Mutations in DNMT1 cause hereditary sensory neuropathy with dementia and hearing loss

DNA methyltransferase 1 (DNMT1) is crucial for maintenance of methylation, gene regulation and chromatin stability. DNA mismatch repair, cell cycle regulation in post-mitotic neurons and neurogenesis are influenced by DNA methylation. Here we show that mutations in DNMT1 cause both central and peripheral neurodegeneration in one form of hereditary sensory and autonomic neuropathy with dementia and hearing loss. Exome sequencing led to the identification of DNMT1 mutation c.1484A>G (p.Tyr495Cys) in two American kindreds and one Japanese kindred and a triple nucleotide change, c.1470-1472TCC>ATA (p.Asp490Glu-Pro491Tyr), in one European kindred. All mutations are within the targeting-sequence domain of DNMT1. These mutations cause premature degradation of mutant proteins, reduced methyltransferase activity and impaired heterochromatin binding during the G2 cell cycle phase leading to global hypomethylation and site-specific hypermethylation. Our study shows that DNMT1 mutations cause the aberrant methylation implicated in complex pathogenesis. The discovered DNMT1 mutations provide a new framework for the study of neurodegenerative diseases.

Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an inflammatory neuropathy, classically characterised by a slowly progressive onset and symmetrical, sensorimotor involvement. However, there are many phenotypic variants, suggesting that CIDP may not be a discrete disease entity but rather a spectrum of related conditions. While the abiding theory of CIDP pathogenesis is that cell-mediated and humoral mechanisms act together in an aberrant immune response to cause damage to peripheral nerves, the relative contributions of T cell and autoantibody responses remain largely undefined. In animal models of spontaneous inflammatory neuropathy, T cell responses to defined myelin antigens are responsible. In other human inflammatory neuropathies, there is evidence of antibody responses to Schwann cell, compact myelin or nodal antigens. In this review, the roles of the cellular and humoral immune systems in the pathogenesis of CIDP will be discussed. In time, it is anticipated that delineation of clinical phenotypes and the underlying disease mechanisms might help guide diagnostic and individualised treatment strategies for CIDP.

Incidence and prevalence of CIDP and the association of diabetes mellitus

BACKGROUND

The reported prevalence of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) varies greatly, from 1.9 to 7.7 per 100,000. CIDP is reported to occur more commonly in patients with diabetes mellitus (DM) but has not been rigorously tested.

OBJECTIVES

To determine the incidence (1982-2001) and prevalence (on January 1, 2000) of CIDP in Olmsted County, Minnesota, and whether DM is more frequent in CIDP.

METHODS

CIDP was diagnosed by clinical criteria followed by review of electrophysiology. Cases were coded as definite, probable, or possible. DM was ascertained by clinical diagnosis or current American Diabetes Association glycemia criteria.

RESULTS

One thousand five hundred eighty-one medical records were reviewed, and 23 patients (10 women and 13 men) were identified as having CIDP (19 definite and 4 probable). The median age was 58 years (range 4-83 years), with a median disease duration at diagnosis of 10 months (range 2-64 months). The incidence of CIDP was 1.6/100,000/year. The prevalence was 8.9/100,000 persons on January 1, 2000. Only 1 of the 23 CIDP patients (4%) also had DM, whereas 14 of 115 age- and sex-matched controls (12%) had DM.

CONCLUSIONS

1) The incidence (1.6/100,000/year) and prevalence (8.9/100,000) of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are similar to or higher than previous estimates. 2) The incidence of CIDP is similar to that of acute inflammatory demyelinating polyradiculoneuropathy within the same population. 3) Diabetes mellitus (DM) is unlikely to be a major risk covariate for CIDP, but we cannot exclude a small effect. 4) The perceived association of DM with CIDP may be due to misclassification of other forms of diabetic neuropathies and excessive emphasis on electrophysiologic criteria.

Diabetic and nondiabetic lumbosacral radiculoplexus neuropathies: new insights into pathophysiology and treatment

Diabetic lumbosacral radiculoplexus neuropathy (DLRPN) (also called diabetic amyotrophy) is a well-recognized subacute, painful, asymmetric lower-limb neuropathy that is associated with weight loss and type II diabetes mellitus. Nondiabetic lumbosacral radiculoplexus neuropathy (LRPN) has received less attention. Comparison of large cohorts with DLRPN and LRPN demonstrated that age at onset, course, type and distribution of symptoms and impairments, laboratory findings, and outcomes are similar. Both conditions are lumbosacral radiculoplexus neuropathies that are associated with weight loss and begin focally with pain but that evolve into widespread, bilateral paralytic disorders. Although both are monophasic illnesses, patients have prolonged morbidity from pain and weakness, and many patients become wheelchair-dependent. Although motor-predominant, there is unequivocal evidence that autonomic and sensory nerves are also involved. Cutaneous nerves from patients with DLRPN and LRPN show pathological evidence of ischemic injury (multifocal fiber loss, perineurial thickening and degeneration, neovascularization, microfasciculation, and swollen axons with accumulated organelles) and microvasculitis (mural and perivascular inflammation, separation and fragmentation of mural smooth muscle layers of microvessels and hemosiderin-laden macrophages). Controlled trials with immune-modulating therapies in DLRPN are in progress, and preliminary data suggest that such therapy may be beneficial in LRPN. It is likely that DLRPN and LRPN are immune-mediated neuropathies that should be separated from chronic inflammatory demyelinating polyneuropathy and from systemic necrotizing vasculitis.

