. Following resection of the arachnoid cyst, the patient failed to awaken from surgery. (A) Unenhanced axial CT image performed at a point 3.5 cm from the vertex shows a diffuse inhomogeneous extra-axial hematoma (arrowheads) filling most of the cranium. The hematoma was seen to cross the sagittal, right coronal and right lambdoid sutures. (B) Contrast-enhanced axial CT image at a point 6.5 cm from the level of the vertex shows the inferior margin of the hematoma (arrowheads), the inferiorly displaced superior sagittal sinus (arrows), and marked hydrocephalus. The anterior cerebral arteries (curved arrow) are displaced across midline due to the fact that the hematoma is larger on the right side. Note the edema within the adjacent right hemisphere due to the mass effect of the hematoma. (C) Coronal image reconstructed from 5 mm contrast-enhanced axial images seen in B. The hematoma (arrowheads) is inhomogeneous, larger on the right, and displaces the enlarged lateral ventricles (open arrows) inferiorly. The exact location of the superior sagittal sinus is difficult to show on this image due to adjacent hyperdensity within the hematoma.
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Table 2 Clinical and radiologic signs of vertex epidural hematoma Clinical Signs and symptoms due to increased intracranial pressure Headache Papilledema Encephalopathy Signs and symptoms due to mass effect on adjacent structures Paraparesis Decreased level of consciousness Radiological CT, hyperdense extradural mass subjacent to vertex of skull MR –Extradural mass subjacent to vertex of skull with signal characteristics that are isointense or hyperintense on T1-weighted images and hypointense or hyperintense on T2-weighted images –Inferior displacement of superior sagittal sinus on MR venography subjacent to vertex of skull
neurological status precluded direct coronal imaging and the diagnosis was difficult on coronal reconstructions from the thick axial images. Our case shows one of the practical problems in making the diagnosis, unless a small vertex EDH is suspected before or during CT scanning, imaging with 10-mm thick axial images (which are routine at most imaging centers) will be performed. Another potential problem is that the hyperdense appearance of a vertex EDH can potentially be mistaken for adjacent bone or thought to be due to volume averaging of bone and brain. Few reports have shown the MR imaging appearance of EDH [12]. In our single case (patient 1) in whom CT and MR imaging could be compared, MR imaging was clearly superior for diagnosis, due to the high signal contrast between hematoma, brain and bone and the fact that multiplanar images could be directly obtained. The signal of the vertex EDH (in which concentrated blood was present) clearly differed from that of the blood-tinged cerebrospinal fluid collection within the postoperative surgical bed (Fig. 1D and E). The signal characteristics, as with any EDH, will vary with the age of the hematoma and species of blood breakdown products present, as well as the pulse sequence [13]. Potential pitfalls in MR imaging of vertex EDHs can occur depending on the age of hematoma and the corresponding signal characteristics compared with adjacent structures. A hyperintense EDH on T1-weighted images could be potentially confused with the signal of fat in adjacent bone marrow on axial images. Similarly, EDHs, which are hypointense on T2-weighted images, can potentially appear similar to lower signal from the adjacent inner table of the skull. Use of multiple pulse sequences minimizes these problems, as well as use of gradient echo images or MR venography to visualize blood flow and vascular structures at the vertex.
