Recurrent familial neuropathy due to liability to pressure palsies

Two families with hereditary neuropathy with liability to pressure palsies (HNPP) were evaluated clinically, electrophysiologically and pathologically (2 index cases). Familial patterns suggest autosomal dominant inheritance. The clinical presentation is characteristic, with recurrent painless transitory mononeuropathy, without evident triggering factors, or caused by trivial trauma or pressure. In affected members neurophysiological studies showed diffuse slowing in nerve conduction, more evident at common sites of entrapment. Somatosensory evoked potentials (SEPs) showed bilateral peripheral abnormalities with proximal nerve incolvement more pronounced in older patients. 40 to 75% of teased fibers displayed sausage-shaped swellings. Ultrastructurally some sausages showed redundant myelin loops and excessive number of myelin lamellae that seem to cause axonal constriction.

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Sommario Due famiglie portatrici di neuropatia ereditaria con predisposizione alla paralisi da compressione (HNPP) sono state valutate dal punto di vista clinico, neurofisiologico e morfologico (2 casi indice). L'eredità in entrambi i casi è autosomica dominante. La presentazione clinica è caratterizzata da mononeuropatie non dolorose, transitorie e ricorrenti, in distretti diversi, precipitate da compressioni o traumi lievi, o senza causa apparente. Nei soggetti più anziani in particolare è presente un quadro clinico di lieve polineuropatia sensitivomotoria. Nei membri affetti le velocità di conduzione del nervo sono rallentate in modo diffuso, con blocchi focali nei comuni siti di intrappolamento. L'esame dei potenziali evocati somatosensitivi ha dimostrato in tutti i soggetti affetti anomalie di tipo periferico, coinvolgenti anche i tratti prossimali in modo più pronunciato nei pazienti anziani. All'esame della singola fibra nervosa isolata, rigonfiamenti della guaina mielinica con l'aspetto caratteristico dei “sausages” sono riscontrabili nel 40 e nel 75% delle fibre esaminate rispettivamente nei 2 casi indice. All'esame ultrastrutturale i “sausages” appaiono formati da un eccessivo numero di lamelle mieliniche, alcune formanti loops, che sembrano costringere l'assone.

     

Hereditary neuropathy with liability to pressure palsies: the same molecular defect can result in diverse clinical presentation

Hereditary neuropathy with liability to pressure palsies (HNPP) is a peripheral nerve disorder characterized by autosomal dominant inheritance, recurrent pressure palsies, reduced motor and sensory conduction velocities and sausage-like swellings (tomacula) of myelin sheaths in nerve biopsy. Two young adult patients are reported as index cases of two families in which HNPP was diagnosed. The first patient presented with recurrent pressure palsies, whereas the second suffered from fasciculations and myokymias in his right hand, with difficulty in writing, and upper and lower limb paraesthesias of 3 years' duration. Electrodiagnostic studies revealed slowing of conduction primarily in common sites of compression in both patients. Sural nerve biopsy revealed the characteristic tomaculous swellings in both patients. DNA analysis showed that both patients have a deletion in chromosome 17p11.2 which is found in the majority of HNPP cases. In light of the common molecular defect, the different clinical symptomatology of the two patients is discussed.     

Hereditary neuropathy with liability to pressure palsies and amyotrophic lateral sclerosis

A 56-year-old male with recurrent painless focal neuropathies and a family history of peripheral neuropathy of unknown etiology presented with progressively worsening of impaired sensations and weakness in his lower extremities. His initial electrodiagnostic evaluation was suggestive of severe sensory and motor peripheral polyneuropathy. The genetic testing was performed for familial causes of peripheral neuropathy as there was a family history of peripheral neuropathy of unknown etiology. The patient was found to have 1.5-Mb deletion in the PMP22 gene which was confirmatory of hereditary neuropathy with liability to pressure palsies (HNPP). He developed progressive upper and lower extremity weakness, bulbar dysfunction and widespread fasciculations during the course of his illness. He was subsequently diagnosed with amyotrophic lateral sclerosis (ALS). This is the second reported case of HNPP associated with ALS. We discuss significant clinical and electrodiagnostic findings of this interesting case.     

