Detection of hereditary neuropathy with liability to pressure palsies among patients with acute painless mononeuropathy or plexopathy

Orphan Peripheral Neuropathies

Objectives:

Generally, neuropathies of peripheral nerves are a frequent condition (prevalence 2–3%) and most frequently due to alcoholism, diabetes, renal insufficiency, malignancy, toxins, or drugs. However, the vast majority of neuropathies has orphan status. This review focuses on the etiology, frequency, diagnosis, and treatment of orphan neuropathies.

Methods:

Literature review

Results:

Rareness of diseases is not uniformly defined but in the US an orphan disease is diagnosed if the prevalence is <1:200000, in Europe if <5:10000. Most acquired and hereditary neuropathies are orphan diseases. Often the causative variant has been reported only in a single patient or family, particularly the ones that are newly detected (e.g. SEPT9, SORD). Among the complex neuropathies (hereditary multisystem disorders with concomitant neuropathies) orphan forms have been reported among mitochondrial disorders (e.g. NARP, MNGIE, SANDO), spinocerebellar ataxias (e.g. TMEM240), hereditary spastic paraplegias (e.g UBAP1), lysosomal storage disease (e.g. Schindler disease), peroxisomal disorders, porphyrias, and other types (e.g. giant axonal neuropathy, Tangier disease). Orphan acquired neuropathies include the metabolic neuropathies (e.g. vitamin-B1, folic acid), toxic neuropathies (e.g. copper, lithium, lead, arsenic, thallium, mercury), infectious neuropathies, immune-mediated (e.g. Bruns-Garland syndrome), and neoplastic/paraneoplastic neuropathies.

Conclusions:

Though orphan neuropathies are rare per definition they constitute the majority of neuropathies and should be considered as some of them are easy to identify and potentially treatable, as clarification of the underlying cause may contribute to the knowledge about etiology and pathophysiology of these conditions, and as the true prevalence may become obvious only if all ever diagnosed cases are reported.

Hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (HNPP) is characterized by recurrent sensory and motor neuropathy in individual nerves starting in adolescence or young adulthood, focal conduction abnormalities at entrapment sites on nerve conduction studies, and sausage-like swellings (tomacula) of the myelin sheaths by nerve biopsy. It is characterized genetically by the deletion of the chromosome 17p11.2-p12 region including the peripheral myelin protein-22 gene in the overwhelming majority of cases. HNPP may be frequently underdiagnosed or misdiagnosed owing to the heterogeneity of clinical and electrophysiological appearance. The main objective of this review is to describe clinical manifestations, paraclinical features such as electrodiagnostic, pathological, radiological and genetics findings, and possible treatments.

Hereditary neuropathy with liability to pressure palsy (HNPP): report of a family with a new point mutation in PMP22 gene

Background

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder most commonly presenting with acute-onset, non-painful focal sensory and motor mononeuropathy. Approximately 80% of patients carry a 1.5 Mb deletion of chromosome 17p11.2 involving the peripheral myelin protein 22 gene (PMP22), the same duplicated in Charcot-Marie-Tooth 1A patients. In a small proportion of patients the disease is caused by PMP22 point mutations.

Case presentation

We report on a familial case harbouring a new point mutation in the PMP22 gene.

The proband is a 4-years-old girl with acute onset of focal numbness and weakness in her right hand. Electroneurography demonstrated transient sensory and motor radial nerves involvement. In her father, reporting chronic symptoms (cramps and exercise-induced myalgia), we uncovered mild atrophy and areflexia on clinical examination and a mixed (predominantly demyelinating) polyneuropathy with sensory-motor involvement on electrophysiological study.

Both carried a nucleotidic substitution c.178 + 2 T > C on intron 3 of the PMP22 gene, involving the splicing donor site, not reported on databases but predicted to be likely pathogenic.

Conclusions

We described a previously unreported point mutation in PMP22 gene, which led to the development of a HNPP phenotype in a child and her father. In children evaluated for a sensory and motor transient episode, HNPP disorder due to PMP22 mutations should be suspected. Clinical and electrophysiological studies should be extended to all family members even in the absence of previous episodes suggestive for HNPP.

Backpack palsy: A rare complication of backpack use in children and young adults - A new case report

Backpack palsy is a well-recognised, albeit rare, complication of carrying backpacks. Although it has been mostly described in cadets during strenuous training, sporadic cases of brachial nerve impairment have been reported in children and young adults. Here we reported the case of a 15-year-old girl who presented with a left-side brachial palsy with axonal denervation of C5C7 motor roots following a school challenge for the Duke of Edinburgh Award. Her symptoms began soon after starting the challenge and included weakness of shoulder abduction and elevation, as well as forearm, wrist and fingers extension. After 6 months of physiotherapy her motor function was completely restored. Backpack palsy can sometimes present in children and young adults. This disorder should be taken in consideration when planning for daily, as well as more challenging, physical activities in these age groups.

