Homozygous SMN1 exons 1-6 deletion: pitfalls in genetic counseling and general recommendations for spinal muscular atrophy molecular diagnosis

We report on a rare homozygous intragenic deletion encompassing exons 1-6 of the SMN1 gene in a patient with spinal muscular atrophy (SMA) born into a consanguineous family. This exceptional configuration induced misinterpretation of the molecular defect involved in this patient, who was first reported as having a classic SMN1 exon 7 deletion. This case points out the possible pitfalls in molecular diagnosis of SMA in affected patients and their relatives: exploration of the SMN1 exon 7 (c.840C/T alleles) may be disturbed by several non-pathological or pathological variants around the SMN1 exon 7. In order to accurately describe the molecular defect in an SMA-affected patient, we propose to apply the Human Genome Variation Society nomenclature. This widely accepted nomenclature would improve the reporting of the molecular defect observed in SMA patients and thus would avoid the commonly used but imprecise terminology "absence of SMN1 exon 7."

[Leptomeningeal dissemination after ethmoidal sinus adenocarcinoma surgery: a rare complication]

INTRODUCTION

Although rare, adenocarcinoma is the most frequent neoplasm of the ethmoid sinus and must be regarded as an occupational disease secondary to chronic wood dust exposure. Few cases with neurological metastasis have been reported.

CASE REPORT

We report the cases of two patients who developed a multiple cranial nerve disorder for the first case and a cauda equina syndrome for the second, after ethmoid adenocarcinoma surgery.

CONCLUSION

Diagnosis of carcinomatous meningitis is difficult and is based on clinical data, CSF analysis and gadolinium-enhanced T1-weighted brain and spinal cord MRI. The implication of surgery is discussed. Prognosis of such a disorder is poor.

Hétérochromie irienne associée à un syndrome de Claude Bernard-Horner acquis

Horner's syndrome (HS) is related to an interruption of the oculosympathetic nerve pathway. The classic clinical findings associated with this condition are ptosis, miosis, and enophthalmos. Heterochromia is typically described in congenital HS, but it is an uncommon finding in acquired HS. We report a case of post-traumatic HS associated with heterochromia. A literature review indicates that this type of heterochromia may be related to a reduction in the number of iris melanocytes. This mechanism may be the same in the physiological iris color modifications in adulthood.

[Finnish amyloid polyneuropathy in a French patient]

INTRODUCTION

Finnish amyloid variety is a rare familial amiloidosis polyneuropathy essentially observed in Finland. It concerns about six hundred people in the world in which five hundred reside in Finland.

OBSERVATION

We report a case of a 58-year-old French woman with a 10-year history of lattice cornea dystrophy. She consulted in January 2004 for impaired swallowing, facial paralysis principally of the right superior territory and symptoms of arthritis which had developed a few months earlier. Observation revealed facial cutis laxa, tongue amyotrophy and some fasciculation. Electroneuromyography showed chronic neurogenic involvement of the facial muscles. Limbs and the sympathetic neuronal system were free of involvement. Pathological examination revealed areas of peri vascular amiloid deposits. Molecular biology confirmed the diagnosis of Finnish amiloidosis: substitution of aspartic acid by tyrosine in the 187 codon in the 9th chromosome (gelsoline gene). This mutation has been previously found in Denmark and the Czech Republic.

CONCLUSION

Finnish amiloidosis is a familial polyneuropathy characterized by an association of cornea lattice dystrophy, cutis laxa and a chronic neurogenic involvement of the cranial nerves. Two mutations are known. Life expectancy is not affected, but quality of life is altered.

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.

[Neuropathy versus neuronopathy: distinctive features]

Neuropathy may be difficult to distinguish from neuronopathy, on both motor and sensory sides. A number of disorders that present with characteristic electro-clinical features are readily recognized. Except for those, distinction of the lesions that concern the peripheral nerve cell or the axon may require support of clinical, electrophysiological and other ancillary tests. Distinction between motor neuropathy and neuronopathy can be based on the abnormalities of nerve conduction and on the signs that relate to the reinnervation process. Signs of terminal axonal reinnervation, such as motor axon reflex, may be observed in axonal neuronopathies, whereas only collateral reinnervation occurs in motor neuronopathies. Sensory axonopathies are usually characterized by clinical and electrophysiological findings that are axon length-dependent, by the course of the disorder that is most often chronic, and by possible reversibility. Sensory neuronopathies are usually subacute and induce clinical deficits that are more or less widespread to the whole body surface rather than distal. Follow-up studies disclose limited or absent recovery. A better knowledge of the structural differences of motor and sensory neurons and axons will improve our understanding and lead to the development of specific tests. Meanwhile, although some parameters and techniques should still be improved, electrophysiological and additional tests are useful to detect and to distinguish the peripheral nerve disorders that affect the nerve cell bodies and their axons.