In general, the vertex EDHs in our series had many CT features typical of EDHs at other sites. However, whereas EDHs usually have a biconvex shape, the EDH in patient 1 had a crescentic shape on coronal reconstruction images (although it appeared biconvex on sagittal images). In addition, while EDHs at other sites generally do not cross suture lines, extension across the sagittal suture was seen in three of our patients. In two of our patients, the tight attachment of the dura to the inner table of the skull (which usually prevents EDH spread) was disrupted as a result of fracture (patient 2) or surgical dissection (patient 1). In patient 4, the attachment of the dura to the inner table of the skull was probably disrupted as the large EDH expanded. Downward displacement of the superior sagittal sinus, which was a sign used for diagnosis of vertex EDH by catheter angiography [1,2] and definitively localizes the hematoma to the epidural space, was observed in two of our patients by either contrast-enhanced CT (patient 4) or MR venography (patient 1). In patient 4, the superior sagittal sinus was seen as a contrast-enhancing linear structure 6.5 cm inferior to the inner table of the skull, seen better on direct axial images than on coronal reconstruction images (Fig. 3). In patient 1, the flow void of the superior sagittal sinus was difficult to distinguish from the hypointense signal of the adjacent dura on T1-weighted sagittal images (Fig. 1E). MR venography, however, clearly demonstrated the displacement of the superior sagittal sinus as an inferior bowing of a long segment of the signal column of the dural sinus (Fig. 1F). Realizing that our results are retrospective and based on a small number of patients without a uniform imaging protocol, we suggest the following guidelines for diagnosis of small vertex EDHs. MR imaging is the imaging method of choice in suspected cases because of the high signal contrast between the lesion and normal brain and because multiplanar imaging can be readily performed. We recommend thin sections (3- or 4-mm thick) T1-weighted and T2-weighted images with a narrow interslice gap in the coronal and sagittal planes when the diagnosis of EDH is being considered. When the diagnosis is equivocal by spin-echo MR imaging, MR venography or gradient echo images can be useful in showing inferior displacement of the superior sagittal sinus, thus specifically localizing the hematoma to the epidural space. When only axial CT imaging is available or appropriate, we recommend thin (3 or 1.5 mm) axial images which will allow smoother reconstructions than that available with thicker axial images. CT examinations in trauma patients should include images using intermediate window settings in order to increase the sensitivity for detection of extra-axial hemorrhage. Contrast administration can be helpful in such patients by showing inferior displacement of the superior sagittal sinus. In future, helical CT is expected to be benefi-
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cial for the diagnosis of vertex EDH due to the fact that it allows finely detailed coronal and sagittal reformat images from thin section axial images. In particular, in difficult cases, CT venography may be helpful by showing inferior displacement of the superior sagittal sinus [14].
References [1] Wylen EL, Nanda A. Vertex epidural hematoma with coronal suture diastasis presenting with paraplegia. J Trauma 1998;45:413 – 5. [2] Borzone M, Rivano C, Altemonte M, Capuzzo T. Acute vertex epidural hematomas surgically treated. Acta Neurochir 1988;93:55 – 60. [3] Zuccarello M, Fiore DL, Trincia G, Pardatscher K, Andrioli GC. Epidural hematoma at the vertex. Acta Neurochir 1982;66:195 – 206. [4] Gallagher JP, Browder EJ. Extradural hematoma experience with 167 patients. J Neurosurg 1968;29:1–13.
.
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[5] Pomeranz S, Wald U, Zagzag D, Gomori M, Schalit M. Chronic epidural hematoma of the vertex: problems in detection with computed tomography. Surg Neurol 1984;22:409 – 11. [6] Guha A, Perin RG, Grossman H, Smyth HS. Vertex epidural hematomas. Neurosurgery 1989;25:824 – 8. [7] Stevenson GC, Brown HA, Hoyt WF. Chronic venous epidural hematoma at the vertex. J Neurosurg 1964;21:887 – 91. [8] Cordell W, Feuer H. Premonitory neurologic signs in a patient with an acute vertex epidural hematoma. Am J Emerg Med 1983;1:288 – 91. [9] Alexander GL. Extradural hematoma at the vertex. J Neurol Neurosurg Psychiatry 1961;24:381 – 4. [10] Jones FW. The vascular lesion in some cases of middle meningeal hemorrhage. Lancet 1912;2:7 – 12. [11] Oka K, Rhoton AL, Barry M, Rodriguez R. Microsurgical anatomy of the superficial veins of the cerebrum. Neurosurgery 1985;17:711 – 47. [12] Song JH, Park JY, Lee HK. Vertex epidural hematomas: considerations in the MRI era. J Korean Med Sci 1996;11:278–81. [13] Fobben ES, Grossman RI, Atlas SW, et al. MR characteristics of subdural hematomas and hygromas at 1.5T. Am J Neurosci Res 1989;10:687 – 93. [14] Casey SO, Alberico RA, Patel M, et al. Cerebral CT venography. Radiology 1996;198:163 – 70.