Hereditary neuropathy with liability to pressure palsies in childhood: Case series and literature update

Hereditary Neuropathy with Liability to Pressure Palsy (HNPP) is a rare condition in childhood with a diverse range of clinical presentations. We analyzed the clinical presentation and electrophysiological data of 12 children with a confirmed PMP22 gene deletion and reviewed the published reports of HNPP in children and compared our data with the reports from the literature review. Peroneal palsy was the most common presentation (42%) followed by brachial plexus palsy in 25% of our cases. Nerve conduction studies were always suggestive of the diagnosis demonstrating 3 major patterns: multifocal demyelination at the area of entrapment, generalized sensory-motor polyneuropathy and a combination of the two first patterns in a vast majority (60%). Surprisingly, there was bilateral or unilateral electrophysiological entrapment of the median nerve at the carpal tunnel in all our patients. The clinical presentation of HNPP in childhood is heterogeneous and electrophysiological findings are helpful in establishing the diagnosis. Any unexplained mononeuropathy or multifocal neuropathy should lead to PMP22 gene testing to look for the deletion. Early diagnosis is important in order to facilitate appropriate genetic counseling and also for the appropriate care for these patients.

Mutational analysis of Greek patients with suspected hereditary neuropathy with liability to pressure palsies (HNPP): a 15-year experience

There has been limited information from population studies regarding the overall frequency of the common 1.5-Mb 17p11.2 deletion and even scarcer data regarding the overall frequency of PMP22 micromutations in patients with a clinical suspicion of hereditary neuropathy with liability to pressure palsies (HNPP). We have analysed 100 consecutive Greek patients referred for HNPP genetic testing over a 15-year period to our Neurogenetics Unit in Athens, a reference centre for all regions of Greece. All patients were screened for the 1.5-Mb deletion and a selected subgroup of deletion-negative patients for PMP22 micromutations. Mutation-positive and mutation-negative patients were compared for various clinical parameters. In total, 54 mutation-positive patients were identified. In index cases, the deletion frequency was 47.8%, and the PMP22 micromutation frequency was 2.2%. Within mutation-positive patients, the common deletion represented 95.7% and PMP22 micromutations 4.3% of cases. Two previously reported PMP22 micromutations (c.364_365delCC and c.79-2A>G) were detected. HNPP index cases had a 2.8-1 male-to-female ratio, similar to mutation-negative patients. A typical phenotype (recurrent or isolated palsies) was present in 82.4% of symptomatic HNPP cases, significantly higher than mutation-negative patients. Sensitivity of proposed electrophysiological diagnostic criteria for HNPP was calculated at 95.7% and specificity at 80.5%. In conclusion, the common HNPP deletion accounts for ∼50% and PMP22 micromutations for ∼2% of cases in a large consecutive cohort of patients with suspected HNPP. The mutational and phenotypic spectrum of HNPP is similar in the Greek population compared with other populations. Proposed electrophysiological diagnostic criteria perform satisfactorily in everyday clinical practice.

Hereditary neuropathy with liability to pressure palsies presenting with sciatic neuropathy

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant disorder associated with recurrent mononeuropathies following compression or trivial trauma. Reports on sciatic neuropathy as the presenting manifestation of HNPP are very scarce. We report on a 21-year-old previously healthy man who was admitted with sensorimotor deficits in his left leg. He had no history of preceding transient episodes of weakness or sensory loss. Clinical and electrophysiological examinations were consistent with sciatic neuropathy. Cerebrospinal fluid investigation and MRI of the nerve roots, plexus, and sciatic nerve did not indicate the underlying aetiology. When extended electrophysiological tests revealed multiple subclinical compression neuropathies in the upper limbs, HNPP was contemplated and eventually confirmed by genetic testing.

Recovery of brachial plexus lesions resulting from heavy backpack use: a follow-up case series

Background

Brachial plexus lesions as a consequence of carrying a heavy backpack have been reported, but the typical clinical course and long-term consequences are not clear. Here we evaluated the clinical course and pattern of recovery of backpack palsy (BPP) in a large series of patients.

