Mapping of a new locus for autosomal recessive demyelinating Charcot-Marie-Tooth disease to 19q13.1-13.3 in a large consanguineous Lebanese family: exclusion of MAG as a candidate gene

Autosomal recessive Charcot-Marie-Tooth disease (CMT) type 4 (CMT4) is a complex group of demyelinating hereditary motor and sensory neuropathies presenting genetic heterogeneity. Five different subtypes that correspond to six different chromosomal locations have been described. We hereby report a large inbred Lebanese family affected with autosomal recessive CMT4, in whom we have excluded linkage to the already-known loci. The results of a genomewide search demonstrated linkage to a locus on chromosome 19q13.1-13.3, over an 8.5-cM interval between markers D19S220 and D19S412. A maximum pairwise LOD score of 5.37 for marker D19S420, at recombination fraction [theta].00, and a multipoint LOD score of 10.3 for marker D19S881, at straight theta = .00, strongly supported linkage to this locus. Clinical features and the results of histopathologic studies confirm that the disease affecting this family constitutes a previously unknown demyelinating autosomal recessive CMT subtype known as "CMT4F." The myelin-associated glycoprotein (MAG) gene, located on 19q13.1 and specifically expressed in the CNS and the peripheral nervous system, was ruled out as being the gene responsible for this form of CMT.

Further evidence for a central reorganisation of synaptic connectivity in patients with hypoglossal-facial anastomosis in man

In normal subjects, electrical stimulation of trigeminal mucosal afferents (lingual nerve - V3) can elicit a short latency (12.5+/-0. 3 ms; mean+/-S.D.) reflex response in the ipsilateral genioglossus muscle (Maisonobe et al., Reflexes elicited from cutaneous and mucosal trigeminal afferents in normal human subjects. Brain Res. 1998;810:220-228). In the present study on patients with hypoglossal-facial (XII-VII) nerve anastomoses, we were able to record similar R1-type blink reflex responses in the orbicularis oculi muscles, following stimulation of either supraorbital nerve (V1) or lingual nerve (V3) afferents. However, these responses were not present in normal control subjects. Voluntary swallowing movements produced clear-cut facilitations of the R1 blink reflex response elicited by stimulation of V1 afferents. In a conditioning-test procedure with a variable inter-stimulus interval, the R1 blink reflex response elicited by supraorbital nerve stimulation was facilitated by an ipsilateral mucosal conditioning stimulus in the V3 region. This facilitatory effect was maximal when the two stimuli (conditioning and test) were applied simultaneously. This effect was not observed on the R1 component of the blink reflex in the normal control subjects. These data strongly suggest that in patients with XII-VII anastomoses, but not in normal subjects, both cutaneous (V1) and mucosal (V3) trigeminal afferents project onto the same interneurones in the trigeminal principal sensory nucleus. This clearly supports the idea that peripheral manipulation of the VIIth and the XIIth nerves induces a plastic change within this nucleus.

[Hereditary neuropathies]

Hereditary neuropathies are the most frequent genetically determined disease in neurology. The peripheral motor and sensory form is the Charcot-Marie-Tooth disease. The underlying genetic defects are now known for many of the demyelinating form. Several studies have identified the mutations on genes coding proteins of peripheral myelin. This has important implications for both diagnosis and genetic counselling in this group of conditions. The genetic defect in most cases of familial amyloid polyneuropathy is better known and should be considered especially in late-onset forms.

[What's new in primary lateral sclerosis?]

Primary lateral sclerosis as a nosological entity distinct from amyotrophic lateral sclerosis has been the subject of controversy since it was first described in the nineteenth century. Primary lateral sclerosis has been defined as a rare, non-hereditary disease characterized by highly progressive spinobulbar spasticity, related to the exclusive loss of precentral pyramidal neurons, with secondary pyramidal tract degeneration and preservation of anterior horn motor neurons. We carried out a study in nine patients with a diagnosis of primary lateral sclerosis. Our clinical, electrophysiological and pathological investigations provide evidence that the disease has a heterogeneous clinical presentation and that degeneration is not restricted to the central motor system but also affects the lower motor neuron. In view of this similarity with amyotrophic lateral sclerosis, primary lateral sclerosis may represent a slowly progressive syndrome closely related to motor neuron disease and amyotrophic lateral sclerosis.

