What remains after transient global amnesia (TGA)? An ultra-high field 7 T magnetic resonance imaging study of the hippocampus.

BACKGROUND AND PURPOSE: The aim was to study whether ultra-high field 7 T magnetic resonance imaging (MRI) can demonstrate chronic focal defects in the hippocampus corresponding to the former acute diffusion-weighted imaging (DWI) lesions and to assess chronic T2-hyperintense hippocampal lesion load in transient global amnesia (TGA) patients. METHODS: Follow-up of 7 T MRI of the hippocampus was performed in 13 patients with documented hippocampal DWI lesions (detected via 3 T MRI) after acute TGA. The location of the DWI lesions was transformed to 7 T T2 images after data co-registration. Additionally, the T2-hyperintense lesion load was estimated in each patient and compared with that of 13 healthy controls. RESULTS: Magnetic resonance imaging (7 T) was performed after a median of 4 months. No structural abnormality at the site of the previous TGA lesion was observed in any case. None of the controls showed DWI lesions. There was no significant difference between patients and controls concerning the number (P = 0.67) or volume (P = 0.45) of T2-hyperintense hippocampal lesions. CONCLUSIONS: Diffusion-weighted imaging lesions in patients with TGA do not provoke any visible sequelae and do not result in hippocampal cavities. The occurrence of incidental hippocampal T2 lesions after TGA is not more frequent than in controls.

Reduced diffusion in a subset of acute MS lesions: a serial multiparametric MRI study.

BACKGROUND AND PURPOSE: MRI studies have focused on newly developing MS lesions to characterize the early pathology of the disease. DWI is highly sensitive to acute and chronic tissue changes in MS. We characterized the development of acute MS lesions by using DWI in a multiparametric MRI protocol. MATERIALS AND METHODS: Seventy-two consecutive patients presenting with a new symptom with definite MS or a CIS suggestive of central nervous system demyelination were screened with MRI. Patients who showed an acute MRI lesion with a reduction of ADC were studied with serial MRI for up to 4 months after presentation. RESULTS: Ten of 72 screened patients who showed a lesion with a reduced ADC were each examined 4-7 times, resulting in 52 examinations in total. We identified a characteristic sequence of signal-intensity changes: 1) days 0-7: slight T2 hyperintensity and prominent ADC reduction (maximum, -66%), faint or no enhancement on postcontrast T1-weighted images; 2) days 7-10: prominent T2 hyperintensity and contrast enhancement, ADC normalization/pseudonormalization; 3) up to 4 weeks: elevated ADC values, prominent enhancement on postcontrast images; 4) after 4 weeks: partial reversibility of T2 hyperintensity, ADC elevation, and resolution of contrast enhancement. CONCLUSIONS: In a subgroup of patients with MS presenting soon after new symptom onset, a transient reduction of the ADC delineated a short and very early phase of MS lesion evolution. Subsequent pseudonormalization of the ADC occurred along with signs of the development of vasogenic edema.

Clinicotopographical correlation of corticospinal tract stroke: a color-coded diffusion tensor imaging study.

UNLABELLED: Background- Small capsular strokes are difficult to assess with regard to the precise location and the extent of pyramidal tract damage with conventional brain imaging. Color-coded diffusion tensor imaging (CDTI) provides a means to visualize the course of the corticospinal tract within the white matter. In addition to T2-weighted MRI, diffusion-weighted MRI and CDTI were used to analyze the topographical patterns of small lacunar corticospinal tract strokes. METHODS: We examined 15 patients with pyramidal tract strokes in the subacute phase (days 3 to 7). Lesions were identified on diffusion-weighted MRI and superimposed on CDTI images. The anatomic location and pattern of the lesion were visualized on CDTI with regard to the corticospinal tract and subsequently compared with the clinical presentation. In addition, infarct areas were evaluated with quantitative parameters: mean diffusivity and lattice anisotropy index of lesions were determined. RESULTS: We identified 5 different patterns of corticospinal tract stroke falling into 2 clinical subgroups: (1) those with marked deficits and minor improvement (6/15) and (2) those with good recovery (9/15). Group 1 had long lesions centered in the pyramidal tract, involving the basal ganglia (anterior choroidal artery); group 2 lesions were very small and/or located anteriorly and medially (periventricular anterior choroidal artery territory; thalamogeniculate, tuberothalamic, and lateral striate branches). Lesions showed a significant increase of mean diffusivity and decrease of lattice anisotropy. CONCLUSIONS: CDTI allows in vivo differentiation of distinct subcortical stroke subtypes. Improved anatomic definition of lesion localization using CDTI may help in better establishing the prognosis for patients after subcortical stroke.