Methods

Thirty-eight consecutive patients with idiopathic BPP were identified from our population of 193,450 Finnish conscripts by means of computerised register. A physiotherapist provided instructions for proper hand use and rehabilitative exercises at disease onset. The patients were followed up for 2 to 8 years from the diagnosis. We also searched for genetic markers of hereditary neuropathy with pressure palsies. Mann-Whitney U-test was used to analyze continuous data. The Fischer's exact test was used to assess two-way tables.

Results

Eighty percent of the patients recovered totally within 9 months after the onset of weakness. Prolonged symptoms occurred in 15% of the patients, but daily activities were not affected. The weight of the carried load at the symptom onset significantly affected the severity of the muscle strength loss in the physiotherapeutic testing at the follow-up. The initial electromyography did not predict recovery. Genetic testing did not reveal de novo hereditary neuropathy with pressure palsies.

Conclusions

The prognosis of BPP is favorable in the vast majority of cases. Electromyography is useful for diagnosis. To prevent brachial plexus lesions, backpack loads greater than 40 kg should be avoided.

[Diagnostic pitfalls in carpal tunnel syndrome]

BACKGROUND

This review focuses on the main aspects of positive and differential diagnosis of carpal tunnel syndrome (CTS) in different clinical situations encountered in daily practice.

STATE OF THE ART

Authentic CTS can be discovered in situations, which alter the usual presentation or therapeutic management. This is the case for instance in pregnant women or in the elderly subject or with acute motor forms where CTS discloses a focal intratunnel disorder (neuroma, lipoma, arterial condition, bone disorder) or a general disease (hereditary neuropathy, amylosis). In certain situations, the clinical manifestations suggest a more proximal compression of the medial nerve (round pronator, Struthers arcade, or superficial flexor) or an inflammatory condition (mononeuritis, inflammatory demyelinising neuropathy). Locoregional disease may also be involved, for instance a plexus (thoracobrachial outlet syndrome, post-radiation plexitis) or radicular condition. The clinical presentation of diffuse polyneuropathy with initial manifestations involving the upper limb (ganglioneuropathies, polyradiculoneuritis, small-fiber neuropathies) may also be misleading. Finally central conditions can sometimes be confused with CTS.

CONCLUSION

A rigorous physical examination and an electroneuromyogram are determining to avoid diagnostic pitfalls.

Genomic rearrangements and gene copy-number alterations as a cause of nervous system disorders

Genomic disorders are a group of human genetic diseases caused by genomic rearrangements resulting in copy-number variation (CNV) affecting a dosage-sensitive gene or genes critical for normal development or maintenance. These disorders represent a wide range of clinically distinct entities but include many diseases affecting nervous system function. Herein, we review selected neurodevelopmental, neurodegenerative, and psychiatric disorders either known or suggested to be caused by genomic rearrangement and CNV. Further, we emphasize the cause-and-effect relationship between gene CNV and complex disease traits. We also discuss the prevalence and heritability of CNV, the correlation between CNV and higher-order genome architecture, and the heritability of personality, behavioral, and psychiatric traits. We speculate that CNV could underlie a significant proportion of normal human variation including differences in cognitive, behavioral, and psychological features.

Brachial plexus lesions after backpack carriage in young adults

Carrying a heavy backpack exerts compression on shoulders, with the potential to cause brachial plexopathy. We evaluated the incidence and predisposing factors of compression plexopathy of the shoulder region in 152,095 military conscripts, hypothesizing that a low body mass index and poor physical fitness predispose to the plexus lesion. Reports of conscripts with neural lesions of the upper arm associated with load carriage were reviewed retrospectively for details associated with the condition onset, symptoms, signs, nerve conduction studies, and electromyographic examinations. Height, weight, and physical fitness scores were obtained from their military training data. The incidence of neural compression after shoulder load carriage in Finnish soldiers was 53.7 (95% confidence interval, 39.5-67.8) per 100,000 conscripts per year. The long thoracic nerve was affected in 19, the axillary nerve in 13, the suprascapular nerve in seven, and the musculocutaneous nerve in six patients. Four patients (7%) had hereditary neuropathy with susceptibility to pressure palsies (HNPP). Symptoms were induced by lighter loads in patients with HNPP. Vulnerability to brachial plexopathy was not predictable from body structure or physical fitness level. To prevent these lesions, awareness of the condition and its symptoms should be increased and backpack designs should be improved.

