Radiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bradley, W. G.
Right arrow Articles by Shey, R. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bradley, W. G.
Right arrow Articles by Shey, R. B.
(Radiology. 2000;214:651-656.)
© RSNA, 2000

How I Do It

MR Imaging Evaluation of Seizures1

William G. Bradley, MD, PhD and Randolph B. Shey, MD

1 From the Departments of Radiology (W.G.B.) and Neurology (R.B.S.), Long Beach Memorial Medical Center, 403 E Columbia St, Long Beach, CA 90806. Received January 29, 1999; revision requested March 31; revision received May 24; accepted July 13. Address reprint requests to W.G.B. (e-mail: wgbradley@pol.net).

Abstract

It is imperative for a radiologist to determine the type of seizure a patient has prior to magnetic resonance (MR) imaging to optimally provide the clinician with the information he or she requires. Specifically, complex partial seizures require evaluation of the frontal lobes and the hippocampus (for mesial temporal sclerosis). These are best evaluated with fluid-attenuated inversion recovery (FLAIR) imaging; the use of intravenously administered contrast material is not required. Other types of chronic seizures are best evaluated with nonenhanced FLAIR or T2-weighted imaging for low-grade tumors, vascular malformations, gliosis after infarction, inflammation, or trauma. The presence of new-onset seizures in an adult or the worsening of chronic seizures warrants T2-weighted or FLAIR imaging and gadolinium-enhanced T1-weighted imaging (to look for primary or metastatic tumors, infections, or inflammatory lesions). If available, echo-planar diffusion imaging should be used also (to look for acute infarcts).

Index terms: Brain, MR, 10.12141, 10.121413, 10.121416, 10.121417, 10.12143 • Magnetic resonance (MR), comparative studies, 10.12141, 10.121413, 10.121416, 10.121417, 10.12143 • Magnetic resonance (MR), contrast enhancement, 10.12143 • Magnetic resonance (MR), echo planar, 10.121416 • Magnetic resonance (MR), inversion recovery, 10.121413 • Magnetic resonance (MR), magnetization transfer contrast, 10.121417 • Seizures

The evaluation of seizures is a common indication for magnetic resonance (MR) imaging and accounts for 1% of all MR imaging studies performed. While computed tomography (CT) can be used in the detection of some lesions, MR imaging is clearly the more sensitive imaging technique, particularly in the detection of early disease (1). The specific MR imaging technique used depends on the specific type of seizures the patient has. Therefore, it is important to obtain an accurate history from the referring clinician. Specifically, it is important to determine if the seizures are of recent onset or if they are chronic and if they are generalized or partial; if they are partial, it is important to determine whether they are simple (motor or sensory) or complex (altered cognition).

New-onset seizures in an adult require the acquisition of routine T1- and T2-weighted images, as well as gadolinium-enhanced images. On the other hand, chronic seizures in an adult probably do not require the last unless the frequency, intensity, or nature of the seizures has changed. (Although gadolinium-based contrast agents are very safe and would probably not harm patients with a history of chronic seizures, the use of these agents in this clinical situation is probably not warranted because of the increased focus on the cost-effectiveness of diagnostic evaluation.)

In children or young adults (13–30 years of age) who present with complex partial seizures, the objective of MR imaging is to depict mesial temporal sclerosis, as well as other temporal or frontal lobe lesions. Mesial temporal sclerosis is best depicted by using thin coronal sections that are angled perpendicularly to the hippocampus with T1-weighted, T2-weighted, or fluid-attenuated inversion recovery (FLAIR) sequences. (FLAIR is ideal because it is a very heavily T2-weighted technique that highlights the high-signal-intensity gliotic hippocampus against the low-signal-intensity cerebrospinal fluid in the enlarged temporal horn.) In older patients with recent-onset complex partial seizures, gadolinium-enhanced images should be obtained to exclude temporal lobe tumors and, less frequently, frontal lobe tumors.

NEW-ONSET SEIZURES IN AN ADULT

The clinical history may suggest the cause of new seizures in an adult. However, in previously healthy elderly patients, a specific cause is identified in no more than 50% of the cases. Of these, more than half are related to acute or chronic cerebrovascular disease; the former is most sensitively and quickly detected at echo-planar diffusion imaging (Fig 1) (2). Metastatic disease is among the most worrisome of the remaining causes. T2-weighted (Fig 2a) and FLAIR images are often sufficient for the depiction of parenchymal metastases, although gadolinium-based contrast material is ubiquitously used and does increase the contrast of the lesion (Fig 2b).



