PURPOSE: Functional MR imaging is the method of demonstrating changes in regional cerebral blood flow produced by sensory, motor, and any other tasks. Functional MR of visual cortex os performed as a patient stares a photic stimulation, so adaptable photic stimulation is necessary. The purpose of this study to evaluate whether the size of photic stimulation can affect the degree of visual cortex activation. MATERIALS AND METHODS: Functional MR imaging was performed in 5 volunteers with normal visual acuity. Photic stimulator was made by 39 light-emitting diodes on a plate ,operating at 8 Hz. The sizes of photic stimulator were full field, half field and focal central field. The MR imager was Siemens 1.5-T Magenton Vision system, using standard head coil. Functional MRI utilized EPI sequence (TR/TE=1.0/51. 0msec, matrix No.=98x128, slice thickness=8mm) with 3sets of 6 imaging during stimulation and 6 imaging during stimulation and 6 imaging during rest, all 36 scanning were obtained. Activated images were obtained using postprocessing software(statistical analysis by Z-zone, and these images were combined with T-1 weighted anatomical images. The activated signals were quantified by numbering the activated pixels, and activation index was obtained by dividing the pixel number of each stimulator size with the sum of the pixel number of 3 study using 3 kinds of stimulators. The correlation between the activation index and the stimulation size was analysed. RESULTS: Mean increase of signal intensities on the activation area using full field photic stimulator was about 9.6%. The activation index was greatest on full field. second on half field and smallest in focal central field in 4, The index of half field was greater than that of full field in 1. The ranges of activation index were full field 43-73%(mean 55%), half field 22-40%(mean 32%), and focal central field 5-24%(13%). CONCLUSION: The degree of visual cortex activation increases with the size of photic stimulator.
Head ; Humans ; Magnetic Resonance Imaging* ; Photic Stimulation ; Visual Acuity ; Visual Cortex* ; Volunteers

BACKGROUND: The natural history of intracranial arterial stenoses, particularly the middle cerebral artery (MCA), remains unknown. To monitor the progression of MCA stenoses over time, we conducted a prospective study using transcranial Doppler (TCD) study. METHODS: We performed TCD study on 14 stroke patients with angiographically documented MCA stenosis. The findings were compared to repeat TCD studies conducted more than 2 months apart with respect to changes in mean flow velocities (mFV) of the stenotic segment. RESULTS: Fourteen patients (13 men and 1 woman; mean age, 51 years) with 18 MCA stenoses were identified. During a mean follow-up period of 7.7 months, mFV corresponding to the areas of stenosis was increased in 7 (39%) arteries, demonstrating TCD evidence of stenosis progression. Three of those with MCA stenosis progression detected on TCD were confirmed with magnetic resonance angiogram. Flow velocities were not significantly changed in the remainder of the stenotic MCAs. Two patients whose MCA stenosis progressed also showed the suspicious development of new stenosis (mFV increase 119% and 41%, respectively) in the initially normal contralateral MCA. CONCLUSION: These findings suggest that MCA stenoses are dynamic lesions, and that they can evolve and cause further reductions of the arterial diameters after relatively short periods of time. TCD can noninvasively detect these changes.
Arteries ; Constriction, Pathologic* ; Female ; Follow-Up Studies* ; Humans ; Male ; Middle Cerebral Artery* ; Natural History ; Prospective Studies ; Stroke ; Ultrasonography, Doppler, Transcranial*

Acute necrotizing encephalopathy is a recently established disease entity, proposed by Mizuguchi et al in 1995, that shows a characteristic symmetric and multifocal involvement of both thalamus, brainstem tegmentum, cerebral periventricular white matter, and cerebellar medulla. It is known to be prevalent in Japan and other Far Ease countries. The etiology of the acute necrotizing encephalopathy remains unknown. The typical course of acute necrotizing encephalopathy is the development of the irreversible neurologic symptoms related to brain lesions. The diagnosis can be made on the basis of the combination of a typical clinical profile and characteristic radiologic findings. We experienced a first case of acute necrotizing encephalopathy in a 9 month old boy in Korea. We report this case with the brief review of related literatures.
Brain ; Brain Stem ; Diagnosis ; Humans ; Infant ; Japan ; Korea ; Male ; Neurologic Manifestations ; Thalamus

