The asymmetric mamillary body: association with medial temporal lobe disease demonstrated with MR.

PURPOSETo determine whether mamillary body atrophy is caused by deafferentation of the mamillary body in patients with mesial temporal sclerosis.METHODSWe studied 36 patients with thin-section MR to assess mamillary body symmetry. These patients included 10 control subjects without seizures and 26 patients with a history of seizures. Thin-section T1 scans were available for all cases. The patients with epilepsy underwent axial and coronal T2 scans as well.RESULTSIn five of eight cases with prior medial temporal lobe resection for intractable epilepsy, there was evidence of unilateral mamillary body atrophy ipsilateral to the resection. Similar findings were evident in three of six patients with MR findings of mesial temporal sclerosis without surgery. Two patients with medial temporal stroke or tumor also had ipsilateral mamillary body atrophy.CONCLUSIONThese findings provide support for the proposed mechanism of mamillary body atrophy caused by prior medial temporal lobe injury.     

Clinical significance of asymmetry of the fornix and mamillary body on MR in hippocampal sclerosis.

PURPOSETo investigate the clinical significance of MR-defined asymmetry of the fornix and mamillary body for presurgical determination of the side of hippocampal sclerosis in patients with temporal lobe epilepsy.METHODSFast spin-echo MR images were evaluated for evidence of an asymmetrically small fornix and mamillary body in 33 patients with pathologically proved hippocampal sclerosis (presurgical hippocampal sclerosis group), 7 patients who had undergone anterior temporal lobectomy (mean, 3 years from surgery) because of hippocampal sclerosis (postsurgical hippocampal sclerosis group), and 34 healthy subjects (control group). Fast spin-echo hippocampal volumetry was performed in each patient.RESULTSIn the control group, 6% (2 of 34) of subjects had MR evidence of asymmetrically small fornix and none (0 of 34) of the subjects had asymmetrically small mamillary body. In the patient population, an asymmetrically small fornix was seen in 42% of presurgical hippocampal sclerosis group, 39% (13 of 33) ipsilateral, and 3% (1 of 33) contralateral, and in 71% of the postsurgical hippocampal sclerosis group (5 of 7), all ipsilateral. In the presurgical hippocampal sclerosis group, hippocampal atrophy measured with MR was more severe in patients with an ipsilaterally small fornix than in patients without. An asymmetrically small mamillary body was found ipsilaterally in 3% (1 of 33) of the presurgical hippocampal sclerosis group and in 57% (4 of 7) of the postsurgical hippocampal sclerosis group; all patients with an asymmetrically small mamillary body in the postsurgical hippocampal sclerosis group also had an asymmetrically small fornix on the same side.CONCLUSIONIn presurgical hippocampal sclerosis patients, an asymmetrically small fornix can be seen ipsilaterally on the side of the hippocampal sclerosis; however, its low frequency, its association with severe hippocampal atrophy only, and the possibility of false-positive results limit its clinical usefulness in determining the side of the seizure focus. An asymmetrically small mamillary body is too rare to be used for presurgical location of hippocampal sclerosis. However, an asymmetrically small fornix and mamillary body are frequently seen on MR images after temporal lobectomy.     

Prevalence of asymmetry of mamillary body and fornix size on MR imaging

BACKGROUND AND PURPOSE: Mamillary body and fornix asymmetry are frequent findings on MR imaging of the brain. We sought to determine the prevalence of asymmetry of the fornix and mamillary body on MR imaging in patients with or without seizures.MATERIALS AND METHODS: MR images were retrospectively evaluated for asymmetry of the mamillary body and fornix in 178 patients who had a history of seizures, of whom 35 had suspected mesial temporal sclerosis (MTS). Additionally, 353 patients who had no limbic system pathology were reviewed. All patients were examined with spin-echo MR imaging, consisting of contiguous axial and/or coronal fluid-attenuated inversion recovery (FLAIR), T2-weighted, and sagittal T1-weighted imaging. Additionally, the patients with seizures had oblique coronal 3-mm T2-weighted, FLAIR, and 1.5-mm magnetization-preparation rapid gradient echo scanning through their temporal lobes.RESULTS: In the patients who had no limbic system pathology or seizure history, 6.5% (23/353) had MR imaging evidence of asymmetric mamillary bodies and 7.9% (28/353) had asymmetric fornix size. Asymmetry of the mamillary body and fornix size was found in 37.1% (13/35) and 34.3% (12/35), respectively, of subjects with suggested hippocampal sclerosis. The prevalence of asymmetry of the mamillary body and fornix was statistically significantly higher in the patients with MTS (χ² test, P <.0001).CONCLUSION: Although asymmetry of the mamillary bodies and fornices is highly associated with MTS, this could also be seen as a normal variation or congenital abnormality.