遗传性压迫易感性神经病（附一家系2例报告）

本文报告遗传性压迫易感性神经病一家系母女 2例患者的临床及电生理资料。2例均在 2 5岁起病 ,呈常染色体显性遗传。临床表现为反复肢体麻木、乏力 ,多于用力、提重物或轻度外伤后出现 ,数日至半个月左右自行好转。电生理检查有弥漫性神经传导速度减慢。周围神经病理特点为节段性脱髓鞘及腊肠样结构形成。已发现大部分本病家系均有 17p11.2上一 1.5Mb片段 (含有 PMP- 2 2基因 )的大缺失 ,少数家系为 PMP- 2 2基因碱基缺失。及时诊断 ,避免重体力劳动和外伤 ,可明显改善患者的预后     

Hereditary neuropathy with liability to pressure palsies (HNPP) in a toddler presenting with toe-walking, pain and stiffness

The typical clinical presentation of hereditary neuropathy with liability to pressure palsies is an adult-onset recurrent, painless monoparesis. Electrophysiological abnormalities - decreased nerve conduction velocities and delayed distal latencies - can be detected even in asymptomatic patients. We describe a toddler, who presented with asymmetric toe walking, painful cramps and stiffness in the legs. He had calf hypertrophy, brisk tendon reflexes and bilateral Babinski signs and the electrophysiological examination was normal. The unlikely diagnosis of hereditary neuropathy with liability to pressure palsies was reached 5 years later, when the boy started to complain of episodic numbness and weakness in the upper extremities. His father, paternal aunt and grandmother had similar symptoms, but they had never been investigated. The typical 1.5 Mb deletion on chromosome 17p11.2–12 was found in our patient and his affected relatives.     

Hereditary neuropathy with liability to pressure palsies: Association with central nervous system demyelination

Hereditary neuropathy with liability to pressure palsies (HNPP) is usually caused by a 1.5-Mb deletion in chromosome 17p11.2, the inverse mutation to the duplication seen in the majority of Charcot-Marie-Tooth type 1A (CMT 1A) patients. Although most patients with HNPP present with pressure palsies secondary to mild trauma, the clinical heterogeneity of the neuropathy has become more apparent following the discovery of the mutation. There are reports of central conduction abnormalities in CMT 1, however, there have been no previous reports of central nervous system (CNS) demyelination in HNPP. We report a case of HNPP with the typical DNA mutation whose clinical features and MRI of the brain suggested concurrent CNS demyelination. Further studies of possible CNS involvement in HNPP are warranted. © 1996 John Wiley & Sons, Inc.     

遗传性压迫易感性神经病(4例临床与病理)

目的从临床、电生理及病理方面对遗传性压迫易感性神经病（ＨＮＰＰ）进行探讨,以提高对本病的认识。方法４例经临床及腓肠神经活检确诊,肌电图检测临床受累或未受累的肢体的感觉或运动传导速度;腓肠神经活检标本分别做ＨＥ、Ｍａｓｏｎ染色和Ｆｌｅｍｍｉｎｇ染色光镜观察。结果肌电图为广泛神经传导异常,甚至出现在临床未受累的神经支配区;腓神经活检显示部分神经纤维明显增粗,轴索正常。结论ＨＮＰＰ与遗传关系密切,但也有散发,电生理检查是重要的筛选手段,神经活检见到髓鞘增粗或典型的腊肠样结构是重要的确诊手段     

Hereditary neuropathy with liability to pressure palsies associated with central nervous system myelin lesions

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder most commonly caused by a 1.5-Mb deletion in chromosome 17p11.2 which contains the peripheral myelin protein-22 (PMP22) gene. Mutations resulting in functional loss of one PMP22 gene copy are less frequent. We present a 51-year-old patient with a l.5-Mb deletion in chromosome 17p11.2 who exhibited signs of peripheral as well as central nervous system lesions. He gave a history of recurrent episodes of limb numbness and weakness with spontaneous but incomplete recovery since age 20. His father and two brothers had similar symptoms. Neurological examination revealed signs of multiple mononeuropathy associated with frontal lobe, corticospinal tract and cerebellar dysfunction, as well as signs of initial cognitive impairment. Electrophysiological investigations showed a demyelinating peripheral nerve disease with multiple conduction blocks and conduction disturbances in both optic nerves. Magnetic resonance imaging of the brain revealed multiple subcortical and periventricular foci of myelin lesions. The association of central and peripheral nervous system lesions in this patient indicates a possible role of PMP22 not only in peripheral but also in central nervous system myelin structure.     

