Fractal organization of trabecular bone images on calcaneus radiographs.

Bone density is not the unique factor conditioning bone strength. Trabecular bone microarchitecture also plays an important role. We have developed a fractal evaluation of trabecular bone microarchitecture on calcaneus radiographs. Fractal models may provide a single numeric evaluation (the fractal dimension) of such complex structures. Our evaluation results from an analysis of images with a varying range of gray levels, without binarization of the image. It is based on the fractional brownian motion model, or more precisely on the analysis of its increment, the fractional gaussian noise (FGN). The use of this model may be considered validated if two conditions are fulfilled: the gaussian repartition and the self-similarity of our data. The gaussian repartition of intermediate lines of these images was tested on a sample of 32,800 lines from 82 images. Following a chi-square goodness-of-fit test, it was checked in 86% of these lines for alpha = 0.01. The self-similarity was tested on 20 images by two estimators, the variance method of Pentland and the spectrum method of Fourier. Self-similarity is defined by lined-up points in a log-log plot of the FGN spectrum or of the variance as a function of the lag. We found two self-similarity areas between scales of analysis ranging from 105 to 420 microns, then above 900 microns, where linear regression produced high mean correlation coefficients (r > or = 0.97). Following this validation, we studied the reproducibility of this new technique. Intra- and interobserver reproducibility, influence of transferring the region of interest, and long-term reproducibility were assessed and given CV of 0.61 +/- 0.15, 0.68 +/- 0.47, 0.53 +/- 0.16, and 2.07 +/- 0.84%, respectively. These data have allowed us to validate the use of this fractal model by checking the fractal organization of our radiographic images analyzed by the model. The good reproducibility of successive x-rays in the same subject allows us to undertake population studies and to envisage longitudinal series.

Single-channel and whole-cell recordings from on-neurone glial cells in Helix pomatia ganglia.

A procedure is described for performing patch-clamp recordings on satellite glial cells kept in place within the nervous ganglia in the mollusc Helix. Glial cell properties were deduced from whole-cell and cell-attached recordings. The glial membrane was found to contain densely packed inwardly rectifying K+ channels. Activation of the neurones, under either current-clamp or voltage-clamp conditions, depolarized the glial cell layer wrapped around the neurones and induced a delayed persistent increase in the K+ channel opening probability. These results suggest that the glial channels opened in response to a signal emanating from the active neurones. This preparation provides a useful means of detecting and analysing neurone-glial interactions at the cell and unitary channel levels.

Maurotoxin, a four disulfide bridges scorpion toxin acting on K+ channels.

Maurotoxin, a toxin from the venom of the Tunisian chactoid scorpion Scorpio maurus, has been purified to homogeneity by gel filtration/reversed-phase HPLC, and characterized. It is a basic and C-terminal amidated 34-residue polypeptide cross-linked by four disulfide bridges. From Edman sequencing results, only six different pairings between the first six half-cystines were retained whereas a disulfide bridge was predicted between the two half-cystines in positions 31 and 34. Modelling based on the structure of charybdotoxin favored two different pairings, one of which possessed two disulfides in common with the general motif of scorpion toxins. The solid-phase technique was used to obtain synthetic maurotoxin, sMTX. The half-cystine pairings of sMTX were determined by enzymatic cleavage and were found to be Cys3 Cys24, Cys9-Cys29, Cys13-Cys19, and Cys31-34, in agreement with experimental data obtained with natural maurotoxin. Both natural and synthetic maurotoxins were lethal to mice following intracerebroventricular injection (LD50, 80 ng/mouse). They blocked the Kv1.1, Kv1.2, and Kv1.3 channels expressed in Xenopus oocytes with almost identical half-effects (IC50) in the range of 40, 0.8 and 150 nM, respectively. They also competed with 125I-apamin (SKca channel blocker) and 125I-kaliotoxin (Kv channel blocker) for binding to rat brain synaptosomes with IC50 of about 5 and 0.03 nM. As the natural and synthetic maurotoxins exhibit indistinguishable physicochemical and pharmacological properties, they are likely to adopt the same half-cystine pairing pattern which is unique among known scorpion toxins. However, this disulfide organization is different from those reported for Pandinus imperator and Heterometrus spinnifer toxins 1 (Pi1 and HsTx1), two novel four-disulfide bridged K+ channel-acting scorpion toxin sharing about 50-70% sequence identity with maurotoxin.

