Single-voxel Proton MR Spectroscopy of the Basal Ganglia in Patients with Neurofibromatosis Type 1

PURPOSE: To demonstrate the proton MR spectroscopic characteristics of non-neoplastic focal basal ganglialesions with high signal intensity on long TR MR images in patients with neurofibromatosis type 1(NF-1), and tocompare them with those of normal-appearing basal ganglia in patients without focal lesions. MATERIALS AND METHODS: Single-voxel proton MR spectroscopy was performed in six patients with NF-1 from two families(three with andthree without non-neoplastic focal brain lesions). All six individual spectra were obtained from basal gangliawith voxel sizes of about 1 x 1 x 1 cm, three from focal pallidal lesions in patients with focal lesions and threefrom normal-appearing basal ganglia in patients without focal lesions. Spectra were acquired using a 1.5T clinicalMR imager and stimulated echo acquisition mode sequence, with the following parameters: 30 ms of echo time, 13.7ms of mixing time, and 2560 ms of repetition time. Zero and first-order phase correction was performed. RESULTS:N-acetyl aspartate(NAA)/creatine(Cr) ratios were similar between focal basal ganglia lesions and normal-appearingbasal ganglia, though the former showed slightly lower choline(Cho)/Cr ratios and slightly higher NAA/Cho ratiosthan the latter. Relatively enhanced resonances around 3.75 ppm, assigned as glutamate/glutamine, were observed inthe spectra of three focal lesions. Lipid resonances around slightly different positions were observed in all sixpatients, regardless of the presence or absence of focal lesions. CONCLUSION: Slightly decreased Cho levels andrelatively enhanced glutamate/glutamine resonances are thought to characterize the focal basal ganglia lesions ofNF-1. Different mobile lipids appear to be present in the basal ganglia of NF-1 patients, regardless of thepresence of focal lesions.

Utility of Diffusion-weighted MR Imaging in Acute Stage of Small Cerebral Infarction

PURPOSE: To demonstrate the usefulness of diffusion-weighted MR imaging(DWI) in patients with small acuteinfarction by comparing it with fast spin-echo T2-weighted MR imaging(FSE T2WI). MATERIAL AND METHOD: Weretrospectively analyzed the results of FSE T2WI in 26 consecutive patients who on DWI showed small discretehyperintensities of less than 1.5cm and whose final clinical diagnosis, within one week of clinical attack, wasacute inforction. Lacunar infarcts accounted for 24 cases and 2 small cortical infarcts for two. The onset ofsymptoms occurred within 12 hours (hyperacute stage) in two patients, within 24 hours in seven, within 3 days innine, and within one week in eight. Infarcts as seen on FSE T2WI were categorized as follows : (-) for cases ofimpossible localization with non-visualization ; (+/-) for cases of equivocal localization with faint visualizationand/or poor differentiation from combined chronic infarcts and chronic ischemic changes, or from subarachnoid CSFin cases of cortical infarction ; and (+) for cases of adequate localization with clear visualization andmoderately good differentiation from the associated brain changes, or from subarachnoid CSF in cases of corticalinfarction. These infarcts were analyzed according to the time of onset of symptoms. RESULT: For the localizationof small acute infarctions, DWI was markedly superior to the category(-), moderately superior to the category(+/-).With regard to the onset of symptoms, DWI was markedly or moderately superior to FSE T2WI in 2/2 (100%) ofhyperacute stage diagnosed within 12 hour of clinical attack, in 4/7(57%) diagnosed within 24 hours, in 5/9 (56%)diagnosed within 3 days, and in 1/8 (13%) diagnosed within 1 week(p<0.05). In 12/26 cases(46%), small acuteinfarcts were localized by DWI better than by FSE T2WI. CONCLUSION: Because the signal was unchanged or itsintensity was poor, small infarcts at the acute stage were frequently difficult to localize by FSE T2WI. Inaddition, differentiation of these from combined chronic infarcts and chronic ischemic change was poor. DWI canlocalize small acute infarcts even when the results of FSE T2WI are negative or inconclusive.

Redundant Nerve Roots of the Cauda Equina: MR Findings

PURPOSE: To evaluate MR findings of redundant nerve roots (RNR) of the cauda equina. MATERIALS AND METHODS: 17 patients with RNR were studied; eight were men and nine were women, and their ages ranged from 46 to 82 (mean63) years. Diagnoses were established on the basis of T2-weighted sagittal and coronal MRI, which showed a tortuous or coiled configuration of the nerve roots of the cauda equina. MR findings were reviewed for location, magnitude, and signal intensity of redundant nerve roots, and the relationship between magnitude of redundancy and severity of lumbar spinal canal stenosis (LSCS) was evaluated. RESULTS: In all 17 patients, MR showed moderate or severe LSCS caused by herniation or bulging of an intervertebral disc, osteophyte from the vertebral body or facet joint, thickening of the ligamentum flavum, degenerative spondylolisthesis, or a combination of these. T2-weighted sagittal and coronal MR images well clearly showed the location of RNR of the cauda equina; in 16 patients (94%), these were seen above the level of constriction of the spinal canal, and in one case, they were observed below the level of constriction. T2-weighted axial images showed the thecal sac filled with numerous nerve roots. The magnitude of RNR was mild in six cases (35%), moderate in five cases (30%), and severe in six cases (35%). Compared with normal nerve roots, the RNR signal on T2-weighted images was iso-intense. All patients with severe redundancy showed severe LSCS, but not all cases with severe LSCS showed severe redundancy. CONCLUSION: Redundant nerve roots of cauda equina were seen in relatively older patients with moderate or severe LSCS and T2-weighted MR images were accurate in identifying redundancy of nerve roots and evaluating their magnitude and location.

Imaging of the Jaw Cysts with a Dental CT Software Program: Distinction of Odontogenic Keratocysts from Other Cysts

PURPOSE: To evaluate the usefulness of a dental CT software program in the assessment of jaw cysts and in the differentiation of odontogenic keratocysts and other cysts. MATERIALS AND METHODS: Seventeen patients with proven jaw cysts (8 maxillae & 9 mandibles) were evaluated with a dental CT software program for location, locularity, the presence or absence of marginal scalloping, and height to length ratio. For the delineation of involvement or displacement of neurovascular bundles, cortical erosion, perforation or expansion, and tooth root resorption by the jaw cysts, images from this program were compared to conventional images. RESULTS: Seventeen lesions icomprised 15 odontogenic cysts (five odontogenic keratocysts, five radicular, three residual and two dentigerous cysts) and two non-odontogenic cysts (one nasopalatine duct cyst and one postoperative maxillary cyst). Images of jaw cysts obtained with the dental CT software program delineated much more clearly than conventional images the status of neurovascular bundle and cortical bone, but there was no clear difference between the two modalities in delineating tooth root erosion. Dental CT findings of five mandibular odontogenic keratocysts were scalloped margin in all, mandibular ramus involvement in four, height to length ratio below 60% in four, and multilocularity in two. The findings of the other 12 cysts (eight maxillae and four mandibles) were unilocularity in all, smooth inner margin in ten, height to length ratio below 60% in only two, and ramus involvement in none. CONCLUSION: Adental CT software program is an improved imaging modality for assessing jaw cysts ; and findings which tend to indicate odontogenic keratocysts are marginal scalloping, mandibular ramus involvement, prominent spread along the marrow space and multilocularity.