Syndrome de Lambert-Eaton et neuroblastome chez l'enfant : à propos de 2 observations

Lambert-Eaton myasthenic syndrome is a paraneoplasic syndrome which can reveal a primitive tumor. Frequently, the first diagnosis is myasthenia gravis. This disease is extremely rare in children. Only 10 cases have been reported in the last 35 years. We report 2 new observations occurring in very young patients, aged 2 and 3 years, with a ganglioneurobastoma as primitive tumor.

Cortical versus spinal dysfunction in amyotrophic lateral sclerosis

Little is known about the possible link between cortical and spinal motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). We correlated the characteristics of the responses to transcranial magnetic stimulation (TMS) with the electromechanical properties and firing pattern of single motor units (MUs) tested in nine ALS patients, three patients with Kennedy's disease, and 15 healthy subjects. In Kennedy's disease, 19 of 22 MUs were markedly enlarged with good electromechanical coupling and discharged with great variability. Their excitatory responses increased with MU size. In ALS, 17 of 34 MUs with excitatory responses behaved as in Kennedy's disease. By contrast, 28 MUs with nonsignificant responses showed poor electromechanical coupling and high firing rates, whereas 28 MUs with inhibitory responses showed moderate functional alterations. This result indicates that in ALS as in Kennedy's disease, sprouting of corticospinal axons may occur on surviving motoneurons. A clear relationship exists between the responsiveness of MUs to TMS and their functional state.

Covariation of corticospinal efficiency and silent period in motoneuron diseases

For a better understanding of the changes affecting the cortically induced silent period (SP) in motoneuron disease, the excitatory and inhibitory effects of transcranial magnetic stimulation were explored repeatedly in 8 patients with amyotrophic lateral sclerosis (ALS), 3 patients with Kennedy's disease (KD), and 10 healthy subjects. In KD, the background electromyogram (EMG) and the motor evoked potential (MEP) area were both enhanced. However, neither the corticospinal efficiency (MEP gain, the ratio between MEP and background EMG) nor the duration of the SP differed from healthy subjects. In ALS patients, the MEP gain and the SP duration decreased conspicuously with time. We conclude that use of the MEP gain improves detection of corticospinal dysfunction in ALS patients. Part of the SP shortening in ALS seems to reflect the reduced activation of cortical or spinal inhibitory networks by the abnormal corticospinal pathway.

Treatment of myasthenia gravis exacerbation with intravenous immunoglobulin: a randomized double-blind clinical trial

BACKGROUND

The optimal dose of intravenous immunoglobulin (IVIG) in acute exacerbation of myasthenia gravis remains unknown. Increasing the treatment duration might provide added efficacy.

OBJECTIVE

To determine the optimal dose of IVIG for treating myasthenia gravis exacerbation.

DESIGN

Randomized double-blind placebo-controlled multicenter trial designed to demonstrate superiority of the 2 g/kg dose over the 1 g/kg dose of IVIG, conducted between November 13, 1996, and October 26, 2002.

PARTICIPANTS

One hundred seventy-three patients aged 15 to 85 years with acute exacerbation of myasthenia gravis.

INTERVENTION

Participants were randomly assigned to receive 1 g/kg of IVIG on day 1 and placebo on day 2 (group 1) vs 1 g/kg of IVIG on 2 consecutive days (group 2).

MAIN OUTCOME MEASURE

Improvement in the myasthenic muscular score after 2 weeks.

RESULTS

The mean improvements in the myasthenic muscular scores after 2 weeks were 15.49 points (95% confidence interval, 12.09-18.90 points) in group 1 and 19.33 points (95% confidence interval, 15.82-22.85 points) in group 2. However, the difference between the 2 groups was not significant (effect size, 3.84 [95% confidence interval, -1.03 to 8.71]; P = .12).

CONCLUSION

This trial found no significant superiority of 2 g/kg over 1 g/kg of IVIG in the treatment of myasthenia gravis exacerbation.

[Pathophysiological characterization of congenital myasthenic syndromes: the example of mutations in the MUSK gene]

Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and are characterized by a dysfunction of the neurotransmission. They are heterogeneous at their pathophysiological level and can be classified in three categories according to their presynaptic, synaptic and postsynaptic origins. We report here the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding a postsynaptic molecule, the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.