A controlled study of peripheral neuropathy after bariatric surgery

BACKGROUND

Although peripheral neuropathy (PN) occurs after bariatric surgery (BS), a causal association has not been established.

OBJECTIVES

To ascertain whether PN occurs more frequently following BS vs another abdominal surgery, to characterize the clinical patterns of PN, to identify risk factors for PN, and to assess if nerve biopsy provides pathophysiologic insight.

METHODS

Retrospective review identified patients with PN after BS. The frequency of PN was compared with that of an age- and gender-matched, retrospectively evaluated cohort of obese patients undergoing cholecystectomy.

RESULTS

Of 435 patients who had BS, 71 (16%) developed PN. Patients developed PN more often after BS than after cholecystectomy (4/126; 3%) (p < 0.001). The clinical patterns of PN were polyneuropathy (n = 27), mononeuropathy (n = 39), and radiculoplexus neuropathy (n = 5). Risk factors included rate and absolute amount of weight loss, prolonged gastrointestinal symptoms, not attending a nutritional clinic after BS, reduced serum albumin and transferrin after BS, postoperative surgical complications requiring hospitalization, and having jejunoileal bypass. Most risk factors were associated with the polyneuropathy group. Sural nerve biopsies showed prominent axonal degeneration and perivascular inflammation.

CONCLUSIONS

Peripheral neuropathy (PN) occurs more frequently after bariatric surgery (BS) than after another abdominal surgery. The three clinical patterns of PN after BS are sensory-predominant polyneuropathy, mononeuropathy, and radiculoplexus neuropathy. Malnutrition may be the most important risk factor, and patients should attend nutritional clinics. Inflammation and altered immunity may play a role in the pathogenesis, but further study is needed.

Signs and symptoms versus nerve conduction studies to diagnose diabetic sensorimotor polyneuropathy: Cl vs. NPhys trial

The purpose was to test whether physicians can validly and reproducibly diagnose diabetic sensorimotor polyneuropathy (DSPN). Twelve physicians assessed 24 patients with diabetes mellitus (DM) on consecutive days (576 examinations) with physical features and voice disguised. Results were compared to gold standard 75% group diagnosis (dx) and a nerve conduction score (Sigma5 NC nds). Masking of patients was achieved. Reproducibility measured by the kappa coefficient and compared to Sigma5 NC nd varied considerably among physicians: median and ranges: signs 0.8 (0.32-1.0); symptoms 0.79 (0.36-1.0), and diagnoses 0.47 (0.33-0.84), both low and high scores indicating poor performance. There was substantial agreement between 75% group dx and confirmed NC abnormality (abn). As compared to Sigma5 NC, individual physicians' clinical dx was excessively variable and frequently inaccurate. Study physician dx from signs and symptoms were excessively variable, often overestimating DSPN. Specific approaches to improving clinical proficiency should be tested.

Chronic immune sensory polyradiculopathy: A possibly treatable sensory ataxia

BACKGROUND

Chronic inflammatory neuropathies can present with a sensory ataxia due to involvement of dorsal root ganglia (DRG) or sensory nerves. Selective inflammatory involvement of sensory nerve roots proximal to the DRG has been postulated.

METHODS

The authors identified 15 patients with a sensory syndrome and normal nerve conduction studies. Sensory nerve root involvement was suggested by either somatosensory evoked potential (SSEP) or imaging abnormalities. CNS disease was excluded.

RESULTS

All patients had gait ataxia, large fiber sensory loss, and paresthesias, and nine had frequent falls. The disease course was chronic and progressive (median duration 5 years, range 3 months to 18 years). Sural sensory nerve action potential amplitudes were preserved and SSEP abnormalities were consistent with sensory nerve root involvement. Five patients had enlargement of lumbar nerve roots on MRI with enhancement in three. The CSF protein was elevated in 13 of 14 patients tested. Three patients had lumbar sensory rootlet biopsies that showed thickened rootlets, decreased density of large myelinated fibers, segmental demyelination, onion-bulb formation, and endoneurial inflammation. Six patients who required aids to walk were treated with immune modulating therapy and all had marked improvement with four returning to normal ambulation.

CONCLUSION

Based on the described clinical features, normal nerve conduction studies, characteristic somatosensory evoked potential (SSEP) abnormality, enlarged nerve roots, elevated CSF protein, and inflammatory hypertrophic changes of sensory nerve rootlet tissue, we suggest the term chronic immune sensory polyradiculopathy (CISP) for this syndrome. This condition preferentially affects large myelinated fibers of the posterior roots, may respond favorably to treatment, and may be a restricted form of chronic inflammatory demyelinating polyradiculoneuropathy.

