The syndrome of diabetic amyotrophy

Back Pain with Leg Pain

PURPOSE OF REVIEW

The clinical diagnostic dilemma of low back pain that is associated with lower limb pain is very common. In relation to back pain that radiates to the leg, the International Association for the Study of Pain (IASP) states: "Pain in the lower limb should be described specifically as either referred pain or radicular pain. In cases of doubt no implication should be made and the pain should be described as pain in the lower limb."

RECENT FINDINGS

Bogduks' editorial in the journal PAIN (2009) helps us to differentiate and define the terms somatic referred pain, radicular pain, and radiculopathy. In addition, there are other pathologies distal to the nerve root that could be relevant to patients with back pain and leg pain such as plexus and peripheral nerve involvement. Hence, the diagnosis of back pain with leg pain can still be challenging. In this article, we present a patient with back and leg pain. The patient appears to have a radicular pain syndrome, but has no neurological impairment and shows signs of myofascial involvement. Is there a single diagnosis or indeed two overlapping syndromes? The scope of our article encompasses the common diagnostic possibilities for this type of patient. A discussion of treatment is beyond the scope of this article and depends on the final diagnosis/diagnoses made.

Immunotherapy for diabetic amyotrophy

BACKGROUND

People with diabetes mellitus (DM) sometimes present with acute or subacute, progressive, asymmetrical pain and weakness of the proximal lower limb muscles. The various names for the condition include diabetic amyotrophy, diabetic lumbosacral radiculoplexus neuropathies, diabetic femoral neuropathy or Bruns-Garland syndrome. Some studies suggest that diabetic amyotrophy may be an immune-mediated inflammatory microvasculitis causing ischaemic damage of the nerves. Immunotherapies would therefore be expected to be beneficial. This is the second update of a review first published in 2009.

OBJECTIVES

To review the evidence from randomised trials for the efficacy of any form of immunotherapy in the treatment of diabetic amyotrophy.

SEARCH METHODS

On 5 September 2016 we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE and Embase. We also contacted authors of relevant publications and other experts to obtain additional references, unpublished trials, and ongoing trials.

SELECTION CRITERIA

We intended to include all randomised and quasi-randomised trials of any immunotherapy in participants with the condition fulfilling all the following: diabetes mellitus as defined by internationally recognised criteria; acute or subacute onset of pain and lower motor neuron weakness involving predominantly the proximal muscles of the lower limbs; weakness that is not confined to one nerve or nerve root distribution; and exclusion of other causes of lumbosacral radiculopathies and plexopathy.

DATA COLLECTION AND ANALYSIS

Two authors independently examined all references retrieved by the search to select those meeting the inclusion criteria.

MAIN RESULTS

We found only one completed placebo-controlled trial (N = 75) using intravenous methylprednisolone in diabetic amyotrophy (Dyck 2006). The results have not been fully published and were not available for analysis. The risk of bias was unclear because there was too little information to make a judgement, but we considered the trial at high risk of selective reporting. The published abstract did not report adverse events. We found no additional trials when the searches were updated in September 2016.

AUTHORS' CONCLUSIONS

There is presently no evidence from randomised trials to support a positive or negative effect of any immunotherapy in the treatment in diabetic amyotrophy.

Entrapment neuropathies in diabetes mellitus

Neuropathy is a common complication of diabetes mellitus (DM) with a wide clinical spectrum that encompasses generalized to focal and multifocal forms. Entrapment neuropathies (EN), which are focal forms, are so frequent at any stage of the diabetic disease, that they may be considered a neurophysiological hallmark of peripheral nerve involvement in DM. Indeed, EN may be the earliest neurophysiological abnormalities in DM, particularly in the upper limbs, even in the absence of a generalized polyneuropathy, or it may be superimposed on a generalized diabetic neuropathy. This remarkable frequency of EN in diabetes is underlain by a peculiar pathophysiological background. Due to the metabolic alterations consequent to abnormal glucose metabolism, the peripheral nerves show both functional impairment and structural changes, even in the preclinical stage, making them more prone to entrapment in anatomically constrained channels. This review discusses the most common and relevant EN encountered in diabetic patient in their epidemiological, pathophysiological and diagnostic features.