Vertex epidural hematomas: imaging findings and diagnostic pitfalls Olin L. Harbury a, James M. Provenzale b,*, Daniel P. Barboriak a b
a Metrolina Imaging Group, Mercy Hospital, Charlotte, NC 28207, USA Department of Radiology, Duke Uni6ersity Medical Center, Box 3803, Durham, NC 27710, USA
Received 19 August 1999; received in revised form 1 February 2000; accepted 1 February 2000
Abstract Purpose: Our purpose was to show the computed tomography (CT) and magnetic resonance (MR) imaging features of vertex epidural hematomas (EDHs) and emphasize pitfalls in the diagnosis of this entity. Subjects and methods: The neuroradiologic studies of four patients (CT in four, MR imaging and MR venography in one) were evaluated for EDH shape, size and appearance. Results: EDHs were biconvex in three patients and crescentic in one patient. CT appearances included a collection that was hyperdense (two patients), generally isodense with a few regions of hyperdensity (one patient) and mixed hyperdense and hypodense (one patient). MR imaging findings in one patient consisted of hyperintense signal on T1-weighted images and hypointense signal on T2-weighted images. Inferior displacement of the superior sagittal sinus was seen in two patients. Diagnosis of a small vertex EDH was difficult on routine axial CT in one patient, but apparent on MR imaging and MR venography. Conclusions: Small vertex EDHs can be difficult to diagnose on routine CT. MR imaging or thin section CT should be performed to exclude the diagnosis in patients with trauma to the skull vertex. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Computed tomography; Epidural hematomas; Magnetic resonance
1. Introduction The skull vertex is an uncommon site for epidural hematoma (EDH) formation, accounting for only 1– 8% of EDHs [1–4]. EDHs at this site typically occur after a traumatic injury of sufficient force to produce a fracture or diastasis of the sagittal suture [1]. Vertex EDHs often cause rapid neurologic deterioration and death. The mortality associated with vertex EDHs is high, reported to be between 18 and 50% in some series [2,3] and rapid diagnosis is important to limit morbidity and mortality. Many authors have noted the difficulty of diagnosing vertex EDHs by computed tomography (CT) [2,3,5,6]. The difficulty arises because lesion conspicuity can be low due to (1) near-isodensity of the EDH and adjacent bone; (2) alignment of the EDH along the scan plane; and (3) volume averaging effects in instances when CT * Corresponding author. Tel.: +1-919-6847409; fax: + 1-9196847138. E-mail address: [email protected] (J.M. Provenzale).
slices are relatively thick compared with the thickness of the EDH. These facts have led some investigators to regard the vertex as a potential ‘blind spot’ on CT imaging [6]. With these facts in mind, we analyzed four cases of vertex EDH to assess imaging features of the lesions further, define difficulties in diagnosis and suggest optimal imaging protocols.
2. Subjects and methods The radiologic files of three hospitals (two community-based hospitals and one tertiary care-teaching hospital) were reviewed for patients with the diagnosis of vertex EDH. Four patients (three men, average age, 33 years) were identified (Table 1). The medical records were reviewed for history of trauma and operative findings at the time of EDH evacuation. Imaging studies were reviewed for the presence of skull fracture and EDH shape, size and appearance. Imaging examinations included CT (four patients), magnetic resonance (MR) imaging (one patient) and
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MR venography (one patient). CT imaging was performed in the axial plane using 10-mm slice thickness at the level of the vertex (three patients) and in the coronal plane using 5-mm slice thickness (one patient). Coronal CT images reconstructed from 10-mm thick axial images were available in two patients, one of which also had reconstructed sagittal images. MR imaging and MR venography was performed in one individual (patient 1). T1-weighted MR images were obtained in the axial plane using a TR of 400 ms, TE of 19 ms and one excitation. T2-weighted images were performed in the sagittal plane using a TR of 2500 ms, TEs of 30 and 90 ms and 0.75 excitations. Coronal MR images were reconstructed from a sagittal 3D-volume acquisition obtained using gradient echo technique using a dedicated independent workstation (General Electric Medical Systems, Milwaukee, WI). MR venography was performed using 2D-phase contrast technique, TR of 25 ms, TE of 10 ms, two excitations and an encoding velocity (Venc) of 20 cm/s.
