Pedunculopontine nucleus stimulation induces monocular oscillopsia.

Two patients with Parkinson's disease with pedunculopontine nucleus (PPN) stimulation for gait impairments reported "trembling vision" during the setting of the electrical parameters, although there was no clinically observable abnormal eye movement. Oculomotor recordings revealed frequency locked voltage dependent vertical or oblique movements of the eye ipsilateral to the active contact, suggesting current spreading to the mesencephalic oculomotor fibres. These results emphasise the difficulty of stimulating this mesencephalic region.

Dynamic echo-planar MR imaging of the diaphragm for a 3D dynamic analysis.

The purpose of this study was to prove the feasibility of 3D reconstructions of the diaphragm during the respiratory cycle using EPI sequences (EPI acquisition, 270 ms/image, on a healthy subject breathing spontaneously and at 0.1 Hz). Continuously recorded respiratory signal allowed for retrospective synchronization with respiratory phases for reconstruction of successive diaphragm surfaces using a specifically designed software. Displacements, area and volume changes of the diaphragm were quantified. Our measurements were comparable with the data in the literature. Reconstructed surfaces allowed in vivo diaphragm dynamic evaluation in terms of displacements, area and volume variations. EPI has adequate spatial and temporal resolution for studying diaphragm dynamics during natural breathing.

Deep brain stimulation of the corpus luysi (subthalamic nucleus) and other targets in Parkinson's disease. Extension to new indications such as dystonia and epilepsy.

Chronic high frequency (130 Hz) stimulation (HFS) of the thalamic target Vim, first used in our group in 1987 as a treatment of tremor of various origins, has been used over the last ten years in 137 patients. Since 1993, this method has been extended to two other targets (subthalamic nucleus (STN): 137 patients and the medial pallidum (GPi): 12 patients), based on recent experimental data in rats and monkeys. STN appears to be a target of major interest, able to control the three cardinal symptoms and to allow the decrease or suppression of levodopa treatment, which then also suppresses levodopa induced dyskinesias. The stereotactic technique is based on the determination of the target using ventriculography, MRI and electrophysiology, with both microrecording of single neuron activity and microstimulation inducing therapeutic symptom suppression and side effects. Chronic electrodes are then placed bilaterally at the best physiologically defined location and then connected to implantable stimulators (either 2 Itrel II or the new double channel Kinetra), operated at 130-185 Hz, 60 ms pulse width, 2.5 to 3.5 volts. There was no operative mortality and permanent morbidity was observed in 3 patients. The mechanisms of action of HFS are not fully understood, but are definitely related to high frequency and are probably different depending on the target. Inhibition of cellular activity or of neural network functions could be induced, by jamming of a retroactive loop for tremor, or by shutdown of neurotransmitter release in STN. Mechanisms within an individual target are also probably different for tremor or for other symptom alleviation. All cardinal symptoms are alleviated from tremor to akinesia and rigidity. This strong improvement allows the decrease of the drug dosage to approximately 30% of the preoperative level, which suppresses the levodopa-induced dyskinesias. The off period dystonias are also suppressed as well as freezings and falls. The effects remain stable over more than 5 years and in the same period, the off stimulation-off medication UPDRS remains stable and does not increase at the usual rate The low rate of permanent complications, the minor side effects and their immediate reversibility, the possibility of bilateral implantation in one session and the long-term persistence of symptom relief are strong arguments which support chronic HFS of STN as the method of choice when a surgical procedure is indicated for the treatment of Parkinson's disease and even more when a bilateral procedure is necessary. Recent data show that STN stimulation could be useful in the treatment of dystonia as well as some forms of epilepsy. It is therefore possible that DBS in STN as well as in other targets could become a potent therapeutic tool in the near future for neurological disorders.

The use of a semi-customized phantom for verification of conformal plans.

