Cervical chordoma with vertebral artery encasement mimicking neurofibroma: MRI findings

A case of cervical chordoma in a 36-year-old white man with hypoesthesia in the neck and right shoulder, neck pain, and restricted neck mobility is presented. Plain radiographs of the cervical spine showed radiolucency of the body of C2 on the right side and enlargement of the right intervertebral foramen at C2–C3 level. Tumor encasement of the vertebral artery was demonstrated by MR imaging and confirmed by conventional arteriography. This proved to be particularly important for preoperative assessment. Received: 8 February 1999; Revised: 26 October 1999; Accepted: 18 November 1999     

MR diagnosis of a congenital abnormality of the thoracic aorta with an aneurysm of the right subclavian artery presenting as a Horner's syndrome in an adult

Congenital abnormality of the aortic arch is a diagnosis made most of the time incidentally in childhood, unless dysphagia or respiratory disorders occur before. A case of a complex aortic arch anomaly with an aneurysm of the right subclavian artery presenting as an isolated Horner's syndrome in an adult is reported herein. Magnetic resonance imaging led to this very unusual diagnosis. Received: 17 March 1999; Revised: 15 July 1999; Accepted: 13 August 1999     

Detection of severe acute pancreatitis by contrast-enhanced magnetic resonance imaging

The aim of the study was to assess the ability of MRI to differentiate between the two forms of severity of acute pancreatitis (AP), which is important for the detection of patients who require intensive monitoring and therapy. The second objective was to evaluate whether the distinction would be possible regardless of the MRI equipment. Magnetic resonance imaging was performed before and after intravenous administration of a gadolinium (Gd) chelate at 1.0 T using the breath-hold multislice rapid gradient-echo turbo fast low-angle shot (FLASH) sequence in 14 patients, and at 1.5 T with the 2D FLASH(50) sequence with fat saturation in 18 patients with acute pancreatitis early in the course of the disease. The patients were classified according to the Atlanta classification system as having the mild (MAP) or severe (SAP) form of the disease. At 1.0 T with use of a body coil, contrast-enhanced MRI failed to distinguish mild from severe pancreatitis. At 1.5 T with a phased-array body coil, the signal intensities of the patients with SAP were statistically significantly lower than those of the MAP group. Our initial clinical experience suggests that MRI with a sufficient magnetic field gradient strength may be useful for separating the two forms of acute pancreatitis in their early phases. Received: 19 January 1999; Revised: 28 May 1999; Accepted: 22 July 1999     

Assessment of patellar maltracking using combined static and dynamic MRI

Between January 1995 and Jul 1997, 474 patients with anterior knee pain resistant to conservative treatment were referred for MR of the knee. The MR examination consisted of routine sequences with an additional patellofemoral dynamic examination using a technique that has been developed at this institution. The dynamic study examines both knees simultaneously, with the patient supine and the quadriceps loaded. No gating or restraint apparatus is needed. Patellar subluxation or tilt was present in 188(40 %) of cases, bilateral in 104 and unilateral in 84 cases (right 39, left 45). It was classified as mild in 51 %, moderate in 39 % and severe in 10 %. Subluxation was more prevalent in females than males (42 % vs. 37 %) and this was most obvious in the severe group where 68 % were female. In 90 knees selected at random, four measurements of patellofemoral morphology were obtained using reconstructed images from a volume gradient echo sequence. These measurements were correlated with the degree of subluxation or tilt. A tibial tubercle distance greater than 20 mm, a femoral sulcus angle greater than 150 degrees, sulcus depth less than 4 mm were specific for subluxation but no measurement proved to be sufficiently sensitive to preclude a tracking study. MRI can be used to define more precisely the anatomy of the extensor mechanism and its relationship to the femur and tibia, in both a static and dynamic setting. In this way, patients with anterior knee pain can be classified more accurately and the outcomes of treatment more reliably assessed. Received: 17 September 1999; Revised: 31 January 2000; Accepted: 4 February 2000     