[Strategies to interpret late waves in routine neurophysiology]

A number of late waves other than F and H spinal waves are commonly observed during motor nerve conduction studies. Simple criteria are available that allow an understanding of their origin and significance. A late wave can be characterized by 1) its origin, proximal or distal to the stimulator, 2) its position with reference to the spinal waves, 3) its latency, stable or not, 4) its appearance in response to all (constant) or not to all stimuli (inconstant), 5) its persistence or not to intense stimuli, 6) its relative threshold, 7) its behavior to paired stimuli (namely if it is or not evoked twice by paired stimuli). By use of these criteria, one may distinguish the late waves that are evoked proximal to the stimulator (indirect late waves), such as the spinal responses (H and F), the motor axon reflex and the indirect double discharge, from those late waves that originate distally to the stimulator (direct late waves) such as the late potential, the myo-axonal ephaptic response and the direct double discharge. Signification of these late waves in relation to peripheral nerve disorders is discussed. Late potentials, motor axon reflex and ephaptic myo-axonal responses are signs of a prior axonal lesions, whereas indirect double discharges relate to an ongoing demyelinating process.

Exercise test in muscle channelopathies and other muscle disorders

We studied the percentage change in compound muscle action potential (CMAP) amplitude and area during and after a 5-min maximal contraction of the muscle. The exercise test (ET) was performed on 64 patients with different muscle disorders and on 46 normal controls. The range of normal ET values was defined as the mean + 2 SD of the control values. The mean sensitivity of the test was 63% in the whole group with ion channel muscle disorders, the highest sensitivity being seen in primary periodic paralysis (81%) and the lowest in chloride channelopathies (17%). In thyrotoxic periodic paralysis, the ET was abnormal in the three of the four patients studied. In patients with myotonic dystrophy, a smaller than normal increase in CMAP amplitude occurred during and after exercise, whereas in proximal myotonic myopathy a normal initial increase in CMAP amplitude was followed by an abnormal decrement. We conclude that the ET can be of use in confirming abnormal muscle membrane excitability in patients with calcium and sodium channelopathies and thyrotoxic periodic paralysis. In chloride channelopathy, the test may also be abnormal, but shows no, or only a small, increase in amplitude or area in the immediate postexercise period. The test may also be abnormal in proximal myotonic myopathy, but is normal in myotonic dystrophy.

High frequency discharge of a fraction (f) of motor unit action potential

Two repetitive discharges, firing at 105 and 180 Hz, were evoked in muscles with chronic denervation. They were delayed following a motor unit action potential (M), and their maximum duration was 800 and 50 ms, respectively. The potential of both high frequency discharges was of low amplitude and short duration. It was considered to be a fraction (f) of the motor unit potential, and to depend on muscle fibres re-innervated by an axonal branch. The repetitive mechanism was tested by double stimulation. It seemed to be an ephaptic re-excitation of the axonal branch by a sprout rather than an ectopic trigger locus on the latter. The antidromic waves, associated with the repetitive discharges on the axonal branch, failed to be transmitted to the main axon. This failure, assimilated to a conduction block, was complete in the first case as M was not repetitive. It was intermittent in the second case as M was firing intermittently. Repetitive activity associated with 'terminal multifocal block' could be relevant to the fractional activation observed by others in some disease states.

Cancellation of single F wave by double stimulation in case of chronic denervation

Single F waves evoked by stimulation with above threshold intensity are cancelled by a second shock, as was previously demonstrated with maximal or sub-maximal intensity. Double stimulation of any intensity thus makes it possible to detect a possible reflex component in the spinal response, by elimination of the F wave. As an H or a heteronymous H reflex may be a sign of a disordered central motor system state, this fast method has a direct clinical utility.