Diabetic autonomic neuropathy

Diabetes mellitus is the commonest cause of an autonomic neuropathy in the developed world. Diabetic autonomic neuropathy causes a constellation of symptoms and signs affecting cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory, and sudomotor systems. Several discrete syndromes associated with diabetes cause autonomic dysfunction. The most prevalent of these are: generalized diabetic autonomic neuropathy, autonomic neuropathy associated with the prediabetic state, treatment-induced painful and autonomic neuropathy, and transient hypoglycemia-associated autonomic neuropathy. These autonomic manifestations of diabetes are responsible for the most troublesome and disabling features of diabetic peripheral neuropathy and result in a significant proportion of the mortality and morbidity associated with the disease.

Diabetic radiculoplexus neuropathies

Diabetic radiculoplexus neuropathies (DRPN) are neuropathies clinically and pathologically distinct from the neuropathy typically associated with diabetes (DPN). DRPN are usually subacute in onset, painful, and often demonstrate a monophasic course with incomplete recovery. Pathologically, these neuropathies are due to ischemic injury from altered immunity and often have features suggestive or diagnostic of microvasculitis. Unlike DPN, immune therapy may be helpful in treatment of these conditions given their pathological substrate and therefore are important to identify early and distinguish from other neuropathies that occur in patient with diabetes.

Diabetic neuropathy part 2: proximal and asymmetric phenotypes

Diabetic neuropathies consist of a variety of syndromes resulting from different types of damage to peripheral or cranial nerves. Although distal symmetric polyneuropathy is the most common type of diabetic neuropathy, many other subtypes have been defined since the 1800s, including proximal diabetic, truncal, cranial, median, and ulnar neuropathies. Various theories have been proposed for the pathogenesis of these neuropathies. The treatment of most requires tight and stable glycemic control. Spontaneous recovery is seen in most of these conditions with diabetic control. Immunotherapies have been tried in some of these conditions however are controversial.

Immunotherapy for diabetic amyotrophy

BACKGROUND

People with diabetes mellitus (DM) sometimes present with acute or subacute, progressive, asymmetrical pain and weakness of the proximal lower limb muscles. The various names for the condition include diabetic amyotrophy or diabetic lumbosacral radiculoplexus neuropathies. Some studies suggest that it may be due to immune-mediated inflammatory microvasculitis causing ischaemic damage of the nerves. Immunotherapies would therefore be expected to be beneficial. This is an update of a review first published in 2009.

OBJECTIVES

We aimed to review the evidence from randomised trials for the efficacy of any form of immunotherapy in the treatment of diabetic amyotrophy.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (7 February 2012), CENTRAL (2012 Issue 1), MEDLINE (January 1966 to January 2012) and EMBASE (January 1980 to January 2012), and contacted authors of relevant publications and other experts to obtain additional references, unpublished trials, and ongoing trials.

SELECTION CRITERIA

We intended to include all randomised and quasi-randomised trials of any immunotherapy in participants with the condition fulfilling all the following: diabetes mellitus as defined by internationally recognised criteria, acute or subacute onset of pain and lower motor neuron weakness involving predominantly the proximal muscles of the lower limbs, weakness that is not confined to one nerve or nerve root distribution and exclusion of other causes of lumbosacral radiculopathies and plexopathy.

DATA COLLECTION AND ANALYSIS

Two authors independently examined all references retrieved by the search to select those meeting the inclusion criteria.

MAIN RESULTS

We found only one completed controlled trial using intravenous methylprednisolone in diabetic amyotrophy (Dyck 2006). The results have not been fully published and were not available for analyses. We found no additional trials when the searches were updated in 2012.

AUTHORS' CONCLUSIONS

There is presently no evidence from randomised trials to support any recommendation on the use of any immunotherapy treatment in diabetic amyotrophy.

Diabetic polyneuropathies: update on research definition, diagnostic criteria and estimation of severity

