Clinical, electrophysiological and magnetic resonance findings in a family with hereditary neuropathy with liability to pressure palsies caused by a novel PMP22 mutation

Literature review of clinical analysis of hereditary neuropathy with liability to pressure palsies

This review summarizes the clinical and electromyography (EMG) characteristics and peripheral myelin protein 22 (PMP22) gene-related diseases of hereditary neuropathy with liability to pressure palsies (HNPP). Clinical, EMG, and laboratory data of patients diagnosed with HNPP at our institution from 2022 to 2023 were retrospectively reviewed. Relevant literature from January 2003 to June 2024 was retrieved from PubMed using the keywords "hereditary neuropathy with liability to pressure palsies" and "HNPP." Clinical manifestations, EMG characteristics, and gene detection results of HNPP were summarized. All patients exhibited transient neurological symptoms and tested positive for the PMP22 deletion. EMG revealed multiple peripheral nerve abnormalities. Sixty-eight studies meeting the inclusion and exclusion criteria were included, comprising 124 HNPP cases (including six from our study), with 67 males and 57 females. The mean age of onset and diagnosis for the 124 cases were 26.5 ± 18 years and 32.7 ± 18.9 years, respectively, with a maximum onset-to-diagnosis interval of 40 years. Typical weakness and numbness in vulnerable areas were observed in 63.7% of cases, with 62% experiencing recurrent episodes. Atypical symptoms were present in 29.8%, while 6.5% were asymptomatic. Patients exhibited pain and muscular dystrophy (17.7%), pes cavus (12.1%), and a family history of HNPP (64.5%). Among symptomatic patients, triggers were traction or compression (57.8%), temperature changes (3.4%), or unclear (38.8%). Heterozygous PMP22 deletions and other PMP22 gene mutations were found in 77.4% and 22.6% of cases, respectively.

Clinical and neurophysiological findings in patients with hereditary neuropathy with liability to pressure palsy and chromosome 17p11.2 deletion

INTRODUCTION

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder, typically presenting with recurrent episodes of mononeuropathy in nerves susceptible to compression, with similar neurophysiological characteristics. However, other clinical and neurophysiological presentations have been reported.

METHODS

We retrospectively analysed the clinical and neurophysiological characteristics of 20 patients with genetically confirmed HNPP. Sixteen patients were studied in our department between 1996 and 2016.

RESULTS

In addition to the typical characteristics of HNPP, we found atypical forms including recurrent positional sensory symptoms in 3 patients, chronic sensorimotor polyneuropathy in one, and non-progressive mononeuropathy in one. Onset was early in 2 patients: one at the age of 7 years, with common peroneal nerve injury, and another at birth, with brachial plexus involvement. By frequency, the main pathological findings in the nerve conduction study were: decreased sensory nerve conduction velocity in the sural (84%) and the median and superficial peroneal nerves (94%); decreased motor nerve conduction velocity in the ulnar nerve through the elbow (97%), and increased motor distal latency of the median and deep peroneal nerves (74%).

CONCLUSION

Our results confirm the clinical variability of HNPP, with the most frequent nerve conduction study findings being the generalised decrease in sensory nerve conduction velocity, in addition to motor involvement, mainly in locations susceptible to nerve compression. The nerve conduction study can detect typical, atypical, and asymptomatic cases of HNPP.

Clinical and neurophysiological findings in patients with hereditary neuropathy with liability to pressure palsy and chromosome 17p11.2 deletion

INTRODUCTION

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder, typically presenting with recurrent episodes of mononeuropathy in nerves susceptible to compression, with similar neurophysiological characteristics. However, other clinical and neurophysiological presentations have been reported.

METHODS

We retrospectively analysed the clinical and neurophysiological characteristics of 20 patients with genetically confirmed HNPP. Sixteen patients were studied in our department between 1996 and 2016.

RESULTS

In addition to the typical characteristics of HNPP, we found atypical forms including recurrent positional sensory symptoms in 3 patients, chronic sensorimotor polyneuropathy in one, and non-progressive mononeuropathy in one. Onset was early in 2 patients: one at the age of 7 years, with common peroneal nerve injury, and another at birth, with brachial plexus involvement. By frequency, the main pathological findings in the nerve conduction study were: decreased sensory nerve conduction velocity in the sural (84%) and the median and superficial peroneal nerves (94%); decreased motor nerve conduction velocity in the ulnar nerve through the elbow (97%), and increased motor distal latency of the median and deep peroneal nerves (74%).