Towards the molecular elucidation of congenital myasthenic syndromes: identification of mutations in MuSK

Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and characterized by a dysfunction of the neurotransmission. They are heterogeneous at the pathophysiological level and can be classified in three categories according to their origin: presynaptic, synaptic or postsynaptic. The strategy for the diagnosis and characterization of CMS relies on the clinic, EMG, muscle biopsy, identification of mutations in genes known to be responsible for CMS and the demonstration that the gene mutations are the cause of the disease by using experimental approaches. As an example of such strategy, we report briefly here the characterization of the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding a postsynaptic molecule, the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed marked pre- and postsynaptic structural abnormalities of the neuromuscular junction as well as a severe decrease in acetylcholine receptor epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The results obtained strongly suggested that the missense mutation, in the presence of a null mutation on the other allele, was responsible for the severe synaptic changes observed in the patient and, hence, is causing the disease. However the molecular origin of a large number of CMS is still unknown. There are hundreds of molecules known to be present at the NMJ and mutations in the genes coding for these synaptic molecules are likely to be responsible for a neuromuscular block.

Functional sparing of intrafusal muscle fibers in muscular dystrophies

In a previous study, we showed that patients with muscular dystrophies (MDs) perceive passive movements, experience sensations of illusory movement induced by muscle tendon vibration, and have proprioceptive-regulated sways in response to vibratory stimulation applied to the neck and ankle muscle tendons. These findings argue for preserved proprioceptive functions of muscle spindles. However, it is unclear whether the function of intrafusal muscle fibers is spared, i.e., whether they retain their ability to contract when submitted to a fusimotor drive. To answer this question, we analyzed the effects of reinforcement maneuvers (mental computation and the Jendrassik maneuver) that are known to increase muscle spindle sensitivity via fusimotor drive in healthy subjects. Nine patients with different MDs participated in the study. Reinforcement maneuvers increased both the mean amplitude of the Achilles tendon reflex (187 +/- 52.9% of the mean control amplitude) and the sensitivity of muscle spindle afferents to imposed movements of the ankle. The same reinforcement maneuvers failed to alter the amplitude of the Hoffmann reflex in the triceps surae muscle. These results suggest that the intrafusal muscle fibers preserve their contractile abilities in slowly progressive MDs. The reasons for a differential impairment of intrafusal and extrafusal muscle fibers and the clinical implications of the present results are discussed.

Transcranial magnetic stimulation in lower motor neuron diseases

OBJECTIVE

To study the diagnostic value of transcranial magnetic stimulation (TMS) in a group of patients with lower motor neuron disease (LMND). Among LMND, several chronic immune mediate motor neuropathies may simulate amyotrophic lateral sclerosis (ALS).

METHODS

Forty patients with LMND were included TMS was performed at the first visit. The patients were seen prospectively every 3 months for a period of 1-4 years.

RESULTS

Three different groups were distinguished at the end of follow-up: (1) ALS group with 7 patients, (2) Pure motor neuropathy with 14 patients and (3) Other LMND including 12 patients with hereditary spinal amyotrophy, 3 patients with Kennedy's disease and 4 patients with post-poliomyelitis. On the basis of the results of TMS variables, 6 out of 7 ALS patients had abnormality of silent period (SP) associated or not with abnormality of excitatory threshold or amplitude ratio. Patients with pure motor neuropathy had normal SP and amplitude ratio. Four out of 14 patients had increased central motor conduction time (CMCT), one had increased CMCT and excitatory threshold, and one patient had a slightly increased excitatory threshold. Considering the abnormality of TMS variables in the groups, SP, excitatory threshold, and amplitude ratio were chosen in a post-hoc attempt to select variables yielding high sensitivity and specificity. The overall sensitivity of TMS for diagnosis of ALS among LMND was 85.7%, its specificity was 93.9%. When only the abnormality of SP was taken into account, the sensitivity was unchanged. But the specificity was improved to 100%.

CONCLUSIONS

TMS helped to distinguish suspected ALS from pure motor neuropathy.