[Macrophagic myofasciitis. Study and Research Group on Acquired and Dysimmunity-related muscular diseases (GERMMAD)]

MACROPHAGIC MYOFASCIITIS: A most unusual inflammatory myopathy, first described by Germmad had been reported with increasing frequency since 1993 in the leading French myopathology centers. We present our experience with this new disease: macrophagic myofasciitis.

CLINICAL FEATURES

By November 1999, 70 cases of macrophagic myofasciitis had been recorded since our first description. The first 22 patients (sex ratio M/F = 1:3) referred with the presumptive diagnosis of polymyositis (n = 11), polymyalgia rheumatica (n = 5), mitochondrial cytopathy (n = 4), and congenital myopathy or muscle dystrophy (n = 1 each). Symptoms included myalgia (91%), anthralgia (68%), marked asthenia (55%), muscle weakness (45%), and fever (32%).

LABORATORY FINDINGS

Abnormal laboratory findings included elevated CK levels (50%), markedly increased erythrocyte sedimentation rate (37%), and myopathic EMG (35%). Muscle biopsy showed a unique myopathological pattern characterized by: i) centripetal infiltration of epimysium, perimysium and perifascicular endomysium by sheets of large cells of the monocyte/macrophage lineage (CD68+, CD1a-, S100-, with a PAS-positive content; ii) absence of necrosis, of both epithelioid and giant cells, and of mitotic figures; iii) presence of occasional CD8+ T-cells; iv) inconspicuous muscle fiber damage. The picture was easily distinguishable from sarcoid myopathy and fasciitis-panniculitis syndromes. The infectious diseases know to be associated with reactive histiocytes, including Whippleís disease, Mycobacterium avium intracellulare infection and malakoplakia, could not be documented. Patients improved under corticosteroid therapy and/or immunomodulatory therapeutic

CONCLUSION

A new inflammatory muscle disorder, characterized by a distinctive pathological pattern of macrophagic myofasciitis is emerging in France.

Autosomal recessive hereditary neuropathy with focally folded myelin sheaths and linked to chromosome 11q23: a distinct and homogeneous entity

We describe a six generation Saudi kindred, with a recessive hereditary motor and sensory neuropathy (HMSN). Four individuals were affected including two children (a boy and a girl) and a 23-year-old man. The fourth (a female) died at the age of 14 years. Onset of the disease was early (< 2 years) and the clinical and neurophysiological features were, generally, quite similar to those of an Italian family linked to chromosome 11q23. The peculiar pathologic pattern was irregular and redundant loops associated with folding of the myelin sheaths. The genetic study confirmed linkage to chromosome 11q23 and refined the location of the gene between D11S1311 and D11S917, a 3.3 cM region. These findings support the existence of a homogeneous and distinct entity within the form of HMSN associated with focally folded myelin sheaths.

[True neurological thoracic outlet syndrome]

The thoracic outlet syndrome (TOS) encompasses various clinical entities affecting the neurovascular bundle crossing the thoracic outlet. Unfortunately, this term often proves to be confusing because many of these entities have little in common beyond their known or presumed lesion site. Neurogenic TOS (true TOS) is caused by compression of the lower trunk in the brachial plexus, the cervical ribs or fibrous band. This syndrome is extremely rare. We consider that this neurological form of TOS is a clearly defined neurological syndrome. We report 10 patients with true TOS. All were females. Stating the onset was difficult because symptoms were progressive and insidious. Pain was the most frequently reported symptom. Sensory deficit was slight or absent. All patients showed unilateral severe atrophy of the thenar muscles. Wasting and weakness developed later. A reduced amplitude of ulnar and median compound muscle action potential associated with a normal amplitude of median sensory nerve action and a reduced amplitude of ulnar sensory nerve action potential were indicative of a chronic axon loss in the lower trunk of the brachial plexus. In all cases, we performed medial antebrachial cutaneous sensory nerve action potential, a C8-T1 innervated nerve. The absence of the medial antebrachial cutaneous sensory nerve action potential in 9 patients and a reduction in amplitude of 50 p. 100 compared to the unaffected side in the other patient, indicated the diagnostic value of this easy and reproductible test. It confirmed a C8-T1 post-ganglionic radicular lesion or a lower brachial plexus neuropathy. Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed in the affected side in 7 patients and in each case the lower part of the brachial plexus was found to be stretched and angulated over a fibrous band, which was removed. Pain was relieved after 1 to 4 weeks. A minimal motor improvement was observed after one year. Electrophysiological results were unchanged.