In the examination for the source of seizures, many tools and methods have been used. The greatest consideration has been given to the study of the focal epilepsies. As a diagnostic or research tool for generalized epilepsy, radiologic imaging has not been extremely useful other than to exclude mass lesions. Temporal lobe epilepsy is a relatively well-defined epileptic syndrome with localized electroencephalographic abnormalities, memory dysfunction, and hippocampal atrophy or mesial temporal sclerosis (MTS) on MR imaging.^1–3 MTS is the most common cause of temporal lobe epilepsy found at surgery. Several studies have confirmed that MR imaging is a reliable technique for locating the origin of temporal lobe epilepsy.^4–9 It has been previously suggested that neuronal damage in the hippocampus may cause atrophy of the ipsilateral limbic system as a result of transneuronal degeneration.¹⁰The purpose of this study was to determine the prevalence of asymmetry of the fornix and mamillary body on MR imaging in patients with or without seizures. These structures may be diminished in size in a greater proportion of patients with MTS.^11–13 We hypothesized that asymmetry of the fornix and mamillary body is not only related to MTS but also could be present as a normal variation or other cause of epilepsy.     

乳头丘脑束的MRI研究

目的 研究常规ＭＲＩ对显示正常及异常乳头丘脑束的价值。方法 对２３例健康志愿者进行了常规ＭＲ扫描，并对其乳头体和乳头丘脑束的大小及信号强度进行比较分析，同时不对２例有乳头体萎缩的病人进行相同的分析。结果在常规ＭＲＩ轴面Ｔ２ＷＩ上可以清楚显示所有正常健康志愿者的乳头丘脑束，穹窿及乳头体。正常乳头丘脑束及乳头体两侧对称，信号均匀，与穹的信号一致；异常的乳头体表现为两侧不对称，一侧明显变小，并且乳头丘脑     

X-linked adrenoleukodystrophy: the role of contrast-enhanced MR imaging in predicting disease progression

BACKGROUND AND PURPOSE: Early assignment of disease progression among patients with X-linked adrenoleukodystrophy (ALD) is critical for the appropriate selection of effective therapy. We evaluated the association between contrast enhancement on T1-weighted spin-echo MR images and disease progression. METHODS: Clinical charts of patients with X-linked ALD were reviewed for age, availability of MR images of the brain, severity of neurologic impairment, and duration and number of follow-up evaluations. Forty-three male patients with X-linked ALD had undergone multiple MR imaging examinations of the brain that consisted of at least sagittal and axial T1-weighted spin-echo, axial double-echo spin-echo, and contrast-enhanced axial T1-weighted spin-echo imaging. The MR images were reviewed for the presence of contrast enhancement. In addition, global disease burden, as shown by the double-echo spin-echo images, was assessed using a visual scoring method (Loes score). RESULTS: Enhancement was seen on the initial T1-weighted spin-echo MR images of 21 (49%) patients; 18 (86%) of the 21 patients had disease progression revealed by the follow-up evaluations based on MR imaging (Loes) and neurologic scores. No enhancement was seen on the initial T1-weighted spin-echo MR images of 22 (51%) patients; for 18 (82%) of the 22 patients, no evidence of disease progression was revealed by the follow-up evaluations. CONCLUSION: There is a very strong association between the presence of contrast enhancement on T1-weighted MR images and X-linked ALD progression based on clinical evaluation and MR imaging.     

