Time-variant analysis of fast-fMRI and dynamic contrast agent MRI sequences as examples of 4-dimensional image analysis.

OBJECTIVES: Image sequences with time-varying information content need appropriate analysis strategies. The exploration of directed information transfer (interactions) between neuronal assemblies is one of the most important aims of current functional MRI (fMRI) analysis. Additionally, we examined perfusion maps in dynamic contrast agent MRI sequences of stroke patients. In this investigation, the focus centers on distinguishing between brain areas with normal and reduced perfusion on the basis of the dynamics of contrast agent inflow and washout. METHODS: Fast fMRI sequences were analyzed with time-variant Granger causality (tvGC). The tvGC is based on a time-variant autoregressive model and is used for the quantification of the directed information transfer between activated brain areas. Generalized Dynamic Neural Networks (GDNN) with time-variant weights were applied on dynamic contrast agent MRI sequences as a nonlinear operator in order to enhance differences in the signal courses of pixels of normal and injured tissues. RESULTS: A simple motor task (self-paced finger tapping) is used in an fMRI design to investigate directed interactions between defined brain areas. A significant information transfer can be determined for the direction primary motor cortex to supplementary motor area during a short time period of about five seconds after stimulus. The analysis of dynamic contrast agent MRI sequences demonstrates that the trained GDNN enables a reliable tissue classification. Three classes are of interest: normal tissue, tissue at risk for death, and dead tissue. CONCLUSIONS: The time-variant multivariate analysis of directed information transfer derived from fMRI sequences and the computation of perfusion maps by GDNN demonstrate that dynamic analysis methods are essential tools for 4D image analysis.

High resolution susceptibility weighted MR-imaging of brain tumors during the application of a gaseous agent.

PURPOSE: To employ a high resolution blood oxygenation level dependent (BOLD) method called susceptibility weighted imaging (SWI) together with the breathing of carbogen to investigate the response of cerebral tumors to this breathing gas and to assess tumor anatomy at high resolution. METHODS: Five patients with cerebral tumors (four glioblastoma multiforme, one astrocytoma [WHO grade II]) were studied using a susceptibility weighted 3D gradient echo, first order velocity compensated sequence (TE = 45 ms, TR = 67 ms, alpha = 25 degrees , FOV = 256 x 192 x 64 mm(3), typical matrix = 512 x 192 x 64), on a 1.5 T MR scanner while they were breathing air and carbogen. Signal changes between the two breathing conditions were investigated. RESULTS: The glioblastomas showed strong but heterogeneous signal changes between carbogen and air breathing, with changes between + 22.4 +/- 4.9 % at the perimeter of the tumors and - 5.0 +/- 0.4 % in peritumoral areas that appeared hyperintense on T (2)-weighted images. The astrocytoma displayed a signal decrease during carbogen breathing (- 4.1 +/- 0.1 % to - 6.8 +/- 0.3 % in peritumoral areas that correspond to hyperintense regions on T (2)-weighted images, and - 3.1 +/- 0.1 % in the tumor-center). CONCLUSIONS: SWI provides high resolution images of cerebral anatomy and venous vascularization. Combined with hypercapnia it allows for regional assessment of tumor activity.

Apparent diffusion coefficient decreases and magnetic resonance imaging perfusion parameters are associated in ischemic tissue of acute stroke patients.

Perfusion-and diffusion-weighted magnetic resonance imaging scans are thought to allow the characterization of tissue at risk of infarction. The authors tested the hypothesis that the apparent diffusion coefficient (ADC) decrease should be associated with the severity of the perfusion deficit in ischemic tissue of acute stroke patients. Perfusion-and diffusion-weighted scans were performed in 11 patients with sudden onset of neurologic deficits within the last 6 hours and T2-weighted magnetic resonance imaging scans were obtained after 6 days. Parameter images of the maximum of the contrast agent concentration, time to peak, relative cerebral blood volume, relative cerebral blood flow, and relative mean transit time were computed from the perfusion-weighted data. A threshold function was used to identify tissue volumes with stepwise ADC decreases. An onionlike distribution of successively decreasing ADC values was found, with the lowest ADC in the center of the ischemic region. Correspondingly, tissue perfusion decreased progressively from the periphery toward the ischemic core. This effect was most pronounced in the time-to-peak maps, with a linear association between ADC decrease and time-to-peak increase. Apparent diffusion coefficient values decreased from the periphery toward the ischemic core, and this distribution of ADC values was strongly associated with the severity of the perfusion deficit.

