Deviation from Archie's law in partially saturated porous media: Wetting film versus disconnectedness of the conducting phase

We experimentally study the electrical transport in partially water-saturated pore network. The porous medium under investigation is a Fontainebleau sandstone, characterized by x-ray tomography. We show the existence of two electrical conductivity regimes. At high water saturation, the electric resistivity follows a well-known Archie law. Below a water saturation S_{w} approximately 0.2 , a strong negative deviation from this Archie law is observed. We attribute this transition to the existence of "a thick liquid film," assuring the ionic conduction in the low saturation regime. A numerical simulation is proposed to confirm this scenario. Two possible protocols are used to distribute the brine phase in the pore network of a three-dimensional microtomography image. The first one is based on a minimization of the interfacial energy. The second takes into account a quasistatic capillary displacement. The classical random-walk algorithm is used to compute the electric conductivity at various water saturations. Without the "thick film," both of the two fluid-placing protocols show a disconnectedness transition of the brine phase when S_{w}<0.2 . Adding this "film" to solid surface, the electrical continuity is maintained. The bending down trend is correctly reproduced, showing that in this range, the electric response cannot be described by a power law as usual.

[Recurrent inflammatory optic neuropathy]

PURPOSE

To analyze clinical and paraclinical characteristics of recurrent isolated optic neuropathy.

PATIENTS

and method: In three university hospitals (Montpellier, Nimes, and Strasbourg), between October 2005 and September 2006, the charts of patients with corticosensitive recurrent isolated optic neuropathy and normal cerebral magnetic resonance imaging included prospectively were reviewed. The following parameters were analyzed: date of the first relapse, age at onset, duration at the time of inclusion, recurrence after steroid withdrawal, unilateral or bilateral involvement, number of relapses, visual acuity, retinal nerve fiber layer thickness, diagnostic workup, and long-term treatment with immunosuppressive or immunomodulatory drugs.

RESULTS

During the predefined period, 13 patients (11 women, 2 men; age, 17-54 years at onset) matched the inclusion criteria. Between two and six relapses of optic neuropathy were observed. The median duration was 4 years. In untreated patients (n=7), a significant (Spearman p=0.0156) inverse correlation was observed between visual acuity and duration of the disease; this correlation was not found in the group of patients (n=6) with long-term treatment (Spearman p=0.1032).

CONCLUSION

The progressive loss of vision over time in this retrospective study of recurrent isolated optic neuropathy could be related to axonal loss. A prospective cohort study is necessary to confirm this hypothesis and to evaluate the benefit of long-term treatment on this progression.

Prefracture syndrome of the hip fracture: a case control study

BACKGROUND

Hip fractures result from both bone fragility and trauma, more often a sideways fall. Spontaneous hip fractures have been described; in such cases, patients reported pain ("prefracture" syndrome) in the hip region for weeks before the fracture.

OBJECTIVES

To identify the proportion of patients who had a pain in the hip region before a hip fracture, to compare this proportion to the one observed in controls and to describe the characteristics of this pain.

PATIENTS AND METHODS

For a period of 6 months, each subject (>65 years) treated for hip fracture was prospectively recruited in an orthopaedic surgery department. Exclusion criteria were: alterations of cognitive functions (defined by a mini mental state <20), refusal, and fractures related to bone metastasis or multiple myeloma. Subjects were compared to sex-matched controls consulting in an acute care geriatrics unit. They were asked about the occurrence of pain in hip region before the fracture and its characteristics.

RESULTS

Thirty-eight patients (31 women, 7 men, mean age 83.1 [+/-7.6]) were included and were compared to 38 sex-matched controls (31 women, 7 men, mean age 82.7 [+/-6.9]). Among the 38 patients with hip fracture, 10 (26.3%) reported a pain in the hip region, compared with 2 (5.3%) in the control group (p=0.01).

CONCLUSION

A better recognition of "prefracture" pain in the elderly may allow adequate management and treatment of patients, in order to avoid a proportion of hip fractures.