CT and MR imaging characteristics of intravestibular lipoma

BACKGROUND AND PURPOSE: Intracranial lipomas are uncommon congenital malformations that most often are asymptomatic. A rare subset of intracranial lipomas arises within the vestibule of the inner ear, which can cause sensorineural hearing loss. We present the CT and MR imaging characteristics of lipomas within the vestibule of the inner ear and propose a pathogenetic mechanism for this malformation. METHODS: We retrospectively reviewed five cases of vestibular lipoma. T1-weighted axial conventional spin-echo and T2-weighted axial fast spin-echo sequences were performed in all five cases. Four patients underwent T1-weighted fat-saturated imaging, and one underwent CT scanning with Hounsfield units measured. RESULTS: Four female patients ranging in age from 10 to 40 years and one 26-year-old male patient had sensorineural hearing loss. Two patients had progressive high-frequency loss; one, sudden-onset high-frequency loss; and two, congenital high-frequency loss. All had lesions within the vestibule that displayed hyperintensity on T1-weighted images, isointensity to slight hypointensity on T2-weighted fast spin-echo images, hypointensity with fat saturation, and fat attenuation on CT scans. Three of the cases were associated with lipoma of the cerebellopontine angle. In none of these cases were the cerebellopontine angle and labyrinthine lipomas contiguous. CONCLUSION: Intravestibular lipoma is considered when a focal hyperintense lesion is identified within the vestibule of the inner ear on T1-weighted MR images. Lesion hypointensity on fat-saturated T1-weighted MR images verifies its lipomatous nature and separates it from intralabyrinthine hemorrhage or highly proteinaceous fluid.     

海马硬化的MRI诊断

目的 探讨海马硬化的ＭＲＩ表现和病理特征。方法 对１６例海马硬化患者进行ＭＲ横断面和垂直于海马长轴的段斜冠状面ＳＥＴ１ＷＩ、Ｔ２ＷＩ和液体衰减恢复序列（ＦＬＡＩＲ）扫描。结果 １６例患者中,１例为双侧海马硬化,１５例为单侧海马硬化（左侧９例,右侧６例）,１５例经手术病理证实,１６例１７个患侧ＭＲＩ表现为患侧海马萎缩变小;Ｔ２ＷＩ（１５侧）和ＦＬＡＩＲ成像（１７例）呈高信号;１１个患侧海马头部浅沟消     

Morphological abnormalities of limbic lobe structures in partial temporal lobe epilepsy

PURPOSE: To evaluate lesions of the different structures of the Papez circuit in association with hippocampal sclerosis. MATERIAL: and methods. 13 patients (32.1+/-8.2 y.o.) suffering from partial, temporal lobe, drug-resistant epilepsy and 20 normal volunteers (31.8+/-7.7 y.o.) were evaluated by MRI on a 1.5 T scanner (Philips): axial T1w 3D Gradient Echo acquisitions, thickness: 1.5mm. Hippocampus and cingulate gyrus volume were calculated after semi-automated segmentation of intrasulcal gray matter using the "Surgiscope Scopeplan" Elekta((R)). The thickness of the posterior column of the fornix and the thickness of the mamillary bodies were also measured. RESULTS: We found 10 cases of ipsolateral hippocampal sclerosis, 6 cases of ipsolateral atrophy of the mamillary body and 4 cases of ipsolateral atrophy of the fornix. We did not find any atrophy of the cingulate gyrus. CONCLUSION: Hippocampal sclerosis can be associated with lesions of limbic lobe structures (fornix and mamillary body), excluding the cingulate gyrus.     