Isolated voluntary facial paresis due to pontine ischemia.

We describe a patient with isolated voluntary facial paresis due to a unilateral lacunar lesion in the contralateral mediodorsal middle base of the pons. Transcranial magnetic stimulation confirmed the involvement of supranuclear corticofacial tract fibers and sparing of the corticolingual and corticospinal connections. This observation demonstrates that the fibers conveying voluntary orofacial activation descend mediodorsally at the level of the middle pons and that the fibers conveying emotional activation may be assumed to converge below this level.

Dysarthria in acute ischemic stroke: lesion topography, clinicoradiologic correlation, and etiology.

BACKGROUND AND PURPOSE: Although dysarthria is a frequent symptom in cerebral ischemia, there is little information on its anatomic specificity, spectrum of associated clinical characteristics, and etiologic mechanisms. METHODS: An investigation of 68 consecutive patients with sudden onset of dysarthria due to a single infarction confirmed by MRI or CT was conducted. RESULTS: Dysarthria was associated with a classic lacunar stroke syndrome in 52.9% of patients. Isolated dysarthria and dysarthria-central facial and lingual paresis occurred in 2.9% (n = 2) and 10.3% (n = 7), respectively. Dysarthria-clumsy hand syndrome was observed in 11.7% (n = 8) of patients and associated with pure motor hemiparesis and/or ataxic hemiparesis in 27.9% (n = 19). The lesions were due to small-vessel disease in 52.9% (n = 36), to cardioembolism in 11.8% (n = 8), and to large-vessel disease in only 4.4% (n = 3) of cases. Infarctions were located in the lower part of the primary motor cortex (5.9%; n = 4), middle part of the centrum semiovale (23.5%; n = 16), genu and ventral part of the dorsal segment of the internal capsule (8.8%; n = 6), cerebral peduncle (1.5%; n = 1), base of the pons (30.9%; n = 21), and ventral pontomedullary junction (1.5%; n = 1). Isolated cerebellar infarctions affected the rostral paravermal region in the superior cerebellar artery territory. CONCLUSIONS: Extracerebellar infarcts causing dysarthria were located in all patients along the course of the pyramidal tract. This finding correlates with the frequent occurrence of associated pyramidal tract signs in 90.7% (n = 62) of patients. Isolated cerebellar infarcts leading to dysarthria were in all cases located in the territory of the superior cerebellar artery.

Ipsilateral facial weakness in upper medullary infarction-supranuclear or infranuclear origin?

We describe two patients with upper medullary infarctions showing ipsilateral facial weakness and relative sparing of the upper facial muscles. Electrophysiological follow-up using transcranial magnetic stimulation of the motor cortex in combination with stimulation of the peripheral facial nerve disclosed a supranuclear (corticofacial) tract lesion in one patient and a partial nuclear/infranuclear intra-axial facial nerve lesion in another.

Abolished laser-evoked potentials and normal blink reflex in midlateral medullary infarction.

We investigated two patients presenting with the rare finding of almost isolated hemianalgesia with a sensory level on the contralateral side sparing the face. Clinical findings, electrophysiological studies (absent laser-evoked pain-related somatosensory potentials, normal electrically evoked somatosensory potentials, magnetically evoked potentials, and blink reflexes), and magnetic resonance imaging showed the ventrolateral medullar tegmentum containing the spinothalamic tract to be affected by lacunar infarction. The blink reflex R2 component was unimpaired in both patients.