A rare genetic disorder in the differential diagnosis of the entrapment neuropathies: hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant, slowly progressive neuromuscular disorder, which is characterized by recurrent acute peripheral nerve palsies. Electrophysiological studies show decreased motor and sensory conduction velocities in both clinically affected and unaffected nerves. Focal thickening of myelin sheath with sausage-like formation, also called tomacula, is seen in nerve biopsies. In genetic studies, 1.5-Mb deletion on chromosome 17p11.2 is detected in approximately 85% of HNPP cases and point mutations are determined in some cases. We describe a 26-year-old man who had a 6-month history of paresthesia in the little fingers of his hands. He was diagnosed with HNPP by neurologic examination, and electrophysiological and histopathologic studies. Studies in his mother and one brother also showed entrapment neuropathy. However, no deletions or point mutations were determined in this family. Other genetic defects apart from the known ones might be present in this disease. The most frequent entrapment syndrome, carpal tunnel syndrome, is also seen in this disease, so physicians dealing with musculoskeletal problems should be alert about this subject. Awareness of HNPP may help avoid unnecessary operative interventions.

The prevalence of hereditary neuropathy with liability to pressure palsies in patients with multiple surgically treated entrapment neuropathies

PURPOSE

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant peripheral neuropathy that results from deletion of a 1.5-Megabase pair (Mb) segment of the short arm (p) of chromosome 17. Hereditary neuropathy with liability to pressure palsies increases susceptibility of peripheral nerves to pressure and trauma and can be associated with symptoms at multiple anatomic entrapment sites. Many patients present with multiple upper-extremity entrapment neuropathies and the etiology is uncertain. We hypothesized that some of these patients have an underlying hereditary neuropathy. The purpose of this study was to determine the prevalence of HNPP in patients with multiple surgically treated upper-extremity entrapment neuropathies.

METHODS

The inclusion criterion for the study was history of more than 1 carpal tunnel release and/or ulnar nerve transposition. The exclusion criteria were history of diabetes or history of Charcot-Marie-Tooth neuropathy. Fifty-nine patients were in the study group. Two patients known to have the 17p11.2 deletion were used as controls. Genomic DNA was extracted from peripheral blood. Each sample was genotyped using polymerase chain reaction (PCR) amplification with short tandem repeat polymorphism markers within the 1.5-Mb region of 17p deleted in HNPP. Markers were scored as homozygous or heterozygous after resolution by polyacrylamide gel electrophoresis and silver staining.

RESULTS

The 2 control patients were homozygous for 11 markers. None of the 59 study patients were homozygous for all markers tested in the deleted region. No study patient had the 17p deletion diagnostic for HNPP. Based on the sample size of 59 patients the 95% confidence interval for the prevalence of the 17p11.2 deletion in this population is 0% to 5%.

CONCLUSIONS

We found no evidence for an association between HNPP and patients who have multiple surgical releases for upper-extremity entrapment neuropathies.

[Regional anaesthesia for labor adn delivery in a parturient with neuropathy with liability to pressure palsy (tomaculous neuropathy)]

Tomaculous neuropathy (or hereditary neuropathy with liability to pressure palsy [HNLPP]) is a rare and hereditary disease which incidence has probably been underestimated. It is characterised by demyelination resulting in numbness and weakness after nerve pressure, injury or stretch. Despite a well-documented genetic pathophysiologic mechanism, implications for anaesthesia in patients with HNLPP are only speculative and the use of regional anaesthesia is debatable. We report here the case of a patient with HNLPP who was followed during two consecutive pregnancies in the same hospital and for whom an expert of the SOS-RA hotline service was consulted before each delivery. For the first delivery, epidural analgesia was performed for labour pain control but a caesarean section was necessary because of failure to progress (0.0625% bupivacaine with 0.2 microg/ml sufentanil for labour then 2% lidocaine with adrenaline for surgery). Two years later, the patient was again seen for a preanaesthetic visit because elective Caesarean section was planned. Spinal anaesthesia using hyperbaric bupivacaine and sufentanil was used. Both deliveries were uneventful and there were no neurologic complaints in the postpartum periods.

Phenotypic Variability Leads to Under-recognition of HNPP

OBJECTIVE

To determine the range of phenotypic expression in individuals with hereditary neuropathy with liability to pressure palsy (HNPP) with the chromosome 17 deletion.

METHODS

Twenty-one patients from 10 families were studied. Genetic testing was performed in at least one member of each family. Every patient was examined clinically, electrophysiological data was available in 18 patients, and a sural nerve biopsy was performed on 4 patients. In addition, a patient symptom questionnaire was administered over the telephone to identify symptomatic individuals from the at-risk population.

RESULTS

The identified phenotypes were those of compressive neuropathy, symmetric peripheral neuropathy (often misdiagnosed as Charcot-Marie-Tooth neuropathy), acute brachial paralysis, and confluent mononeuropathy multiplex. Many individuals were oligosymptomatic and these formed the majority of undiagnosed patients.