Surface coil MR imaging of abdominal viscera. Part III. The pancreas

Eight healthy volunteers and 11 patients with pancreatic abnormalities were studied using a conventional body coil and a prototype magnetic resonance (MR) surface coil. Final pathologic diagnoses included carcinoma of the head (six), body (one), and tail of the pancreas (two) and chronic pancreatitis (two). In surface coil images of the volunteers, the body and tail of the pancreas was visualized in all cases but one, and the pancreatic duct was seen in five of eight cases. In-plane spatial resolution of 0.9 X 0.9 mm and 5-mm section thickness was obtained. At the same time, pancreatic surface coil images had a twofold improvement in the signal-to-noise ratio (SNR) compared with body coil images. T1-weighted spin-echo images gave greater SNR, reduced motion artifacts, provided superior anatomic detail, and offered more diagnostic information than comparable T2-weighted images. Significant abnormalities detected only by surface coil imaging included a small tumor surrounded by reactive edema and periglandular tumor invasion. This study demonstrates that surface coil imaging of the pancreas not only is feasible but provides an improved method for examining the pancreas by MR.     

MR imaging of the normal appendix in children

Our objective was to assess the ability of MR imaging in the detection of the normal appendix, and to describe the MR appearance of the normal appendix. There were 15 healthy volunteers (11 girls, 4 boys; mean age 12.3 years) who underwent MR imaging on a 1.0-T unit. The imaging protocol included axial and coronal T2-weighted ultra turbo spin-echo (UTSE)-weighted images, axial T1-weighted turbo spin-echo (TSE) and coronal short tau inversion recovery (STIR)/TSE sequences. Confidence regarding the detection was scored from 1 (high confidence) to 3 (low confidence). Thickness was measured and MR appearance described. Clinical control after 2 weeks revealed no signs or symptoms of acute appendicitis. The normal appendix was seen in 86% on T2/UTSE-weighted images and in 73% on T1/TSE-weighted images and in none on STIR/TSE images. On axial T2/UTSE-weighted images, normal appendix had a hyperintense center and a hypointense wall, and was mostly hypointense on T1/TSE-weighted images, with a mean thickness of 4.5 mm. Magnetic resonance imaging seems to be an accurate method for the assessment of the normal appendix in children; thus, MR imaging might be an alternative to CT if US examinations are inconclusive.     

Altered vertebrobasilar flow in children: angiographic,MR, and MR angiographic findings.

PURPOSETo characterize the clinical, MR, MR angiographic, and conventional angiographic findings in vertebrobasilar disease in children.METHODSEight children with posterior circulation ischemia and infarction had conventional spin-echo MR and MR angiography of the head and neck. Six patients had conventional angiography.RESULTSSix patients had alteration of vertebral or basilar artery flow void on spin-echo images. MR angiography showed all six cases of angiographically proved vertebrobasilar dissection or occlusion despite overestimating the extent of arterial abnormality in two patients. In two patients the intracranial peripheral branch cutoff shown at angiography was correctly predicted on screening MR angiography.CONCLUSIONPosterior circulation infarction in children is usually secondary to traumatic injury to the vertebrobasilar circulation. MR and MR angiography noninvasively show vertebrobasilar flow disturbances and compare favorably with angiography in documenting dissection or occlusion of the vertebrobasilar circulation. MR angiography may obviate the need for invasive angiography in these children at diagnosis and during follow-up of anticoagulation therapy.     

Diffusional anisotropy of the human brain assessed with diffusion-weighted MR: relation with normal brain development and aging.

PURPOSETo analyze diffusional anisotropy in frontal and occipital white matter of human brain quantitatively as a function of age by using diffusion-weighted MR imaging.METHODSTen neonates (< 1 month), 13 infants (1-10 months), 9 children (1-11 years), and 16 adults (20-79 years) were examined. After taking axial spin-echo images of the brain, diffusion-sensitive gradients were added parallel or perpendicular to the orientation of nerve fibers. The apparent diffusion coefficient parallel to the nerve fibers (0) and that perpendicular to the fibers (90) were computed. The anisotropic ratio (90/0) was calculated as a function of age.RESULTSAnisotropic ratios of frontal white matter were significantly larger in neonates as compared with infants, children, or adults. The ratios showed rapid decrease until 6 months and thereafter were identical in all subjects. In the occipital lobe, the ratios were also greater in neonates, but the differences from other age groups were not so prominent as in the frontal lobe. Comparing anisotropic ratios between frontal and occipital lobes, a significant difference was observed only in neonates.CONCLUSIONSDiffusion-weighted images demonstrated that the myelination process starts earlier in the occipital lobe than in the frontal lobe. The changes of diffusional anisotropy in white matter are completed within 6 months after birth. Diffusion-weighted imaging provides earlier detection of brain myelination compared with the conventional T1- and T2-weighted images.     