CONCLUSION

Our results confirm the clinical variability of HNPP, with the most frequent nerve conduction study findings being the generalised decrease in sensory nerve conduction velocity, in addition to motor involvement, mainly in locations susceptible to nerve compression. The nerve conduction study can detect typical, atypical, and asymptomatic cases of HNPP.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

A New Point Mutation in the PMP22 Gene in a Family Suffering From Atypical HNPP

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant inherited disorder commonly presenting with acute-onset, non-painful focal sensory and motor mono neuropathy. In 80% of cases, the genetic defect is a 1.5 Mb deletion on chromosome 17p11.2, including PMP22. Only few cases of partial deletion and point mutations in PMP22 are involved in HNPP. We investigated a 62-years-old man with lower limb plexopathy first considered as Garland’s syndrome. A month later, his 29 years old son also consulted for paresthesia on the peroneal nerve. Targeted sequencing of the PMP22 gene identified a c.370delT (p.Trp124Glyfs*31) in both affected patients. We report a new PMP22 point mutation associated with an atypical clinical phenotype of HNPP, a painful plexopathy of the lower limb worsenen by diabetes and a mere paresthesia, but a typical ENMG. This study illustrates the large spectrum of the disease, and emphasizes the importance of a complete ENMG and family history.

Pain and small-fiber affection in hereditary neuropathy with liability to pressure palsies (HNPP)

Background and aims Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal - dominant hereditary neuropathy caused by a deficiency in the peripheral protein PMP-22, due to deletion on chromosome 17p11,2 or in some rare cases point mutations in the PMP-22 gene. The clinical picture is characterized by recurrent mononeuropathies in nerves which frequently may be exposed to pressure, such as the median, ulnar, radial and peroneal nerves or also a more general neuropathy. Although pain is reported to be an unusual clinical symptom, there have been reports of pain in a surprisingly high proportion of these patients. Since pain may be explained by mechanisms in afferent small unmyelinated C- nerve fibers, an assessment of the function of small nerve fibers has been requested. The purpose of the present study was to investigate the presence of pain and the possible affection of afferent small nerve-fibers, A-δ and C-fibers, by quantitative sensory testing (QST)-assessment of thermal thresholds, as well as quantitative sudomotor axon reflex (QSART), a quantitative, validated assessment of efferent postganglionic sumodotor function. QST values were compared to values of age- and sex matched healthy subjects. Methods The 19 patients were investigated clinically, with an emphasis on pain characteristics, with nerve conduction studies (NCS) of major nerves in upper- and lower extremity, small fiber testing (QST, measurement of thermal thresholds) and with QSART. Results A total of 10 patients reported numbness in some extremity, suggesting entrapment of individual nerves as well as a general neuropathy, as verified by NCS in nine patients. A total of 15 patients had findings compatible with a general polyneuropathy. A total of eight patients reported pain, seven patients with pain in the feet, described as burning, aching, shooting and six with severe pathological QST values, mainly cold detection, but also four patients with elevated thresholds to warmth. Four of the patients had signs of a severe sensory neuropathy on NCS, with no sural findings. One patient had only pain in the arms, with only minor changes on NCS and with normal QST-values. Cold detection thresholds (CD) were significantly elevated (reduced sensibility) on the dorsum of the foot (mean of two feet), in patients [26.0 °C (19.7-28.0)] as compared with healthy subjects [28.6 °C (27.4-29.6) p = 0.000]. There were also significantly elevated warmth detection thresholds (WD) in feet in patients 39.5 °C (36.4-42.9) compared to healthy subjects [37.7 °C (36.1-39.4) p = 0.048]. However, there were no significant differences in QST values between patients with and without pain. Conclusions Of a total of 19 patients with verified HNPP, eight patients (42.1%) suffered from neuropathic pain, mainly in both feet. Implications Due to the high percentage of pain in HNPP, it is important not to disregard this diagnosis in a patient presenting with pain. Since there are no significant differences in QST values in patients with and without pain, routine QST studies in HNPP do not seem necessary.