Peripheral Neuropathy: A Practical Approach to Diagnosis and Symptom Management

Peripheral neuropathy is one of the most prevalent neurologic conditions encountered by physicians of all specialties. Physicians are faced with 3 distinct challenges in caring for patients with peripheral neuropathy: (1) how to efficiently and effectively screen (in less than 2 minutes) an asymptomatic patient for peripheral neuropathy when they have a disorder in which peripheral neuropathy is highly prevalent (eg, diabetes mellitus), (2) how to clinically stratify patients presenting with symptoms of neuropathy to determine who would benefit from specialty consultation and what testing is appropriate for those who do not need consultation, and (3) how to treat the symptoms of painful peripheral neuropathy. In this concise review, we address these 3 common clinical scenarios. Easily defined clinical patterns of involvement are used to identify patients in need of neurologic consultation, the yield of laboratory and other diagnostic testing is reviewed for the evaluation of length-dependent, sensorimotor peripheral neuropathies (the most common form of neuropathy), and an algorithmic approach with dosing recommendations is provided for the treatment of neuropathic pain associated with peripheral neuropathy.

History of standard scoring, notation, and summation of neuromuscular signs. A current survey and recommendation

In this article, we trace the history of scoring, notation, and summation of the neuromuscular signs of muscle weakness and decrease of tendon reflexes and sensation. We recommend a standard system to promote consistency in the effort introduced by Mitchell and Lewis to "represent systems and force by their signs." The scoring of neuromuscular signs began with Mitchell and Lewis in the 19th century who used pluses, minuses, and N (for normal) to express the activity of muscle stretch reflexes. Henry Plummer introduced an ordinal scoring approach for muscle weakness, reflex decrease and increase, and sensation loss. In 1919, he and Walter Sheldon and Henry Woltman introduced standard pre-printed examination forms with written instructions for notation and scoring. Robert Lovett, a Boston orthopedist, scored weak muscles of poliomyelitis patients from 2 (mild weakness) to 6 (paralyzed), 1 being normal. Lovett's approach was used, after reversing the order of the grades and decreasing each grade by 1, by a Committee of the Medical Research Council for evaluating return of muscle weakness after nerve injury. Despite dissimilarity to existing reflex and sensation scores and uneven width of grades, this approach was widely adopted for use in neurologic practice. We introduced the Neuropathy Impairment Score using a combination of the Mitchell, Plummer, and Lovett approaches, summing all individual scores of a standard set of neuromuscular examinations. In a non-representative survey of 19 neuromuscular physicians from different countries, we find that there is a considerable variability in the approaches used for grading. Assuming that scoring is useful, we herein suggest (a) impairments should be scored separately from hyperfunction and (b) for the scoring of impairments (muscle weakness, reflex decrease, and sensation loss), the same ordinal scoring approach should be used with 0 as normal and 1, 2, ... representing increasing impairment based on the judgment of percentage abnormality with corrections made for age, sex, physical fitness, and physical characteristics.

Diabetic Neuropathies

Diabetes mellitus is associated with a wide spectrum of neuropathy syndromes, ranging from a mild asymptomatic distal sensory neuropathy to a severe disabling radiculoplexus neuropathy. As the pathophysiology of these separate conditions is better understood, classification of the various phenotypes becomes important because of treatment implications. Here we provide a short summary of the history of the classification of diabetic neuropathies and try to describe the most common forms classified according to their presumed pathophysiology. We have tried to include epidemiological data where available, as well as histopathology of nerve in several diabetic neuropathies.

Uniform demyelination and more severe axonal loss distinguish POEMS syndrome from CIDP

OBJECTIVE

POEMS syndrome (the acronym reflects the common features: Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal protein and Skin changes) is a paraneoplastic disorder with a 'demyelinating' peripheral neuropathy that is often mistaken for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The nerve conduction study (NCS) and electromyography (EMG) attributes that might differentiate POEMS from CIDP and lead to earlier therapeutic intervention were explored.

METHODS

NCS/EMG of POEMS patients identified through retrospective review from 1960 to 2007 were compared with matched CIDP controls.

RESULTS

138 POEMS patients and 69 matched CIDP controls were compared. POEMS patients demonstrated length dependent reduction in compound muscle action potentials, low conduction velocities, prolonged distal latencies and prolonged F wave latencies. Compared with CIDP controls, POEMS patients demonstrated: (1) greater reduction of motor amplitudes, (2) greater slowing of motor and sensory conduction velocities, (3) less prolonged motor distal latencies, (4) less frequent temporal dispersion and conduction block, (5) no sural sparing, (6) greater number of fibrillation potentials in a length dependent pattern and (7) higher terminal latency indices (TLI). TLI ≥0.38 in the median nerve demonstrated a sensitivity of 70% and specificity of 77% in discriminating POEMS from CIDP.

CONCLUSIONS

NCS/EMG of POEMS syndrome suggests both axonal loss and demyelination. Compared with CIDP, there is greater axonal loss (reduction of motor amplitudes and increased fibrillation potentials), greater slowing of the intermediate nerve segments, less common temporal dispersion and conduction block, and absent sural sparing. These findings imply that the pathology of POEMS syndrome is diffusely distributed (uniform demyelination) along the nerve where the pathology of CIDP is probably predominantly proximal and distal. Median motor TLI may be useful in clinically distinguishing these disorders.