View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1a. New-onset seizures from an acute infarct in a 57-year-old man. (a) Transverse single-shot echo-planar diffusion MR image (b = 1,000) demonstrates focal areas of high signal intensity that represent acute ischemia and cytotoxic edema from occlusion of the right middle cerebral artery 4 hours after a seizure. The regions of interest (1, 2, 3) were drawn to measure the volume of the ischemic lesion for a quantitative stroke protocol. (b) Transverse T2-weighted spin-echo MR image (3,000/80 [repetition time msec/echo time msec]) obtained at the same level as a is essentially normal.

 


View larger version (162K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1b. New-onset seizures from an acute infarct in a 57-year-old man. (a) Transverse single-shot echo-planar diffusion MR image (b = 1,000) demonstrates focal areas of high signal intensity that represent acute ischemia and cytotoxic edema from occlusion of the right middle cerebral artery 4 hours after a seizure. The regions of interest (1, 2, 3) were drawn to measure the volume of the ischemic lesion for a quantitative stroke protocol. (b) Transverse T2-weighted spin-echo MR image (3,000/80 [repetition time msec/echo time msec]) obtained at the same level as a is essentially normal.

 


View larger version (133K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2a. New-onset seizures from a metastatic sarcoma in a 12-year-old boy. (a) Transverse T2-weighted spin-echo MR image (3,000/90) shows that the only definite cortical (ie, seizure-producing) focus (short arrow) is isointense to the gray matter. The intraventricular (long arrow) and subependymal (arrowhead) masses are also isointense to the gray matter, but they should not produce seizures. (b) Transverse enhanced T1-weighted spin-echo MR image (500/22) demonstrates three enhancing metastases. With this technique, the cortically based lesion (arrow) is now clearly distinguished from the gray matter. (Although the large central mass could also produce seizures by means of venous occlusion, there was no evidence of this on images of adjacent sections [not shown]).

 


View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2b. New-onset seizures from a metastatic sarcoma in a 12-year-old boy. (a) Transverse T2-weighted spin-echo MR image (3,000/90) shows that the only definite cortical (ie, seizure-producing) focus (short arrow) is isointense to the gray matter. The intraventricular (long arrow) and subependymal (arrowhead) masses are also isointense to the gray matter, but they should not produce seizures. (b) Transverse enhanced T1-weighted spin-echo MR image (500/22) demonstrates three enhancing metastases. With this technique, the cortically based lesion (arrow) is now clearly distinguished from the gray matter. (Although the large central mass could also produce seizures by means of venous occlusion, there was no evidence of this on images of adjacent sections [not shown]).

 
Unfortunately, not all metastases spread to the parenchyma where they are depicted on T2-weighted images. Twenty percent of hematogenous metastases to the brain affect the leptomeninges, where they irritate the cortex and, thereby, produce seizures early in the course of the disease. Conventional T2-weighted MR images are notoriously insensitive in the depiction of leptomeningeal carcinomatosis particularly in its early stages before it breaks through the cortical mantle to elicit vasogenic edema in the underlying white matter. In early leptomeningeal disease, evaluation with use of gadolinium enhancement is mandatory (Fig 3). Traditionally, T1-weighted images have been obtained before and after the administration of gadolinium-based contrast materials. Recent evidence suggests that contrast material–enhanced FLAIR images may be even more sensitive than unenhanced FLAIR or contrast-enhanced T1-weighted images for cortical processes that may cause seizures (3).



View larger version (168K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3. New-onset seizures from leptomeningeal carcinomatosis (carcinoma of the lung) in a 59-year-old woman. Although this transverse enhanced T1-weighted spin-echo MR image (500/20) depicts multiple enhancing lesions, only the largest lesions were seen on the nonenhanced T2-weighted images (not shown) because of the presence of vasogenic edema.

 
Another technique that has recently become available is the use of magnetization transfer to increase the sensitivity of gadolinium-enhanced T1-weighted imaging (4). Several years ago, it was shown that the use of double and triple doses of gadolinium-based contrast materials resulted in the depiction of more lesions than did the use of routine single doses (5). Now, by using a magnetization transfer prepulse after a single dose, it is possible to obtain the contrast enhancement normally seen with the use of triple doses (6). Magnetization transfer is a spectroscopic prepulse that saturates normal brain much more than it does edematous brain, which is the result of metastatic disease or other seizure-producing processes. Thus, normal brain has lower signal intensity, while the metastasis stands out with greater contrast enhancement (6).