We have developed a technique for inverse treatment planning of prostate therapy designed to improve the degree of conformation between the dose distribution and the target volume. We compared the inverse plan with a "standard" four-field box technique as well as a four-field technique using oblique fields ("cross technique"). We validated the dosimetry of the inverse plan using Fricke gel solution in phantom specifically designed for this purpose. The phantom is a Plexiglas tank with a cross section, which approximates the dimensions of the pelvis. Anatomical data from computed tomography (CT) images of a patient were used to simulate organs in our phantom. This allows us to calculate dose distributions with the external geometry of the phantom and internal anatomy of the patient. Dose-volume histograms (DVHs) for the three different plans were calculated. The phantom containing the Fricke gel was irradiated according to the inverse plan. Magnetic resonance (MR) images was used to determine the dose distribution delivered to the phantom. We observe, on DVHs, that the inverse plan significantly reduces the dose to the rectum and the bladder but slightly increases the inhomogeneity inside the target volume. Correlation is good between isodoses on MR images and calculated isodoses. We conclude that inverse planning software can greatly improve the conformal degree of treatment to the prostate. This technique could be applied to other complex anatomic sites at which dose to organs at risk is a limiting factor and increased dose to the target volume is indicated. Our phantom and the Fricke gel solution are convenient to carry out validation of conformal treatments.

Coexistence of plasma cell granulomas of lung and central nervous system.

A rare case of concurrent plasma cell granulomas (PCG) of the lung and the central nervous system (CNS) is reported. A 30-year-old man was presented with recurrent left headaches lasting for two years. Computerized tomographic (CT) scan and magnetic resonance imaging (MRI) of the head disclosed a process extending from the lateral aspect of the left cavernous sinus to the tentorium cerebelli and the infratemporal fossa through the foramen ovale. At the same time, chest-X ray and CT scan showed three symptomless masses of the pulmonary right lower lobe. Histological examination of cerebral samples and of one of the pulmonary nodules revealed the presence of a fibrous tissue containing numerous lymphocytes and plasma cells as well as remnants of vascular and respiratory structures. Immunohistochemical study proved these cells to be polyclonal. Ultrastructural analysis confirmed the presence of lymphoid cells and failed to disclose any argument for meningioma or histiocytosis X. The differential diagnostic problems of PCG are discussed as well as considerations about clinicopathological features, histogenesis and pathogenesis of inflammatory pseudotumours (IPT).

Percutaneous intradiscal radio-frequency thermocoagulation. A cadaveric study.

STUDY DESIGN: This study examined the effect of radio-frequency thermocoagulation on cadaveric disc material. Radio-frequency lesions are induced to decompress the nerve root by coagulating the nucleus pulposus. OBJECTIVES: The purpose of this study was to assess the potential of the radio-frequency lesion technique for treating lumbar disc herniation percutaneously. The effect of radio-frequency thermocoagulation on cadaveric disc material was studied. SUMMARY OF BACKGROUND DATA: An intradiscal bipolar electrode is used for the thermocoagulation of the nucleus pulposus. METHODS: Lumbar discs of 27 adult cadavers were used for the experiments within 72 hours of donors' deaths. The physical and thermal parameters of intradiscal radio-frequency thermocoagulation were determined experimentally. Acute macroscopic and histologic changes before and after thermocoagulation were investigated. The temperature distribution of the tissue surrounding the disc was measured during the operation using thermocouples to evaluate potential heat damage. Also, computed tomography and magnetic resonance imaging of the disc were performed before and after thermocoagulation. RESULTS: Macroscopic observation showed that the lesion induced by radio-frequency thermocoagulation is homogeneous and intense without necrosis, and is limited to the nucleus pulposus. Histologically, the endplates and vertebral bodies were unaffected and an architectural disorganization of the stroma of the nucleus pulposus was seen. The temperature increase of the tissue surrounding the discs did not exceed 3-4 C. CONCLUSION: A bipolar electrode and a radio-frequency alternating current permits percutaneous intradiscal thermocoagulation for destruction of a portion of disc material in a cadaveric spine.

Discrimination between cross-country and downhill skiers by pulmonary and local 31PNMR evaluations.

