$260 Tuesday, November 8, 2005 Poster Abstracts

sensitivity of combined grey/white matter (GM/WM) analyses versus GM-only analyses. Method: The patients were 16 children (10 boys) aged 5.9 to 15.2 years (111.3 ± 2.8 years; mean ± SD) with epilepsy and FCD or neoplasia. The control group comp tired 24 normal children (12 boys), age and sex matched to the patients. MRI volumes were spatially normalised to a custom template (using SPM2 VBM), then segmented into GM and WM. The G M segment from each patient was subsequently contras- ted with the mean GM segment of the control group. Maps showing increased/decreased areas of grey matter were generated and compared with visually identified lesions and electro-clinical localisation. A similar approach was utilised in combined G M / W M analyses. Results: The GM-oniy analysis lesion detection rate was identical for FCD and neoplasia at 5/8. The best combined GM/WM technique substantially increased the yield, detecting 8/8 FCD and 6/8 neoplasia. Relative to other GM/WM combinations, increased GM/decreased WM produced the highest yield overall. Conclnsion: VBM identified abnormalities concordant with visually identified lesions. As FCD is a disorder involving both GM and WM, combined G M / W M VBM analysis is essential and superior to GM-only methods.

0632 Magnetic ~eSonanCe inmging and spectroscopy in Adult-Onset Citrullinaemia

Lim, CCT ~,2, Wong, YC 1, Tan, K 1 , Xu, MS 1, Au, WL 1, Umapathi, T ~, Hui, F ~. iNational Neuroscience Institute, SNgapore; 2National University of Singapore, Singapore

Background: Citrullinemia is a rare inherited disorder caused by an enzyme defect in the urea cycle, leading to accumulation of plasma ammonia, citrulline, and glutamate. We present the diffusion-weighted M R imaging (DWI) and spectroscopy (MRS) findings in two patient with undiagnosed adult-onset citrullinenffa. Method: A 25-year-old man with recurrent coma, and a 27-year-old man with giddiness, altered mental state and psychiatric ssanptoms underwent MRS (single-voxel point resolved spectroscopy TR/TE 1500/30 ms) and DWI (echo-planar imaging, 3 orthogonal directions, b - 1000). Results: MRS revealed decreased N A A and elevated glutamate/ glutanffne levels in the basal ganglia. DWI showed hyperintensities in the basal ganglia, cingnlated gyms, insula, and in the depths of the cortical sulci. Both patients had extremely elevated plasma ammonia level, with raised citrulline level and absence of argininosuccinic acid. One patient died before blood test results were known. Conclusion: MRS can detect abnormal metabolite accumulation in the brain, and DWI can delineate the extent of involvement in citru- llinemJa. Although rare, tiffs characteristic pattern of neuroimaging should be recognised.

0633 Diffusion tensor MR tractography visualizes corticospinal tract degeneration in Amyotrophie Lateral Sclerosis

LhI1, CCT 1,z, Cheng, SliT 1, Yin, H 3, Lin, M 3, Guo, XG 3. 2Nationai Neuroscience Institute, Singapore; 2National University of Singapore, Singapore; 3Chinese PLA General Hospital, Beijing, China

Background: Motor neuron damage and cortical spinal tract (CST) degeneration are pathological features of amyotrophic lateral sclerosis (ALS). Recently, several reports have found that diffusion tensor M R imaging (DTI), measuring fractional anisotropy (FA) and mean diffusivity (MD), was useful in diagnosing upper motor neuron involvement. We applied a novel tractography technique that measures the fiber volume of the CST. Method: Eight ALS patients were compared to normal controls. Fractional anisotropy (FA) and mean diffusivity (MD), were measured at the posterior limb of the internal capsule (PIC), fiber tracking using

fiber assignment by continuous tracking (FACT) was performed to quantify the fiber volume of the CST and the posterior thalamic radiation (PTR), a non-motor tract. Results: Patients showed significantly lower FA (p < 0.001) but not MD (p - 0.0878) titan controls in the PIC. In the CST, the volume of fibers was decreased in the CST compared to nomtal controls (lJ - 0.0274) but not the PTR (lJ -- 0.3171). Conehision: FA and fiber tracking can visualise and measure mxonal degeneration in the CST in ALS, DTI markers of upper motor neuron damage in ALS have the potential to be used as surrogate markers in measuring disease progression, which would be helpful in future studies and clinical trials.

0634 A case series of conduction aphasia with neuroimaging correlation.

I.iu, K 1, Wang, K 2,Dai, D 1 , Wong, K 1 , Wong, A 1 , Chan, y2, Woo, j1. 1Division of Geriatric and Neurology" of Department of Medicine and Therapeutics, Prince of Wales Hospital, Shatin, Hong Kong, People's Republic of China; 2Diagnostic Radiology and Organ Imaging Department Prince of Wales Hospital, Shatin, Hong Kong, People's Republic of China

Baekg~ouud: The pathophysiology of the syndrome of conduction aphasia had been viewed as a discom~ection between posterior and the anterior language areas. The arcuate fascicuhis(AF ) has been thought to be anatomical linkage between Wernicke's area and Broca's area. However, its actual role in the syndrome remains difficult to be clarified. Methods: A retrospective case series of 6 patients with the clinical syndrome of conduction aphasia were studied for the presentation, aetiology and associated clinical features. All patients underwent CT brain, Three had SPECI" scan, Three had MRI of brain in which two .were also examined by M R diffusion tensor tractography to delineate the area of destruction in the white matter. Results: Different modalities including SPECT can help to locate the anatomical lesion and functional deficit area in patients having con- duction aphasia. M R diffusion tensor can clearly define the interrup- tion of the AF in some patients. A video of the 2 patients is shown. Conehision: Presentation of conduction aphasia as expressive aphasia while CT shows a posteriorly situated lesion; clinically often misdiagnosed as expressive Broca's dysphasia;2) motor deficits are usually minimal; 3) a mJsdiagnosis of dementia can occur; 4) Neuroimaging with M R diffusion can demonstrate the involvement of 'AF" in the syndrome; 5) Conduction aphasia typically has deficits in the expressive , repetitive component of speech and improves on repetitive testing; 6) some patients presents also with visual agnosia as demonstrated on one of our patients; 7) longer term follow up of these patients is required to morfitor for cognitive deterioration and development of dementing features.

0635 Combined DC-Magnetoencephalography and time-resolved near- hd~a~ed spectroscopy: An app~oadl to etla~acte~ise Neurovascula~ Coupling non-invaSively in the huInan b~ain

Mackert, BM l, Leistner, S ~, Sander, T ~, Liebert, A ~, Wabnitz, H ~, Burghoff, M a, Macdonald, R ~, Trahms, L ~, Curio, G ~ . 1Department of Neurology, Campus Benjamin Franklin, Charite - University Medicine Berlin, Germany; ~Physikalisch-Technische Bundesanstalt, Institute Berlin, Germany

Most functional brain imaging methods detect neuronal activa- tion indirectly through the accompanying neurovascular/metabolic response. Awareness, however, is increasing that the link between neuronal and vascular/metabolic task-related responses is not a simple linear transform. As DC- magnetoencephalography (DC-MEG) measures low amplitude neuronal activity in the time scale of vascular responses and time-resolved near-infrared spectroscopy (trNIRS)