Genetic, cytogenetic and physical refinement of the autosomal recessive CMT linked to 5q31-q33: exclusion of candidate genes including EGR1

Charcot-Marie-Tooth disease is an heterogeneous group of inherited peripheral motor and sensory neuropathies with several modes of inheritance: autosomal dominant, X-linked and autosomal recessive. By homozygosity mapping, we have identified, in the 5q23-q33 region, a third locus responsible for an autosomal recessive form of demyelinating CMT. Haplotype reconstruction and determination of the minimal region of homozygosity restricted the candidate region to a 4 cM interval. A physical map of the candidate region was established by screening YACs for microsatellites used for genetic analysis. Combined genetic, cytogenetic and physical mapping restricted the locus to a less than 2 Mb interval on chromosome 5q32. Seventeen consanguineous families with demyelinating ARCMT of various origins were screened for linkage to 5q31-q33. Three of these seventeen families are probably linked to this locus, indicating that the 5q locus accounts for about 20% of demyelinating ARCMT. Several candidate genes in the region were excluded by their position on the contig and/or by sequence analysis. The most obvious candidate gene, EGR1, expressed specifically in Schwann cells, mapped outside of the candidate region and no base changes were detected in two families by sequencing of the entire coding sequence.

Electrophysiological diagnosis of motor neuron disease and pure motor neuropathy

Motor neuron disease (MND) is a group of disorders in which there is degeneration of upper and lower motor neurons to a variable degree. Amyotrophic lateral sclerosis is the most frequent form of the disease, presenting with both upper and lower motor neuron involvement. Frequently, especially in the early stages of the disease, only lower motor neuron signs are present. In these conditions, some pure motor neuropathies may resemble MND. The diagnosis is of importance because some of these motor neuropathies are "dysimmune" disorders and may respond to immune therapies. In such diseases the multifocal motor neuropathy with conduction block appears to be the more frequent. In MND and pure motor neuropathies, the electrophysiological examination is the most decisive test. In MND, it is of diagnostic importance. In addition, it is useful in the assessment of disease severity and progression, in the evaluation of therapeutic trials and in the understanding of etiopathogenesis of the disease. In pure motor neuropathies, the presence of conduction block leads to immune treatment with good response in more than 50% of the cases.

[Macrophagic myofasciitis: description and etiopathogenic hypotheses. Study and Research Group on Acquired and Dysimmunity-related Muscular Diseases (GERMMAD) of the French Association against Myopathies (AFM)]

PURPOSE

A new type of inflammatory myopathy of unknown etiology has recently been described in France. The myopathy, called macrophagic myofasciitis, had never been described in the literature.

METHODS

In December 1998, 35 cases of macrophagic myofasciitis were reported, showing an increase in its incidence since the description of the first case in 1993. The first 22 cases are described.

RESULTS

The 22 patients were each referred with a presumptive diagnosis of either polymyositis (11 patients), polymyalgia rheumatica (5 patients), mitochondrial cytopathy (4 patients), or congenital myopathy or muscle dystrophy (1 patient for each). Clinical symptoms included myalgias (91%), arthralgias (68%), marked asthenia (55%), muscle weakness (45%), and fever (32%). Laboratory findings included elevated CK levels (50%) and a marked increased in the erythrocyte sedimentation rate (37%). Electromyographic recordings showed the existence of myopathy (35%). Muscle biopsy showed a unique pattern characterized by: (i) centripetal infiltration of the epimysium, perimysium and perifascicular endomysium by non epitheloid, cells of the monocyte/macrophage lineage (CD68+, CD1a-, S100-) with both large cytoplasm and PAS-positive content; (ii) absence of necrosis, of both epithelioid and giant cells, and of mitotic figures; (iii) occasional CD8+ T-cells; and, (iiii) minimal myocyte suffering. The disease symptoms were easily distinguishable from those of sarcoid myopathy and fasciitis-panniculitis syndromes. Infectious diseases known to be associated with reactive histiocytosis, including Whipple's disease, Mycobacterium avium intracellulare infection and malakoplakia, could not be documented. Patients' condition improved under corticosteroid therapy, associated or not with non-specific antibiotic therapy.

