Dixièmes Journées des Maladies du Système Nerveux Périphérique Neuropathies aux statines, mythe ou réalité?

BACKGROUND

Statins are lipid-lowering drugs widely used in the world. They are effective and safe in the treatment and in the primary and secondary prevention of cerebrovascular and cardiovascular diseases. Besides they are known for their muscular side-effects. It has been suggested that they also have a toxic effect on the peripheral nervous system.

STATE OF ART

Case reports and retrospective studies emphasize the possibility that statins can induce peripheral nerves side-effects. A single prospective study contradicts this hypothesis. Statins are hydroxymethyl glutaryl coenzyme A reductase (HMGCoA reductase) inhibitors, this action is responsible for the lipid-lowering effect but can also explain the nervous toxicity. Statins interfere with cholesterol synthesis that may alter myelin and nerve membrane function and they prevent mitochondrial respiratory chain enzyme synthesis which may disturb neuron energy use.

CONCLUSIONS

It can be considered that statins have an insignificant toxicity on peripheral nerves. The relevance of their prescription must be however well evaluated and treated patients must be closely followed.

Myasthenia gravis exacerbation or unmasking associated with telithromycin treatment

Telithromycin, a new ketolide antibiotic, has been implicated in the exacerbation or unmasking of myasthenia gravis. This retrospective study presents two clinical reports and summarizes eight other suspected cases notified to the French pharmacovigilance system, highlighting a potentially life-threatening risk of telithromycin treatment in myasthenic patients. An important common feature was that, in seven cases, symptomatology occurred within 2 hours of first telithromycin intake--notably in cases of severe exacerbation.

P2X1 receptors mediate sympathetic postjunctional Ca2+ transients in mesenteric small arteries

Brief, spatially localized Ca(2+) transients occur in the smooth muscle adjacent to perivascular nerves of small arteries during neurogenic contractions. We named these "junctional Ca(2+) transients" (jCaTs) and postulated that they arose from Ca(2+) entering smooth muscle cells through P2X(1) receptors activated by neurally released ATP. Nevertheless, the lack of potent, subtype-selective P2X-receptor antagonists made determining the exact molecular identity of the channels difficult. Here we used small, pressurized mesenteric arteries from P2X(1)-receptor-deficient mice (KO) to test the hypothesis that jCaTs arise from Ca(2+) entering the smooth muscle cell via P2X(1) receptors. In wild-type (WT) arteries, confocal microscopy of fluo-4 fluorescence during electrical field stimulation (EFS) of perivascular sympathetic nerves revealed jCaTs in the smooth muscle cells adjacent to the perivascular nerves, similar to those reported previously in rat arteries, and alpha-latrotoxin (2.5 nM) markedly increased the frequency of "spontaneous" jCaTs. In the KO arteries, however, neither EFS nor alpha-latrotoxin elicited any jCaTs. A potent P2X-receptor agonist, alpha,beta-methylene ATP (10.0 microM), elicited strong contractions and increased intracellular Ca(2+) concentration in WT arteries but elicited neither in KO arteries. A biphasic vasoconstriction in response to EFS was observed in WT arteries. In KO arteries, however, the initial rapid, transient component of the biphasic vasoconstriction was absent. The data support the hypothesis that jCaTs represent Ca(2+) that enters the smooth muscle cells through P2X(1) receptors activated by neurally released ATP and that this Ca(2+) is involved in the initial rapid component of the sympathetic neurogenic contraction.

[Diagnostic value of autoantibodies to MAG by ELISA Bühlmann in 117 immune-mediated peripheral neuropathies associated with monoclonal IgM to SGPG/SGLPG]

The neuropathies associated with monoclonal IgM gammopathy reacted with glycoconjugated targets on a very antigenic epitope on the sulfated glucuronic glycolipids corresponding to SGPG and SGLPG (sulfoglucuronyl paragloboside and sulfoglucuronyl lactosaminyl paragloboside), myelin-associated glycoprotein (MAG) and sulfatide. Sometimes monoclonal IgM binds to a broad spectrum of gangliosides. The detection of targets of autoantibodies has considerable importance in the diagnosis and management of patients. It is not known whether the results of antibody tests are equally sensitive and specific for identification of involved auto-antigens. In this study we evaluated the results obtained using IgM reactivity against MAG by enzyme-linked immunosorbent assay (ELISA Bühlmann) with IgM reactivity against SGPG/SGLPG obtained by overlay thin-layer chromatography. We selected 117 patients with anti-SGPG/SGLPG monoclonal gammopathy and peripheral neuropathy and a control group of 102 peripheral neuropathies with 24 having IgM high titres of monoclonal IgM anti-ganglioside antibodies. The anti-MAG sensitivity was 0.97, specificity was 0.86. There is a crossreactivity between 8 (57%) monoclonal IgM antibodies anti-MAG and anti-ganglioside GM1 and 2 (28%) anti-disialylated gangliosides. These results indicate that in clinical practice, anti-MAG ELISA is useful for eliminating anti-MAG neuropathy, as well as for positive diagnosis for titres upper than 10,000 BTU. It is also alpha good test to appreciate clinical improvement after Rituximab treatment.