Comparison of clinical and electrophysiological features of patients with hereditary neuropathy with liability to pressure palsies with or without pain

BACKGROUND

Hereditary neuropathy with liability to pressure palsies (HNPP) is a rare neuropathy with a heterogeneous clinical profile. Painless recurrent palsies are the usual presentation, but neuropathic pain could be predominant or inaugural. Browsing the medical literature, we only found two articles reffering to this important clinical feature. Whether there are differences between patients with or without pain is unclear. The main objective of this study was to compare the clinical and electrophysiological features of these patients and to evaluate the impact on their disability.

METHODS

All patients diagnosed with HNPP at the Limoges University Hospital Centre were included and separated into two groups according to the presence or absence of neuropathic pain. In each case, the clinical, genetic, electrodiagnostic, therapeutic features and the modified Rankin Scale (mRS) were evaluated.

RESULTS

Out of 23 patients, 52% presented with neuropathic pain. There was no difference between groups regarding to clinical and electrophysiological features, except for the amplitude of the ulnar sensory nerve (p < 0,003). The amplitudes of sensory nerve action potentials (SNAPs) seemed to be higher in patients with pain, but were below the lower limit of normal. Patients with pain had a higher mRS than patients without pain (p < 0,007).

CONCLUSION

This study supports previous published results and highlights a trend for higher sensory amplitudes in HNPP patients with pain. We found a prevalence of neuropathic pain of 52% in patients with HNPP, underlining the need to systematically assess pain in such patients in order to improve their management.

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.

Characterisation of pain in people with hereditary neuropathy with liability to pressure palsy

Hereditary neuropathy with liability to pressure palsy (HNPP) has historically been considered a pain-free condition, though some people with HNPP also complain of pain. This study characterised persistent pain in people with HNPP. Participants provided cross-sectional demographic data, information on the presence of neurological and persistent pain symptoms, and the degree to which these interfered with daily life. The painDETECT and Central Sensitization Inventory questionnaires were used to indicate potential neuropathic, central sensitisation and musculoskeletal (nociceptive) pain mechanisms. Additionally, participants were asked if they thought that pain was related to/part of HNPP. 32/43 (74%) subjects with HNPP had persistent pain and experience this pain in the last week. Of those with pain, 24 (75%) were likely to have neuropathic pain and 27 (84%) were likely to have central sensitisation. All 32 participants felt that their pain could be related to/part of their HNPP. Significant negative impact of the pain was common. Pain characterisation identified neuropathic pain and/or central sensitisation as common, potential underlying processes. Pain may plausibly be directly related to the underlying pathophysiology of HNPP. Further consideration of including pain as a primary symptom of HNPP is warranted.

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.

PMP22 exon 4 deletion causes ER retention of PMP22 and a gain-of-function allele in CMT1E

OBJECTIVE

To determine whether predicted fork stalling and template switching (FoSTeS) during mitosis deletes exon 4 in peripheral myelin protein 22 KD (PMP22) and causes gain-of-function mutation associated with peripheral neuropathy in a family with Charcot-Marie-Tooth disease type 1E.

METHODS

Two siblings previously reported to have genomic rearrangements predicted to involve exon 4 of PMP22 were evaluated clinically and by electrophysiology. Skin biopsies from the proband were studied by RT-PCR to determine the effects of the exon 4 rearrangements on exon 4 mRNA expression in myelinating Schwann cells. Transient transfection studies with wild-type and mutant PMP22 were performed in Cos7 and RT4 cells to determine the fate of the resultant mutant protein.

RESULTS

Both affected siblings had a sensorimotor dysmyelinating neuropathy with severely slow nerve conduction velocities (<10 m/sec). RT-PCR studies of Schwann cell RNA from one of the siblings demonstrated a complete in-frame deletion of PMP22 exon 4 (PMP22Δ4). Transfection studies demonstrated that PMP22Δ4 protein is retained within the endoplasmic reticulum and not transported to the plasma membrane.

CONCLUSIONS

Our results confirm that that FoSTeS-mediated genomic rearrangement produced a deletion of exon 4 of PMP22, resulting in expression of both PMP22 mRNA and protein lacking this sequence. In addition, we provide experimental evidence for endoplasmic reticulum retention of the mutant protein suggesting a gain-of-function mutational mechanism consistent with the observed CMT1E in this family. PMP22Δ4 is another example of a mutated myelin protein that is misfolded and contributes to the pathogenesis of the neuropathy.