Long-term reproducibility optimization of an x-ray process for bone architectural evaluation during osteoporosis.

Non-invasive and in vivo assessment of bone architectural changes at high resolution is of considerable interest in osteoporosis. In this note, the use of an x-ray acquisition system in the evaluation of the architectural quality of trabecular bone by radiographic texture analysis is optimized to achieve good long-term reproducibility. First, radiographic and digitization processes are modelled and defined. Procedures to make radiographs and their digital images are fixed. Then, measurements of the modulation transfer function (MTF) of the entire acquisition chain were completed. These measurements provide an MTF in excess of 30% at a spatial frequency of 2.5 lp/mm. Also, results of a fractal texture analysis made on digital images of calcaneus radiographs show a mean coefficient of variation of 2.07%. These data show that good long-term reproducibility can make the x-ray acquisition system efficient for patient follow-up, or evaluation of treatment regimes for osteoporosis. Finally, it is shown that fractal texture parameters are statistically different in an osteoporotic population and in a control group. Therefore, this system should also be of medical interest.

Biomechanical properties of human os calcanei: relationships with bone density and fractal evaluation of bone microarchitecture.

The relationship between bone strength and bone mass is well established. The link between trabecular microarchitecture and biomechanical properties has been less extensively explored. To address this question, we have tested the mechanical behaviour of calcaneus bone samples and investigated the correlations between mechanical properties on the one hand, bone density and fractal analysis of microarchitecture on the other hand. Mechanical properties of 43 human os calcanei were determined by uniaxial compression testing of samples from tuber calcanei. Ash density, bulk density and dual energy X-ray absorptiometry of the samples were measured. Fractal analysis of the trabecular bone on calcaneus radiographs was performed by two estimators derived from the fractional Brownian motion model. The mechanical properties of human os calcis were found to correlate with age and density measurements. Fractal parameters derived from the bone texture analysis showed weaker but significant correlations with bone strength. Fractal analysis of texture could account in part for the variations of bone strength, but in this study cannot explain better than density the mechanical properties of trabecular bone. Nevertheless, it provides a non-invasive means of assessing molecular bone microarchitecture.

Electrochemical generation of the Fenton's reagent: application to atrazine degradation.

The degradation of refractory chemicals in water requires chemical oxidation by hydroxyl radicals. Among the systems that may be used to generate OH(o), the Fenton's reagent consists of the mixing of ferrous iron and hydrogen peroxide. Even though this system is very simple, the oxidation of an organic compound is difficult to control and the ferrous iron regeneration is limited. Very recently, electrochemical systems have merged that allow the electrochemical production of ferrous iron and/or hydrogen peroxide, thereby allowing the generation of OH(o). So a simple electro-Fenton system has been used and tested for its efficiency in producing hydroxyl radicals. Atrazine was chosen as a model organic compound as its reaction with OH(o) has been extensively studied. Comparison with the classical Fenton system gives advantage to the electrochemical system, due to a more thorough oxidation of atrazine.

Lipoma in the cerebellopontine angle.

A case of lipoma in the cerebellopontine angle is reported. Intracranial lipomas are very rare, especially in the cerebellopontine angle. To our knowledge, only four cases, including our own, have been operated upon. Until now, total extirpation has not been possible. The singular appearance on computed tomography scanning of this dysembryoplasia is presented together with a bibliography of this subject.

[Follow-up MRI after trans-sphenoidal surgery]. / L'irm aprés chirurgie transsphénoïdale.

The authors report their 10 year experience on postsurgical MRI of the sphenoidal region. All patients underwent MRI examination 4 days after surgery, then between 2 and 3 months and one year or more after surgery. The reproducibility of pulse sequences is mandatory to make a diagnosis of recurrent adenoma as early as possible.

[Rathke's cleft cyst]. / Kystes de la poche de Rathke.

Rathke's cleft cyst (RCC) are frequent benign cystic sellar lesions. Most RCC are small, intrasellar and asymptomatic. Larger cysts may compress adjacent structures and rarely become symptomatic. Diagnosis is strongly suggested at MRI by the presence of a midline non-enhancing lesion located exactly between the anterior and posterior lobes of the pituitary gland. Even if its signal is variable and related to intracystic protein concentration, it must be homogeneous with no fluid-fluid level. Once a diagnosis of RCC made, routine MR and clinical follow-up is sufficient for incidental asymptomatic cysts whereas the rare symptomatic lesions are neurosurgically resected.