Hereditary neuropathy with liability to pressure palsies: description of seven patients without known family history

Objectives –  Hereditary neuropathy with liability to pressure palsies (HNPP) is an inherited disorder resulting in a polyneuropathy with particular involvement at sites of entrapment, and is often underdiagnosed or misdiagnosed. We report findings on seven patients referred for evaluation of focal mononeuropathies or polyneuropathies of undetermined etiology, in whom we established a diagnosis of HNPP.
Materials and methods –  We retrospectively reviewed clinical, electrophysiological and laboratory data for patients diagnosed with HNPP over a 4-year period at our institution.
Results –  All patients had transient or recurrent neurological symptoms, some with residual deficits. No patients had a family history of any neuropathy. Electrodiagnostic studies revealed abnormal conduction findings at symptomatic and asymptomatic sites. Testing for the Peripheral Myelin Protein ( PMP22 ) deletion was positive in all patients.
Conclusions –  A high index of clinical suspicion and thorough electrodiagnostic evaluation can lead to correct diagnosis of HNPP, despite the absence of a positive family history.     

Epidemiology of hereditary neuropathy with liability to pressure palsies (HNPP) in south western Finland

An epidemiological study of hereditary neuropathy with liability to pressure palsies (HNPP) was carried out in south western Finland, with a population of 435 000. The diagnosis was established in 69 patients from 23 unrelated families through family and medical history, clinical neurological and neurophysiological examinations and with documentation of the deletion at gene locus 17p11.2 in at least one member of each family. This gave a prevalence of at least 16/100 000, which is remarkably high. However, due to the insidious nature of HNPP, most probably it is still an underestimation. This is the first population-based prevalence figure reported for HNPP. The prevalence is somewhat lower than that obtained for CMT in the same population, which agrees with the proposal that HNPP and CMT 1A are reciprocal products of the same unequal crossing-over. The clinical pictures of our patients were, in general, similar to those previously described in HNPP.     

Sonographic features in hereditary neuropathy with liability to pressure palsies

Introduction: Diagnostic nerve ultrasound is becoming more commonly used by both radiologists and clinicians. The features of different neuromuscular conditions must be described to broaden our understanding and ability to interpret findings. Methods: Our study examines the sonographic features of 7 subjects with hereditary neuropathy with liability to pressure palsies (HNPP) in comparison to 32 controls by measuring the nerve cross‐sectional area (CSA) of the median, ulnar and tibial nerves. Results: Significant differences (P < 0.05) in nerve size were found. The HNPP group had a larger CSA for the median nerve at the wrist and ulnar nerve at the elbow (entrapment sites), but not the forearms. The tibial nerve at the ankle was also larger in the HNPP group, suggesting possible concomitant tibial neuropathy at the ankle. Conclusion: These results will help shape imaging protocols to better detect conditions with non‐uniform nerve enlargements. Muscle Nerve 2011     

Hereditary neuropathy with liability to pressure palsies: electrophysiological and genetic study of a family with carpal tunnel syndrome as only clinical manifestation

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disease characterized by recurrent sensory or motor manifestations. The molecular basis of HNPP is a deletion on chromosome 17p11.2. We studied a family (father, 61 years; mother, 55 years; 6 children of mean age 25.3 years) showing symptoms of carpal tunnel syndrome in 4 members (the parents and 2 sons). No one of them reported episodes of nerve palsy. In all the patients, except the mother and the younger son, electrophysiologic evaluation showed a sensorimotor polyneuropathy with delayed sensorimotor latencies. Genetic analysis was carried out in the parents and the eldest son. The 17p11.2 deletion was detected in the father and son, indicating paternal transmission of the disease. Clinical manifestations of HNPP may be atypical. Sometimes there is no history of acute nerve palsy, as in this family. For this reason, the frequence of HNPP might be underestimated. Electrophysiological examination is of great importance for the diagnosis of HNPP. Genetic analysis is a rapid and reliable diagnostic tool that can be combined with simplified electrophysiological examination, avoiding the need for nerve biopsy. In conclusion, the diagnosis of HNPP should be invoked in early onset entrapment neuropathies. Received: 8 November 2002 / Accepted in revised form: 28 March 2003 Correspondence to: R. Del Colle     

Recurrent familial neuropathy with liability to pressure palsies

Summary Electrophysiological, histological and ultrastructural studies on two patients (one family) with familial neuropathy and a liability to pressure palsies are reported. There was slowing of nerve conduction velocities and increase of distal latencies of clinically affected and clinically non-affected nerves. These alterations were confirmed by biopsy of the sural nerve which had the characterized signs of the disease. Pathogenetically there seems to be an endogeneous metabolic defect of the Schwann cell to synthetize a normal myelin sheath, which is responsible for the particular susceptibility to mechanical damage.