the sagittal suture (Fig. 2) and another had a recent bifrontal craniotomy. In three individuals (patients 2, 3 and 4), the EDH had a convex shape at the interface with brain and in patient 1, a concave shape was seen. Vertex EDH was difficult to diagnose by CT in one patient (Fig. 1) but was much more apparent by MR imaging, which showed a hematoma which was slightly hyperintense relative to gray matter on T1-weighted images and hypointense on T2-weighted images (Fig. 1C and D). A fluid collection was seen within the postoperative bed, which at surgery was found to be only slightly blood-tinged cerebrospinal fluid (Fig. 1D and E). The patient’s neurologic signs resolved following evacuation of the EDH, even though the fluid collection within the tumor resection bed was not evacuated. This suggests that the EDH (and not the fluid collection within the postoperative bed) was the source of the neurologic deterioration. MR venography in patient 1 showed inferior displacement of the superior sagittal sinus (Fig. 1F).
3. Results
4. Discussion
Two patients developed vertex EDHs following head trauma and two other patients had vertex EDH after cranial surgery (resection of a falx meningioma in patient 1 and following resection of a high cervical arachnoid cyst in patient 4) (Table 1). Fractures were seen in both the patients with a history of trauma, at the vertex in one patient and high parietal bone in the other patient. At surgery, venous bleeding sites were identified in all four patients (Table 1). On CT imaging, EDHs were relatively isodense relative to gray matter in one patient with a few regions of hyperdensity (Fig. 1), hyperdense in two patients (Fig. 2) and inhomogeneous with both hypodense and hyperdense components in one patient (Fig. 3). In three patients, the EDH extended across the sagittal suture (Table 1). One of these patients had a fracture involving
Vertex EDHs are usually post-traumatic in origin and often follow fracture at the level of the vertex or diastasis of the sagittal suture. In one series, 92% of patients with vertex fractures were found to have EDHs [2]. Signs and symptoms due to vertex EDHs are variable and appear to depend on the source of hemorrhage, size of hematoma, and rapidity of hematoma formation [1,2]. Most patients with vertex EDH due to laceration of the superior sagittal sinus become comatose within a few hours (Table 2) [1,2]. Less commonly, a slow and steady neurologic decline over the course of many hours is seen, sometimes after a symptom-free interval of many hours or days [3,5,7,8]. Acute worsening manifested as headache, encephalopathy and decreased level of consciousness can occur due to venous obstruction and thrombosis caused by the mas-
Table 1 Vertex epidural hematomas: imaging and operative findings Case
Age/gender
Precipitating event
Fracture site
CT appearance
MR appearance
Hemorrhage site
1
26, F
Meningioma resection
None (craniotomy)
Isodense to gray matter
T1-slightly hyperintense
Dural vein
2
45, M
Struck on head
Vertex
Hyperdense
T2-mixed hyper and hypointense signal –a
3
23, M
Struck on head
High parietal
Hyperdense
–a
4
37, M
Drainage of cervical spine arachnoid cyst
None
Inhomogeneous predominantly hypodense
–a
a
–, Not performed.
Diploic space and dural veins Margin of superior sagittal sinus Emissary veins
152
O.L. Harbury et al. / European Journal of Radiology 36 (2000) 150–157
Fig. 1.
