The nosology of genetic peripheral neuropathies in Swedish children

Etiologic spectrum of biopsy-proven peripheral neuropathies in childhood from a resource-poor setting

There are only a few studies describing the etiologic spectrum of biopsy-proven peripheral neuropathies in children. This study reviewed the clinical, electrophysiological, and pathologic profile of 239 children (≤18 years of age) who have undergone nerve biopsy in a tertiary care centre for neurologic disorders and analyzed the etiologic spectrum and utility of nerve biopsy. The clinical profile, neuropathologic findings, and other investigations were combined to infer the final diagnosis. Neuropathy was detected in 199 biopsies; axonal pathology in 43%; demyelination in 41%; mixed pattern in 8%; and nonspecific findings in 8%. The major diagnostic categories included hereditary neuropathies (48%), heredodegenerative and metabolic disorders (27%), and inflammatory neuropathies (12%). Nerve biopsy proved most helpful in diagnosis of demyelinating and inflammatory neuropathies, reiterating its usefulness in specific situations.

Diagnosis and management of pediatric peripheral neuropathies in resource-poor settings

The diagnosis of a peripheral neuropathy in a child who resides in the majority of resource-poor settings is based on the history taken and the clinical examination. The majority of children, unless they demonstrate additional clinical markers, will lack a more definitive diagnosis beyond the label ‘peripheral neuropathy’. The treatable, typically acquired conditions, which are prevalent in these settings, are the priority to identify. This would include neuroinfections, neuroinflammation, toxins and vitamin deficiencies. The management of children with peripheral neuropathies in resource-poor settings must be approached in a different manner to that of more ‘resource-equipped’ settings. Secondary or tertiary centers are scarce, often significant distances away from the patient, and this leads to long delays before access is possible. Most children present to primary healthcare settings and are seen by practitioners with little training in the features suggestive of a peripheral neuropathy. As such, basic aids to assist the healthcare worker in the early recognition and interventions of a child with a peripheral neuropathy are important. In addition, there must be recognition of the child with a rapidly progressive neuropathy where a life-threatening condition is present, and urgent referral to a tertiary setting made wherever possible.

Hereditary peripheral neuropathies of childhood: an overview for clinicians

This review focuses on the "pure" hereditary peripheral neuropathies where peripheral nerve disease is the main manifestation and does not address neurodegenerative disorders associated with but not dominated by peripheral neuropathy. Aetiologies of childhood-onset peripheral neuropathies differ from those of adult-onset, with more inherited conditions, especially autosomal recessive. Charcot-Marie-Tooth disease is the commonest neuromuscular disorder. The genetic labels of CMT (Charcot-Marie-Tooth) disease types 1-4 are the preferred sub-type terms. Clinical presentations and molecular genetic heterogeneity of hereditary peripheral neuropathies are diverse. For most patients worldwide, diagnostic studies are limited to clinical assessment. Such markers which could be used to identify specific sub-types include presentation in early childhood, scoliosis, marked sensory involvement, respiratory compromise, upper limb involvement, visual or hearing impairment, pyramidal signs and mental retardation. These key markers may assist targeted genetic testing and aid in diagnosing children where DNA testing is not possible.

Homozygous hypertrophic hereditary motor and sensory neuropathies

We compared 25 autosomal dominant hereditary motor and sensory neuropathy (HMSN) type I patients with 7 subjects affected by hypertrophic HMSN with non-dominant inheritance. All the autosomal dominant HMSN I cases carried the chromosome 17p11.2 duplication, providing evidence that it is widely represented in HMSN I families. The second group included: two siblings born to unrelated, unaffected parents and suffering from hypertrophic HMSN of strikingly different severity; two sisters with HMSN I phenotype, born to first-cousin unaffected parents; two brothers with HMSN III phenotype born to unrelated parents both showing HMSN II phenotype; a child with classic HMSN III phenotype, born to unrelated, unaffected parents. The 17p11.2 duplication was not found in any of the patients of the second series or in their parents. Our data provide further evidence that: HMSN III is heterogeneous and encompasses the homozygous expressions of different neuropathic genes; it is advisable to separate autosomal recessive hypertrophic HMSN from dominant HMSN Ia, because they appear to be due to different DNA mutations.

Hereditary motor and sensory neuropathy: HMSN type II (neuronal type) and X-linked HMSN

The neuronal forms of hereditary motor and sensory neuropathy (HMSN) are genetically heterogeneous with observed autosomal dominant, autosomal recessive and X-linked dominant inheritance. All three forms are characterized by degeneration of select populations of motor and sensory neurons with accompanying atrophy and degeneration of their axons. Large calibre myelinated fibres are predominantly affected and fibre degeneration and fibre loss progresses from distally to proximally. Attempts of regeneration are noted in all except the severe childhood form. The clinical picture is that of peroneal and distal leg muscle wasting and weakness, distal sensory loss and areflexia. Hand muscles may be severely affected in the autosomal recessive and X-linked dominant forms. Motor and sensory nerve conduction velocities are only moderately slowed and evoked maximum compound motor and sensory amplitudes are reduced according to the degree of fibre loss. The gene locus remains unknown in both the autosomal dominant and autosomal recessive types. For the X-linked dominant HMSN, the gene locus has been mapped closely by linkage analysis to DNA loci in the pericentromeric region of the X-chromosome.

Early morphological features in dominantly inherited demyelinating motor and sensory neuropathy (HMSN type I)

Seventeen cases of dominantly inherited demyelinating motor and sensory neuropathy (HMSN type I) with infantile onset were studied. Not only clinical and electrophysiological data, but also the g ratio (axon diameter to fibre diameter), considered to be a distinguishing feature between HMSN type I and HMSN type III, showed overlap. Morphological and morphometrical investigations already revealed a lack of small and large diameter myelinated axons at an early stage, and a demyelinating process most active in early childhood followed later by axonal loss. It was concluded that the histopathology of HMSN type I cannot be sufficiently explained by axonal atrophy with secondary demyelination.