[What are the clinical criteria of amyotrophic lateral sclerosis by clinical form?]

The diagnosis of ALS requires the presence of lower and upper motor neuron degeneration and a progressive spread of symptoms and signs. Due to the lack of any biological diagnostic marker, the World Federation of Neurology established clinical and paraclinical criteria (El Escorial 1991; Airlie House 1998). These criteria allow to establish a diagnosis with various levels of certainty. In practice they have a low sensitivity, especially at the beginning of the disease, and may delay the diagnosis. They exclude also some clinical forms and are not helpful in the differential diagnosis.

[Electrophysiological manifestations of chronic inflammatory demyelinating polyradiculoneuropathy]

There are four basic electrophysiological parameters of demyelination: reduced motor conduction velocity, prolonged distal motor latency and F waves, and motor conduction blocks. These parameters are combined to determine an electrophysiological set of criteria for chronic inflammatory demyelinating polyneuropathy (CIDP). Whereas their specificity is good, their sensitivity level does not exceed 75 percent. However, these sets of criteria are not commonly used especially in benign forms, at the beginning of the disease, in associated forms or in case of secondary axonal degeneration. We can push the limits using others criteria such as the terminal latency index, sensory criteria, or by the contribution of others electrophysiological procedures such as the radicular stimulation or sensory evoked potentials. Due to the therapeutic implications, any axonal neuropathy without aetiologia, with at least one demyelinating electrophysiological criteria, could be considered as a putative CIDP.

[Screening for anti-glycolipid antibody profiles from patients with immune-mediated peripheral neuropathies by Dotzen Ganglio Profile Antibodies]

The presence of anti-glycolipid specific antibodies have been found to be associated with acute and chronic immune-mediated peripheral neuropathies. Recently a number of anti-glycolipid antibody assays have became commercially available. In this study we established specific anti-glycolipid antibody profiles in a series of sera by the Dotzen Ganglio Profile antibodies. This kit screens for the simultaneous detection of ten anti-glycolipid antibodies against GM3, GM2, GM1, GD3, GD1a, GD1b, GT1a, GT1b, GQ1b gangliosides and sulfatides of the IgM and IgG classes. Sera from 89 patients with acute and chronic neuropathies were selected in a well-characterized cohort of banked sera with anti-glycolipid antibody profiles identified by in-house immunodot assay. Serum from 52 clinical variants of Guillain-Barré syndrome with IgG autoantibody profiles and 37 chronic acquired peripheral neuropathy with IgM autoantibody profiles were tested. The assay correctly identified with good agreement 50 of 52 IgG antibody profiles and 32 of 37 IgM antibody profiles. The assay compared well with in-house immunodot assay. It is easy to screen 10 crossreacting glycolipid antibodies to establish specific antibody profiles to define different subgroups of immune-mediated peripheral neuropathies for classification and immune management.

Polyradiculonévrites inflammatoires démyélinisantes chroniques : stratégie diagnostique

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) comprises a group of dysimmune neuropathies easily diagnosed in more than half of the patients. Diagnosis is based on clinical, electrophysiological and biological clues. In some patients, diagnosis is unclear because of the debated value of the available clues. In such circumstances, dysimmune neuropathies may not be diagnosed, leading to insufficient treatment. This is an important category of patients because immunomodulatory drugs have proven efficacy. The CIDP spectrum includes a relatively wide range of diseases. Besides the easily recognized classic forms, there are many clinical variants, sometimes with a paucisymptomatic presentation leading to uncertain diagnosis. The French CIDP study group has established guidelines for diagnostic strategy in CIDP patients. The first part of this paper is devoted to the clinical aspects of the disease, classical forms and variants. In the second part, the results of electrophysiological studies are reported. In a third chapter, complementary examinations useful for diagnosis are discussed. The fourth chapter deals with the diagnostic strategy, discussed in relation to the different situations which may be encountered in clinical practice. details the technical modalities of appropriate electrophysiological studies and presents normal results together with those indicating demyelinating neuropathy. Nerve biopsy technique and results are given in appendix II.