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Fig. 1. (Continued) Twenty-seven year-old woman (patient 1) with somnolence and paraparesis after complete resection of a falx meningioma. Following CT and MR imaging, she underwent evacuation of a vertex EDH with resolution of neurologic signs over the next few days. (A) Unenhanced 10-mm thick axial CT image shows an extra-axial hematoma (arrows) which is relatively isodense compared with gray matter. (B) Magnified view of Fig. 1A shows the EDH (arrows) is slightly hyperintense to normal brain tissue. The EDH was difficult to see on coronal images (not shown) reconstructed from the 10-mm thick axial images. (C) Axial T2-weighted (2500/90, 0.75 [TR/TE/excitations]) MR image shows the EDH (arrows) as a collection which has an anterior hyperintense component and a hypointense posterior component. (D) Coronal MR images reconstructed from a sagittal 3D volume acquisition using gradient echo technique show the hematoma (solid arrows) extending over both hemispheres, displacing brain tissue inferiorly. On this image, the EDH has a convex surface at the interface with brain. The postoperative surgical bed (open arrows) is seen as a cavity flanked by brain tissue, which is still deformed due to the previous compressive effect of the resected falcine meningioma. At the time of re-operation for evacuation of the EDH, solely blood-tinged cerebrospinal fluid without an active bleeding source was seen within the postsurgical cavity. Neurologic symptoms resolved following evacuation of the EDH. (E) Unenhanced sagittal T1-weighted (400/19/1) MR image shows the EDH (arrowheads) as an inhomogeneous collection, which is predominantly isointense relative to gray matter and separated from brain tissue by a hypointense rim. It is difficult to distinguish the flow void of the superior sagittal sinus from the hypointense signal of the dura. On this image, the EDH appears to have a biconvex shape. The hemorrhagic cerebrospinal fluid collection (arrows) is predominantly hyperintense. Note the residual deformity of the brain adjacent to the surgical resection bed following removal of the large meningioma. (F) Sagittal image from a 2D-phase contrast MR venogram (25/10/2, Venc 20 cm/s) shows inferior displacement of the superior sagittal sinus (arrowheads).
sive effect of the hematoma [9]. Increased intracranial pressure, manifested clinically as headache, papilledema and encephalopathy is often present (Table 2), even with a relative small hematoma, due to impairment of venous drainage or diminished cerebrospinal fluid resorption rather than the compressive effect of the hematoma on adjacent brain parenchyma [3,5,7]. Because of these facts, the significance of even a small vertex EDH should not be underestimated. Furthermore, vertex EDH can be the only radiologic manifestation of intracranial trauma [1]. Therefore, physicians treating patients, who are initially asymptomatic and in whom the finding of a vertex EDH has been overlooked on imaging studies, can assume a false sense of security regarding neurologic outcome. In all our patients, a venous bleeding site was identified at surgery. It was shown early in this century that (1) venous laceration alone can produce fatal EDH; and (2) the vascular grooves found along the inner table of the skull (through which fracture associated with EDH often extends) contain the middle meningeal vein rather than the middle meningeal artery [10]. In addition to the superior sagittal sinus, other potential sources of hemorrhage include the meningeal veins,
venous lacunae, meningeal sinuses (which are aligned alongside the superior sagittal sinus and receive drainage from cortical veins), the diploic space and small arteries supplying midline structures [11]. Most series of patients with vertex EDH have been published in the neurosurgical literature [2–7,9], and these lesions have received relatively little attention in the radiologic literature. In one series of 348 patients with EDH studies in the pre-CT era, the prevalence of EDHs occurring at the vertex was 4%, but none of 168 EDH patients studied after the advent of CT were found to have a vertex EDH [3], suggested a limited ability to establish the diagnosis. Similar data in multiple neurosurgical series have led to the conclusion that a normal CT does not rule out vertex EDH. Some authors have proposed that in any case of suspected vertex EDH (especially in the presence of a fracture involving the vertex, or diastasis of the sagittal suture), coronal CT imaging should be performed and that catheter angiography is indicated if the diagnosis is still in doubt [2,5,6]. These reports led us to review our series to determine whether vertex EDHs are, in fact, difficult to diagnose by CT and to examine the role of MR imaging.