Diffusion-weighted MR imaging of cholesteatoma in pediatric and adult patients who have undergone middle ear surgery

OBJECTIVE: The aim of this prospective study was to determine the role of diffusion-weighted MR imaging combined with conventional MR imaging for the detection of residual or recurrent cholesteatoma in patients who have undergone middle ear surgery. SUBJECTS AND METHODS: Twenty-two patients who had undergone resection of cholesteatoma were referred for MR imaging. MR imaging (1.5 T) was performed using a diffusion-weighted single-shot spin-echo echoplanar sequence, a proton density and T2-weighted double-echo turbo spin-echo sequence, and T1-weighted spin-echo sequences before and after IV injection of gadopentetate dimeglumine (0.1 mmol/kg of body weight). An experienced reviewer evaluated the diffusion-weighted MR images for the presence of a high-signal-intensity cholesteatoma. Imaging findings were correlated with findings from surgery in 17 patients and with findings from clinical follow-up examination in five patients. RESULTS: Diffusion-weighted MR imaging combined with conventional MR imaging depicted 10 of 13 cholesteatomas (sensitivity, 77%). The three lesions that were missed were smaller than 5 mm. All the MR images of patients without cholesteatoma were correctly interpreted as showing negative findings for cholesteatoma (specificity, 100%). The positive predictive value and negative predictive value were 100% and 75%, respectively. CONCLUSION: Diffusion-weighted MR imaging combined with conventional MR imaging can confirm residual or recurrent cholesteatoma in patients who have undergone middle ear surgery by showing a high-signal-intensity lesion. Because tumors smaller than 5 mm may be missed, a diffusion-weighted MR imaging study with negative findings does not exclude small residual or recurrent cholesteatoma.     

Fast spin-echo MR in hippocampal sclerosis: correlation with pathology and surgery.

PURPOSETo identify the extent of hippocampal sclerosis in temporal lobe epilepsy with fast spin-echo MR and correlate it with histopathologic findings and surgical outcome.METHODSMR images of 30 patients with temporal lobe epilepsy and pathologically proved hippocampal sclerosis and 30 control subjects were obtained using a fast spin-echo technique with 4000/100/4 (repetition time/echo time/excitations), 16 echo train, 2- to 3-mm section thickness with interleave, 256 x 256 matrix, and 18-cm field of view. Criteria for MR diagnosis of hippocampal sclerosis included hippocampal atrophy diagnosed with MR volumetry and/or T2-weighted signal change. Hippocampal sectional areas were plotted, and T2 signal changes were topographically evaluated to identify the extent of hippocampal sclerosis, which was subsequently correlated with histopathologic findings and surgical outcome.RESULTSHippocampal sclerosis was diffuse, involving both hippocampal head and body, in 96.7% of patients (29 of 30 patients). One patient had normal MR findings. Focal hippocampal sclerosis was not seen. Histopathologic findings of hippocampal sclerosis were present in all 29 patients who had abnormal MR findings. Eighty-six percent of patients (18 of 21 patients), who were followed for at least 1 year after temporal lobectomy, were seizure free (81%, 17 of 21 patients) or significantly improved (5%, 1 of 21 patients).CONCLUSIONFast spin-echo MR enables accurate definition of the extent of hippocampal sclerosis in patients with temporal lobe epilepsy. All cases of hippocampal sclerosis identified in this study involved the hippocampus diffusely. However, leaving the posterior portion of the hippocampus during surgery does not seem to be a major factor influencing surgical outcome.     

Magnetic resonance imaging of small medullary infarctions

Small infarctions of the medulla produce typical neurologic deficits and can be clinically recognized fairly reliably. High-field magnetic resonance imaging with a 1.5 T prototype scanner successfully demonstrated very tiny medulla infarctions in three of five patients. These lesions were imaged readily by a fairly rapid (approximately 1-2 min scan time) partial-saturation technique and confirmed on multiple spin-echo images. In addition, in two cases vertebral occlusion ipsilateral to the infarction was suggested by high signal on T2 weighted spin-echo images.     