Polyneuropathies in paediatrics

Non-acute polyneuropathies (PNPs) encountered in paediatrics are reviewed. Emphasis is placed on three main groups of conditions: the relatively rare but treatable dysimmune PNP (chronic relapsing dysimmune polyneuropathies, CRDP); the more common hereditary motor/sensory neuropathies (HMSN and HSN); and the often missed symptomatic neuropathies of some heredodegenerative and neurometabolic disorders. Diagnostic procedures are discussed. One conclusion drawn is that so far metabolic screening procedures do not give any diagnostic or aetiological information in HMSN or in HSN, nor in heredoataxias or heredoparaplegias. When a specific neurometabolic disease is suspected from the clinical symptomatology, individually structured investigations are necessary.

Autosomal recessive motor and sensory neuropathy with excessive myelin outfolding

Two Japanese persons with consanguinous parents had a motor and sensory neuropathy of the hypertrophic type with excessive myelin outfolding in the myelinated fibers. A morphometric analysis of the biopsied sural nerve was made. Excessive myelin outfolding, segmental demyelination, and remyelination and decrease in the density of both large and small myelinated fibers were evident. Using linear regression, myelin spiral length was shorter relative to axonal area. These patients may have a new variant of hereditary motor sensory neuropathy.

Hereditary motor and sensory neuropathies: a genetic and epidemiological study in the province of Turin, Italy

A clinical, genetic and epidemiological study of hereditary motor and sensory neuropathies (HMSN) was performed in the province of Turin, Italy. The patients were allocated to 5 groups, according to genetic and electroneurographic features. The high proportion of males among recessive and sporadic cases in the present series may suggest the existence of a recessive X-linked form of the disease. The crude prevalence rate was 3.18 (+/- 0.72)/100.000 population for all cases. The slow progression rate and the frequently mild symptoms of the disease, already suggested in literature, are confirmed by the analysis of the survival curves of the cases.

Congenital neuropathy with prevailing axonal changes. A clinical and histological report

A case of congenital neuropathy associated with an unclassified chronic brain disorder is described. Morphological findings differ from the reported congenital neuropathies where primary myelin change have been usually found. In contrast, sural nerve biopsy showed marked signs of active or past axonal degeneration; at the teasing and morphometric analysis there was also some evidence of segmental demyelination. Atypical onion bulb formations (Evans and Murray type) and a very poor demyelination activity stressed the prevailing axonal involvement with possibly secondary segmental demyelination.

Hereditary motor and sensory neuropathy of demyelinating and remyelinating type in children. Ultrastructural and morphometric studies on sural nerve biopsy specimens from ten sporadic cases

Ten autosomal recessive/sporadic cases of hereditary motor and sensory neuropathy type I (HMSN I), nine of which originated from the northern part of Sweden, were included in the study. Parents were free from neurologic symptoms. Motor and sensory conduction velocity was normal when recorded, i.e., in 19 and 17 parents, respectively. Sural nerve biopsies from the ten cases revealed a varying degree of onion bulb formation. In eight of the cases the onion bulbs consisted of abundant basement membranes, whereas the Schwann cells were few and sometimes lacking. There were in some cases considerable differences between separate fascicles as to the loss of myelinated nerve fibers. In the six biopsies in which teasing was performed signs of present and previous demyelination were noticed. Numerous internodal segments were abnormally thin with reference to their length. In many such segments there were marked local thickenings of the nerve fiber. In cross sections the probable counterparts to these thickenings were nerve fibers with unduly thick myelin sheaths and complex folding of the myelin. Ultrastructural axonal changes were seen in the majority of the cases. The pathogenetic and diagnostic implications of the present findings are discussed.

Hereditary motor and sensory neuropathies in Swedish children. II. Neuronal-axonal types

Clinical, neurophysiological and laboratory data are given for 32 children (30 kinships) considered to represent hereditary motor and sensory neurophaties (HMSN) of neuronal-axonal types. In 25 families (27 cases) one of the parents was found to be affected. In one both parents were normal. The mode of inheritance in the 27 patients with familial neuronal-axonal HMSN was concluded to be autosomal dominant HMSN II (Lambert type). The disability was mild to moderate and, on an average, less pronounced than in de- and remyelinating types of HMSN. Seven out of 27 were early toe-walkers of the secondary type. Cavus feet were noted in 25, hand atrophies in eight and mild scoliosis in five. Sensory complaints were recorded in 21. The nerve conduction velocities (NCVm and NCVs) of children and parents were slightly subnormal in a few. EMG proved to be the most important parameter for identifying subclinically affected parents.

Hereditary motor and sensory neuropathies in Swedish children. III. De- and remyelinating type in 10 sporadic cases

Clinical, neurophysiological and certain other laboratory data are given for 10 children considered to represent sporadic cases of de- and remyelinating hereditary motor and sensory neuropathies (HMSN). In all 10 families the parents had been found to be non-affected and said to be non-consanguineous. Nine of the 10 families originated from the two most northerly Swedish counties, but none from the Gothenburg area. The median age at clinical onset was 3 years. Gait abnormalities and/or foot deformities were common reasons for referral. Scoliosis developed in all 10 and hand atrophies in 7 children. In the majority there was neurological deterioration through childhood. Nerve conduction velocities, both motor and sensory, were consistently and markedly reduced. The protein level in cerebrospinal fluid (medium 657 mg/l) was slightly to moderately raised in 7 of 9 examined children and greater than or equal to 1 500 mg/l in the remaining two. The fatty acid pattern of serum lecithin was consistently normal in all 10.