Longitudinal study of intraneural perineurioma--a benign, focal hypertrophic neuropathy of youth

The natural history of intraneural perineurioma has been inadequately studied. The aim of this study was to characterize the clinical presentation, electrophysiologic and imaging features and outcome of intraneural perineurioma. We ask if intraneural perineurioma is a pure motor syndrome that remains confined to one nerve and should be treated by surgical resection. We examined the nerve biopsies of cases labelled perineurioma and selected those with diagnostic features. Thirty-two patients were identified; 16 children and 16 adults; 16 males and 16 females. Median age of onset of neurological symptoms was 14 years (range 0.5-55 years) and median age at evaluation was 17 years (range 2-56 years). All patients had motor deficits; however, mild sensory symptoms or signs were experienced by 27 patients; 'prickling' or 'asleep numbness' in 20, mild pain in 13 and sensory loss in 23. The sciatic nerve or its branches was most commonly affected in 15, followed by brachial plexus, radial nerve and ulnar nerve (four each). Magnetic resonance imaging demonstrated nerve enlargement (29/32), T1 isointensity (27/32), T2 hyperintensity (25/32) and contrast enhancement (20/20). Diagnoses were made based on targeted biopsy of the focal nerve enlargement identified by imaging. Neurological impairment was of a moderate severity (median Neuropathy Impairment Score was 12 points, range 2-49 points). All patients had focal involvement with 27 involving one nerve and five involving a plexus (one bilateral). Long-term follow-up was possible by telephone interview for 23 patients (median 36 months, range 2-177 months). Twelve patients also had follow-up neurologic evaluation (median 45 months, range 10-247 months). The median Neuropathy Impairment Score had changed from 12.6 to 15.4 points (P = 0.19). In all cases, the distribution of neurologic findings remained unchanged. Median Dyck Disability Score was 3 (range 2-5) indicating a mild impairment without interfering with activities of daily living. Ten patients judged their symptoms unchanged, nine slightly worse and four slightly better. We conclude intraneural perineurioma is a benign hypertrophic (non onion bulb) peripheral nerve tumour that presents insidiously in young people and is motor predominant with mild sensory involvement. It is most often a mononeuropathy, but a plexopathy can occur. Diagnosis of this condition requires clinical suspicion, imaging, targeted fascicular biopsy of the lesion and expertise of nerve pathologists. As these tumours are static or slowly progressive, remain confined to their original distribution and have low morbidity, they probably should not be resected routinely. Because intensive evaluation is needed for diagnosis, intraneural perineurioma is probably under-recognized.

Multifocal motor neuropathy: pathologic alterations at the site of conduction block

The pathologic changes of nerves in multifocal motor neuropathy (MMN), a rare neuropathy with selective focal conduction block of motor fibers in mixed nerves, remain essentially unstudied. Fascicular nerve biopsy of 8 forearm or arm nerves in 7 patients with typical MMN was undertaken for diagnostic reasons at the site of the conduction block. Abnormalities were seen in 7 of 8 nerves, including a varying degree of multifocal fiber degeneration and loss, an altered fiber size distribution with fewer large fibers, an increased frequency of remyelinated fiber profiles, and frequent and prominent regenerating fiber clusters. Small epineurial perivascular inflammatory infiltrates were observed in 2 nerves. We did not observe overt segmental demyelination or onion bulb formation. We hypothesize that an antibody-mediated attack directed against components of axolemma at nodes of Ranvier could cause conduction block, transitory paranodal demyelination and remyelination, and axonal degeneration and regeneration. Alternatively, the antibody attack could be directed at components of paranodal myelin. We favor the first hypothesis because in nerves studied by us, axonal pathological alteration predominated over myelin pathology. Irrespective of which mechanism is involved, we conclude that the unequivocal multifocal fiber degeneration and loss and regenerative clusters at sites of conduction block explains the observed clinical muscle weakness and atrophy and alterations of motor unit potentials. The occurrence of conduction block and multifocal fiber degeneration and regeneration at the same sites suggests that the processes of conduction block and fiber degeneration and regeneration are linked. Finding discrete multifocal fiber degeneration may also provide an explanation for why the functional abnormalities remain unchanged over long periods of time at discrete proximal to distal levels of nerve and may emphasize a need for early intervention (assuming that efficacious treatment is available).

Mass spectrometric-based proteomic analysis of amyloid neuropathy type in nerve tissue

OBJECTIVE

To determine the specific type of amyloid from nerve biopsies using laser microdissection (LMD) and mass spectrometric (MS)-based proteomic analysis.