CONCLUSION

A new inflammatory muscle disorder of unknown etiology, characterized by a distinctive pathological pattern of macrophagic myofasciitis, is emerging in France. Diagnosis is based on muscular biopsy. Numerous clinical, epidemiological and etiopathologic studies initiated by the GERMMAD (Groupe d'études et de recherche sur les maladies musculaires acquises) are in progress.

Spectrum of clinical and electrophysiologic features in HNPP patients with the 17p11.2 deletion

OBJECTIVE

To study the clinical and electrophysiologic features of a large series of carriers of the 17p11.2 deletion.

BACKGROUND

The 17p11.2 deletion is associated in most patients with recurrent acute nerve palsies, which is the typical presentation of hereditary neuropathy with liability to pressure palsies (HNPP). Nevertheless, a few other phenotypes have been reported.

METHODS

On the basis of clinical and electrophysiologic data, the authors conducted a retrospective study of 99 individuals with the 17p11.2 deletion referred to their neurogenetic department between 1993 and 1997.

RESULTS

In addition to the typical presentation of HNPP, they describe five other phenotypes in 15 patients: recurrent positional short-term sensory symptoms, progressive mononeuropathy, Charcot-Marie-Tooth disease-like polyneuropathy, chronic sensory polyneuropathy, and chronic inflammatory demyelinating polyneuropathy-like, recurrent subacute polyneuropathy; and 14 asymptomatic patients. In all the deletion carriers, regardless of their phenotype and by the second decade, the authors found a characteristic, multifocal electrophysiologic neuropathy consisting of a diffuse increase in distal motor latencies contrasting with normal or moderately reduced motor nerve conduction velocities, a diffuse reduction in sensory nerve action potential, and multiple focal slowing of nerve conduction at the usual sites of entrapment. The key diagnostic criterion is a bilateral slowing of sensory and motor nerve conduction at the carpal tunnel with at least one abnormal parameter for motor conduction in one peroneal nerve.

CONCLUSION

The authors confirm the clinical phenotypic heterogeneity of the 17p11.2 deletion and suggest that electrophysiologic examination is a reliable tool for screening suspected HNPP patients in its various clinical presentations.

[Distal Miyoshi muscular dystrophy in a Moroccan patient]

BACKGROUND

Muscular dystrophy usually involves a deficiency in the proximal muscles. We report a case of distal muscular dystrophy in a Moroccan patient.

CASE REPORT

A 21-year-old Moroccan complained of progressive onset weakness of the lower limbs and frequent falls. The neurological examination demonstrated amyotrophy involving both legs and almost complete regression of the posterior muscle compartment. Clinical findings were confirmed by muscle scans. The electromyogram showed a progressive myogenic process. Creatine kinase was elevated. The severe dystrophic aspect was evidenced at muscle biopsy and led to the diagnosis of distal Miyoshi muscular dystrophy.

DISCUSSION

Miyoshi muscular dystrophy, a distal myopathy transmitted by autosomal recessive inheritance, is usually observed in young adults who present characteristic amyotrophy of the posterior leg muscles. The proximal muscles of the lower and upper limbs may become involved during the disease course. Approximately one-third of the patients require wheel chair assistance after 10 years. Creatine kinase levels are constantly elevated. The differential diagnosis with other muscular dystrophies predominating in the distal muscles, particularly Steinert's myotonic dystrophy and inclusion body myositis, is discussed.

Ultrastructural protein zero expression in Charcot-Marie-Tooth type 1B disease

Charcot-Marie-Tooth type 1B (CMT 1B) disease, an inherited demyelinating peripheral neuropathy, results from different point mutations located in the P0 gene on chromosome 1 q21-23. We have quantified, at the ultrastructural level, the immunocytochemical expression of the P0 protein in two unrelated CMT 1B patients with mutations (Ser 78 to Leu and Asn 122 to Ser) located in two different exons in the extracellular domain of the protein. A twofold decrease in P0 expression was observed in compact myelin in each case, compared with age-matched controls. The severity of the phenotypes showed no direct relationship to the levels of P0 protein expression in these 2 patients.