The purpose of the present study was to correlate data on calf muscle metabolism using 31P nuclear magnetic resonance spectroscopy with measurements of whole body maximal oxygen consumption and maximal power output, and to determine whether the combination of these data could be used to predict athletic ability. Experiments were performed in a 2.35 Tesla, 35 cm diameter electromagnet on the leg muscle of sedentary human subjects (N = 6) and groups of athletes trained for endurance (cross-country skiers, N = 7) or strength performance (downhill skiers, N = 5). The exercise protocol consisted of successive plantar flexions performed at graded fractions of the maximal voluntary contraction (MVC). The results obtained from NMR investigation (changes in content of inorganic phosphate: Pi, phosphocreatine: PC and muscle ATP, and intracellular pH) were then compared with those of maximal O2 consumption (VO2max) and maximal power (MP). When the data on athletes were compared with those obtained on sedentary subjects, the curves illustrating the relationship between the imposed load and the Pi/PC ratio were significantly shifted toward high output power for a given Pi/PC value. It also appeared from this study that specific training in force development (downhill skiing) induced a slighter decrease in PC level than for endurance (cross-country skiers) despite improvement in physical performance. A slight but significant intracellular acidification was observed in the muscles of sedentary subjects and downhill skiers for contraction at, respectively, 50% and 80% of MVC, but not in the skeletal muscles of cross-country skiers.(ABSTRACT TRUNCATED AT 250 WORDS)

[Carotid stenoses. Non-invasive exploration]. / Sténoses carotidiennes. Apport des explorations non traumatisantes.

Doppler flowmeter and ultrasound imaging techniques, currently associated (duplex), have made important contributions to the simple and early non invasive diagnosis of carotid stenosis lesions in the cervical region for more than 20 years. These exploratory methods are reliable when a significant degree of stenosis (greater than about 60%) exists. Moderate degrees of stenoses or plaques are evaluated morphologically, calcifications and ulcerations being enhanced by staining techniques. But the evaluations have not really demonstrated exact correlations between anatomicopathologic and ultrasound images. The intracranial arteries and the circle of Willis are explored indirectly during the cervical examination by cautious compressive maneuvers or directly by trans-cranial Doppler. Whereas angiography competes with ultrasound imaging as a standard examination in the neck region, it nevertheless remains effective for the study of the intracranial arteries. Newer techniques, such as high-field MRI angiography, tridimensional ultrasonography or ultrasound recording of vascular flow rate without Doppler, will doubtlessly transform the diagnosis of symptomatic or asymptomatic carotid stenosis. From the strategic point of view, ultrasound imaging techniques will retain their role of a decisional pivot, since they are simple to use and are of very wide accessibility to competent vascular physicians in the context of an organized care network.

Muscle bioenergetics in skiers: studies using NMR spectroscopy.

Sedentary human subjects (n = 6) and two homogeneous groups of athletes, trained for down-hill skiing (n = 5) and cross-country skiing (n = 7), were subjected to cardiorespiratory testing and to evaluation of the bioenergetics of calf muscles by means of Phosphorus Nuclear Magnetic Resonance Spectroscopy. The exercise consisted of successive plantar flexions performed at graded fractions of the maximal voluntary contraction force. It appears from this study that the decrease in phosphocreatine level induced by exercise at 80% of maximal voluntary contraction, was smaller in the muscles of athletes who trained for cross-country skiing, than in the muscles of down-hill skiers and control subjects. Intracellular acidosis was virtually absent in cross-country athletes. The rate of restitution of phosphocreatine, after the exercise, was higher in both groups of skiers, compared to sedentary subjects. The maximal oxygen consumption and the maximal alactic power were higher in athletes than in sedentary subjects. NMR data and mechanical measurements are used in consideration with functional systemic indexes to characterize the capabilities of skiers.

Effect of training on the calf muscle energy metabolism. A 31P-NMR study on four elite downhill skiers challenged with a standardized exercise protocol.