DESIGN, SETTING, AND PATIENTS

Twenty-one nerve biopsy specimens (17 sural, 3 sciatic, and 1 root amyloidoma) infiltrated by amyloid were studied. Immunohistochemical subtyping was unable to determine the specific amyloid type for these 21 cases, but the clinical diagnosis was made based on additional testing. Clinical diagnosis was made through evaluation of serum monoclonal proteins, biopsy of bone marrow for acquired monoclonal immunoglobulin light chain amyloidosis, and kindred evaluations with DNA sequencing of transthyretin (TTR) and gelsolin (GSN) genes. Our study included 8 cases of acquired monoclonal immunoglobulin light chain amyloidosis, 11 cases of transthyretin amyloidosis (3 with the Val30Met mutation, 2 with the Val32Ala mutation, 2 with the Thr60Ala mutation, 1 with the Ala109Ser mutation, 1 with the Phe64Leu mutation, 1 with the Ala97Ser mutation, and 1 not sequenced), and 2 cases of gelsolin amyloidosis (1 with the Asp187Asn mutation and 1 not sequenced). One patient with transthyretin amyloidosis and 1 patient with gelsolin amyloidosis with no specific mutation identified were diagnosed based on genetic confirmation in their first-degree relative. Congophilic proteins in the tissues of these 21 cases underwent LMD, were digested into tryptic peptides, and were analyzed using liquid chromatography electrospray tandem MS. Identified proteins were reviewed using bioinformatics tools with interpreters blinded to clinical information.

MAIN OUTCOME MEASURE

Specific amyloid type was ascertained by LMD tandem MS and compared with clinical diagnosis.

RESULTS

Specific types of amyloid were accurately detected by LMD/MS in all cases (8 cases of acquired monoclonal immunoglobulin light chain amyloidosis, 2 cases of gelsolin amyloidosis, and 11 cases of transthyretin amyloidosis). Incidental serum monoclonal proteins did not interfere with detection of transthyretin amyloidosis in 2 patients. Additionally, specific TTR mutations were identified in 10 cases by LMD/MS. Serum amyloid P-component and apolipoprotein E proteins were commonly found among all cases.

CONCLUSIONS

Proteomic analysis of nerve tissue using LMD/MS distinguishes specific types of amyloid independent of clinical information. This new proteomic approach will enhance both diagnostic and research efforts in amyloidosis and other neurologic diseases.

The spectrum of diabetic neuropathies

Diabetes mellitus is associated with many different neuropathic syndromes, ranging from a mild sensory disturbance as can be seen in a diabetic sensorimotor polyneuropathy, to the debilitating pain and weakness of a diabetic lumbosacral radiculoplexus neuropathy. The etiology of these syndromes has been studied extensively, and may vary among metabolic, compressive, and immunological bases for the different disorders, as well as mechanisms yet to be discovered. Many of these disorders of nerve appear to be separate conditions with different underlying mechanisms, and some are caused directly by diabetes mellitus, whereas others are associated with it but not caused by hyperglycemia. This article discusses a number of the more common disorders of nerve found with diabetes mellitus. It discusses the symmetrical neuropathies, particularly generalized diabetic polyneuropathy, and then the focal or asymmetrical types of diabetes-associated neuropathy.

The natural history and long-term outcome of 57 limb sarcoidosis neuropathy cases

Fifty-seven patients with biopsy-proven sarcoidosis causing limb neuropathy were reviewed in order to delineate the characteristic symptoms, impairments, disability, course, outcome and response to corticosteroid treatment of limb sarcoid neuropathy. Typically the neuropathy had a definite date of symptomatic onset. Prominent were positive neuropathic sensory symptoms (P-NSS), especially pain, overshadowing weakness and sensory loss. P-NSS were the main cause of disability. Almost always the pattern was asymmetric and not length-dependent (unlike distal polyneuropathy). We inferred (from kind and distribution of symptoms, signs and electrophysiologic and other test results) that the pathologic process was focal or multifocal, involving most classes of nerve fibers and variable levels of proximal to distal levels of roots and peripheral nerves. Additional features aiding in diagnosis were: systemic symptoms such as fatigue, malaise, arthralgia, fever and weight loss; involvement of multiple tissues (i.e. skin, lymph nodes and eye); the patterns of neuropathy; MRI features; and ultimately tissue diagnosis. Axonal degeneration predominated, although an acquired demyelinating process was observed in 3 patients. For most cases, the disease had a chronic, monophasic course. MRI studies done in later years of affected neural structures were helpful in identifying leptomeningeal thickening, hilar adenopathy; and enlargement and T2 enhancement of nerve roots, plexuses, and limb nerves. Corticosteroid treatment appeared to ameliorate symptoms more than impairments. Several variables were associated with neuropathic improvement: CSF pleocytosis, short duration between symptom onset and treatment, and a higher grade of disability at first evaluation-a possible rationale for future earlier diagnosis and treatment.