[Torticollis and C1-C2 rotation subluxation. Apropos of a case. The value of a dynamic scanner and of a 3-dimensional scanner]. / Torticolis et sub-luxation rotatoire C1-C2. A propos d'un cas. Intérêt du scanner dynamique et du scanner en trois dimensions.

The authors report the rare and complex case of a girl who had been followed since the age of 3 years for hydrocephalus the cause of which was found only when she was 6-year old. The causative agent was a pilocytic astrocytoma of the cerebellum. On April 10, 1990, she underwent subtotal excision of the tumour, associated with radiotherapy. Four months later she developed an increasingly painful and irreducible torticollis which did not respond to tractions. Dynamic CT scans and 3-dimensional CT scans were performed in the fourth month and provided a diagnosis of right C1-C2 rotatory subluxation. There was no history of injury and no sign of inflammatory process. Rotatory subluxation is a very rare lesion difficult to diagnose, and few cases have been published, although the signs are those of classical torticollis in children. When medical treatment fails, often due to belated diagnosis, the only surgical treatment is uni- or bilateral C1-C2 arthrodesis. If the diagnosis can be made at an early stage, reduction of the rotatory luxation is usually easy and without consequences to the child. It is therefore recommended to perform a dynamic CT scan and a 3D CT scan as soon as possible in all children with lasting painful torticollis.

[Hand-Schüller-Christian disease with tumor localization in the posterior fossa]. / Maladie de Hand-Schüller-Christian avec localisation tumorale dans la fosse postérieure.

A 19-year-old girl had been suffering since the age of 4 from Hand-Schüller-Christian disease. The condition was diagnosed by biopsy of a cranial bone lacuna. Later on, she developed diabetes insipidus and bilateral exophthalmos, both being typical signs of Hand-Schüller-Christian disease. At the age of 14, an intracranial tumour in the posterior cerebral fossa was discovered by computerized tomography, but in view of her parent's refusal of surgery, she was operated upon only 4 years later for obstructive hydrocephalus with intracranial hypertension. Two years after this operation, she presented with neurological signs of compression of the medulla oblongata, including tetraparesis and respiratory disorders, and the tumour was resected. Following a brief improvement she died of major hydroelectrolytic disorders due to her irreducible unstable diabetes insipidus. A review of the literature on Hand-Schüller-Christian disease and its rare association with intracranial tumours is analysed. The occurrence of such tumours raise important therapeutic problems and make the prognosis considerably worse.

[Cerebral alveolar echinococcosis. Apropos of a surgically-treated case. Review of the literature]. / Echinococcose alvéolaire cérébrale. A propos d'un cas opéré. Revue de la littérature.

The authors present a case of a cerebral echinococcosis in a male farmer operated upon 9 and 6 years ago for pulmonary and hepatic localisations of Alveolar Echinococcosis. Cerebral lesions were diagnosed by CT scan and MRI and were totally removed. The follow-up was uneventful. A review of the literature revealed only eighteen previously reported surgical cases. The authors comment the epidemiology of this endemic parasitic disease, and the particular aspects of its cerebral localisation.

[Peroperative echography in neurosurgery. Its value and applications 10 years later]. / L'échographie peropératoire en neurochirurgie. Son intérêt et ses applications dix ans après.

Intraoperative ultrasound imaging has many advantages over other imaging methods. The authors present their experience from hundred patients over ultrasound scanning. A large iconography is exposed. Not only the intracerebral lesions such as gliomas or metastases but also abscess or cysts can be controlled or biopsied directly. Per-operative ultrasonography is interesting for spinal cord lesions and spinal traumas. Ten years from the first utilisation in neurosurgery, the method is always used, its cost is low and its practice is very easy.

[Glioblastoma of the cerebellum in a child. Apropos of a case. A review of the literature]. / Glioblastome du cervelet chez un enfant. A propos d'un cas. Revue de la littérature.

Authors present a case of glioblastoma of cerebellum in a 11-year old child. Symptoms and signs are those of other tumors of posterior fossa. Diagnosis was made by CT Scan and pathologist. In spite of radiotherapy, he died one year after craniotomy. Only twenty cases of glioblastoma of cerebellum in childhood were described in the literature.