Recurrent posterior reversible encephalopathy syndrome (PRES).

Posterior reversible encephalopathy syndrome is a proposed cliniconeuroradiological entity characterized by headache, altered mental status, cortical blindness, seizures, and other focal neurological signs, and a diagnostic magnetic resonance imaging picture. A variety of different etiologies have been reported like hypertension, pre-eclampsia/eclampsia, cyclosporin A or tacrolimus neurotoxicity, uraemia and porphyria. With early diagnosis and prompt treatment, the syndrome is usually fully reversible. We report a case of recurrent PRES of unknown aetiology following intensive care unit treatment and only moderately elevated blood pressure. Clinicians as well as radiologists must be familiar with this clinically frightening, underdiagnosed condition to assure timely diagnosis and treatment to prevent persistent deficits.

Projecting the sulcal pattern of human brains onto a 2D plane--a new approach using potential theory and MRI.

A new method is introduced to project the sulcal pattern of the brain surface onto a 2D plane. Twin brains are compared against each other using the planar representation. We obtained T1-weighted Flash-3D MRI volumes from 14 male twins (seven monozygotic, seven dizygotic) with 3 mm-thick coronal slices. The projection is based on potential theory: A virtual electrostatic field is calculated between the area of the segmented brain and a surrounding spherical electrode. Field lines starting from each border point of the segmented brain follow the gradient towards the sphere, leading to field line concentrations due to the underlying sulci. The unwrapped sphere surface with the number of field lines per area unit is used as the 2D representation of the sulcal pattern. The resulting brain projections show a distinctive pattern, and a visual assignment of the twin pairs from the unsorted set is possible because of a high similarity of the patterns between twin pairs. Global correlation coefficients for each pair of maps yield significantly higher values for matching monozygotic twin pairs (mean = 20.2, range 12.3-25.6) than for unmatched pairs (mean = 13.0, range 1.1-28.5). As a conclusion, our method allows us to map the location and depth of the sulci on a 2D plane. The resulting maps allow quantitative inter-individual comparisons on the entire brain or parts of the brain surface.

Time course of lesion development in patients with acute brain stem infarction and correlation with NIHSS score.

BACKGROUND AND PURPOSE: diffusion weighted magnetic resonance imaging (MRI) is highly sensitive in detecting acute supratentorial cerebral ischemia and Diffusion Weighted Imaging (DWI) lesion size has been shown to correlate strongly with the neurologic deficit in middle cerebral artery territory stroke. However, data concerning infratentorial strokes are rare. We examined the size and evolution of acute brain stem ischemic lesions and their relationship to neurological outcome. METHODS: brain stem infarctions of 11 patients were analyzed. We performed DWI in all patients and in 7/11 patients within 24 h, T2W sequences within the first 2 weeks (10/11 patients) and follow-up MRI (MR2) within 3-9 months (median 4.8 months) later (12/12 patients). Lesion volumes were compared with early and follow-up neurologic deficit as determined by National Institutes of Health Stroke Scale (NIHSS) score. RESULTS: the relative infarct volumes--with MR2 lesion size set to 100%--decreased over the time (P<0.02) with a mean shrinking factor of 3.3 between DWI (MR0) and the follow-up MRT (P<0.02), and 1.6 between early T2W (MR1) and MR2 (P<0.04). The mean DWI volume size (MR0) was larger than the early T2W (P<0.02). Although neurological outcome was good in all patients (mean NIHSS score of 1.3 at follow-up), early NIHSS and follow-up NIHSS scores were strongly correlated (r=0.9, P<0.00). NIHSS score at follow-up was highly correlated with lesion size of DWI (MR0; r=0.71, P<0.04) and T2W of MR1 (r=0.86, P<0.001). CONCLUSIONS: in this study, we saw a shrinking of the brain stem infarct volume according to clinical improvement of patients. Great extension of restricted diffusion in the acute stage does not necessarily implicate a large resulting infarction or a bad clinical outcome.