As the age at which patients present with seizures decreases below 60 years, the percentage of primary brain tumors increases. These seizures are best evaluated with the combination of nonenhanced T2-weighted or FLAIR images and T1-weighted images before and after the administration of gadolinium-based contrast material (Fig 4). In general, the higher the grade of the tumor, the greater the degree of enhancement. (A prominent exception to this is the grade I pilocytic astrocytoma that enhances despite its low grade). T2-weighted or FLAIR images can demonstrate necrotic portions of the tumor in glioblastoma multiforme and surrounding vasogenic edema. A nonenhanced T1-weighted image is useful in showing subacute hemorrhage (methemoglobin), which has high signal intensity (Fig 5a). After the administration of gadolinium-based contrast materials, it may be impossible to distinguish an enhancing tumor from methemoglobin on T1-weighted images (Fig 5b). This finding, as well as the low signal intensity on a T2-weighted image from acute hemorrhage (intracellular deoxyhemoglobin) or early subacute hemorrhage (intracellular methemoglobin) (Fig 5c), suggests the presence of hemorrhagic metastases or higher-grade primary brain tumors (ie, anaplastic astrocytoma [grade III] or glioblastoma multiforme [grade IV]). Thus, each of the specific MR imaging sequences used in the evaluation has a role in the characterization of the features of brain tumors.



View larger version (158K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4. New-onset seizures from glioblastoma multiforme in a 42-year-old man. Transverse enhanced T1-weighted spin-echo MR image (500/20) demonstrates a large enhancing mass with a nonenhancing necrotic region (arrow). (Necrosis is the distinguishing characteristic of glioblastoma.)

 


View larger version (163K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 5a. New-onset seizures from hemorrhagic metastases (breast carcinoma) in a 45-year-old woman. (a) Transverse nonenhanced T1-weighted spin-echo MR image (500/22) demonstrates a small high-signal-intensity lesion (short solid arrow), a larger high-signal-intensity lesion with a surrounding dark rim (long solid arrow), and a nearly isointense lesion with a subtle fluid level (open arrow). (b) Transverse enhanced T1-weighted spin-echo MR image (500/22) demonstrates tumor enhancement (arrow) along the superior margin of the nearly isointense lesion shown in a. (c) Transverse T2-weighted spin-echo MR image (3,000/90) shows that the two high-signal-intensity lesions in a can now be identified as extracellular methemoglobin surrounded by low-signal-intensity hemosiderin. The low-signal-intensity dependent portion of the previously isointense lesion is intracellular deoxyhemoglobin (arrowhead). Another acutely hemorrhagic lesion (containing deoxyhemoglobin) is noted in the right insular cortex (arrow). (Both T1- and T2-weighted images are required to adequately stage hemorrhage [7]).

 


View larger version (159K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 5b. New-onset seizures from hemorrhagic metastases (breast carcinoma) in a 45-year-old woman. (a) Transverse nonenhanced T1-weighted spin-echo MR image (500/22) demonstrates a small high-signal-intensity lesion (short solid arrow), a larger high-signal-intensity lesion with a surrounding dark rim (long solid arrow), and a nearly isointense lesion with a subtle fluid level (open arrow). (b) Transverse enhanced T1-weighted spin-echo MR image (500/22) demonstrates tumor enhancement (arrow) along the superior margin of the nearly isointense lesion shown in a. (c) Transverse T2-weighted spin-echo MR image (3,000/90) shows that the two high-signal-intensity lesions in a can now be identified as extracellular methemoglobin surrounded by low-signal-intensity hemosiderin. The low-signal-intensity dependent portion of the previously isointense lesion is intracellular deoxyhemoglobin (arrowhead). Another acutely hemorrhagic lesion (containing deoxyhemoglobin) is noted in the right insular cortex (arrow). (Both T1- and T2-weighted images are required to adequately stage hemorrhage [7]).