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Fig. 2. Forty-five year-old man (patient 2) who was struck on the top of the head and developed right hemiplegia and aphasia within a few hours. (A) Unenhanced axial CT image at the level of the vertex shows a extra-axial hematoma (arrows) crossing the midline. (B) Magnified view of Fig. 2A shows that the hematoma (arrows) is hyperdense compared with normal brain tissue. A small interhemispheric subdural hematoma (arrowheads) is also present. (C) Unenhanced coronal CT image using wide window technique shows a hyperdense epidural collection (solid arrows) crossing the midline subjacent to a fracture, which extended through the sagittal suture (open arrows). At surgery, bleeding from the diploic space and epidural venous hemorrhage were seen.
The diagnosis of vertex EDH should be suspected in any patient with a vertex fracture or sutural diastasis at the vertex on bone window images or the CT scanogram, or in whom disruption of the superior
sagittal sinus is suspected. In our series, vertex EDHs were not difficult to diagnose by CT in three patients because they were thick and/or had attenuation characteristics that differed significantly from adjacent par-
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enchyma and bone. However, diagnosis was difficult in patient 1 because the hematoma was thin and relatively isodense to gray matter. Because the short axis is usually perpendicular to the CT imaging plane, diagnosis of thin vertex EDHs by CT can be difficult. This is
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due, in part, to the fact that CT imaging is often performed in the axial plane using thick (10 mm) slices through this region of the brain (as was the case in our patient). Coronal imaging could have alleviated the problem of diagnosis in patient 1 but the patient’s poor
Fig. 3. Thirty-seven year-old man (patient 4) with a history of hydrocephalus and ventriculoperitoneal shunt that developed syringomyelia and a high cervical arachnoid cyst. Following resection of the arachnoid cyst, the patient failed to awaken from surgery. (A) Unenhanced axial CT image performed at a point 3.5 cm from the vertex shows a diffuse inhomogeneous extra-axial hematoma (arrowheads) filling most of the cranium. The hematoma was seen to cross the sagittal, right coronal and right lambdoid sutures. (B) Contrast-enhanced axial CT image at a point 6.5 cm from the level of the vertex shows the inferior margin of the hematoma (arrowheads), the inferiorly displaced superior sagittal sinus (arrows), and marked hydrocephalus. The anterior cerebral arteries (curved arrow) are displaced across midline due to the fact that the hematoma is larger on the right side. Note the edema within the adjacent right hemisphere due to the mass effect of the hematoma. (C) Coronal image reconstructed from 5 mm contrast-enhanced axial images seen in B. The hematoma (arrowheads) is inhomogeneous, larger on the right, and displaces the enlarged lateral ventricles (open arrows) inferiorly. The exact location of the superior sagittal sinus is difficult to show on this image due to adjacent hyperdensity within the hematoma.