Effect of long-term vigabatrin administration on the immature rat brain

PURPOSE: To determine whether the neuropathologic changes produced by vigabatrin (VGB; gamma-vinyl GABA) administration in the developing rat brain are reversible. METHODS: We injected rats daily with VGB (25-40 mg/kg/day, s.c.) from age 12 days for 2 weeks followed by 2 weeks of a drug-free period. Behavioral testing, magnetic resonance (MR) imaging, biochemical assays, and histologic technique were used to assess the adverse effect of VGB in developing brain and its reversibility. RESULTS: At the end of 2 weeks' VGB administration: (a) there was a hyperactivity and a shortened latency to escape out of cool water; (b) white matter appeared hyperintense in T2 and diffusion-weighted MR images with 4-15% increases in T2; (c) microvacuolation, TUNEL-positive nuclei, and swollen axons were observed in the corpus callosum; (d) myelin staining indicated a reduction in myelination, as did the reduction in activities of myelin and oligodendrocyte-associated enzymes and the decrease in myelin basic protein on Western blots. Two weeks after stopping VGB administration: (a) MR images were normal, and microvacuolation was no longer in the white matter; (b) reduction in myelination reversed partially; (c) the T2 relaxation time remained elevated in the hypothalamus; and (d) the behavioral response remained abnormal. CONCLUSIONS: Long-term VGB administration to young rats causes brain injury, which recovers partially on its cessation. The observed cell death, disrupted myelination, and alterations in behavior indicate a need for further safety assessment in infants and children.     

Quantitative volumetric analyses of brain magnetic resonance imaging from rat with chronic neuroinflammation

Brain inflammation may have a pathogenic role in many neurodegenerative diseases, including Alzheimer's disease. In the present study, we investigated the effects of chronic neuroinflammation upon anatomical changes in two regions of interest in the temporal lobe using high-resolution magnetic resonance imaging techniques. We show that chronic infusion of lipopolysaccharide into the fourth ventricle for 4 consecutive weeks enlarged the lateral ventricles and significantly decreased the size of the hippocampal formation and the temporal lobe region. These changes are comparable to those observed in humans during the early stages of Alzheimer's disease.     

Effect of a neuronal sodium channel blocker on magnetic resonance derived indices of brain water content during global cerebral ischemia

Diffusion-weighted magnetic resonance imaging (DWI) with calculation of the apparent diffusion coefficient (ADC) of water is a widely used noninvasive method to measure movement of water from the extracellular to the intracellular compartment during cerebral ischemia. Lamotrigine, a neuronal Na(+) channel blocker, has been shown to attenuate the increase in extracellular concentrations of excitatory amino acids (EAA) during ischemia and to improve neurological and histological outcome. Because of its proven ability to reduce EAA levels during ischemia, lamotrigine should also minimize excitotoxic-induced increases in intracellular water content and therefore attenuate changes in the ADC. In this study, we sought to determine the effect of lamotrigine on intra- and extracellular water shifts during transient global cerebral ischemia. Fifteen New Zealand white rabbits were anesthetized and randomized to one of three groups: a control group, a lamotrigine-treated group, or a sham group. After being positioned in the bore of the magnet, a 12-min 50-s period of global cerebral ischemia was induced by inflating a neck tourniquet. During ischemia and early reperfusion there was a similar and significant decrease of the ADC in both the lamotrigine and control group. The ADC in the sham ischemia group remained at baseline throughout the experiment. Lamotrigine-mediated blockade of voltage-gated sodium channels did not prevent the intracellular movement of water during 12 min 50 s of global ischemia, as measured by the ADC, suggesting that the ADC decline may not be mediated by voltage-gated sodium influx and glutamate release.     