Renal autoregulation in P2X1 knockout mice

Autoregulation of renal blood flow is an established physiological phenomenon, however the signalling mechanisms involved remain elusive. Autoregulatory adjustments in preglomerular resistance involve myogenic and tubuloglomerular feedback (TGF) influences. While there is general agreement on the participation of these two regulatory pathways, the signalling molecules and effector mechanisms have not been identified. Currently, there are two major hypotheses being considered to explain the mechanism by which TGF signals are transmitted from the macula densa to the afferent arteriole. The adenosine hypothesis proposes that the released adenosine triphosphate (ATP) is hydrolysed to adenosine and this product stimulates preglomerular vasoconstriction by activation of A(1) receptors on the afferent arteriole. Alternatively, the P2 receptor hypothesis postulates that ATP released from the macula densa directly stimulates afferent arteriolar vasoconstriction by activation of ATP-sensitive P2X(1) receptors. This hypothesis has emerged from the realization that P2X(1) receptors are heavily expressed along the preglomerular vasculature. Inactivation of P2X(1) receptors impairs autoregulatory responses while afferent arteriolar responses to A(1) adenosine receptor activation are retained. Autoregulatory behaviour is markedly attenuated in mice lacking P2X(1) receptors but responses to adenosine A(1) receptor activation remain intact. More recent experiments suggest that P2X(1) receptors play an essential role in TGF-dependent vasoconstriction of the afferent arteriole. Interruption of TGF-dependent influences on afferent arteriolar diameter, by papillectomy or furosemide treatment, significantly attenuated pressure-mediated afferent arteriolar vasoconstriction in wild-type mice but had no effect on the response in P2X(1) knockout mice. Collectively, these observations support an essential role for P2X(1) receptors in TGF-mediated afferent arteriolar vasoconstriction.

[Anti-GD1b IgG positive case of overlapping Ficher's and Guillain-Barré syndromes]

We describe a patient who developed overlapping sensory ataxic form of Guillain-Barré syndrome (GBS) and Miller Fisher syndrome (MFS) following Campylobacter jejuni infection. Two cerebrospinal fluid examinations shown albuminocytologic dissociation associated with Campylobacter jejuni infection after tongue pierced. He had high titers of monospecific anti-GD1b IgG antibody. Because of the rarety of this disorder the diagnostic was difficult. There is a close association of IgG anti-ganglioside GD1b antibodies in sensory ataxic GBS. The findings of the present study show that antibody to GD1b ganglioside is one of the immunological factors in the pathogenesis of sensory ataxic form of GBS, a rare specific immuno-clinical variant form of GBS with prominent sensory ataxia.

[Electrodiagnostic assessment of neuromuscular junction disorders]

Electrodiagnosis of neuromuscular junction disorders relies on repetitive nerve stimulation tests (RS) and single-fiber EMG (SFEMG). RS tests are usually performed on proximal and distal nerves (axillary, accessory, radial, facial, ulnar, median, peroneal). Ischemic test substantially improves ulnar RS sensitivity. More recently RS of masseter and hypoglossal nerves have been proposed to increase RS sensitivity in patients with bulbar symptoms in myasthenia gravis (MG). RS of phrenic and long thoracic nerves could be used in MG patients with respiratory symptoms. Sensitivities of these tests are widely different but they are complementary. SFEMG is far more sensitive but technical difficulties have limited its use. In generalized MG, RS should be performed first. Clinically involved muscles should be examined first, then other muscles. If RS tests are negative, SFEMG of facial muscles can be used. In ocular MG, SFEMG, if available, is the best option. In Lambert-Eaton myasthenic syndrome, a single shock on ulnar nerve before and after a brief maximum voluntary contraction should be used to demonstrate increment and 3 Hz RS a decrement. If negative, median and radial nerves should be studied. Additionally electrodiagnosis features of congenital myasthenic syndromes and botulism are reviewed.

[Symptomatic carriers of dystrophinopathy with chromosome X inactivation bias]

Several studies have recently highlighted the fact that the clinical involvement in females carrying a mutation in the dystrophin gene could be more frequent than usually thought, suggesting the need of a careful cardiac follow-up. Except for the classical chromosomal rearrangements, it was shown that a bias in the X chromosome inactivation process could be found in some affected females. We report two families illustrating different situations. The propositus of the first family, aged 32, presented with a proximal muscular weakness, increasing for three years, as well as elevated muscular enzymes in blood. Her brother suffered from classical Duchenne muscular dystrophy. Her mother was more severely affected, whereas her sister remained asymptomatic. A duplication of exons 3 to 7 of the dystrophin gene was found in all four patients. The affected carrier from the second family was a sporadic case. She has been suffering from proximal muscular weakness for six years. Muscle biopsy showed a mosaic pattern of the immunostaining using specific antidystrophin antibodies. A stop mutation was found in exon 52. Her ten year-old daughter, carrying the mutation, was asymptomatic. In both families, the inactivation profiles were in accordance with the clinical presentation. We discuss the different mechanisms that may lead to the inactivation bias in these patients, as well as the advantage and limits of using the X chromosome inactivation test as a tool for diagnosis and prognosis purpose in symptomatic carriers for dystrophinopathies.