Diabetic cervical radiculoplexus neuropathy: a distinct syndrome expanding the spectrum of diabetic radiculoplexus neuropathies

Diabetic lumbosacral radiculoplexus neuropathy is a subacute painful, asymmetrical lower limb neuropathy due to ischaemic injury and microvasculitis. The occurrence of a cervical diabetic radiculoplexus neuropathy has been postulated. Our objective was to characterize the clinical features and pathological alterations of diabetic cervical radiculoplexus neuropathy, to see if they are similar to diabetic lumbosacral radiculoplexus neuropathy and due to ischaemic injury and microvasculitis. We identified patients with diabetic cervical radiculoplexus neuropathy by review of the Mayo Clinic database from 1996 to 2008. We systematically reviewed the clinical features, laboratory studies, neurophysiological findings, neuroimaging and pathological features and compared the findings with a previously published diabetic lumbosacral radiculoplexus neuropathy cohort. Eighty-five patients (56 males, 67 with Type 2 diabetes mellitus) were identified. The median age was 62 years (range 32-83). The main presenting symptom was pain (53/85). At evaluation, weakness was the most common symptom (84/85), followed by pain (69/85) and numbness (56/85). Neuropathic deficits were moderate (median motor neuropathy impairment score 10.0 points) and improved at follow-up. Upper, middle and lower brachial plexus segments were involved equally and pan-plexopathy was not unusual (25/85). Over half of patients (44/85) had at least one additional body region affected (30 contralateral cervical, 20 lumbosacral and 16 thoracic) as is found in diabetic lumbosacral radiculoplexus neuropathy. Recurrent disease occurred in 18/85. Neurophysiology showed axonal neuropathy (80/80) with paraspinal denervation (21/65), and abnormal autonomic (23/24) and sensory testing (10/13). Cerebrospinal fluid protein was elevated (median 70 mg/dl). Magnetic resonance imaging showed brachial plexus abnormality in all (38/38). Nerve biopsies (11 upper and 11 lower limbs) showed ischaemic injury (axonal degeneration, multifocal fibre loss 15/22, focal perineurial thickening 16/22, injury neuroma 5/22) and increased inflammation (epineural perivascular inflammation 22/22, haemosiderin deposition 6/22, vessel wall inflammation 14/22 and microvasculitis 5/22). We therefore conclude that (i) diabetic cervical radiculoplexus neuropathy is a predominantly monophasic, upper limb diabetic neuropathy with pain followed by weakness and involves motor, sensory and autonomic fibres; (ii) the neuropathy begins focally and often evolves into a multifocal or bilateral condition; (iii) the pathology of diabetic cervical radiculoplexus neuropathy demonstrates ischaemic injury often from microvasculitis; and (iv) diabetic cervical radiculoplexus neuropathy shares many of the clinical and pathological features of diabetic lumbosacral radiculoplexus neuropathy, providing evidence that these conditions are best categorized together within the spectrum of diabetic radiculoplexus neuropathies.

Eplontersen for Hereditary Transthyretin Amyloidosis With Polyneuropathy

Importance

Transthyretin gene silencing is an emerging treatment strategy for hereditary transthyretin (ATTRv) amyloidosis.

Objective

To evaluate eplontersen, an investigational ligand-conjugated antisense oligonucleotide, in ATTRv polyneuropathy.

Design, Setting, and Participants

NEURO-TTRansform was an open-label, single-group, phase 3 trial conducted at 40 sites across 15 countries (December 2019-April 2023) in 168 adults with Coutinho stage 1 or 2 ATTRv polyneuropathy, Neuropathy Impairment Score 10-130, and a documented TTR variant. Patients treated with placebo from NEURO-TTR (NCT01737398; March 2013-November 2017), an inotersen trial with similar eligibility criteria and end points, served as a historical placebo ("placebo") group.

Interventions

Subcutaneous eplontersen (45 mg every 4 weeks; n = 144); a small reference group received subcutaneous inotersen (300 mg weekly; n = 24); subcutaneous placebo weekly (in NEURO-TTR; n = 60).

Main Outcomes and Measures

Primary efficacy end points at week 65/66 were changes from baseline in serum transthyretin concentration, modified Neuropathy Impairment Score +7 (mNIS+7) composite score (scoring range, -22.3 to 346.3; higher scores indicate poorer function), and Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (Norfolk QoL-DN) total score (scoring range, -4 to 136; higher scores indicate poorer quality of life). Analyses of efficacy end points were based on a mixed-effects model with repeated measures adjusted by propensity score weights.

Results

Among 144 eplontersen-treated patients (mean age, 53.0 years; 69% male), 136 (94.4%) completed week-66 follow-up; among 60 placebo patients (mean age, 59.5 years; 68% male), 52 (86.7%) completed week-66 follow-up. At week 65, adjusted mean percentage reduction in serum transthyretin was -81.7% with eplontersen and -11.2% with placebo (difference, -70.4% [95% CI, -75.2% to -65.7%]; P < .001). Adjusted mean change from baseline to week 66 was lower (better) with eplontersen vs placebo for mNIS+7 composite score (0.3 vs 25.1; difference, -24.8 [95% CI, -31.0 to -18.6; P < .001) and for Norfolk QoL-DN (-5.5 vs 14.2; difference, -19.7 [95% CI, -25.6 to -13.8]; P < .001). Adverse events by week 66 that led to study drug discontinuation occurred in 6 patients (4%) in the eplontersen group vs 2 (3%) in the placebo group. Through week 66, there were 2 deaths in the eplontersen group consistent with known disease-related sequelae (cardiac arrhythmia; intracerebral hemorrhage); there were no deaths in the placebo group.