Relevance of the antibody index to diagnose Lyme neuroborreliosis among seropositive patients

BACKGROUND

No consensual criteria exist to diagnose neuroborreliosis. The intrathecal anti-Borrelia antibody index (AI) is a necessary criterion to diagnose neuroborreliosis in Europe, but not in the United States. Previous studies to determine the diagnostic value of the AI found a sensitivity ranging from 55% to 80%. However, these studies included only typical clinical cases of meningitis or meningoradiculitis, and none had a control group with CSF anti-Borrelia antibodies.

METHODS

We studied a sample of 123 consecutive patients with clinical signs of neurologic involvement and CSF anti-Borrelia antibodies. We determined the AI for all patients and a final diagnosis was made. Patients were then divided into three groups (neuroborreliosis, possible neuroborreliosis, control).

RESULTS

Thirty of the 40 patients with neuroborreliosis had a positive AI (AI sensitivity = 75%). Two of the 74 patients with another neurologic diagnosis had a positive AI (AI specificity = 97%).

CONCLUSION

The antibody index has a very good specificity but only moderate sensitivity. Given the lack of consensual criteria for neuroborreliosis and the absence of a "gold standard" diagnostic test, we propose pragmatic diagnostic criteria for neuroborreliosis, namely the presence of four of the following five items: no past history of neuroborreliosis, positive CSF ELISA serology, positive anti-Borrelia antibody index, favorable outcome after specific antibiotic treatment, and no differential diagnosis. These new criteria will need to be tested in a larger, prospective cohort.

Primary progressive multiple sclerosis: a comparative study of the diagnostic criteria

We assessed the different sets of diagnostic criteria for primary progressive multiple sclerosis (PPMS), in order to determine their sensitivity when applied to a cohort of 261 PPMS patients. According to the Thompson criteria, 168 patients (64.4%) had definite PPMS, 84 patients (32.2%) had probable PPMS, and nine patients (3.4%) had possible PPMS; according to the McDonald criteria, 180 patients (69%) had PPMS; according to the revised McDonald criteria, 194 patients (74.3%) had PPMS. Our findings indicate that the revised McDonald criteria are more sensitive than the original McDonald criteria, but less sensitive than the Thompson criteria. Multiple Sclerosis 2007; 13: 622-625. http://msj.sagepub.com

Nuclear magnetic resonance diffusion with surface relaxation in porous media

Nuclear magnetic resonance (NMR) diffusion simulations with surface relaxation were performed numerically in unconsolidated and consolidated porous media by a random walk technique. Two uniform and nonuniform models of surface relaxation were proposed and compared. The apparent diffusion coefficient and extinction function were determined and studied in the fast, slow and intermediate diffusion regimes of relaxation. According to theoretical predictions, it was observed that the extinction function does not depend on surface relaxivity parameter rho 2 in the slow diffusion regime. The apparent diffusion coefficients are independent of rho 2 in the fast diffusion regime and tend to be superposed onto a single curve in the slow one. The evolution of the apparent diffusion coefficients is gathered by a reduced representation in the fast diffusion regime.

Ataxie avec sensibilité au gluten, mythe ou réalité ?

INTRODUCTION

Gluten ataxia refers to the association of idiopathic ataxia despite exhaustive investigations with gluten sensitivity defined by anti-gliadin antibodies (AGA) presence in blood. This is a controversial concept.

PATIENTS AND METHODS

We screened 33 patients, who were hospitalized in 2003 and had subacute or chronic ataxia for presence of circulating AGA. Twelve patients were positive and their clinical and biological features were studied.

RESULTS

Among the twelve patients, we concluded that gluten ataxia was present in only eight, including one case of celiac disease. Among these eight patients, five had the usual features of gluten ataxia (progressive cerebellar ataxia affecting mainly lower limbs), but one patient presented unusual left cerebellar hemisyndrome and the two others displayed polyneuropathy with proprioceptive ataxia. Cerebellar atrophy was confirmed with magnetic resonance imaging in five cases and association with other antibodies was found in six cases. Among the four other patients positive for AGA, investigations revealed one case of multiple sclerosis, one case of late-onset Friedreich ataxia, one case of basilar tuberculous meningitis and one case of type 2 diabetes.