Magnetic stimulation using a triple-stimulation technique in patients with multifocal neuropathy without conduction block

It has been suggested previously that multifocal motor neuropathy (MMN) without conduction block (CB) or other features of demyelination is axonal in nature. Conventional transcranial magnetic stimulation (TMS) and the triple-stimulation technique (TST) performed on 10 MMN patients without CB revealed a proximal focal CB in 4 patients. In 3 other patients, the amplitude ratio obtained in response to conventional TMS was abnormally low, but the area ratio was normal. The TST amplitude ratio and area ratio were normal in these 3 patients. This pattern suggested the occurrence of temporal dispersion without CB. The occurrence of temporal dispersion or CB was associated with a relatively satisfactory response to intravenous immunoglobulins. These findings suggest that some forms of MMN previously thought to be axonal are in fact proximal variants of MMN with CB.

Neuromuscular diseases associated with antigliadin antibodies. A contentious concept

Many neurological syndromes associated with antigliadin antibodies have been published. The most frequent are cerebellar ataxia and peripheral neuropathy. Such cases are reported under the title of gluten ataxia or of coeliac neuropathy. However, associations do not prove cause. Herein, a short review is made of the literature and the author's personal experience. Many unsolved questions remain. Gluten sensitivity is probably an immunological response in genetically susceptible individuals with or without enteropathy. Antigliadin antibodies are present in healthy adults, in some idiopathic ataxias and neuropathies. A gluten-free diet is effective on gastrointestinal but not on neurological symptoms. Whether antigliadin antibodies are elevated is more of a waiting classification than a definite diagnosis. Finally, the relationship between antigliadin antibodies and neurological diseases is very weak.

Myositis in infiltrative lymphocytosis syndrome: clinicopathological observations and treatment

Diffuse infiltrative lymphocytosis syndrome (DILS) is characterized by the presence of persistent circulating CD8 lymphocytosis and visceral CD8 lymphocytic infiltration, predominantly in the salivary glands and lungs in a subset of human immunodeficiency virus (HIV) patients. Myositis has been rarely documented in DILS. We report here the histopathological abnormalities and treatment response of an HIV patient with DILS associated myositis. Muscle biopsy revealed features of polymyositis but electron microscopy study showed intranuclear filamentous inclusions of 18 nm diameter, without intracytoplasmic inclusion. Treatment with intravenous immunoglobuline was useful.

MUSK, a new target for mutations causing congenital myasthenic syndrome

We report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M). The muscle biopsy showed dramatic pre- and postsynaptic structural abnormalities of the neuromuscular junction and severe decrease in acetylcholine receptor (AChR) epsilon-subunit and MuSK expression. In vitro and in vivo expression experiments were performed using mutant MuSK reproducing the human mutations. The frameshift mutation led to the absence of MuSK expression. The missense mutation did not affect MuSK catalytic kinase activity but diminished expression and stability of MuSK leading to decreased agrin-dependent AChR aggregation, a critical step in the formation of the neuromuscular junction. In electroporated mouse muscle, overexpression of the missense mutation induced, within a week, a phenotype similar to the patient muscle biopsy: a severe decrease in synaptic AChR and an aberrant axonal outgrowth. These results strongly suggest that the missense mutation, in the presence of a null mutation on the other allele, is responsible for the dramatic synaptic changes observed in the patient.

Neonatal lower motor neuron syndrome associated with maternal neuropathy with anti-GM1 IgG

The authors report a newborn with motor neuropathy associated with anti-GM1 antibodies from an affected mother. This finding suggests that the disorder was due to transplacental transfer of pathogenic antibodies.

Is muscle spindle proprioceptive function spared in muscular dystrophies? A muscle tendon vibration study

Muscular dystrophies (MDs) are characterized by the degeneration of skeletal muscle fibers. The aim of the present study was to determine whether the intrafusal fibers of muscle spindles are also affected in MD. The functional integrity of muscle spindles was tested by analyzing their involvement in the perception of body segment movements and in the control of posture. Twenty MD patients (4 with dystrophinopathy, 5 with myotonic dystrophies, 5 with fascioscapulohumeral MD, and 6 with limb-girdle dystrophies) and 10 healthy subjects participated in the study. The MD patients perceived passive movements and experienced illusory movements similar to those perceived by healthy subjects in terms of their direction and velocity. Vibratory stimulation applied to the neck and ankle muscle tendons induced postural responses in MD patients with spatial and temporal characteristics similar to those produced by healthy subjects. These results suggest that the proprioceptive function of muscle spindles is spared in muscular dystrophies.