 


View larger version (157K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 5c. New-onset seizures from hemorrhagic metastases (breast carcinoma) in a 45-year-old woman. (a) Transverse nonenhanced T1-weighted spin-echo MR image (500/22) demonstrates a small high-signal-intensity lesion (short solid arrow), a larger high-signal-intensity lesion with a surrounding dark rim (long solid arrow), and a nearly isointense lesion with a subtle fluid level (open arrow). (b) Transverse enhanced T1-weighted spin-echo MR image (500/22) demonstrates tumor enhancement (arrow) along the superior margin of the nearly isointense lesion shown in a. (c) Transverse T2-weighted spin-echo MR image (3,000/90) shows that the two high-signal-intensity lesions in a can now be identified as extracellular methemoglobin surrounded by low-signal-intensity hemosiderin. The low-signal-intensity dependent portion of the previously isointense lesion is intracellular deoxyhemoglobin (arrowhead). Another acutely hemorrhagic lesion (containing deoxyhemoglobin) is noted in the right insular cortex (arrow). (Both T1- and T2-weighted images are required to adequately stage hemorrhage [7]).

 
Almost since its introduction, MR imaging has been used to guide brain tumor biopsy prior to treatment. This guidance has allowed neurosurgeons to avoid necrotic areas of the tumor (which provide nondiagnostic material) while focusing on solid portions of the tumor, which enhance with gadolinium-based contrast material (Fig 4). Recent advances in MR imaging technology have provided us with an even better tool for use in the localization of the most vascular portion of the tumor; this portion is also likely to have the highest grade (8). Echo-planar perfusion imaging (8) is used to generate maps of the perfusion characteristics of the brain during the 40 seconds or so it takes a bolus of gadolinium-based contrast material to traverse the cerebral vasculature (9). Echo-planar imaging is a recent development made possible by high-performance gradients (9,10). In the past, many people focused on differences in field strength as an initial indicator of magnet quality. Now, additional discriminators are gradient performance and the capability to perform echo-planar imaging. The advantage of echo-planar imaging is that a single image can be acquired in one-tenth of a second, thereby eliminating motion artifact (10).

While fast imaging itself is an improvement, currently, the primary use for echo-planar imaging is in diffusion imaging performed for the detection of the cytotoxic edema associated with early cerebral ischemia (2,11). It has also been recently noted that certain tumors with high ratios of nuclear-cytoplasmic ratios (eg, lymphoma) have restricted diffusion and, therefore, appear bright, similar to an acute infarct, on echo-planar diffusion images (12). Thus, with the introduction of systems capable of echo-planar MR imaging, we now have two new tools with which to better characterize brain tumors prior to biopsy.

CHRONIC SEIZURES

Chronic seizures that have not changed in character can be divided into those that are surgically treatable and those that are not. Unfortunately, it is usually not possible to distinguish these two classifications on the basis of the clinical presentation alone; therefore, imaging is performed. Chronic seizures that are not surgically treatable result from small cortical scars caused by prior trauma, infection, inflammation, or infarction. Depending on their size, these scars may or may not be seen as regions of cortical gliosis (high signal intensity on intermediate-weighted or FLAIR images) or as focal areas of encephalomalacia and sulcal widening on T1- and T2-weighted images. Included in the category of seizures that may be treated surgically are brain tumors (usually slowly growing, benign [grade I or II] gliomas, since metastases tend to grow more rapidly), vascular malformations (arteriovenous malformations [Fig 6] and cavernous angiomas [Fig 7]), demyelinating lesions, and (rarely) cortical dysplasia (Fig 8). (While complex partial seizures also tend to be chronic, these are discussed later.)



View larger version (142K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 6. Worsening seizures due to hemorrhage from a arteriovenous malformation in a 31-year-old man. Transverse, T2-weighted spin-echo MR image (3,000/80) shows both intraparenchymal (large arrow) and intraventricular hemorrhage (small arrow). The low signal intensity of the hemorrhage on this image is consistent with acute hemorrhage (deoxyhemoglobin) 48 hours after a seizure.

 


View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 7a. Chronic seizures from a cavernous angioma in a 55-year-old man. (a) Transverse T2-weighted spin-echo MR image (3,000/90) demonstrates a classic mulberry lesion (arrow), that is, low-signal-intensity hemosiderin that surrounds multilobulated high-signal-intensity methemoglobin. (b) Sagittal T1-weighted spin-echo MR image (500/22) demonstrates high-signal-intensity methemoglobin (arrow).