[Antiganglioside autoantibody profiles in Guillain-Barré syndrome]

We established anti-ganglioside antibody profiles in GBS and studied the frequency, fine specificity and clinical correlate. IgG and IgM antibodies to 8 gangliosides were tested by immunodot-blot in 249 consecutive patients with Guillain-Barré syndrome with large variability in clinical expression, referred to our laboratory over a 8-year period. IgG and IgM anti-GM1 antibodies were measured by Elisa. Thin-layer chromatography overlayed by serum was used to control positivity. 89/249 GBS (36%) had characteristic anti-ganglioside antibody profile. Isotypes were, IgG (62%), IgG + IgM (26%) and IgM (12%). Antecedent infections were found in 62% of GBS included more frequently Campylobacter jejuni and cytomegalovirus. Various autoantibody profiles were described with an immunodominant ganglioside. We detected 6 characteristic anti-ganglioside profiles with fine specificity and immunodominant ganglioside corresponding to 6 immuno-clinical variants of GBS: 1) anti-GM1 and GD1b IgG and IgG > IgM in the acute motor axonal neuropathy after Campylobacter jejuni infection in 41 GBS; 2) anti-GD1a IgG in 6 severe motor axonal GBS after Campylobacter jejuni infection; 3) selectively anti-GQ1b IgG in 17 typical Miller Fisher syndrome with areflexia, ataxia and ophthalmoplegia; 4) anti- GT1b ganglioside and polysialogangliosides IgG (n = 9) in two separate cranial nerve variants, ophthalmoplegic SGB and lower cranial nerve variants depending upon the presenting deficit; 5) anti-GD1b IgG in 5 pure ataxic sensory GBS (4%); 6) anti-GM2 IgM in 11 severe GBS with antecedent CMV infection (8%). 34 GBS (14%) had low levels of anti-GM1 and GD1b IgM antibodies which are not disease specific and may simply represent part of the naturally occurring autoantibody population or a secondary response to disease. 126 GBS (50%) had no antibodies, predominantly in classical form. Associations between isotype, fine specificity and clinical presentation permit the definition of homogeneous immuno-clinical variants. Various autoantibody profiles with diagnostic and prognostic value are easy to perform by immunodot blot in acute peripheral neuropathies.

Intraoperative monitoring of facial EMG responses during microvascular decompression for hemifacial spasm. Prognostic value for long-term outcome: a study in a 33-patient series

Lateral spread responses (LSR), an electrophysiological characteristic of hemifacial spasm (HFS), can be recorded during surgery. This work aims at evaluating the prognostic value of the persistence or suppression of the LSR at the end of the microvascular decompression (MVD) procedure of the facial nerve. Thirty-three patients with HFS, which had been evolving for 5.5 years, underwent MVD with intraoperative EMG. Monitoring required the placement of a needle in the frontalis and mentalis muscles. Responses were recorded after stimulation of inferior or superior branches of the facial nerve to search for abnormal ephaptic LSR. Preoperative abnormal LSRs were present in all patients. In 23 patients, LSR disappeared with vascular decompression and was not present upon closure. Among those patients, 20 were considered clinically cured and three still presented with mild/moderate spasm at 3-month follow-up. At late follow-up, 22 patients were free of spasm. One patient had recurrence of spasm at month 10. On the contrary, 10 patients had persistent abnormal LSR upon closure. Among those, seven were cured at early follow-up (3 months on average), whereas spasm disappeared at late follow-up (12 to 36 months) in the other three patients. The prognostic value of LSR monitoring is questionable; a good clinical result may be obtained in patients who presented with persistent LSR at the end of MVD. Delayed cure strongly supports the hypothesis that HFS is not only due to the mechanical pulsations of the elongated artery against the root exit zone of the facial nerve, but also to demyelination of the nerve and/or hyperactivity of the facial motornucleus generated by the neurovascular compression.

Mitochondrial creatine kinase binding to liposomes and vesicle aggregation: effect of cleavage by proteinase K

Mitochondrial creatine kinase and its proteinase K nicked-derivative interaction with liposomes induced slight secondary structure changes evidenced by infrared spectra. In nondenaturing conditions, the N-terminal (K1) and the C-terminal (K2) fragments remained associated with each other and bound to liposomes. When the two fragments were separated by denaturation, K2 was soluble, whereas most of K1 was adsorbed onto liposomes. The three-dimensional structure of uncleaved mtCK suggests that the C-terminal moiety, which contains positively charged surface residues, interacted with membranes. After denaturation and renaturation of the nicked enzyme, both peptides did not refold properly and did not reassociate with each other. The misfolded K1 fragment bound to the membrane through a stretch of positive residues, which were buried in the native enzyme. The lack of binding of the ill-folded K2 peptide could be related to the disruption of the optimal disposition of its positive charges, responsible for the correct interaction of native mtCK with membrane.