[Neurophysiology of systemic diseases]

Connective tissue diseases represent a varied and challenging group of disorders. Neuromuscular structures are highly susceptible targets for damage. In this review, the neurophysiological explorations of the neuromuscular complications are examined with particular attention to the peripheral nerve system. The most common presentations are sensorimotor polyneuropathy, mononeuritis multiplex, distal symmetric neuropathy, compression neuropathy and trigeminal sensory neuropathy.

[Chorea-acanthocytosis: report of a new family]

Chorea-acanthocytosis is a rare cause of chorea. The genetic origin of the disease was proven with the isolation of the gene on chromosome 9q21. We report the case of two sisters who had two different expressions of this disease. The first sister developed secondary epilepsy associated with abnormal movement of the face. The second presented abnormal movements of the face and apathy. Both improved with serotoninergic treatment. Diagnosis was suggested on the basis of clinical findings and confirmed by identification of acanthocyes and integrity of the Kell blood antigen. Search for acanthocytes should be performed in all patients with chorea. Chorea associated with acanthocytosis has a better prognosis than chorea arising from other causes. Other neurological manifestations or complications may be present or mot; long-term follow-up in a specialized center iq needed for prevention.

[Guillain-Barré syndrome revealing visceral leishmaniasis in an immunocompetent woman]

Visceral leishmaniasis is an endemic parasitic infection rarely observed in association with Guillain-Barré syndrome in immunocompetent patients. A 40-year-old immunocompetent woman was admitted to our unit with recent onset difficulty in walking. The neurological examination and electrophysiological study led to the diagnosis of Guillain-Barré syndrome. During hospitalization, she developed cytopenia involving all three lines revealing visceral leishmaniasis. A few cases of visceral leishmaniasis with neuropathy have been reported, mainly in tropical regions. Neuropathological manifestations of visceral leishmaniasis are probably underestimated. The question is whether Guillain-Barré syndrome and visceral leishmaniasis are causally related.

[Muscle granuloma: anatomoclinical correlation and immunohistochemistry in seven cases]

Granulomatous inflammation is infrequently observed in muscle biopsy. We report a series of 7 patents presenting with granulomas in muscle. Two of them had a history of sarcoidosis In 4 other cases, muscle Involvement revealed systemic sarcoidosis. Among the 6 cases of sarcoidosis, we observed 2 with acute myositis and 4 chronic forms. The last patient presented with polymyositis in association with melanoma. In sarcoidosis, muscle biopsy showed a granulomatous inflammation of varying intensity, which was generally associated with mononuclear inflammatory cells. Most of granulomas were located in the perimysium and the endomysium and necrosis was absent. Inflammatory cells were predominantly macrophages and CD4 positive lymphocytes. On the contrary, in the case of paraneoplastic polymyositis,granulomas were rare, most of inflammatory cells were CD8 positive lymphocytes and numerous areas of necrosis were observed. Class I MHC molecules were expressed on the membrane of muscle fibers. As a general rule, requisite examinations must be performed to search for sarcoidosis in patients exhibiting granulomas on muscle biopsy.

[Clinical and radiological features and clinical course of orbital myositis]

Orbital myositis is idiopathic inflammation of the extraocular muscles in the absence of thyroid orbitopathy and often is included under broad description pseudotumor. We report here a series of three cases. Data from literature, combined with our own results yield a distinguishing pattern of orbital myositis suggesting that the term "orbital pseudotumor" is no longer a useful concept. The diagnostic criteria purposed here are: acute orbital pain exacerbated on eye movement; enlargement of one or more extraocular muscles with the respect of other orbital structures on muscle CT scan; absence of clinical and biological thyroid dysfunction: absence of signs of anterior uveitis or scleritis or visual decrease; rapid response to immunomodulator treatment.