 


View larger version (134K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 7b. Chronic seizures from a cavernous angioma in a 55-year-old man. (a) Transverse T2-weighted spin-echo MR image (3,000/90) demonstrates a classic mulberry lesion (arrow), that is, low-signal-intensity hemosiderin that surrounds multilobulated high-signal-intensity methemoglobin. (b) Sagittal T1-weighted spin-echo MR image (500/22) demonstrates high-signal-intensity methemoglobin (arrow).

 


View larger version (141K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 8. Cortical dysplasia in a 26-year-old man with chronic seizures. Transverse T2-weighted spin-echo MR image (3,000/90) shows thickened, disordered gray matter in several locations, including the left frontal lobe (arrow).

 
Since most imaging studies performed to evaluate chronic seizures are negative (65% of epilepsy cases are idiopathic [13]), clinicians tend to order less expensive, more readily available CT studies in place of MR imaging studies. However, even the early MR imaging technology available 15 years ago depicted 10% more of the surgically correctable lesions than did CT (14). By using modern MR imaging techniques such as FLAIR imaging, the detection rate at MR imaging compared to CT should be even greater (15). This is true because seizures generally arise from cortically based lesions, and CT is relatively limited in the evaluation of the cortical gray matter relative to MR imaging because of the beam-hardening artifacts beneath the dense calvarium.

The intravenous administration of contrast material is usually not required in the evaluation of chronic seizures. In general, tumors that have a sufficiently low grade to be chronic do not enhance (with the exception of the previously noted pilocytic astrocytomas that are histologically grade I but do enhance) (16). Whether primary gliomas enhance or not, they should be detectable on good intermediate- or T2-weighted images and, particularly, on FLAIR images. Imaging of vascular malformations does not require the use of contrast materials. Arteriovenous malformations should be visible with almost any MR imaging sequence because of their vascular flow voids (Fig 6), that is, low signal intensity of the rapidly flowing blood, which appears dark against the higher signal intensity of the stationary brain. On nonenhanced MR images, cavernous angiomas usually have high signal intensity in the center (methemoglobin) and low signal intensity at the periphery (particularly on T2-weighted images) (Fig 7) due to T2 shortening from the magnetically susceptible hemosiderin.

Cortical dysplasia results from a migrational abnormality that occurs prior to birth, with disorganization of the differentiation of gray matter and white matter (Fig 8). While larger lesions may be seen with good contrast between gray and white matter by using any nonenhanced MR technique (Fig 8), the depiction of subtle lesions may require the use of thin-section three-dimensional gradient-echo techniques (17) or inversion recovery techniques with phase-sensitive reconstruction (18). Although conventional volume head coils are usually adequate, newer high-spatial-resolution limited-coverage phased-array head coils have been proved to be even more sensitive for the detection of cortical dysplasia (17).

As noted above, any change in the frequency, intensity, or character of chronic seizures warrants evaluation at MR imaging to depict acute hemorrhage (Fig 6) or infarction. If an obvious cause is not detected, gadolinium enhancement should be used to exclude the presence of tumor.

COMPLEX PARTIAL SEIZURES

At least a third of the time, the pathologic process underlying complex partial seizures is mesial temporal sclerosis. Many theories for the cause of mesial temporal sclerosis have been advanced; the current theory is uncontrolled febrile convulsions in childhood (19,20). Regardless of the cause, mesial temporal sclerosis can be easily identified at MR imaging without the use of contrast material.

Ideally, 3-mm coronal sections are angled approximately 30° (angled anteriorly at the top to be perpendicular to the hippocampus, which is best seen on parasagittal sections [Fig 9a]). The best image is an angled coronal image (Fig 9b) obtained through the interpeduncular cistern, which gives the appearance of a diamond or rectangle in the middle of the pons (21). On T1-weighted inversion-recovery or FLAIR images, the temporal horn on the side on which symptoms appear is enlarged secondary to atrophy of the hippocampus. Other portions of the ipsilateral corpus striatum (eg, the fornix and the mamillary body) may also be atrophic in more advanced cases. On T2-weighted or FLAIR images, high-signal-intensity gliosis may be seen in the hippocampus (Fig 9). As noted previously, fast FLAIR images are ideal because they demonstrate the enlarged temporal horn and the high signal intensity of the gliotic hippocampus. By using such MR imaging techniques, sensitivities for mesial temporal sclerosis in the 80%–90% range compared with pathologic findings have been shown (21).