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Table 2 Clinical and radiologic signs of vertex epidural hematoma Clinical Signs and symptoms due to increased intracranial pressure Headache Papilledema Encephalopathy Signs and symptoms due to mass effect on adjacent structures Paraparesis Decreased level of consciousness Radiological CT, hyperdense extradural mass subjacent to vertex of skull MR –Extradural mass subjacent to vertex of skull with signal characteristics that are isointense or hyperintense on T1-weighted images and hypointense or hyperintense on T2-weighted images –Inferior displacement of superior sagittal sinus on MR venography subjacent to vertex of skull
neurological status precluded direct coronal imaging and the diagnosis was difficult on coronal reconstructions from the thick axial images. Our case shows one of the practical problems in making the diagnosis, unless a small vertex EDH is suspected before or during CT scanning, imaging with 10-mm thick axial images (which are routine at most imaging centers) will be performed. Another potential problem is that the hyperdense appearance of a vertex EDH can potentially be mistaken for adjacent bone or thought to be due to volume averaging of bone and brain. Few reports have shown the MR imaging appearance of EDH [12]. In our single case (patient 1) in whom CT and MR imaging could be compared, MR imaging was clearly superior for diagnosis, due to the high signal contrast between hematoma, brain and bone and the fact that multiplanar images could be directly obtained. The signal of the vertex EDH (in which concentrated blood was present) clearly differed from that of the blood-tinged cerebrospinal fluid collection within the postoperative surgical bed (Fig. 1D and E). The signal characteristics, as with any EDH, will vary with the age of the hematoma and species of blood breakdown products present, as well as the pulse sequence [13]. Potential pitfalls in MR imaging of vertex EDHs can occur depending on the age of hematoma and the corresponding signal characteristics compared with adjacent structures. A hyperintense EDH on T1-weighted images could be potentially confused with the signal of fat in adjacent bone marrow on axial images. Similarly, EDHs, which are hypointense on T2-weighted images, can potentially appear similar to lower signal from the adjacent inner table of the skull. Use of multiple pulse sequences minimizes these problems, as well as use of gradient echo images or MR venography to visualize blood flow and vascular structures at the vertex.
In general, the vertex EDHs in our series had many CT features typical of EDHs at other sites. However, whereas EDHs usually have a biconvex shape, the EDH in patient 1 had a crescentic shape on coronal reconstruction images (although it appeared biconvex on sagittal images). In addition, while EDHs at other sites generally do not cross suture lines, extension across the sagittal suture was seen in three of our patients. In two of our patients, the tight attachment of the dura to the inner table of the skull (which usually prevents EDH spread) was disrupted as a result of fracture (patient 2) or surgical dissection (patient 1). In patient 4, the attachment of the dura to the inner table of the skull was probably disrupted as the large EDH expanded. Downward displacement of the superior sagittal sinus, which was a sign used for diagnosis of vertex EDH by catheter angiography [1,2] and definitively localizes the hematoma to the epidural space, was observed in two of our patients by either contrast-enhanced CT (patient 4) or MR venography (patient 1). In patient 4, the superior sagittal sinus was seen as a contrast-enhancing linear structure 6.5 cm inferior to the inner table of the skull, seen better on direct axial images than on coronal reconstruction images (Fig. 3). In patient 1, the flow void of the superior sagittal sinus was difficult to distinguish from the hypointense signal of the adjacent dura on T1-weighted sagittal images (Fig. 1E). MR venography, however, clearly demonstrated the displacement of the superior sagittal sinus as an inferior bowing of a long segment of the signal column of the dural sinus (Fig. 1F). Realizing that our results are retrospective and based on a small number of patients without a uniform imaging protocol, we suggest the following guidelines for diagnosis of small vertex EDHs. MR imaging is the imaging method of choice in suspected cases because of the high signal contrast between the lesion and normal brain and because multiplanar imaging can be readily performed. We recommend thin sections (3- or 4-mm thick) T1-weighted and T2-weighted images with a narrow interslice gap in the coronal and sagittal planes when the diagnosis of EDH is being considered. When the diagnosis is equivocal by spin-echo MR imaging, MR venography or gradient echo images can be useful in showing inferior displacement of the superior sagittal sinus, thus specifically localizing the hematoma to the epidural space. When only axial CT imaging is available or appropriate, we recommend thin (3 or 1.5 mm) axial images which will allow smoother reconstructions than that available with thicker axial images. CT examinations in trauma patients should include images using intermediate window settings in order to increase the sensitivity for detection of extra-axial hemorrhage. Contrast administration can be helpful in such patients by showing inferior displacement of the superior sagittal sinus. In future, helical CT is expected to be benefi-
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cial for the diagnosis of vertex EDH due to the fact that it allows finely detailed coronal and sagittal reformat images from thin section axial images. In particular, in difficult cases, CT venography may be helpful by showing inferior displacement of the superior sagittal sinus [14].
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