[Guillain-Barre syndrome and its frontiers]

Knowledge concerning Guillain-Barré syndrome (GBS) has been largely extended these past ten years. The first description by Guillain, Barre and Strohl in 1916 established the main clinical and biological characteristics of the syndrome: acute motor weakness affecting at least one limb associated with areflexia. The syndrome was at first restricted to the concept of an acute inflammatory demyelinating polyneuropathy after the first large electrophysiological and histological studies (Asbury et al., 1969). This restricted definition of the GBS was changed by the report of Feasby in 1986 of an axonal variant of the syndrome. This proposal remained controversial until large studies reported that GBS in Northern China occurs in epidemics, predominantly involving young adults and children and characterized electrophysiologically by pure motor axonal features (AMAN). Additional studies showed that another GBS variant may result from an attack against both motor and sensory axons (AMSAN). Previously in 1956 CM Fisher described a clinical triad of ataxia, areflexia and ophthalmoplegia associated with albumino-cytologic dissociation and excellent recovery which was considered immediately part of the GBS. The physiopathology of the syndrome was recently determined (anti-GQ1b antibodies). A number of clinical variant of more limited scope have also been described. Plasma exchanges and intravenous immunoglobulin (IVIg) are the gold standard therapies for the demyelinating form and probably for the other variants despite the absence of controlled trials.

[Guillain-Barré syndrome and its frontiers]

Knowledge concerning Guillain-Barré syndrome (GBS) has been largely extended these past ten years. The first description by Guillain, Barre and Strohl in 1916 established the main clinical and biological characteristics of the syndrome: acute motor weakness affecting at least one limb associated with areflexia. The syndrome was at first restricted to the concept of an acute inflammatory demyelinating polyneuropathy after the first large electrophysiological and histological studies (Asbury et al., 1969). This restricted definition of the GBS was changed by the report of Feasby in 1986 of an axonal variant of the syndrome. This proposal remained controversial until large studies reported that GBS in Northern China occurs in epidemics, predominantly involving young adults and children and characterized electrophysiologically by pure motor axonal features (AMAN). Additional studies showed that another GBS variant may result from an attack against both motor and sensory axons (AMSAN). Previously in 1956 CM Fisher described a clinical triad of ataxia, areflexia and ophthalmoplegia associated with albumino-cytologic dissociation and excellent recovery which was considered immediately part of the GBS. The physiopathology of the syndrome was recently determined (anti-GQ1b antibodies). A number of clinical variant of more limited scope have also been described. Plasma exchanges and intravenous immunoglobulin (IVIg) are the gold standard therapies for the demyelinating form and probably for the other variants despite the absence of controlled trials.

[Acute encephalitis complicating acute polyradiculoneuritis]

We report the case of a 43-year-old man who developed an acute encephalopathy after IVIg therapy for AIDP. Imaging studies showed predominantly posterior leukoencephalopathy. The signs and symptoms of the encephalopathy completely resolved by steroids. Two patients with acute encephalopathy, following IVIg therapy, were reported previously in the literature. However, our observation differed from them by the presence of a marked pleiocytosis of cephalospinal fluid before beginning of IgIV. Two hypothesis may be made: a post-infectious meningo-encephalo-AIDP or a complication of IgIV. This side effect, even rare, has not to be underestimated.

Terminal latency index and modified F ratio in distinction of chronic demyelinating neuropathies

OBJECTIVE

To evaluate indexes calculated from standard electrophysiological data in differentiating chronic demyelinating polyneuropathy (CDP).

METHODS

Nerve conduction study of upper limbs was investigated in 19 chronic inflammatory demyelinating polyneuropathy (CIDP) patients, 25 anti-myelin-associated glycoprotein/sulfated glucuronyl paragloboside antibodies (MAG/SGPG) CDP patients, 13 Charcot-Marie-Tooth disease type 1A (CMT1A) patients and 22 controls. Terminal latency index (TLI) was used to compare the wrist-to-thenar muscle segment with the elbow-to-wrist conduction velocity. Modified F ratio (MFR) was used to compare the spinal cord-to-elbow segment latency with that of the wrist-to-thenar muscle segment.

RESULTS

Compared with controls, TLI was decreased in 21 anti-MAG/SGPG CDP patients while MFR was either decreased or was normal. In 16 CIDP patients, MFR was increased while TLI was either normal or increased. In CMT1A both TLI and MFR were in normal ranges. The sensitivity of MFR as a supportive finding in CIDP was found to be 84% and its specificity 89%. The sensitivity of TLI as a mean of diagnosis of anti-MAG/SGPG CDP was found to be 93% and its specificity 90%.