Conclusions and Relevance

In patients with ATTRv polyneuropathy, the eplontersen treatment group demonstrated changes consistent with significantly lowered serum transthyretin concentration, less neuropathy impairment, and better quality of life compared with a historical placebo.

Trial Registration

ClinicalTrials.gov Identifier: NCT04136184; EU Clinical Trials Register: EudraCT 2019-001698-10.

An update on the classification and treatment of vasculitic neuropathy

Vasculitic neuropathy usually presents with painful mononeuropathies or an asymmetric polyneuropathy of acute or subacute onset. The disorder should be classified as being systemic or non-systemic. Systemic vasculitis should be further classified into one of the primary and secondary forms. Although specific treatment regimens vary among neurologists, basic principles can be applied. Corticosteroids and cytotoxic drugs have been the mainstay of treatment for most forms of vasculitic neuropathy. Here we discuss dosing, potential side-effects, and management recommendations of conventional treatments. New treatments showing promise include intravenous immunoglobulin and biological agents and trials of the newest treatments are being reviewed. Future trials should compare commonly used treatment regimens and better establish the efficacy of newer, potentially safer, treatments.

Modeling chronic glycemic exposure variables as correlates and predictors of microvascular complications of diabetes

OBJECTIVE

The degree to which chronic glycemic exposure (CGE) (fasting plasma glucose [FPG], HbA1c [A1C], duration of diabetes, age at onset of diabetes, or combinations of these) is associated with or predicts the severity of microvessel complications is unsettled. Specifically, we test whether combinations of components correlate and predict complications better than individual components.

RESEARCH DESIGN AND METHODS

Correlations and predictions of CGE and complications were assessed in the Rochester Diabetic Neuropathy Study, a population-based, cross-sectional, and longitudinal epidemiologic survey of 504 patients with diabetes followed for up to 20 years.

RESULTS

In multivariate analysis, A1C and duration of diabetes (and to a lesser degree age at onset of diabetes but not FPG) were the main significant CGE risk covariates for complications. A derived glycemic exposure index (GE(i)) correlated with and predicted complications better than did individual components. Composite or staged measures of polyneuropathy provided higher correlations and better predictions than did dichotomous measures of whether polyneuropathy was present or not. Generally, the mean GE(i) was significantly higher with increasing stages of severity of complications.

CONCLUSIONS

A combination of A1C, duration of diabetes, and age at onset of diabetes (a mathematical index, GE(i)) correlates significantly with complications and predicts later complications better than single components of CGE. Serial measures of A1C improved the correlations and predictions. For polyneuropathy, continuous or staged measurements performed better than dichotomous judgments. Even with intensive assessment of CGE and complications over long times, only about one-third of the variability of the severity of complications is explained, emphasizing the role of other putative risk covariates.

The gene for HMSN2C maps to 12q23-24: a region of neuromuscular disorders

BACKGROUND

Hereditary motor and sensory neuropathy type 2C (HMSN2C, Charcot-Marie-Tooth 2C [CMT2C]) is an autosomal dominant motor and sensory neuropathy involving limb, diaphragm, vocal cord, and intercostal muscles.

OBJECTIVE

To identify the chromosome localization for this disorder in one large American family of English and Scottish ethnicity.

METHODS

Variable clinical severity led the authors to combine several approaches to accurately identify affected patients. Genome-wide two-point linkage analysis, high-definition mapping, and multipoint and recombinant haplotype analyses were performed. Mutation analysis of the triplet repeat region of ataxin-2 was also carried out.

RESULTS

The initial genome-wide scan identified a region at 12q24, and fine mapping provided a maximal lod score of 4.73 (D12S1645 and D12S1583 at theta = 0.01 and 0, respectively). With multipoint analysis, a higher lod score of 5.17 was obtained and localized to the same region at 119.0 cM. Haplotype analysis narrowed the region to approximately 5.0 cM between D12S1646,D12S1330 and D12S105,D12S1339 (12q23.3-24.21). Ataxin-2, the gene responsible for spinocerebellar ataxia type 2 (SCA2), localizes to this region, but no triplet repeat expansion or point mutations within the repeat were found.

CONCLUSIONS

The gene for HMSN2C maps to 12q23-24. This region is associated with SCA2, scapuloperoneal spinal muscular atrophy, and congenital distal spinal muscular atrophy. Further studies are needed to demonstrate the specific gene alteration and its relationship with nearby genes.

Impaired glycemia and diabetic polyneuropathy: the OC IG Survey

OBJECTIVE

To test whether diabetic polyneuropathies (DPNs), retinopathy, or nephropathy is more prevalent in subjects with impaired glycemia (IG) (abnormality of impaired fasting glucose [IFG], impaired glucose tolerance [IGT], or impaired HbA(1c) [IA1C]) than in healthy subjects (non-IG).

RESEARCH DESIGN AND METHODS

Matched IG and non-IG volunteers were randomly identified from population-based diagnostic and laboratory registries, restudied, and reclassified as non-IG (n = 150), IG (n = 174), or new diabetes (n = 218).