Uterine MR imaging: effects of hormonal stimulation

Magnetic resonance (MR) imaging characteristics of the uterine corpus were evaluated in 40 women divided into five physiologic categories (nine premenarchal, 13 reproductive age not taking hormones, seven reproductive age taking oral contraceptives, six reproductive age taking gonadotropin releasing hormone analog, and five postmenopausal). Images were generated using a 0.35-T magnet and a double spin-echo technique. On both T1-weighted and T2-weighted images, premenarchal and postmenopausal uteri were small and relatively featureless. Uteri on T2-weighted images in reproductive age women not taking exogenous hormones showed variations in endometrial and myometrial width, signal intensity, and T1 and T2 values during the menstrual cycle. Oral contraceptives and gonadotropin releasing hormone analogs caused endometrial atrophy and alterations in myometrial signal intensity and T1 and T2 values. A detailed gynecologic history is therefore essential in the evaluation of uterine anatomy in patients undergoing pelvic MR imaging.     

MR imaging of meniscal tears with discoid lateral meniscus

Objective: To study MR findings of meniscal tears with discoid lateral menisci (DLMs) and to evaluate the incidence and accuracy of MRI compared to arthroscopical surgery. Material and methods: MR appearances of surgically proved torn discoid lateral menisci (DLM) were studied in 57 knees (40 patients). They were all performed with a 1.5T MR before surgery. MR sequences included T1- and T2* weighted images on both coronal and sagittal planes and 3D-axial images with a slice thickness of 0.7 mm. Result: Of 57 DLMs, there were 32 complete DLMs and 25 incomplete DLMs. Twenty-five of 32 complete DLMs had tears; including seven with intrasubstance tear, five with radial tear, five with other kinds of tears and eight with severe tears involving whole meniscus. On the other hand, 13 of 25 incomplete DLMs had tears; including two with intrasubstance tear, six with radial tear, four with other kinds of tears and one with severe tears. All DLMs were correctly diagnosed on MR images. Twenty-seven of 38 tears with DLM were correctly identified on conventional 2D MR images. This yielded 71.1% sensitivity, 100% specificity and 80.7% overall accuracy. When adding axial 3D MR images to 2D MR images, 36 of 38 tears were correctly diagnosed. A combination of both techniques yielded a sensitivity of 94.7% and a specificity of 100%. Ten of 11 radial tears with DLM were correctly identified on 3D axial images, where only three of them could be diagnosed on conventional 2D images. Eight of nine intrasubstance tears were correctly identified on 3D axial images, where six of them could be diagnosed on conventional 2D images. Conclusion: DLMs had a much higher incidence of meniscal tears than normally shaped lateral menisci and MR is the only modality of choice to evaluate them before surgery. Especially 3D axial MR images were quite useful in the detection of intrasubstance and radial tears often associated with DLMs.     

Anovaginal and rectovaginal fistulas: endoluminal sonography versus endoluminal MR imaging

OBJECTIVE: The exact location of anovaginal and rectovaginal fistulas cannot be determined by physical examination and conventional techniques. The objective of our study was to compare the accuracy of endoluminal sonography and endoluminal MR imaging in revealing the location of anovaginal and rectovaginal fistulas. MATERIALS AND METHODS: Nineteen consecutive patients (age range, 28-56 years; median age, 39 years) with clinical indications of an anovaginal or rectovaginal fistula were included in our retrospective study. Endoluminal sonography was performed using a 7.5-MHz transducer. Endoluminal MR imaging was performed at 0.5 T for 10 patients and 1.5 T for nine patients; axial T2-weighted gradient-echo, coronal and sagittal T2-weighted turbo spin-echo (0.5 T), or axial and radial T2-weighted turbo spin-echo and axial T2-weighted fat saturated turbo spin-echo (1.5 T) images were obtained. For a variety of reasons, surgery of the fistula was not attempted in six of these 19 patients. The imaging findings were compared with the findings obtained during surgery in the remaining 13 patients. RESULTS: In 12 of the 13 patients, the fistula was found during surgery: seven of the fistulas were anovaginal, and five were rectovaginal. Findings of endoluminal sonography were true-positive in 11 patients, true-negative in one, and false-negative in one. Findings of endoluminal MR imaging were true-positive in 11 patients, false-negative in one, and false-positive in one. Positive predictive value for endoluminal sonography and endoluminal MR imaging were 100% and 92%, respectively. Imaging findings for anal sphincter defects were comparable. CONCLUSION: Endoluminal sonography and endoluminal MR imaging have comparable positive predictive values in revealing the location of anovaginal and rectovaginal fistulas.     