This study evaluates the effects of a 6 months' training period on the bioenergetics of the calf muscle of elite athletes by means of phosphorus-31 Nuclear Magnetic Resonance Spectroscopy (31P-NMR). Four downhill skiers, belonging to the Spanish National Team, performed a standardized exercise protocol using their right leg inside a wide-bore 2.35 Tesla magnet. The inorganic phosphate/phosphocreatine (Pi/PC) ratio and intracellular pH (pHi) were measured at steady-state during an exercise protocol composed of 5 work levels between 20% and 80% of the maximum voluntary contraction (MVC), before and after the training period. The measured values, which were markedly scattered at the beginning, regrouped after training. This was caused by a shift towards lower Pi/PC ratios and by a lower pHi acidification in three of the four subjects. This result suggests that 31P-NMR is a good tool to evaluate changes in the muscle aerobic capacity of athletes induced by training.

Skeletal involvement as the initial disease manifestation in Hodgkin's disease: a review of 6 cases.

Initial signs of malignant lymphoma are rarely due to bone lesions. We reviewed 6 cases with early skeletal involvement, recently observed in the rheumatology and hematology departments. In 3 patients, magnetic resonance imaging (MRI) was added to traditional investigations, including radiography, radionuclide bone scan and computerized tomography. We stress the possibility of bone involvement in the clinical onset of malignant lymphoma and the usefulness of early bone assessment using MRI.

Effect of prior exercise in Pi/PC ratio and intracellular pH during a standardized exercise. A study on human muscle using [31P]NMR.

Seven subjects underwent a standard localized exercise of calf muscles in order to investigate whether the metabolic exercise-induced steady-state, as revealed by the evaluation of inorganic phosphate/phosphocreatine ratio, depends on the conditioning of the muscle just prior to the exercise. The experimental protocols consisted of two separate experiments using first [31P]nuclear magnetic resonance spectroscopy and second (on 3 subjects) infrared oxyphotometry to respectively follow variation of energy metabolism and tissular deoxygenation. The exercise consisted of 240 successive plantar flexions (0.5 Hz frequency) against a high load equivalent to 80% of the maximal voluntary contraction. This exercise was accomplished before cold exercise and after warm exercise, a warming-up period bringing to approximately 50% of VO2max. The results showed that: (1) steady-state level of phosphate/phosphocreatine and intracellular acidosis was significantly lowered by warming-up; (2) cold and warm exercise steady-state of calculated adenosine diphosphate values were not significantly different; (3) cold exercise rapidly induced a high tissular deoxygenation that is not observed during warm exercise; and (4) time-constant of phosphocreatine resynthesis is lowered after warm exercise but the initial slope of time-evolution is not modified. Parallel experiments also showed that phosphate/phosphocreatine steady-state was not modified in comparison with warm exercise when the same power of exercise was reached by stepwise incrementation of the charge. From these results we postulate that a better tissue oxygenation due to a global or localized warming-up allows to reach the same mechanical performance with a lower decrease of PCr content, owing to a faster adjustment of oxidative metabolism during the transitional period.(ABSTRACT TRUNCATED AT 250 WORDS)

[Acute aortic dissection and peripheral ischemia. Diagnostic and therapeutic problems. Remote control using nuclear magnetic resonance]. / Dissection aortique aiguë et ischémie périphérique. Problèmes diagnostiques et thérapeutiques. Contrôle à distance par résonance magnétique nucléaire.