RESULTS

Frequency (%) of DPN in non-IG, IG, and new diabetes was 3 (2.0%), 3 (1.7%), and 17 (7.8%) narrowly defined (no other cause for polyneuropathy) and 19 (12.7%), 22 (12.6%), and 38 (17.4%) broadly defined. Mean and frequency distribution of composite scores of nerve conduction and quantitative sensation tests were not significantly different between IG and non-IG but were worse in new diabetes. Frequency of retinopathy and nephropathy was significantly increased only in new diabetes. In secondary analysis, small but significant increases in retinopathy and nephropathy were found in IGT, IFG, and IGT combined groups.

CONCLUSIONS

In population studies of Olmsted County, Minnesota, inhabitants, prevalence of typical DPN, retinopathy, and nephropathy was significantly increased only in subjects with new diabetes-not in subjects with IG as defined by American Diabetes Association (ADA) criteria of abnormality of IFG, IGT, or IA1C. For atypical DPN, such an increase was not observed even in subjects with new diabetes. In medical practice, explanations other than IG should be sought for patients with atypical DPN (chronic idiopathic axonal polyneuropathy) who have IG.

Monotonicity of nerve tests in diabetes: subclinical nerve dysfunction precedes diagnosis of polyneuropathy

OBJECTIVE

The objective of this study was to test whether monotone worsening of nerve function, attributable to diabetes, can be demonstrated before criteria for diabetic sensorimotor polyneuropathy (DSPN) have been met. Which nerve tests are best?

RESEARCH DESIGN AND METHODS

From a prevalence cohort of 504 individuals in the Rochester Diabetic Neuropathy study (RDNS), we identified 238 individuals (group 1) who at first examination were without polyneuropathy (DSPN) by a sum score of the normal deviates (from percentiles) of five attributes of nerve conduction of the legs (i.e., their five nerve conduction normal deviate values were <97.5th percentile) and were followed longitudinally two or more times. Of these 238, 90 (group 2) were followed six or more times at yearly or bi-yearly intervals. We compared different nerve tests for the ones most sensitive and reliable in showing latent nerve dysfunction and monotone (the extent to which a variable measured repeatedly over time reveals a significant trend of worsening or improvement).

RESULTS

In group 1 patients, the mean sum score of five attributes of nerve conduction (sigma 5 NC nds) at baseline was 1.08 and at the last examination (only patients with Sigma 5 NC nds <97.5th percentile) was 3.63, markedly higher than that in healthy subjects (only of individuals with Sigma 5 NC nds <97.5th percentile) (-0.12), indicating a subtle latent shift of nerve conduction tests toward abnormality. Serial evaluations of many individual and especially sum scores of nerve conduction tests in group 2 patients showed statistically significant worsening with time, even when nerve conduction tests were still well within normal limits. Neurologic signs also worsened but barely to significant levels; however, symptoms and quantitative sensation tests did not. Considering the composite score sigma 5 NC nds, 42 (of 90 group 2 patients) showed significant worsening, 22 were still without DSPN by nerve conduction test criteria, and some were even below the 50th percentile at the last evaluation.

CONCLUSIONS

Subtle and latent functional worsening of nerve conduction can be demonstrated even before nerve conduction test criteria for DSPN have been met. For demonstrating monotone worsening, the order (from best to worst) of tests was: some composite scores of nerve conduction and individual attributes of nerve conduction. We did not show monotone worsening of symptoms or of quantitative sensation test results. In multivariate analysis of risk factors and their association with worsening sigma 5 NC nds, 24-h microalbuminuria (a marker of microvessel disease) was found to be a significant covariate, an indication that the asymptomatic alterations of nerve conduction are meaningful.

Meralgia paresthetica: relation to obesity, advanced age, and diabetes mellitus

OBJECTIVE

To determine the incidence of meralgia paresthetica (MP) and its relationship to diabetes mellitus (DM) and obesity.

METHODS

A population-based study was performed within Olmstead County Minnesota, from January 1, 1990, to December 31, 1999. MP incidence and its association with age, gender, body mass index (BMI), and DM were reviewed.

RESULTS

A total of 262 patients with MP, 262 normal controls, and 262 BMI-matched normal controls with mean age of 50 years were identified (51% men). The age- and sex-adjusted incidence of MP was 32.6 per 100,000 patient years, whereas the incidence of MP in people with DM was 247 per 100,000 patient years, 7 times the occurrence of MP in the general population. Of the patients with MP, 28% had DM vs 17% of BMI-matched controls and the majority of people with MP developed DM after the diagnosis of MP. Patients with MP are 2 times more likely to develop DM (odds ratio 2, 95% confidence interval 1.3-3.0, p = 0.0027). The mean BMI of patients with MP (30.1 kg/m(2), obese class I) was significantly higher than that of age- and gender-matched controls (27.3 kg/m(2), overweight). MP incidence increased 12.9 per 100,000 patient years in the hemidecade study period with an associated increase in both BMI (2.2 kg/m(2)) and average age (3 years).

CONCLUSIONS

MP is a frequent painful neuropathy associated with obesity, advancing age, and DM. The incidence rate of MP is predicted to increase as these demographics increase in world populations. Because MP associates with DM beyond weight- and age-matched controls, more aggressive counseling of these patients in prevention of DM may be warranted.