CONCLUSIONS

The results of TLI and MFR facilitates distinction between different types of CDP. In CIDP, MFR was significantly higher and TLI showed no change; in the anti-MAG/SGPG CDP, TLI and MFR were significantly lower; in CMT1A, TLI and MFR showed no change in comparison with the controls.

[Infectious myopathies]

Infectious myopathies are rare acquired affections which have, generally, a good prognostic. Many types of viral infections can cause transient inflammatory myopathies. HIV myopathy may be present early in the HIV infection, but more often it is a complication of fully developed AIDS. Influenza virus myositis tend to be more severe in adults than in children. Group B coxsackie virus has been isolated from striated muscle of patients with epidemic myalgia. Parasitic infections of muscle include trichinosis, toxoplasmosis, and cysticercosis. Trichinosis is the most frequent parasitic myositis. The ocular, lingual or pharyngeal weakness and/or hypereosinophilia suggest the diagnosis. Pyomyositis, is a located zone of suppuration of muscle due to staphylococcus in 90% of the cases. It is a common occurrence in tropical climates, but has been recognized increasingly in temperate climates.

[Proximal myotonial myopathy (PROMM): clinical and histology study]

We report 13 French patients with proximal myotonic myopathy. PROMM is a recently delineated multisystem disorder with dystrophic myopathy, myotonia and cataracts. This syndrome is genetically distinct from myotonic dystrophy (DM) by the absence of abnormal CTG repeat expansion. The geographical origin varies but 4 families originated from Poland. Of late onset, muscle weakness is diffuse and predominantly affected proximal and axial muscles. Facial involvement and myotonia were moderate or absent, but in all cases myotonic discharges were detected on EMG. 6 patients suffered from myalgia. Cataracts occurred in 11 patients, mainly indistinguishable from those in DM. Cardiac arrythmia occurred in 7 patients. Muscle biopsy revealed rare structural changes of the muscle fibers and selective type I atrophy, common in DM, could not be found on morphometric analysis. PROMM has a distinct clinical spectrum from DM which includes a predominantly proximal muscle weakness, with troubling pain, a more favourable prognosis and a different histopathological pattern.

Transcranial magnetic stimulation (TMS): compared sensitivity of different motor response parameters in ALS

Owing to the low sensitivity of clinical signs in assessing upper motor neuron (UMN) involvement in ALS, there is a need for investigative tools capable of detecting abnormal function of the pyramidal tract. Transcranial magnetic stimulation (TMS) may contribute to the diagnosis by reflecting a UMN dysfunction that is not clinically detectable. Several parameters for the motor responses to TMS can be evaluated with different levels of significance in healthy subjects compared with ALS patients. The central motor conduction time, however, is not sensitive in detecting subclinical UMN defects in individual ALS patients. The amplitude of the motor evoked potential (MEP), expressed as the percentage of the maximum wave, also has a low sensitivity. In some cases, the corticomotor threshold is decreased early in the disease course as a result of corticomotor neuron hyperexcitability induced by glutamate. Later, the threshold increases, indicating a loss of UMN. In our experience, a decreased silent period duration appears to be the most sensitive parameter when using motor TMS in ALS. TMS is also a sensitive technique for investigating the corticobulbar tract, which is difficult to study by other methods. TMS is a widely available, painless and safe technique with a good sensitivity that can visualize both corticospinal and corticobulbar tract abnormalities. The sensitivity can be improved further by taking into account the several MEP parameters, including latency and cortical silent period decreased duration.

[Lower motor neuron disease and signs of dysimmunity]

Twenty-two patients (12 men, 10 women, age range 16 to 60) affected with an adult-onset, sporadic, lower motor neuron disease were studied. Motor weakness was associated with a severe muscular atrophy but never in a peripheral nerve distribution. Weakness predominated in the proximal parts of the limbs in 3 cases, in distal parts in 10 cases involving predominantly the upper limbs in 10. It was diffuse in all four limbs in six cases and was monomelic in the last 2 two others. Reflexes were generally lost in weak muscles. Electrodiagnostic findings consisted of pure motor axonal features, subtle sensory involvement was present in 3 cases with an IgM monoclonal gammopathy, in only one case the neurological syndrome was associated with a lymphoproliferative disorder despite complete investigations. All patients had dysimmune biological features (MGUS or anti-GM1 antibodies). We studied SMN gene in 12 patients and found no deletion. 16 patients were treated with IVIg and five improved but in 2 cases the improvement was transcient and lasted less than six months. Intravenous cyclophosphamide (1g/m(2) repeated monthly during 6 to 9 months) was used in six patients and three improved. Among these three patients two received also plasma exchanges on two days before the infusion. In all three patients, muscle weakness gradually deteriorated in the months following the end of the treatment. Nor the weakness pattern nor the type of biological marker was predictive of a good response to treatment. Lower motor neuron diseases appear to be much less sensitive to treatment than multifocal motor neuropathy with conduction block. However, treatment with IVIg or cyclophosphamide must be considered in the most severe forms or in case of a young onset.