View larger version (149K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 9a. New-onset complex partial seizures due to mesial temporal sclerosis in a 23-year-old man. (a) Parasagittal T1-weighted spin-echo MR image (500/20) demonstrates the hippocampus (arrow). To optimally visualize the hippocampus, the superior part of the coronal sections should be angled 30° forward in the plane of the arrow. (b) Angled coronal fast FLAIR image (10,000/147/2,200 [repetition time msec/echo time msec/inversion time msec]; echo train length, eight) obtained through the interpeduncular cistern (open arrow) demonstrates an enlarged temporal horn (arrowhead) and a high-signal-intensity gliotic left hippocampus (solid arrow).

 


View larger version (193K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 9b. New-onset complex partial seizures due to mesial temporal sclerosis in a 23-year-old man. (a) Parasagittal T1-weighted spin-echo MR image (500/20) demonstrates the hippocampus (arrow). To optimally visualize the hippocampus, the superior part of the coronal sections should be angled 30° forward in the plane of the arrow. (b) Angled coronal fast FLAIR image (10,000/147/2,200 [repetition time msec/echo time msec/inversion time msec]; echo train length, eight) obtained through the interpeduncular cistern (open arrow) demonstrates an enlarged temporal horn (arrowhead) and a high-signal-intensity gliotic left hippocampus (solid arrow).

 
Recently, MR spectroscopy has been used in the evaluation of mesial temporal sclerosis (22). The use of single-voxel proton spectroscopy adds about 10 or 15 minutes to the total examination time and shows decreased N–acetylaspartate–to-creatine ratios in the hippocampus on the affected side. (N–acetylaspartate is decreased because it is a neuronal marker and because there are fewer neurons in the affected hippocampus. Creatine is used as a reference standard for most MR spectroscopic measurements because it usually does not change with disease).

CONCLUSION

During the past 2 decades of its existence, clinical MR imaging has been proved to be useful for the evaluation of seizures. It should be the first imaging examination used in the detection of underlying, potentially life-threatening pathologic processes. As with all imaging procedures, the more detailed the history provided the radiologist, the better the customization of the MR examination for the specific clinical presentation (Fig 10). While some clinicians may argue against providing the history (on the basis that it would bias the interpretation), without the history, all patients would undergo T1-weighted transverse imaging before and after the administration of gadolinium-based contrast materials and would undergo angled coronal FLAIR imaging in addition to the usual transverse FLAIR or T2-weighted imaging. Although all of these sequences should probably be used if the history includes only seizures, lack of additional details will tend to unnecessarily increase the cost of the examination (through use of contrast material and extra imaging sequences). By alerting radiologists to whether seizures are of recent onset, chronic, or complex partial, clinicians can help the radiologists to select the proper MR technique, maximize the detection of disease, minimize the cost, and provide them with the information they require.



View larger version (19K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 10. Diagram shows the seizure evaluation algorithm.

 