6-fluoroDOPA metabolism in rat striatum: time course of extracellular metabolites

6-[18F]Fluoro-L-DOPA (FDOPA) is an imaging agent used in the study of dopamine terminals in the living brain using positron emission tomography (PET). To better understand the role of tracer metabolism in dynamic FDOPA PET studies, the pharmacokinetics of individual FDOPA metabolites in extracellular space in the striata of anesthetized rats was investigated using in vivo microdialysis. Brain tissues were also analysed to obtain FDOPA metabolite distribution in the combined intracellular and extracellular spaces. Total extracellular [18F] radioactivity in rat striata was observed to rise and peak at 30 min post-injection (p.i.) and declined with clearance half-life of 2 h. In the extracellular space, the dominant FDOPA metabolite at early times was FDOPAC, followed by FHVA at 50 min, then F-sulfoconjugates at 70 min and finally 3-O-methyl-6-Fluoro-L-DOPA (3OMFD) at later times. These results are consistent with the sequential metabolism and brain clearance of L-DOPA and its metabolites. Analysis of whole striatal tissue confirmed the intraneuronal localization of fluorodopamine most likely stored in vesicles. A new but not unexpected finding was the enrichment of 3OMFD in intraneuronal striatal space which is perhaps a factor in its slow cerebral clearance. Since FDOPA PET data reflects the overall pharmacokinetics of several [18F]-metabolites, the observed different rates of formation and clearance and also different neuronal localization of each metabolite contribute to the measures obtained in dynamic FDOPA PET studies. These metabolic steps and their role in tracer kinetics are, thus, important factors to consider in ascribing physiologic significance to PET-derived measures.     

Chemical shift imaging spectroscopy and memory function in temporal lobe epilepsy

PURPOSE: Hippocampal neuron loss and associated memory deficits are characteristic of intractable temporal lobe epilepsy (TLE). Proton chemical shift imaging (CSI) spectroscopy is a sensitive tool for detecting neuronal loss. The aim of this study was to investigate the correlation between memory functions and results provided by CSI spectroscopy of the hippocampal structures. METHODS: Ten patients with cryptogenic TLE participated. The study protocol involved both the acquisition of high-spatial-resolution CSI spectroscopy and neuropsychological evaluation, including memory testing and intracarotid sodium amytal test (IAT). The analysis of the CSI data was based on normative data obtained in 30 healthy volunteers. Memory functions were represented by verbal, visual, and general memory indices. RESULTS: A significant correlation was found between CSI spectroscopy of the hippocampal formation and the verbal memory indices for the dominant hemisphere. In addition, there was a significant correspondence of the qualitative judgment "hippocampal pathology indicated by CSI spectroscopy" and both "material specific memory deficit" and "memory deficit in the IAT." CONCLUSIONS: Our results demonstrate that CSI spectroscopy of the hippocampal structures is strongly related to lateralized memory deficits in patients with TLE. This suggests that CSI spectroscopy may be useful in the prediction of postoperative outcome in respect of seizure control and memory.     

Open MRI-Guided Microsurgery of Intracranial Tumours. Preliminary Experience Using a Vertical Open MRI-Scanner

Summary ? Objectives. A number of different image-guided surgical techniques have been developed during the past decade. None of these methods can provide the surgeon with information about the dynamic changes that occur intra-operatively. The development of open configurated MRI-scanners leads to new perspectives in the intra-operative management and resection control of intracranial tumours.  Material and Method. Using a vertical open 0.5 T MRI-scanner for intra-operative MR image guided neurosurgery, forty-four patients (20 female/24 male) with different intracranial tumours have been operated on since August 1997. The patients ranged in age from 20 to 70 years (mean±standard deviation=47.2±15.9 ys).  Results. In 36 (82%) of 44 patients the tumours were completely removed with the aid of MR image-guidance. In 8 cases (18%) complete removal was not achieved. Postoperatively 6 (14%) of 44 patients developed neurological deficits which were transient in 5 cases (paresis, dysphasia). In these patients the tumours were located in or near eloquent brain areas (sensorimotor cortex/speech center).  Conclusion. Intra-operative MRI is helpful for navigation as well as determining of tumour margins to achieve a complete and safe resection of intracranial lesions. Complications related to the surgical procedure are reduced and the risk of neurological deterioration due to tumour removal and postoperative complications is minimized. It can be concluded that the intra-operative application of interventional MRI technology may represent a major step foreward in the field of neurosurgery.