A simple technique for making a stereotactic localiser both CT and MRI compatible

Summary Stereotactic neurosurgery requires the utmost precision. This can be achieved with modern imaging methods, provided special localisers are used which produce reference points for the calculation of stereotactic coordinates. Since not every substance can be visualised in every imaging modality, various localisera are normally used. These contain, for example, thin steel wires for CT or copper sulphate for MRI. By using a mixture of jopamidol and copper sulphate at a ratio of 11, it is possible to make the reference points of a localiser visible in both CT as well as in MRI. In this way, the entire stereotactic planning can be carried out using only one single localiser. This not only simplifies the procedure, it also reduces costs.     

Transcranial magnetic stimulation in the treatment of psychiatric disorders

Transcranial magnetic stimulation (TMS) is a new technology that applies the principles of electromagnetism to deliver an electrical field to the cerebral cortices. Well established in diagnostic electrophysiology, TMS is now being studied as a treatment for psychiatric disorders. Evidence suggests this technique is safe and acceptable to patients. The future may see the application of TMS in obsessive-compulsive disorder, post-traumatic stress disorder and mania. There is strong evidence that it will become an accepted treatment of depression.     

Cardiac effects of contrast media in MR angiography: evaluation in an experimental model of myocardial ischemia

RATIONALE AND OBJECTIVES: The authors evaluated the cardiac tolerability of paramagnetic contrast agents for magnetic resonance (MR) angiography in an in vitro model of ischemic rat heart. MATERIALS AND METHODS: The left anterior descending coronary artery was temporarily occluded in a perfused rat heart model to induce cardiac ischemia and reperfusion. A dose of 0.4 mL of gadobenate dimeglumine, of gadopentetate dimeglumine, or of D-mannitol was injected directly into the aorta both during the ischemia and during the reperfusion period. The left ventricular pressure and heart rate were recorded. RESULTS: Myocardial ischemia resulted in decreased cardiac activity, with a reduction in left ventricular pressure and heart rate. A further decrease in cardiac activity was temporarily induced by injection of contrast medium during both the ischemic and early reperfusion phases. Less marked responses were induced by a hyperosmolal solution of mannitol. CONCLUSION: These results suggest that the transient cardiac effects induced by bolus injection of paramagnetic contrast medium may be regarded as the combined effects of the osmotoxicity of the contrast medium solution and the chemotoxicity of the contrast medium molecule.     

Surgical Findings in Idiopathic Trigeminal Neuropathy Mimicking a Trigeminal Neurinoma

Summary  Idiopathic trigeminal neuropathy is a benign disorder where the main clinical feature is facial numbness limited to the territory of one or more divisions of the trigeminal nerve, persisting for a few weeks to several years and in which no underlying disease can be identified. The case of a 37-year-old man with a brief history of sensory and motor trigeminal symptoms who showed magnetic resonance imaging (MRI) findings consistent with a small trigeminal neurinoma is reported. The patient was operated on but no tumour could be found during surgery and a biopsy was taken from the portio major. Pathological diagnosis was chronic non granulomatous inflammatory reaction with areas of coagulation necrosis. Control MRI showed complete resolution of the trigeminal abnormalities. It is concluded that in patients with MRI findings suggestive of a small trigeminal schwannoma, benign idiopathic trigeminal neuropathy should also be considered in the differential diagnosis. A conservative approach with sequential MRI studies may avoid an unnecessary surgical exploration.     

Primary anorectal malignant melanoma: Report of a case

(Received for publication on Aug. 18, 1997; accepted on May 15, 1998)     

Periictal diffusion-weighted imaging in a case of lesional epilepsy

PURPOSE: Diffusion-weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period. METHODS: A periictal DWI study was performed on a 35-year-old patient during focal status epilepticus with repetitive prolonged focal motor seizures originating from a lesion in the right frontal lobe. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps. RESULTS: On DWI, a single area of signal increase (decrease in ADC) was found in the region of focal electrocorticographic seizures that was mapped intraoperatively. CONCLUSIONS: Ictal/postictal DWI may be a useful technique for seizure localization in patients with lesional epilepsy.     

The Effect of Conformation on Membrane Permeability of an Acyloxyalkoxy-linked Cyclic Prodrug of a Model Hexapeptide

Purpose. To determine the different conformations of the acyloxyalkoxy-linked cyclic prodrug 1 of the model hexapeptide 2 in solution and to investigate the relationship between these solution conformations and the cellular permeability characteristics of this prodrug. Methods. Two-dimensional Homonuclear Hartmann-Hahn spectroscopy, Rotating-Frame Overhouser effect spectroscopy, circular dichroism and molecular dynamics simulations were used to find the solution conformers of cyclic prodrug 1. Results. Our spectroscopic findings suggest that cyclic prodrug 1 exhibits a major and a minor conformer in solution. The major conformer appears to have a well-defined secondary structure, which involves a -turn and 4 1 intramolecular hydrogen bond, creating a compact structure with a reduced average hydrodynamic radius compared to the model hexapeptide 2. Conclusions. The increased ability of cyclic prodrug 1 to permeate membranes compared to the model hexapeptide 2 could be due to reduction in the average hydrodynamic radius of the molecule facilitating paracellular flux and/or the reduction in the hydrogen bonding potential facilitating transcellular flux.