A diffusion-weighted MRI study of acute ischemic distal arm paresis.

OBJECTIVE: To study the site of the ischemic lesion, the underlying cause, and the prognosis of acute stroke with distal arm paresis. METHOD: The authors investigated 14 consecutive patients with acute distal arm paresis with a diagnostic stroke protocol and early MRI, including T2-weighted images, diffusion-weighted images (DWI), and perfusion-weighted images (PWI). Acute DWI lesions were shown on coregistered T2-weighted images for analysis of the exact anatomic lesion location. RESULTS: Patients showed a uniform (7/14), radial (3/14), or ulnar (4/14) distribution of hand paresis. In all cases, DWI identified small lesions located in the motor cortex. Topographic lesion analysis, which was correlated with the clinical deficit, showed lesions centered in the hand knob area (2/14), involving the lateral (6/14), medial (4/14), or both (2/14) borders of the hand knob. PWI (calculated time-to-peak maps) did not show a mismatch between the DWI lesion and the PWI lesion. In six patients, DWI and PWI lesions were identical in size and location; no definite perfusion deficit was seen in eight patients. In agreement with PWI, no patient showed clinical worsening, and six patients recovered completely within a week. Further investigations showed a potential source of embolus in 11 cases. CONCLUSIONS: Acute ischemic distal arm paresis is usually caused by a small cortical lesion in the motor hand cortex attributable to distal Rolandic artery obstruction without additional tissue at risk. These findings confirm the observed benign clinical course and its apparent main cause (artery-to-artery or cardiac embolism).

KAMEDIN: a telemedicine system for computer supported cooperative work and remote image analysis in radiology.

The software system KAMEDIN (Kooperatives Arbeiten und MEdizinische Diagnostik auf Innovativen Netzen) is a multimedia telemedicine system for exchange, cooperative diagnostics, and remote analysis of digital medical image data. It provides components for visualisation, processing, and synchronised audio-visual discussion of medical images. Techniques of computer supported cooperative work (CSCW) synchronise user interactions during a teleconference. Visibility of both local and remote cursor on the conference workstations facilitates telepointing and reinforces the conference partner's telepresence. Audio communication during teleconferences is supported by an integrated audio component. Furthermore, brain tissue segmentation with artificial neural networks can be performed on an external supercomputer as a remote image analysis procedure. KAMEDIN is designed as a low cost CSCW tool for ISDN based telecommunication. However it can be used on any TCP/IP supporting network. In a field test, KAMEDIN was installed in 15 clinics and medical departments to validate the systems' usability. The telemedicine system KAMEDIN has been developed, tested, and evaluated within a research project sponsored by German Telekom.

Image transfer and computer-supported cooperative diagnosis.

The KAMEDIN system was designed as a low-cost communication tool as part of a computer-supported cooperative work project that included synchronized user interaction, telepointing and audioconferencing. During a five-month field trial, it was used for medical image transfer and cooperative diagnosis in 14 clinics and medical departments in Germany. During the field test, 297 teleconsultations were performed via ISDN and 875 MByte of data were transferred. An image compression ratio of 2-3 was obtained, so that the total quantity of data transferred corresponded to 14,000-21,000 magnetic resonance images or 3500-5250 computerized tomography images. Furthermore, 694 local sessions were conducted for the preparation of teleconsultations and the review of transferred images. Participants learned to handle the KAMEDIN system in a few hours. This was mainly owing to the design of the user-oriented graphical user interface and the restriction of the system to a set of essential image-processing functions.