Reflexes elicited from cutaneous and mucosal trigeminal afferents in normal human subjects

It has been shown that in patients in whom the central stump of the hypoglossal nerve has been anastomosed to the peripheral stump of a lesioned facial nerve, supraorbital nerve stimulation can elicit a short-latency reflex (12.5+/-0.6 ms; mean+/-S.D.) in facial muscles similar to the R1 disynaptic blink reflex response, but not followed by an R2 blink reflex component46. Thus in addition to replacing the facial neurons at peripheral synapses, these hypoglossal nerves contribute to a trigemino-hypoglossal reflex. The aim of this work was to study the type of reflex activities which can be elicited in both facial and tongue muscles by electrical stimulation of cutaneous (supraorbital nerve) or mucosal (lingual nerve) trigeminal (V) afferents in normal subjects. The results show that although stimulation of cutaneous V1 afferents elicits the well-known double component (R1-R2) blink reflex response in the orbicularis oculi muscles, it does not produce any detectable reflex response in the genioglossus muscle, even during experimental paradigms designed to facilitate the reflex activity. Conversely, stimulation of mucosal V3 afferents can elicit a single reflex response of the R1 type in the genioglossus muscle but not in the orbicularis oculi muscles, even during experimental paradigms designed to facilitate the reflex activity. These data are discussed in terms of two similar but separate circuits for the R1 responses of cutaneous (blink reflex) and mucosal (tongue reflex) origins. They suggest that in patients with hypoglossal-facial (XII-VII) nerve anastomosis, the short-latency trigemino-'hypoglossal-facial' reflex of the R1 blink reflex type observed in facial muscles following supraorbital nerve stimulation could be due to changes in synaptic effectiveness of the central connectivity within the principal trigeminal nucleus where both cutaneous and mucosal trigeminal afferents project.

True neurogenic thoracic outlet syndrome: electrophysiological diagnosis in six cases

We report 6 patients with true neurogenic thoracic outlet syndrome. All were female and presented unilateral severe atrophy of the thenar muscles. Pain in the affected upper limb was frequently reported, but sensory deficit was slight or absent. Reduced amplitude of ulnar and median compound muscle action potential associated with a normal amplitude of median sensory nerve action potential (SNAP) and a reduced amplitude of ulnar SNAP was indicative of a chronic axon loss in the lower trunk of the brachial plexus. The absence of the medial antebrachial cutaneous SNAP in 5 patients and a reduction in amplitude compared to the unaffected side in the other patient indicated a C8-T1 postganglionic radicular lesion or a lower brachial plexus neuropathy. Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed, and in each case the lower part of the brachial plexus was found to be stretched and angulated over a fibrous band, which was removed. Pain was relieved after 1-4 weeks, but at 1 year, there was only minimal motor improvement and the electrophysiological results were unchanged.

True neurogenic thoracic outlet syndrome: electrophysiological diagnosis in six cases

We report 6 patients with true neurogenic thoracic outlet syndrome. All were female and presented unilateral severe atrophy of the thenar muscles. Pain in the affected upper limb was frequently reported, but sensory deficit was slight or absent. Reduced amplitude of ulnar and median compound muscle action potential associated with a normal amplitude of median sensory nerve action potential (SNAP) and a reduced amplitude of ulnar SNAP was indicative of a chronic axon loss in the lower trunk of the brachial plexus. The absence of the medial antebrachial cutaneous SNAP in 5 patients and a reduction in amplitude compared to the unaffected side in the other patient indicated a C8-T1 postganglionic radicular lesion or a lower brachial plexus neuropathy. Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed, and in each case the lower part of the brachial plexus was found to be stretched and angulated over a fibrous band, which was removed. Pain was relieved after 1-4 weeks, but at 1 year, there was only minimal motor improvement and the electrophysiological results were unchanged.

Electrophysiological determination of the site involved in generating abnormal muscle responses in hemifacial spasm

In patients with hemifacial spasm (HFS), abnormal muscle responses due to abnormal cross-transmission are observed in facial muscles. However, the site in the facial nerve responsible for the cross-transmission remains a matter of controversy. We have developed a model in which by considering the electrophysiological parameters involved in producing the abnormal muscle response, we can determine the site of the abnormal cross-transmission within the facial nerve. This model was applied to HFS patients with three different etiologies: idiopathic, post-Bell's palsy, and post-XII-VII anastomosis. Our data show that: in idiopathic HFS, the cross-transmission may occur in the facial nerve at the level of the pontocerebellar angle; in post-Bell's palsy, it is inside the petrous bone; and in XII-VII anastomosis, it must be in the extracranial part of the facial nerve. The possible mechanisms for this cross talk are discussed in terms of ephaptic transmission or of a central hyperexcitability in the facial motor nucleus.