CONCLUSION

Screening for AGA presence should be systematically performed at presentation of patients with unknown etiology ataxia; in the event AGA are present without any other etiology, treatment with gluten-free diet must be discussed. However, the responsibility of AGA in the pathogenesis of neurological signs is highly debatable and further experimental work is required. Two pathophysiological hypotheses are suggested: (1) overexpression of cerebellar epitopes, in case of primary cerebellar pathology, leading to excessive immune response directed against these epitopes; and (2) molecular mimicry with cross-reactivity of antigens usually directed against gliadin, but also recognizing Purkinje cells epitopes.

[Vogt-Koyanagi-Harada syndrome]

INTRODUCTION

Vogt-Koyanagi-Harada syndrome is a rare, inflammatory disease with manifestations affecting the ocular, central nervous, audito-vestibular, and integumentary systems. Vogt-Koyanagi-Harada syndrome is more frequent in Asia but is also described in Europe. We report three new non asiatic cases of this syndrome.

OBSERVATIONS

The three patients had bilateral panuveitis and hypoacusia. Two of them had peripheral facial palsy, two of them had vestibular syndrome and one of them lymphocytic meningitis. In each case we found characteristic HLA II typing and in one case we discovered the simultaneous presence of three auto-antibodies: anti-retina (anti-Arrestin type), anti-choroid and anti-cochlea. These patients were treated by corticosteroids but required an additional treatment by cyclophosphamide (0.8g/m2). The clinical course was favorable with visual sequelae for two and auditory one for one.

DISCUSSION

These biological and therapeutic elements and a review of the recent literature are in favor of an autoimmune origin of this syndrome.

L’amyotrophie bulbaire et spinale liée au chromosome X : une étude clinique, neurophysiologique et moléculaire de 12 patients issus de 4 familles

INTRODUCTION

Spinal and bulbar muscular atrophy (SBMA) is an X-linked, late-onset neuro-endocrine disorder resulting from an expansion of a CAG repeat in the androgen receptor gene. Material and method. We report the detailed phenotypic study in a series of 12 SBMA patients evaluated in four kindreds.

RESULTS

Clinical phenotypic spectrum varied considerably, ranging from childhood-onset weakness and atrophy mimicking limb-girdle myopathy in patients with 53 CAG repeats to isolated hyperCKemia in an adult with 42 CAG repeats. All male patients had gynecomastia. Two female carriers presented with paresthesias and hand action tremor. Homozygous deletions of SMN1 and SMN2 genes were not found in any patients.

CONCLUSION

This report demonstrates that SBMA may present with a wider clinical spectrum than previously described and suggests that clinical phenotype severity in SBMA is partially linked to the number of CAG repeats. It also suggests that SMN1 and SMN2 genes do not act as modifying genes in SBMA.

Aggravation aiguë régressive d’une maladie de Charcot-Marie-Tooth de type 1B : la Protéine P0 peut-elle agir comme un auto-antigène ?

INTRODUCTION

The natural history of Charcot-Marie-Tooth neuropathy is marked by accentuated motor and sensitive deficits suggestive of acute polyradiculoneuritis or, more generally, chronic inflammatory demyelinizing polyneuropathy.

OBSERVATION

A 41-year-old woman, with Charcot-Marie-Tooth (CMT) 1B neuropathy associated with a P0 gene mutation, developed several episodes of ataxia which resolved after intravenous administration of IgG or corticosteroids.

CONCLUSION

The sudden increase of a motor or sensitive deficit in this patient with CMT type I led to two hypotheses: chance association between an inherited and an inflammatory neuropathy, or a dysimmune inflammatory reaction, the mutated protein acting like an autoantigen. These two hypotheses are discussed.