Footnotes

Abbreviation: FLAIR = fluid-attenuated inversion recovery

References

  1. Bradley WG, Waluch V, Yadley RA, Wycoff RR. Comparison of CT and MR in 400 patients with suspected disease of the brain and cervical spinal cord. Radiology 1984; 152:695-702.[Abstract/Free Full Text]
  2. Tong DC, Yenari MS, Albers GW, O'Brien M, Marks MP, Moseley ME. Correlation of perfusion- and diffusion-weighted MRI with NIHSS score in acute (<6.5-hour) ischemic stroke. Neurology 1998; 50:864-870.[Abstract/Free Full Text]
  3. Bradley WG, Soong JC, Chen DY, et al. Gadolinium-enhanced FLAIR is better than gadolinium-enhanced T1-weighted images for detecting some cortical processes (abstr). Radiology 1998; 209(P):426.
  4. Mathews VP, Elster AD, King JC, et al. Combined effects of magnetization transfer and gadolinium in cranial MR imaging and MR angiography. AJR Am J Roentgenol 1995; 164:169-172.[Abstract/Free Full Text]
  5. Bradley WG, Yuh WTC, Bydder GM. Use of MR imaging contrast agents in the brain. J Magn Reson Imaging 1993; 3:190-218.
  6. Mehta RC, Pike GB, Haros SP, Enzmann DR. Central nervous system tumor, infection, and infarction: detection with gadolinium-enhanced magnetization transfer MR imaging. Radiology 1995; 95:41-46.[Medline]
  7. Bradley WG. MR appearance of hemorrhage in the brain. Radiology 1992; 189:15-26.[Abstract/Free Full Text]
  8. Sugahara T, Korogi Y, Kchi M, et al. Correlation of MR imaging–determined cerebral blood volume maps with histologic and angiographic determination of vascularity of glioma. AJR Am J Roentgenol 1998; 171:1479-1486.[Abstract/Free Full Text]
  9. Bradley WG, Chen DY, Atkinson DJ. Using high performance gradients. In: Bradley WG, Bydder GM, eds. Advanced MR imaging techniques. London, England: Martin Dunitz, 1997; 31-62.
  10. Bradley WG, Atkinson DJ, Chen DY, Edelman RR. Fast spin echo and echo planar imaging. In: Stark DD, Bradley WG, eds. Magnetic resonance imaging. 3rd ed. St Louis, Mo: Mosby–Year Book, 1999; 125-158.
  11. Noguchi K, Nagayoshi T, Watanabe N, et al. Diffusion-weighted echo-planar MRI of lacunar infarcts. Neuroradiology 1998; 40:448-451.[Medline]
  12. Teich DL, Bradley WG, Mandelker MD, et al. Some tumors are bright on diffusion imaging (abstr). Radiology 1998; 209(P):204.
  13. Hauser WA, Annegers JF, Kurland LT, Sergievsky GH. Incidence of epilepsy and unprovoked seizures in Rochester, Minnesota: 1935–1984. Epilepsia 1993; 34:453-468.[Medline]
  14. Sperling MR, Wilson G, Engel J, Babb TL, Phelps M, Bradley WG. Magnetic resonance imaging in intractable partial epilepsy: correlative studies. Ann Neurol 1986; 20:57-62.[Medline]
  15. Wieshmann WUC, Barker GJ, Symms MR, Bartlett PA, Stevens JM, Shorvon SD. Fast fluid-attenuated inversion-recovery imaging: first experience with a 3D version in epilepsy. Neuroradiology 1998; 40:483-489.[Medline]
  16. Boyko O. Pediatric brain tumors. In: Stark DD, Bradley WG, eds. Magnetic resonance imaging. 3rd ed. St Louis, Mo: Mosby–Year Book, 1999; 1467-1482.
  17. Grant PE, Vigneron DB, Barkovich AJ, et al. High resolution imaging of the brain. Magn Reson Imaging Clin N Am 1998; 6:139-154.[Medline]
  18. Moran PR, Kumar NG, Karstaedt N, Jackels SC. Tissue contrast enhancement: image reconstructing algorithm and selection of TI in inversion recovery MRI. Magn Reson Imaging 1986; 4:229-235.[Medline]
  19. Rein AG. Temporal mesial sclerosis syndrome in epilepsy. Neurologia 1998; 113:132-144.
  20. Shinnar S. Prolonged febrile seizures and mesial temporal sclerosis. Ann Neurol 1998; 43:411-412.[Medline]
  21. Tein RD, Felsberg GJ, de Castro CC, et al. Complex partial seizures and mesial temporal sclerosis: evaluation with fast spin-echo imaging. Radiology 1993; 189:835-842.[Abstract/Free Full Text]
  22. Mendes-Ribeiro JA, Soares A, Simoes-Ribeiro F, et al. Reduction in temporal N-acetylaspartate and creatine (or choline) ratio in temporal lobe epilepsy: does this 1H–magnetic resonance spectroscopy finding mean poor seizure control?. J Neurol Neurosurg Psychiatry 1998; 65:518-522.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 J. Neurol. Neurosurg. PsychiatryHome page
S P Liimatainen, J A Raitanen, A M Ylinen, M A Peltola, and J T Peltola
The benefit of active drug trials is dependent on aetiology in refractory focal epilepsy
J. Neurol. Neurosurg. Psychiatry, July 1, 2008; 79(7): 808 - 812.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Neuroradiol.Home page
C. J. Wall, E. J. Kendall, and A. Obenaus
Rapid Alterations in Diffusion-weighted Images with Anatomic Correlates in a Rodent Model of Status Epilepticus
AJNR Am. J. Neuroradiol., November 1, 2000; 21(10): 1841 - 1852.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bradley, W. G.
Right arrow Articles by Shey, R. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bradley, W. G.
Right arrow Articles by Shey, R. B.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
RADIOLOGY RADIOGRAPHICS RSNA JOURNALS ONLINE