[Intramedullary neurinoma. Apropos of a case. Review of the literature]. / Neurinome intramédullaire. A propos d'un cas. Revue de la littérature.

The authors present a case of intramedullary neurinoma. A 44 years old patient was admitted for lumbar pain and bilateral sciatica. Neurological examination was normal except for dysuria and diminution of Achilles tendon reflexes. Lumbar spine X-rays and spinal cord angiogram were normal, but myelogram and myelo-scan revealed a fusiform enlargement of the conus medullaris. MRI confirmed this aspect. Total removal of an intramedullary tumor was done, using ultrasonography, operating microscope and ultrasonic aspiration. The post-operative course was uneventful, with, as sequelae a perineal hypoesthesia. Histological examination of the excised tumor revealed a neurinoma. The epidemiology, clinical features, radiology, and surgical treatment of such rare intramedullary tumors are discussed.

[Remodeling the cranial vault in anterior craniosynostoses. Our therapeutic experience of trigonocephaly and plagiocephaly]. / Le remodelage de la voûte du crâne des crâniosténoses antérieures. Techniques personnelles de traitement des trigonocéphalies et des plagiocéphalies.

The authors propose two simple techniques to improve the adaptation of the frontal vault after remodeling the orbito-naso-frontal flap in anterior craniostenosis. In trigonocephaly: the metopic suturectomy is enlarged by lateral translation of the two half frontal bones, then to fall the place the coronal suture is used. The temporal plates are moved forward and turned to fill the failure of fronto-temporal junction due to valgisation of orbito-naso-frontal band. In plagiocephaly: the frontal flattened flap is cut with oblique radial osteotomies starting at bregma so called "Daisy petal". The first internal petal is sacrificed. The others are rotated axially in a medial direction. Internal table corticotomies must be performed at two levels to recurve the flattening and to obtain a curve in the coronal plane. In this two techniques the pericranium and dura-mater must be carefully teated to obtain a better adaptation of the new bone shape and to permit the spontaneous reossification.

[Pituitary gland imaging in Cushing's disease]. / L'imagerie dans la maladie de Cushing.

Specific MR techniques are required for optimal detection of adenocorticotropic hormone secreting adenomas responsible for Cushing's disease. Adequate MR sequences, high resolution coronal T1 and T2 - weighted images, dynamic MR imaging, post-gadolinium delayed images, dose of gadolinium adjusted for each sequence can routinely demonstrate pituitary adenomas less than 3 mm in Cushing's disease.

[Cervical chordoma. Apropos of a case]. / Chordome cervical. A propos d'un cas.

The chordomas are malignant tumors arising from the remnants of the posterior spinal chord. The chordomas of the cervical spine are rare (5% of the spinal chordomas). A new case of spine chordoma at C5 level in a 76 years old woman is reported. The diagnosis depends on the results of the histological studies and especially the studies of the labelled elements as Protein S100 or Cytokeratin. Firstly a double osteosynthesis was realized by an anterior and posterior approach. There was no radiotherapy after this operation. A new operation for a fracture of odontoid process was necessary one year later. There was no recurrence. The patient was complaining from pains, two years after the first operation in relation to lateral recurrence. A third operation by an anterior approach was realized. A radiotherapy of 50 Gy was applied on the same level. The first osteosynthesis was with acrylic cement and the second one with an autologous bone graft and a plate after removing the cement without problem. Actually she is in good health, 78 years old.

[Cauda equina syndrome complicating cutaneous T-cell lymphoma (mycosis fungoides)]. / Compression de la queue de cheval compliquant un lymphome cutané à cellules T (mycosis fongoïde).

Authors present a case of a cutaneous T. cell lymphoma (mycosis fungoides) complicated by a cauda equina syndrome. Crural and sciatic radicular pain were due to epidural lumbar involvement by tumoral process. After surgical decompression completed by chemotherapy the evolution was uneventful. This case is the second one reported in the literature.

[Solitary plasmacytoma simulating pituitary adenoma]. / Plasmocytome solitaire simulant un adénome hypophysaire.

A case of solitary plasmocytoma of the sphenoid is reported, masquerading as pituitary adenoma. At the time of surgery, the patient had no findings of multiple myeloma. The tumor was removed by trans-sphenoidal route and radiotherapy delivered. The post-operative course was uneventful, and two years later, there is no sign of recurrency or extension of multiple myeloma.