Neurilemmomas of the extremities are nerve sheath tumors involving peripheral nerves of the extremities. We analyzed MR images of 16 surgically proved tumors in 12 patients and compared the MR images with gross pathologic specimens in two tumors (2/16). Spin echo T1-weighted images were obtained in all the patients but T2-weighted images were obtained in six patients with a gradient echo technique. Gadolinium dimeglumine enhanced T1-weighted images were obtained in 11 patients (15/16). Signal on T1-weighted images was iso or slightly higher than that of the adjacent muscles. Signal on T2-weighted images ranged from homogeneous high to heterogeneous. After Gadolinium injection, all the 15 tumors showed enhancement. Small sized tumors were enhanced homogeneously but there was a tendency tobe enhanced heterogeneously to the central portion with peripheral rim enhancement as the size of the tumors increased. Pathologically, the enhanced portion was correlated the with solid protion was correlated the with solid portion of the tumors. Also encapsulation of the mass (12/16), suspended nerve strings (9/16) and bony erosion (1/16) were detected. MR characteristics of neurilemmoma include heterogeniety on enhanced T1 and T2 weighted images, encapsulation, and suspended nerve strings. Signal heterogeneity on enhanced T1 and T2 weignted images may be attributed to the variable cellularity, cystic changes, vascularity and focal hemorrhage of the tumors.
Extremities ; Gadolinium ; Hemorrhage ; Humans ; Magnetic Resonance Imaging* ; Muscles ; Nerve Sheath Neoplasms ; Neurilemmoma* ; Peripheral Nerves ; Population Characteristics

Neurilemmomas of the extremities are nerve sheath tumors involving peripheral nerves of the extremities. We analyzed MR images of 16 surgically proved tumors in 12 patients and compared the MR images with gross pathologic specimens in two tumors (2/16). Spin echo T1-weighted images were obtained in all the patients but T2-weighted images were obtained in six patients with a gradient echo technique. Gadolinium dimeglumine enhanced T1-weighted images were obtained in 11 patients (15/16). Signal on T1-weighted images was iso or slightly higher than that of the adjacent muscles. Signal on T2-weighted images ranged from homogeneous high to heterogeneous. After Gadolinium injection, all the 15 tumors showed enhancement. Small sized tumors were enhanced homogeneously but there was a tendency tobe enhanced heterogeneously to the central portion with peripheral rim enhancement as the size of the tumors increased. Pathologically, the enhanced portion was correlated the with solid protion was correlated the with solid portion of the tumors. Also encapsulation of the mass (12/16), suspended nerve strings (9/16) and bony erosion (1/16) were detected. MR characteristics of neurilemmoma include heterogeniety on enhanced T1 and T2 weighted images, encapsulation, and suspended nerve strings. Signal heterogeneity on enhanced T1 and T2 weignted images may be attributed to the variable cellularity, cystic changes, vascularity and focal hemorrhage of the tumors.
Extremities ; Gadolinium ; Hemorrhage ; Humans ; Magnetic Resonance Imaging* ; Muscles ; Nerve Sheath Neoplasms ; Neurilemmoma* ; Peripheral Nerves ; Population Characteristics

PURPOSE: The purpose of this study is to find helpful MR findings for predicting a naplastic oligodendrogl lomas. MATERIALS AND METHODS: Retrospective analysis of 46 MR images and 37 CT scans was performed for 46 patients with pathologically-proven cerebral oligodendrogliomas. A neuropathologist graded the tumors as one of low-grade (n=16), intermediate-grade (n=l2), or anaplastic oligodendroglioma (n=18). MR imaging features were retrospectively analysed with respect to histologic grading of the tumors. RESULTS: Contrast enhancement was observed always in anaplastic group (17 /17), in a portion of intermediate-grade group (4/10) but not in low-grade group (0/14). Peritumoral edema was observed infrequently in anaplastic group (4/18) or intermediate-grade group (1/12). Cystic changes (25/46) or calcifications on CT Scans (14/37) were not related with histologic grading. Grossly identifiable hemorrhage was rare in this series (2/46). Among the various imaging features, only tumor enhancement and peritumoral edema were statistically significant for trend test (p<0.05). CONCLUSION: When considering the diagnosis of oligodendrogliomas, the presence of contrast enhancement or peritumoral edema is a helpful features suggesting anaplastic oligodendrogliomas.
Diagnosis ; Edema ; Hemorrhage ; Humans ; Loma ; Magnetic Resonance Imaging ; Oligodendroglioma* ; Retrospective Studies ; Tomography, X-Ray Computed

To evaluate the radiographic characteristics of osteochondritis dissecans (OCD) and useful parameter for predicting mechanical stability, we retrospectively analysed 26 plain radiographic examinations and seven MR imagings in 28 cases of OCD in 24 patients. Typical radiologic findings were osteochondral defect with sclerotic rim of variable thickeness and osteochondral fragment. Sites of osteochondral defect were medial (35.9%) or lateral (32%) femoral chondyle and medial (7.1%) or lateral (25%) side of talar dome. Sclerotic rim was seen in 24 cases (85%) and osteochondral fragments including nine loose bodies were seen in 21 cases (75%). The size of osteochondral defect with unstable fragment (average 2.05cm) and loose body (2.04cm) in the knee joint were similar to, but statistically larger than that with stable fragment (1.35cm). All osteochondral defects were well visualized on MR images. Abnormalities of articular cartilage and effusion in the interface between the parent bone and fragment were seem in five cases of which there were confirmed three unstable cases arthroscopically. We conclude that size of defect may be a good parameter for predicting mechanical stability and MRI may be useful in the diagnosis of OCD and determining the methods of treatment.
Cartilage, Articular ; Diagnosis ; Humans ; Knee Joint ; Magnetic Resonance Imaging ; Osteochondritis Dissecans* ; Osteochondritis* ; Parents ; Retrospective Studies