[Epilepsy in an adult with chromosome 22q11 micro-deletion]

Chromosome 22q11 deletion is a frequent genetic anomaly, recently discovered, responsible for DiGeorge syndrome and velo-cardio-facial syndrome. The spectrum of clinical features is large: dysmorphic syndrome, mental delay, conotroncal cardiopathy; neurologic manifestations are not rare. Case report is a 28 year old man who presented a symptomatic epilepsy caused by stroke, associated with conotroncal cardiopathy, mental delay, hypocalcemia and facial dysmorphy. A cytogenetic study confirmed the chromosome 22q11 deletion.

Microinfusion of the metabotropic glutamate receptor agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid into the nucleus accumbens induces dopamine-dependent locomotor activation in the rat

Although the striatum has one of the highest densities of metabotropic glutamate receptor (mGluR) binding sites in the brain, little is known about their physiological role. In this study we characterized the contribution of mGluRs located in the ventral part of the striatum (the nucleus accumbens) to the control of extrapyramidal motor function. Activation of mGluRs by local infusion of the selective agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD; 25, 50 and 100 nmol/0.5 microl) into the nucleus accumbens induced a dose-dependent increase in locomotor activity in rats. Intra-accumbens infusion of a selective antagonist of mGluRs, alpha-methyl-4-carboxyphenylglycine (MCPG) did not modify spontaneous locomotion but decreased the locomotor response to 1S,3R-ACPD. This effect appeared to be mediated by dopamine, since blockade of dopamine receptors with haloperidol (0.05 and 0.1 mg/kg i.p.) dose-dependently reduced 1S,3R-ACPD-induced locomotor activation. Furthermore, D-amphetamine (0.5 mg/kg, i.p.) combined with intra-accumbens infusion of 1S,3R-ACPD (100 nmol) potentiated the locomotor hyperactivity response to a higher level than that seen with a single treatment with either drug. In contrast, D-amphetamine-induced hypermotility was abolished by infusion of MCPG (100 nmol) into the nucleus accumbens. These results demonstrate that glutamate may control extrapyramidal motor function through metabotropic receptors. Furthermore, activation of metabotropic glutamate receptors appears to act in synergy with the dopamine system at the level of the nucleus accumbens to produce a motor stimulant response.

[Guillain-Barré syndrome of axonal type, Campylobacter jejuni infection and anti-ganglioside GM1 antibodies]

Infection by Campylobacter jejuni (C. jejuni) has been reported in 17 to 55 p. 100 of the GBS. The "axonal" GBS has been recently attributed to such an association. It is characterized by rapid progression to severe widespread paralysis, respiratory failure, poor and delayed recovery. The acute "axonal" form of Guillain-Barré syndrome has been and remains a matter of controversy. A typical case of GBS with serological evidence of recent C. jejuni infection and increased antibodies to GM1 is reported. An immune mechanism remains most likely. Recent studies have suggested the hypothesis of "shared epitope" between C. jejuni and peripheral nervous system cell (Gal beta 1-3 N Acetylgalactosamine epitope). Such a cross-reactivity could provoke a severe form of GBS with a poor recovery in some predisposed hosts (antiganglioside antibodies, HLA "immunogenic" groups such as B8, B35 or DR3).

[A case of transient amnesia caused by cerebral thrombophlebitis: contribution of neuroimaging to physiopathogenesis of transient amnesia]

We report a case of transient global amnesia (TGA), in a right-handed woman, which was due to a cerebral venous thrombosis. In our knowledge it is the first case reported. MRI and SPECT revealed the existence of a dysfunction in the right internal temporal region. Such a localization leads us to discuss the specialisation of each hippocampus.