CONCLUSIONS

The presence of mild symptoms and the marked phenotypic variability of the disease result in underdiagnosis of HNPP.

Peroneal neuropathy after weight loss

The objectives of this study were to evaluate the clinical and electrophysiological findings in peroneal mononeuropathies following a weight-reduction diet. Thirty patients with acute peroneal palsy and weight loss were studied. Complete nerve conduction studies (NCS) were performed in upper and lower limbs. NCS showed conduction block (CB) of the peroneal nerve at the fibular head that recovered in 29 patients within 3 weeks to 3 months. Severity of CB was correlated with clinical weakness. Three patients had abnormalities consistent with polyneuropathy (PNP). NCS in asymptomatic relatives confirmed familial neuropathy. Nerve biopsy and molecular study were consistent with hereditary neuropathy with liability to pressure palsies (HNPP). One of these peroneal palsies (6 months) recovered after neurolysis. Weight loss might be a risk factor in peroneal mononeuropathies. NCS is a tool in the diagnosis of the site and severity of the nerve injury. Testing should be considered for relatives of patients with PNP because peroneal mononeuropathies may be the first expression of HNPP.

Hereditary neuropathy with liability to pressure palsies in children

The clinical and neurophysiologic findings of two children presenting with focal weakness and atrophy in unusual nerve distributions and no apparent antecedent injuries are reported. Patient 1 presented with a droopy left shoulder that was initially attributed to scoliosis. Patient 2 presented with right biceps brachii atrophy that was first brought to his parent's attention during a routine physical examination. In addition to documenting focal spinal accessory and musculocutaneous mononeuropathies as the cause of weakness in Patients 1 and 2, respectively, nerve conduction studies also revealed evidence of superimposed diffuse demyelinating polyneuropathy in both children. The latter findings suggested the diagnosis of hereditary neuropathy with liability to pressure palsies and led to definitive DNA diagnoses.

Charcot-marie-tooth disease and related neuropathies: molecular basis for distinction and diagnosis

Great advances have been made in understanding the molecular basis of Charcot-Marie-Tooth disease (CMT) and related neuropathies, namely Dejerine-Sottas disease (DSD), hereditary neuropathy with liability to pressure palsies (HNPP) and congenital hypomyelination (CH). The number of newly uncovered mutations and identified genetic loci is rapidly increasing, and, as a consequence, the classification of these disorders is becoming more complicated. Molecular genetics, animal models, and transfected cell studies are shedding light on function and dysfunction of proteins involved in hereditary myelinopathies-peripheral myelin protein 22 (PMP22), myelin protein zero (PO), connexin 32 (Cx32), and early growth response 2 (EGR2). Gene dosage effect, loss of function, gain of toxic function, and dominant negative effect are possible mechanisms whereby different gene mutations may exert their detrimental action on peripheral nerves. A tentative rational approach to clinical and molecular diagnosis based on genotype-phenotype correlation analysis is described.

Entrapment neuropathies

Entrapment neuropathies occur when nerves are chronically compressed or mechanically injured at specific locations. Some of these focal neuropathies such as carpal tunnel syndrome are common, and others such as neurogenic thoracic outlet syndrome are rare. This article highlights recent advances and interesting observations that cover a wide spectrum of such focal neuropathies. Selected disorders that can affect individual peripheral nerves and masquerade as 'entrapment neuropathies' are also emphasized.

Molecular basis of inherited neuropathies

Considerable advances in our knowledge of the most frequently encountered group of inherited neuropathies, Charcot-Marie-Tooth neurpathy (CMT) and related disorders, have recently been made by genetic studies demonstrating that these disorders are caused by duplication, deletion or point mutations of specific genes of the peripheral myelin. The present classification of CMT and related disorders is based on a combination of clinical, neurophysiological, and genetic findings, and new genes and distinct mutations responsible for different clinical phenotypes are continuously being added. The genes that encode peripheral myelin protein of 22 kDa, protein zero, connexin-32 and early growth response-2 are the genes known to be involved in the pathogenesis of inherited neuropathies. Overexpression or underexpression of peripheral myelin protein of 22 kDa are causative for the most frequent forms of CMT-CMT1A and hereditary neuropathy with liability to pressure palsies--but the mechanisms that lead to incorrect myelin formation and maintenance are still unknown. Point mutations in the myelin genes can determine a loss of function, but in some cases an aberrant protein can act through a dominant negative or a toxic gain of function mechanism, disrupting the regular and precise relationship between the different myelin genes. Animal and in-vitro models of inherited neuropathies have been developed and will probably give the information that is necessary to clarify the pathogenetic mechanisms of demyelination.