Drug-induced nonconvulsive status epilepticus with low dose of tiagabine.

In placebo-controlled trials, the overall incidence of nonconvulsive status epilepticus was no higher in the tiagabine-treated group than in the placebo-group. Case reports of nonconvulsive status epilepticus under tiagabine suggested a specific role of dose levels, since in these patients symptoms occurred mostly at 40 mg/day or higher. We report a case of complex partial status epilepticus in a patient receiving a low dose of tiagabine and review all 11 case reports of nonconvulsive status epilepticus in patients on tiagabine, with regard to daily doses. Our analysis suggests an individual risk threshold of unknown aetiology.

Aneurysm of the extracranial carotid artery with spontaneous echo contrast revealed by duplex sonography.

A 56-year old male patient without cerebrovascular disease or risk factors presented with a painless, pulsatile right-sided cervical swelling. Ultrasonography showed a large aneurysm of the right common and internal carotid artery with homogeneous thickening of the vessel wall as well as a parietal thrombus and a dilation of the left common and internal carotid artery with markedly reduced blood flow velocities. In the enlarged lumen of the right internal carotid artery spontaneous echo contrast was apparent with slow, ineffective but orthograde blood flow motions. Ensuing diagnostic procedures revealed multiple aneurysms involving the aorta and its branches. Despite surgical removal of the aneurysm and glucocorticoid therapy, the patient died from a ruptured aneurysm of a coronary artery a few weeks later. Post-mortem examination showed panarteritis consistent with Takayasu's disease. Spontaneous echo contrast is a frequent echocardiographic finding in patients with atrial fibrillation and mitral stenosis, indicating decreased blood flow. This is associated with an increased risk of embolism. In our patient, spontaneous echo contrast indicated severely disturbed haemodynamics due to a large aneurysm of the carotid artery. In the rare case of multiple aneurysms, differential diagnosis should include dissections, infections, and connective tissue diseases. Takayasu's arteritis, however, should also be considered, which usually presents with stenoses, but may be associated with multiple aneurysms of the aorta or its branches. If the diagnostic criteria are present, immunosuppressive treatment should be initiated.

[Long QT syndrome causing grand mal epilepsy: case report, pedigree, therapeutic options, and review of the literature]. / Long-QT-Syndrom als Differenzialdiagnose einer Grand-Mal-Epilepsie: Fallbericht, Stammbaum, Therapieoptionen und Literaturübersicht.

A 24-year-old female with a history of epileptic seizures was admitted after prolonged cardiac resuscitation. The clinical course together with additional examinations led to the diagnosis of severe hypoxic cerebral damage, with poor prognosis for neurological outcome. In her initial ECG, as in the ECGs of several family members, QT prolongation was diagnosed. Meticulous history taking and ensuing genetic analysis led to the diagnosis of familial long QT syndrome (LQTS) with a mutation in the LQT-2 gene (HERG). In retrospect, the previous seizure episodes have to be considered cardiac syncopes. Two family members had previously died suddenly, and ECG and genetic analysis revealed that a total of eight family members were affected. These relatives were prophylactically treated with beta blockers or supplied with automated implantable cardioverter defibrillating devices. The literature concerning LQTS, diagnosis and prognosis of cerebral hypoxic damage, and differentiation between seizures and cardiac syncopes is discussed.

Initial DWI and ADC imaging may predict outcome in acute disseminated encephalomyelitis: report of two cases of brain stem encephalitis.