This study concerns 7 cases of acute aortic dissection associated with visceral and/or lower limb ischemia. Only those cases are included which raised diagnostic and therapeutic problems. Patients were excluded who had purely angiographic involvement of an aortic branch and minor rapidly resolving ischemic syndromes. Five of the 7 patients presented type B (type III or distal) and 2 type A (type I or proximal) dissection. All patients received anti-hypertensor medical treatment. All but one had undergone surgery at least once at the acute stage. Five had been followed up and monitored by magnetic resonance imaging (MRI). One type A and 4 type B dissections were thus reviewed between the 15th month and the 9th year. Diagnostically, aortography was found to be inaccurate twice because of incomplete exploration of the thoracoabdominal aorta. Therapeutically, a case of intraoperative death occurred during replacement of the ascending aorta. Thus, out of the 6 patients who survived the acute stage, 4 are alive and asymptomatic, one has been lost sight of and the other died in year 5 after surgery for chronic dissecting aneurysm of the aortic arch. Among the 5 patients examined by MRI, 4 presented aortic ectasia, chronic dissecting aneurysm of the aortic arch and/or a descending aorta with a diameter between 45 and 65 mm. The patient with subnormal aortic diameter had his ascending aorta replaced (the follow-up period at this writing is only 27 months). Among 3 patients who were examined twice, one showed improvement after a year's interval, with a 5-mm increase in the caliber of the dissected aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

[Detection of parietal lesions using magnetic resonance imaging in arrhythmogenic dysplasia of the right ventricle]. / Mise en évidence par l'IRM des lésions pariétales au cours de dysplasies arythmogènes du ventricule droit.

Seven patients with arrhythmogenic right ventricular dysplasia were explored by magnetic resonance imaging (MRI), using the spin-echo technique (TR = the patient's own RR cycle; TE = 28 ms, 56 ms, 84 ms) with multiple, contiguous, 7 to 10 mm thick sections performed in two planes: axial plus sagittal or frontal planes. In 5 out of 7 patients, MRI showed dysplastic lesions in the right ventricular wall presenting typically as fat-like high signals contrasting with the normal myocardium. In 2 patients, no lesion was clearly visualized. The parietal lesions were located in the anterior wall of the right ventricle and conus arteriosus in 5 cases and in the lower wall of the right ventricle in one patient who had two dysplastic areas. In 3 patients the lesions extended up to the tip of the interventricular septum and of the left ventricle. In the 2 patients whose lesions were most extensive, their predominance in the subepicardial region and the concordance between the sites of abnormalities at MRI and angiography were clearly observed. Thus, despite its present technical limitations MRI seems to be one of the first techniques capable of visualizing the parietal lesions in patients with arrhythmogenic right ventricular dysplasia.

[Magnetic resonance imaging in studying injuries of the ligaments and menisci of the knee. 85 cases controlled by arthroscopy]. / L'imagerie par résonance magnétique dans l'exploration des lésions ménisco-ligamentaires du genou. 85 examens contrôlés par arthroscopie.

The authors report a prospective study of eighty-five patients with suspected meniscal or ligament lesions examined using Magnetic Resonance Imaging (MRI). In all cases, the results were compared with the findings at arthroscopy. The technique seems to be a good non-invasive diagnostic procedure, whose accuracy is 87 p. cent for the medial meniscus, 95 p. cent for the lateral meniscus and 100 p. cent for the anterior cruciate ligament (ACL). The most interesting indications at the present time are in the diagnosis of meniscal lesions, the evaluation of the menisci in chronic cruciate ligaments insufficiency, and the diagnosis of acute tears of the ACL (especially when examination is limited by pain or muscle spasm). In the future, MRI should take the place of arthrography. The total scanning time is rather short, as most lesions are detected by T1 weighted sagittal images.

[MRI features of expansive processes of soft tissues. Contribution to etiologic diagnosis. Apropos of 32 cases]. / Séméiologie IRM des processus expansifs des parties molles. Apport au diagnostic étiologique. A propos de 32 observations.

This study concerns the investigation of 32 soft-tissue tumors by MRI, subsequently verified by biopsies or surgery (n = 28) or other investigations (n = 4). MRI can suggest the diagnosis in some cases: lipomas cysts, hematomas, neuromas, desmoid tumors, hemangiomas, by contrast analysis and morphologic aspects; sometimes, malignant lesions are suspected on particular anatomic criteria. MRI is excellent in the evaluation of local extension. MRI can therefore be performed when the staging of soft tissue tumor is incompletely provided by other investigations (CT or US).