[Molecular genetic diagnosis and clinical features of hereditary neuropathy with liability to pressure palsies in Belarusian patients]

OBJECTIVE

To analyze the molecular defect, a phenotype of hereditary neuropathy with liability to pressure palsies (HNPP, OMIM 162500), in patients with PMP22 gene mutation caused by 1.5 Mb deletion at 17p11.2. and present the principles of diagnosis and genetic counselling.

MATERIAL AND METHODS

Patients were selected on the basis of the results of the clinical/genealogical analysis, neurological examination and ENMG study. Genomic DNA was isolated from peripheral blood leukocytes.

RESULTS AND CONCLUSION

DNA diagnosis was performed in 5 families (the PMP22 deletion was found in 9 patients). The authors described clinical and electrophysiological characteristics and presented a diagnostic protocol. Identification of the mutation makes it possible to confirm the clinical diagnosis, assess genetic risks for the outcome and perform a prenatal DNA diagnosis in HNPP families.

Clinical and neurophysiological features of the hereditary neuropathy with liability to pressure palsy due to the 17p11.2 deletion

ABSTRACT The hereditary neuropathy with liability to pressure palsies (HNPP) is an autossomal dominant disorder manifesting recurrent mononeuropathies. Objective Evaluate its clinical and nerve conduction studies (NCS) characteristics, searching for diagnostic particularities. Method We reviewed the neurological manifestations of 39 and the NCS of 33 patients. Results Family history was absent in 16/39 (41%). The onset complaints were weakness in 24, pain in 6, sensory deficit in 5 and paresthesias in 4. Pain was seen in 3 other patients. The following neuropathy patterns were found: multiple mononeuropathy (26), mononeuropathy (7), chronic sensorimotor polyneuropathy (4), chronic sensory polyneuropathy (1) and unilateral brachial plexopathy (1). NCS showed a sensorimotor neuropathy with focal conduction slowing in 31, two had mononeuropathy and another brachial plexopathy. Conclusion HNPP presentation is variable and may include pain. The most frequent pattern is of an asymmetrical sensory and motor neuropathy with focal slowing at specific topographies on NCS.

Effect of low frequency transcutaneous magnetic stimulation on sensory and motor transmission

Peripheral nerve injury diminishes fast conducting large myelinated afferent fibers transmission but enhances smaller pain transmitting fibers firing. This aberrant afferent neuronal behavior contributes to development of chronic post-traumatic peripheral neuropathic pain (PTP-NP). Non-invasive dynamic magnetic flux stimulation has been implicated in treating PTP-NP, a condition currently not adequately addressed by other therapies including transcutaneous electrical nerve stimulation (TENS). The current study assessed the effect of low frequency transcutaneous magnetic stimulation (LFTMS) on peripheral sensory thresholds, nerve conduction properties, and TENS induced fast afferent slowing effect as measured by motor and sensory conduction studies in the ulnar nerve. Results indicated sham LFTMS with TENS (Sham + TENS) significantly (P = 0.02 and 0.007, respectively) reduces sensory conduction velocity (CV) and increases sensory onset latency (OL), and motor peak latency (PL) whereas, real LFTMS with TENS (Real + TENS) reverses effects of TENS on sensory CV and OL, and significantly (P = 0.036) increases the sensory PL. LFTMS alone significantly (P < 0.05) elevates sensory PL and onset-to-peak latency. LFTMS appears to reverse TENS slowing effect on fast conducting fibers and casts a selective peripheral modulatory effect on slow conducting pain afferent fibers.

Spectrum of suprascapular nerve lesions: normal and abnormal neuromuscular imaging appearances on 3-T MR neurography

OBJECTIVE. In this article, we will review the normal anatomy and imaging features of various neuromuscular abnormalities related to suprascapular neuropathy. CONCLUSION. Suprascapular neuropathy can be difficult to distinguish from rotator cuff pathology, plexopathy, and radiculopathy. Electrodiagnostic studies are considered the reference standard for diagnosis; however, high-resolution 3-T MR neurography (MRN) can play an important role. MRN enables direct visualization of the nerve and simultaneous assessment of the cervical spine, brachial plexus, and rotator cuff.