Two young patients with acute disseminated encephalomyelitis (ADEM) of the brain stem are described. In spite of similar lesion sites in the brain stem, reaching from the upper medulla to the mesencephalon, the outcomes of the patients were very different: one made a full clinical recovery within three weeks while the other remained in a locked-in state more than a year after the disease episode. Both patients also differed in magnetic resonance imaging (MRI) findings on admission. The patient who remained in a locked-in state had pathological diffusion weighted imaging (DWI) scans and decreased apparent diffusion coefficient maps initially, with severe tissue destruction on follow up computed tomography, while the patient who recovered fully showed initially increased apparent diffusion coefficient values and almost complete resolution of MRI changes on follow up. Thus a comparison of these two cases may indicate differences in the underlying pathology in ADEM (vasogenic v cytotoxic oedema) that may be crucial for estimating tissue damage and clinical outcome.

[Differential diagnosis of solitary neurosarcoidosis]. / Differenzialdiagnose der isolierten Neurosarkoidose.

Sarcoidosis is an inflammatory multisystemic disease characterised by noncaseating epithelioid granulomas. The lung is affected in over 90% of patients. According to clinical criteria, the nervous system is involved in 5-9%. However, in autopsy series this number increases to 25%. Solitary involvement of the nervous system without signs of systemic disease is rare and diagnostically cryptic. Due to the wide variety of neurologic symptoms, definite diagnosis of sarcoidosis is possible only by histopathological proof of noncaseating epithelioid granulomas. We report a 51-year-old woman who presented with chronic basal meningitis and involvement of the peripheral and central nervous system due to solitary neurosarcoidosis. Diagnostic procedures and differential diagnosis are discussed.

[Epidemiologic and clinical aspects of HIV infection in homosexual patients and intravenous drug addicts in a comparative study]. / Epidemiologische und klinische Aspekte der HIV-Infektion bei homosexuellen Patienten und intravenös Drogenabhängigen im Vergleich.

The clinical course of HIV-infection was analysed in a group of homosexual patients (n = 76, 72%) compared to intravenous drug abusers (IVDA, n = 30, 28%) in a retrospective cross-sectional study. The mean age of homosexual patients was 37.5 years compared to 28 years for IVDA. The following diseases are found significantly more frequently in homosexual patients compared to IVDA: Pneumocystis-carinii pneumonia (PCP) 17.1% vs. 0% (p < 0.05); Kaposi' sarcoma 16% vs. 0% (p < 0.05); diarrhoea 47.4% vs. 23.3% (p < 0.05); oral candidiasis 51.3% vs. 23.3% (p < 0.01); non-specific pneumonia of bacterial aetiology or due to unknown organisms 30% vs. 0% (p < 0.001) und seborrhoeic dermatitis 13.2% vs. 0% (p < 0.05). In contrast, viral hepatitis, non-specific abscesses and gonorrhoea were seen significantly more often in IVDA. The data show clearly that the spectra of HIV-associated diseases and HIV-unconnected diseases are significantly different in the two main groups. A risk-oriented preventive prophylaxis of HIV-related diseases and other infections is therefore required for each of these groups.

The masseter reflex: postprocessing methods and influence of age and gender. Normative values of the masseter reflex.

OBJECTIVES: Normative values of the masseter reflex are scarce. We studied the latencies, amplitudes and side differences of the masseter reflex in 105 healthy volunteers between the ages of 5 and 78 years. METHODS: Latencies were calculated as the mean of 10 single sweeps and, simultaneously, measured from the summation curve. Short-term reproducibility was determined in 33 volunteers by retesting the reflex after 1 week. RESULTS: There was a positive correlation between age and latencies and a negative correlation between age and amplitude. Maximal normal latencies were 8.3 ms for men and 7.9 ms for women in the age group below 50 years and 9.1 and 9.2 ms for the age group above 50 years. Latency differences between the right and left sides of >0.4 ms for subjects aged below 50 years and >0.5 ms for subjects aged above 50 years exceeded the 95% confidence interval. Amplitudes did not depend on gender. Calculated as a percentage of the side with higher amplitude, differences above one third could be accepted as abnormal. CONCLUSION: The masseter reflex appears to be a stable and robust clinical test, if age and gender differences are taken into account.