Magnetic resonance (MR) images of 14 consecutive patients with pathologically proven primary intracranial lymphoma were reviewed. All patients had a brain MR imaging before any treatment and were immunologically competent. MR images were acquired using 2.07 (n= 6) or 0.57 (n= 8) machine. The MR images were reviewed regarding the location, multiplicity, size, signal intensity, margin, shape, and the extent of surrounding edema of the lesion. Seven patients had multiple lesions, 2 to 4 in number. A total of 26 lesions was found; 25 were parenchymal lesions and one was dural lesion. The location of tumor was either central (r= 11) or peripheral (n= 14). The size of tumor was variable ranging from 0.6cm to 6.0cm in its maximal diameter. The tumors were isointense (n= 19) or hypointense (n= 7) relative to gray matter on T1-weighted images, isointense (n= 24) or hyperintense (n=2) on proton-density weighted images, and isointense (n= 21) or hyperintense (n= 5) on 78-weighted images. On gadolinium-enhanced T1-weighted images of 13 patients strong enhancement was seen in 22 of 23 lesions. Nineteen lesions showed smooth, well-defined margin, whereas remaining 7 lesions showed irregular, ill-defined margin. The shape of the tumor was diverse; round of ovoid (n= 15), lobulated (n= 9), or short linear (n= 2). These results suggest that one should consider the diagnosis of CNS lymphoma in cases with single or multiple masses that abut CSF space and show iso-or similar intensity to gray matter with strong enhancement on MR images.
Brain ; Diagnosis ; Edema ; Gray Matter ; Humans ; Lymphoma* ; Magnetic Resonance Imaging*

PURPOSE: To describe MR findings of cerebral venous sinus thrombosis. MATERIALS AND METHODS: We reviewed 11 MR images of six patients with cerebral venous sinus thrombosis. The MR images were retrospectively analyzed in terms of location and signal intensity of the thrombi, parenchymal lesions such as hemorrhage and edema, and changes in follow-up study obtained in 4 patients. RESULTS: The thrombus in venous sinus was visualized on MRI in all six patients. The most frequently involved sites were superior sagittal sinus(n=4) and left transvere sinus(n=4). Signal intensity of the thrombus was isointense or hyperintense on both T1 - and T2-weighted images with loss of normal signal void of the sinus on all sequences in all patients. Parenchymal lesion was present in five of six cases, manifested as local hemorrhage in three and edema in three cases(one case overlapped). Local edema seen in three patients was completely resolved on follow-up study of seven to 29 days intervals. CONCLUSION: It is concluded that iso- or high signal intensity with loss of signal void in venous sinus is virtually diagnostic of venous sinus thromosis. If there are local parenchymal lesions such as hemorrhage and/or edema of unknown causes, cerebral venous sinus thrombosis should be included in differential diagnosis.
Diagnosis, Differential ; Edema ; Follow-Up Studies ; Hemorrhage ; Humans ; Magnetic Resonance Imaging ; Retrospective Studies ; Sinus Thrombosis, Intracranial* ; Thrombosis

PURPOSE: To elucidate the incidence of Gd-DTPA enhancement of the optic nerve/sheath complex (ONC) in patients with various ophthalmopathies using fat-suppression MRI. MATERIALS AND METHODS: Orbit MRI with fat-suppression technique (ChemSat) was performed in 58 patients with normal and various orbital lesions. The fat-suppression MR was done with and without Gd-DTPA injection in all cases. MR findings were reviewed retrospectively in a blind fashion with respect to presence or absence of contrast enhancement of the O NC. RESULTS: Contrast enhancement of the ONC was seen in 86% (6/7) of cavernous sinus lesions, 80% (8/10) of intraconal lesions excluding the ONC, 57% (16/28) of ONC lesions, 38% (3/8) of ocular lesions, and 2% (1/55) of normal orbits. The ONC enhancement was the most common in optic nerve/sheath tumors (10/10), and pseudotumors (6/6), cavernous sinus dural arteriovenous malformations (3/3) and cavernous sinus thrombosis (2/2), and less frequently seen in optic neuritis (3/14). CONCLUSION: Enhancement of the ONC may be seen in lesions of the cavernous sinusand orbit other than optic nerve/sheath lesion.
Arteriovenous Malformations ; Cavernous Sinus ; Cavernous Sinus Thrombosis ; Gadolinium DTPA ; Humans ; Incidence* ; Magnetic Resonance Imaging* ; Optic Neuritis ; Orbit* ; Retrospective Studies