Transneuronal degeneration in patients with temporal lobe epilepsy: evaluation by MR imaging

The aim of this study was to assess the MR imaging findings of transneuronal degeneration of limbic system in the patients with temporal lobe epilepsy, and to detect the influence of surgery on the anatomy of the limbic system. Axial and coronal T1- and T2-weighted MR images were retrospectively analyzed in 34 patients with temporal lobe epilepsy, focusing on transneuronal degeneration. In 17 of the 34 patients, MR images were also analyzed after selective amygdalo-hippocampectomy. Atrophy of the fornix, mamillary body, mamillothalamic tract (MTT), and thalamus ipsilateral to the epileptic focus was demonstrated on MR images in 14.7, 17.6, 8.8, and 11.8% of the 34 patients, respectively. Focal hyperintensity of the thalamus was found on T2-weighted images in 8.8% of the 34 patients. In 17 patients who were evaluated before and after surgery, transneuronal degeneration was seen more frequently after surgery: fornix (11.8 vs 29.4%), mamillary body (11.8 vs 52.9%), MTT (5.9 vs 11.8%), and thalamus (11.8 vs 11.8%). Transneuronal degeneration of the limbic system is clearly demonstrated by MR imaging in patients with temporal lobe epilepsy, and surgical intervention induces transneuronal degeneration more frequently.     

The role of functional MR imaging in patients with ischemia in the visual cortex.

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging is based on changes in regional blood flow. The purpose of this study was to evaluate the role of fMR imaging for detection of a vascular compromised status in the occipital lobe in patients with ischemia in the visual cortex. METHODS: We performed fMR imaging in seven control subjects and seven patients with symptoms and signs of visual cortical transient ischemia and/or infarct. fMR imaging was performed using a gradient-echo sequence with the 2D fast low-angle shot technique. An axial slice including both visual cortices was selected, and stimulation of the visual cortex was performed using a red photostimulator. The number of activated pixels in each primary visual cortex area were counted and an asymmetry ratio [AR (%) = 100 x (R-L)/(R+L)/2] was calculated. Patients and control subjects underwent visual field examination, conventional MR imaging, and vascular imaging (MR angiography in all patients and control subjects, conventional catheter angiography in two patients). fMR imaging results were compared with the results of a visual field examination, conventional MR imaging, and vascular imaging. RESULTS: fMR imaging of the patients showed significant activation asymmetry (P <.05) compared with that of control subjects. Vascular abnormalities in the posterior circulation were found in all seven patients. By conventional MR imaging, five patients were found to have infarction in the occipital lobe and the remaining two patients showed no abnormality. In visual field examination, six of the seven patients showed homonymous hemi- or quadrantanopsia suggesting postchiasmic abnormalities, and the remaining patient had normal findings. fMR imaging showed decreased activity in the visual cortices corresponding to vascular abnormalities (seven of seven patients), permanent infarction (five of seven patients), or visual field defect (six of seven patients). Two patients with normal conventional MR imaging had vascular lesions in the posterior circulation, and fMR imaging showed decreased activity in the corresponding visual cortices. One patient with normal visual field examination had multifocal stenosis in the posterior cerebral artery without infarction, and fMR imaging showed decreased activity in the corresponding visual cortex. CONCLUSION: fMR imaging of the visual cortex may be a sensitive method for the detection of vascular-compromised status in the occipital lobe.