[Value of gadolinium magnetic resonance imaging of the lumbosacral roots in acute polyradiculoneuritis]

Four patients with acute inflammatory polyradiculoneuropathy were evaluated with MRI. In 3 of 4 cases, gadolinium enhancement was observed in the nerve roots of cauda equina, on frontal and horizontal slices. This enhancement was correlated with the severity of the clinical picture and the cerebrospinal-fluid inflammatory protein concentration and supports the inflammatory nature of this forms of acute polyradiculoneuropathy.

Early seizures after acute stroke: a study of 1,640 cases

We evaluated prospectively the occurrence of seizures within 15 days of a first stroke or transient ischemic episode in 1,640 patients to study relation between seizures and type of stroke. Seizures occurred in 90 patients (5.4%), including 36 (4.4%) of 814 with infarct owing to atheroma, 21 (16.6%) of 126 with infarct owing to cardiogenic embolus, 3 (1%) of 273 owing to lacunar infarct, 5 (1.9%) of 259 owing to transient ischemic attack (TIA), 21 (16.2%) of 129 owing to supratentorial hematoma, and 4 (16.6%) of 24 owing to subarachnoid hemorrhage. Thirteen (14.6%) of 89 subcortical infarcts were associated with seizures. Seizures were the initial sign of stroke in 80 (89%) of 90 cases and were usually single and partial. Seizure symptoms were most often motor, sensory, or visual.

[Gyratory epileptic seizures. Radioclinical correlations]

The authors report 3 cases of gyratory seizures whose epileptic nature was demonstrated on the following features. They appeared with a loss of consciousness. In 2 cases, they ended with a tonic-clonic generalized fit and in the 3 cases, they were mixed with other generalized seizures. From an etiological point of view, in 2 cases, a deep lesion was discovered, the first one near the paracentral lobule, the second in the para-thalamic area. The third one was an idiopathic generalized epilepsy on clinical and electroencephalographic grounds. These 3 cases focus on the difficulties to classify gyratory seizures that may appear in 2 opposite situations, namely in symptomatic partial epilepsy and in idiopathic generalized epilepsy.

[Investigation via electroencephalogram with sphenoidal electrodes of a case of reading epilepsy: role of the temporal lobe in the emotional evocation of seizures]

Reading epilepsy in a 20-year-old male. Electroencephalographic study with sphenoidal electrodes localized the onset of critical spikes in the temporal areas (especially the left). The frequency and diffusion of critical spikes were increased when material read had an emotional content. This case report supports the "communication" hypothesis as opposed to hypotheses that emphasize proprioceptive and other "lower order" stimuli in evoking seizures while reading. The authors discuss the role of the temporal lobe in reading: lexical function, treatment of visual information and emotional integration of stimuli.

[Electrophysiologic data on myasthenic syndromes of the Lambert-Eaton type. A series of 23 cases]

The electrophysiological data of 23 adult patients with Lambert-Eaton myasthenic syndrome (LEMS) have been reviewed. Lung carcinoma was disclosed in 17. In six cases with an EMG follow-up ranging between one and 17 years no carcinoma was detected. The results of repetitive nerve stimulation test (RNS) were not statistically different between the 2 groups. Low CMAP ulnar amplitude was present in all patients (mean: 1.7 mV). Decremental response at low rate of stimulation (3 Hz) was present in 17/20 (means: 30%). An abnormal incremental response at high rate of stimulation was present in all cases (mean: 826%). The authors emphasize the interest of a 50 Hz stimulation for 4 s. Increase of the 'F-wave' amplitude was noticed in some cases. Electrophysiological changes suggestive of an associated mild neuropathy were noticed in eight patients but H-reflex was present in 3/3 cases. SFEMG abnormalities were found in 6/6 cases. In one case, stimulated SFEMG showed more blockings and an increased jitter with low rate of stimulation. In one case the electrical pattern of RNS could be misinterpreted as myasthenia gravis in one tested muscle only. The author's results suggest that CMAP amplitude and RNS test could be used to appreciate the short-term improvement of LEMS with treatment and in some cases for the long-term follow-up.