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Zusammenfassung Es werden zwei Fälle einer familären rezidivierenden polytopen Neuropathie dargestellt. Es wird das klinische und elektrophysiologische Bild und die Charakteristika der lichtmikroskopischen und elektronenmikroskopischen Nervenveränderungen beschrieben. Elektrophysiologisch konnte nachgewiesen werden, daß die Verlangsamung der Nervenleitgeschwindigkeit und der distalen Latenzzeit auch klinisch nicht lädierte Nerven betrifft. Die typischen histologischen Merkmale dieser Krankheit waren in der Biopsie des N. suralis erkennbar. In pathogenetischer Hinsicht muß man wohl annehmen, daß es sich um eine endogene metabolische Entgleisung der Schwannschen Zelle handelt, die nicht mehr fähig ist, eine normale Myelin zu produzieren, die dann den mechanischen Noxen gegenüber besonders empfindlich wird.

     

Familial neuropathy with liability to pressure palsies. Report of a case

A case of hereditary neuropathy with liability to pressure palsies is described. The main histological findings in sural nerve were focal thickenings of myelin-?sausages?, ?tomaculae?- and wide variability of internodal length. Numerous fibers with signs of remyelination were present, while there was little evidence of active demyelination. There were moderate axonal changes. Electrophysiological study revealed slowed conduction velocity in peripheral nerves. The possibility of a congenital myelin defect in this disease is discussed. This work was supported by Polish Academy of Sciences grant N^o 10.4.2.02./5.1.     

Visual and somatosensory evoked potentials and F-wave latency measurements in hereditary neuropathy with liability to pressure palsies

Summary Pattern shift visual evoked potentials (VEPs), cervical and cortical somatosensory evoked responses (SEPs) and motor conduction velocities studied by F-wave latency measurements were investigated in two family members with hereditary neuropathy with liability to pressure palsies (HN-PP). In both cases the VEPs and SEP conduction times N 13–N 20 were normal. A bilateral pathological increase of latencies of early SEP components, N 9–N 13 transit times and F-wave latencies revealed a lesion in the proximal parts of the median nerves close to the spinal cord in the older patient. These abnormalities emphasize the close relationship of HN-PP with hereditary polyradiculopathy (Mayer 1975).

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Zusammenfassung Bei zwei Familienmitgliedern mit einer familiären Neuropathie mit Neigung zu Druckparesen wurden visuelle schachbrettmusterevozierte Potentiale (VEPs), cervicale und corticale somatosensorisch evozierte Potentiale (SEPs) sowie die Leitgeschwindigkeiten mit Hilfe der F-Wellen-Latenzen untersucht. In beiden Fällen waren die VEPs und SEP-Leitungszeiten N 13–N 20 normal. Eine beidseitige pathologische Latenzverlängerung früher SEP-Komponenten und verzögerte Leitungszeiten von N 9–N 13 und der F-Welle deuteten auf eine proximale rückenmarksnahe Läsion der Nn. mediani beim älteren Patienten hin. Diese Befunde machen die enge Beziehung des Krankheitsbildes zur hereditären Polyradikulopathie (Mayer 1975) deutlich.

     

Hereditary neuropathy with liability to pressure palsies

Journal of Neurology - Hereditary neuropathy with liability to pressure palsies (HNPP) is characterized by recurrent sensory and motor neuropathy in individual nerves starting in adolescence or...     

Loss-of-function phenotype of hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (HNPP) provides a human model to investigate the role of PMP22 in myelinated peripheral nerve, since the disease is caused by a deletion of one of the two PMP22 alleles. To systematically characterize the phenotype of HNPP, we prospectively evaluated the clinical features and electrophysiological findings in 17 genetically confirmed patients, 7 men and 10 women, ranging in age from 9 to 66 years (mean, 41 +/- 13). Fifteen symptomatic patients presented with episodes of transient focal weakness or sensory loss that were usually related to particular activities causing nerve compression, including stretching or minor repetitive focal trauma. No patient sought medical attention for symptoms of a symmetric polyneuropathy. Neurological examinations were either normal or mildly abnormal. Neither focal slowing of nerve conduction studies, nor reduction in compound muscle action potential (CMAP) or sensory nerve action potential (SNAP) amplitudes consistently predicted the site of symptoms. We conclude that the majority of patients with HNPP present with transient, recurrent, focal symptoms of weakness or sensory loss in the distribution of individual nerves or plexus, and that a diffuse symmetric sensorimotor polyneuropathy is an unusual presentation of HNPP. These studies suggest that the function of PMP22, at least in part, is to stabilize myelin so that it will be protected from injuries resulting from repetitive, minor trauma.