[EEG periodic lateralized activities associated with ischemic cerebro-vascular strokes: physiopathologic significance and localizing value]

Eleven cases of periodic lateralized epileptiform discharges (PLED) with stroke (9 cases) or transient ischemic attacks are reported. PLEDs are often associated with depression of conscience (81%) or partial pure motor epileptic seizures (90%). PLEDs and seizures seem independent on EEG. Ischemic strokes associated with PLEDs have some characteristic features: old age, vascular risk factors, parieto-occipital areas infarcts and frequent association with TIAs. PLEDs seem to be often associated with watershed infarcts. The relations between PLEDs and cerebral ischemia are discussed.

[Electrophysiologic investigation of the anterior temporal and frontal lobes: sphenoidal and intraorbital electrodes]

The authors have evaluated the interest of sphenoidal electrodes in detection of internal temporal spikes, and intra-orbital electrodes in the detection of orbito-frontal spikes. From a study of 26 patients, 21 with sphenoidal electrodes, 3 with intra-orbital electrodes and 2 with both electrodes, they observed the sensitivity and specificity of such electrodes in detecting spikes with no traduction upon extra-cranial electrodes, or with an unsuspected traduction as spikes at a distance from deep electrodes, or spikes on 2 foci, or bisynchronous discharges. Sphenoidal and intra-oribital electrodes constitute a non-invasive method that provides excellent information in the exploration of the mesiobasal cerebral face. Indications for the use of such a method are complex absences without EEG traduction or with an unsuspected traduction and without abnormalities on CT scan, in the context of functional surgery of epilepsy.

[Identification of temporal epileptic seizures using percutaneous sphenoidal electrodes]

The authors have evaluated the indications, methods and results of sphenoidal electrodes in epilepsy. This method makes it possible to study the hippocampal area which cannot be studied by extracranial electrodes. It also localizes in a temporal lobe complex seizures without electrical events, or complex seizures giving bilateral temporal spikes or a fronto-temporal focus of spikes. It may even show evidence of temporal focus in cases with bilateral and synchronous spikes. Thus, sphenoidal electrodes enable temporal seizures to be identified and localized, leading to more specific neuroradiological explorations and therefore helping in the selection of patients for specific surgery.

[Local complications after axillary block anesthesia]

The authors treated a local complication after axillary block, probably after intraneural injection of lidocaine. At the operation severe epineural fibrosis was found and released. The result was good after some months. After this the authors realized a study with 14 hand surgeons, and only few cases like the first case were found. This technique axillary block, is very reliable technique, but very few local complications can occur, and it's necessary to know them. It's possible to avoid this local problem with a serious technique to realize axillary block. Never intraneural injection and never many punctures to research paresthesia from the nerves of the brachial plexus.

[Familial benign neonatal seizures: EEG, clinical, prognosis and genetic features]

The authors describe 3 families in which several members presented convulsions exclusively during the neonatal period. The EEG and clinical findings showed typical short neonatal convulsions lasting several months and with no apparent etiology. The dominantly inherited transmission is certain. Prognosis is very good, although 14% of the cases in the literature present an onset of epilepsy after 20 years of age. Even though this phenomenon is unusual, the rarity of its description probably stems from lack of knowledge rather than low incidence. We thus would like to show that, even in the neonatal period, familial epilepsy can occur.

[Elevation of gamma-glutamyltransferase levels in treated epileptic patients]

Plasma levels of gamma-glutamyl transpeptidase were measured prospectively in 75 epileptic patients treated with one of the following drugs: phenobarbitone (n = 20), phenytoin (n = 23), carbamazepine (n = 18) or sodium valproate (n = 14). A significant increase in gamma-glutamyl transpeptidase levels was observed from the 7th day of treatment onward. The increase was particularly pronounced in the phenytoin group, with mean and maximum values of 104.10 and 215 mU/ml respectively, followed by the phenobarbitone group (mean 68.15, max. 124 mU/ml), the carbamazepine group (mean 49.83, max. 100 mU/ml) and the sodium valproate group (mean 35.42, max. 70 mU/ml). This was due to enzyme induction being highest with phenytoin and phenobarbitone which are strongly liposoluble and have prolonged half-life. Any epileptic patient with plasma gamma-glutamyl transpeptidase levels higher than those found in this study may be suspected of having viral or alcoholic hepatitis.

[Orthostatic arterial hypotension and giant aneurysm of the basilar trunk]

The authors report two observations of giant aneurysm of basilar artery, where the first neurological signs were preceded or escorted by a postural hypotension. They emphasize the place of rhombencephon in the control of blood pressure and they bring together their cases with those reporting a postural hypotension revealing a lesion of medulla. They insist upon the necessity to look a peripheric and central neurological lesion in front of a postural hypotension.

[Evaluation of changes in gamma-glutamyltransferase in chronic treatment with antiepileptic agents]

To know the intensity of liver enzyme induction during a treatment with anticonvulsant, the authors have measured gamma GT before and at the 7th, 30th, 60th days after a treatment by one of the 4 major anticonvulsant as phenobarbital, diphenylhydantoin, carbamazepine and sodium valproate. All alcoholic patients, and all the patients having a liver disease have been eliminated. The results show that diphenylhydantoin is the most important inductor of gamma GT with an elevation that can reach 312% of basal level, followed by phenobarbital, when sodium valproate and carbamazepine are the weakest inductors. More, induction by carbamazepine in women is more weak than in man. Age takes a place in intensity of induction with a major induction observed between 30 and 50 years old for phenobarbital, and above 50 years old for sodium valproate. These effects are not dependent of an hepatitis. The knowledge of the upper levels of gamma GT induction by anticonvulsant appear to us usefull for several reasons: carbamazepine and sodium valproate being the weakest inductors, they must be chosen in priority in women under contraceptive treatment. Any abnormal elevation of gamma GT need to look of an alcoholic intoxication, an hepatitis or a liver cancer.

[Rare cause of myoclonus with giant SEP's: methyl bromide poisoning. Apropos of a case with unilateral predominance]

Giant and asymmetric SEPs were recorded in a patient with predominantly unilateral, spontaneous and intention myoclonus due to voluntary intoxication with methyl bromide as soon as day 3 after intoxication. The N10 Erb's point potential, cervical N13 and scalp recorded P15 potentials were found to be normal in latency, morphology and amplitude. The somesthetic informations could be considered as normally processed up to the subcortical levels of the somatosensory pathways. The parietal cortical potentials N20 and P25 and the frontal cortical potentials P22 and N30, contralateral to myoclonus, were abnormally large. This suggests that myoclonus could be related with an abnormal reactivity of somatomotor and somatosensory cortices to the afferent volleys triggered by voluntary movements. The prerolandic components P22 and N30 were found to be relatively more enhanced than the parietal N20 and P15.

[Mental confusion in childhood migraine]

From 3 cases reports, the authors emphasize the importance of acute confusional migraine in childhood. It is more frequent than in adulthood and it is often the presenting problem making the diagnosis more difficult.

[Value of studies of sensory nerve conduction velocity using needle electrodes in children under 3-years-old]

The authors show the interest of near-nerve recording of sensory action potentials in children less than 3 years old. This technique provides precious information for the morphology and amplitude of sensory potentials. Normal values are calculated from the median and the tibial nerve of control subjects.

[Cerebral ischemia and synthetic estrogens. The role of immunologic mechanisms. Apropos of 2 cases]

The authors report 2 cases of stroke in 2 young women using oral contraception with production of anti-ethinyl-oestradiol antibodies. From literature, they recall the mechanisms of production of theses antibodies, their frequence in women with and without stroke and the different hypothesis lied to their pathogen action.

[Type E botulism. Two recent cases (author's transl)]

Two brothers, aged 29 and 31, developed severe type E botulism 12 hours after eating salted herrings. The younger died rapidly, the other survived after treatment with type E botulinus antitoxin under intensive care. Limited electromyographic exploration of the surviving patient showed characteristic signs of presynaptic block. This method may be helpful in the diagnosis of atypical forms of the disease. Type E botulism is uncommon in France. It is almost exclusively transmitted by raw, smoked or salted fish and, for some obscure reason, rarely affects all those who shared the same meal. Contrary to types A and B botulism, it usually responds to its specific antitoxin, which must be administered as early as possible. The other therapeutic measures (tracheostomy, controlled ventilation, tube feeding) are the same for all types.