Prior to a joint meeting of the Neurodiab Association and International Symposium on Diabetic Neuropathy held in Toronto, Ontario, Canada, 13-18 October 2009, Solomon Tesfaye, Sheffield, UK, convened a panel of neuromuscular experts to provide an update on polyneuropathies associated with diabetes (Toronto Consensus Panels on DPNs, 2009). Herein, we provide definitions of typical and atypical diabetic polyneuropathies (DPNs), diagnostic criteria, and approaches to diagnose sensorimotor polyneuropathy as well as to estimate severity. Diabetic sensorimotor polyneuropathy (DSPN), or typical DPN, usually develops on long-standing hyperglycaemia, consequent metabolic derangements and microvessel alterations. It is frequently associated with microvessel retinal and kidney disease-but other causes must be excluded. By contrast, atypical DPNs are intercurrent painful and autonomic small-fibre polyneuropathies. Recognizing that there is a need to detect and estimate severity of DSPN validly and reproducibly, we define subclinical DSPN using nerve conduction criteria and define possible, probable, and confirmed clinical levels of DSPN. For conduct of epidemiologic surveys and randomized controlled trials, it is necessary to pre-specify which attributes of nerve conduction are to be used, the criterion for diagnosis, reference values, correction for applicable variables, and the specific criterion for DSPN. Herein, we provide the performance characteristics of several criteria for the diagnosis of sensorimotor polyneuropathy in healthy subject- and diabetic subject cohorts. Also outlined here are staged and continuous approaches to estimate severity of DSPN.

Update on the management of diabetic polyneuropathies

The prevalence of diabetic polyneuropathy (DPN) can approach 50% in subjects with longer-duration diabetes. The most common neuropathies are generalized symmetrical chronic sensorimotor polyneuropathy and autonomic neuropathy. It is important to recognize that 50% of subjects with DPN may have no symptoms and only careful clinical examination may reveal the diagnosis. DPN, especially painful diabetic peripheral neuropathy, is associated with poor quality of life. Although there is a better understanding of the pathophysiology of DPN and the mechanisms of pain, treatment remains challenging and is limited by variable efficacy and side effects of therapies. Intensification of glycemic control remains the cornerstone for the prevention or delay of DPN but optimization of other traditional cardiovascular risk factors may also be of benefit. The management of DPN relies on its early recognition and needs to be individually based on comorbidities and tolerability to medications. To date, most pharmacological strategies focus upon symptom control. In the management of pain, tricyclic antidepressants, selective serotonin noradrenaline reuptake inhibitors, and anticonvulsants alone or in combination are current first-line therapies followed by use of opiates. Topical agents may offer symptomatic relief in some patients. Disease-modifying agents are still in development and to date, antioxidant α-lipoic acid has shown the most promising effect. Further development and testing of therapies based upon improved understanding of the complex pathophysiology of this common and disabling complication is urgently required.

Treatment of diabetic and nondiabetic lumbosacral radiculoplexus neuropathy

OPINION STATEMENT

Lumbosacral radiculoplexus neuropathy (LRPN) is a multifocal, asymmetric, painful neuropathic disorder affecting multiple levels of lumbosacral plexus, nerve roots, and distal nerves that emerge from the plexus. The disorder was first described in diabetic patients (DLRPN) and was later found to occur in nondiabetic patients as well. There have been debates as to the pathogenesis of DLRPN and LRPN. Recent detailed and extensive pathologic studies, however, have shown that the main pathogenesis is inflammation and microvasculitis affecting various components in the peripheral nerves, resulting in ischemic injury to the nerves. Even though studies on the natural history of this disorder have shown that the majority of patients recover within a few years after the attack without any treatment (although recovery is incomplete in many cases), it is a common practice, based on the pathophysiology and case series, to administer immunotherapy. Preliminary data from a controlled clinical trial failed to show significant improvement in outcomes measured by neurologic deficits (as judged by the Neuropathy Impairment Score) but did show improvement in symptoms (pain and positive sensory symptoms). Choices of immunotherapy include corticosteroids, intravenous immunoglobulin, plasma exchange, or a combination. Pain management, physical therapy, and treatment of depression remain mainstays for managing this disorder.

Painless diabetic motor neuropathy: a variant of diabetic lumbosacral radiculoplexus Neuropathy?

OBJECTIVE

Occasionally, diabetic patients develop painless, lower-limb, motor predominant neuropathy. Whether this is a variant of diabetic lumbosacral radiculoplexus neuropathy (DLRPN) (a painful disorder from ischemic injury and microvasculitis), a variant of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) or another disorder is unsettled. Here, we characterize the clinical and pathological features of painless diabetic motor predominant neuropathy.

METHODS

We identified patients with this syndrome who underwent nerve biopsy. We compared pathological features to 33 DLRPN and 25 CIDP biopsies.

RESULTS

23 patients were identified (22 had type 2 diabetes mellitus); 12 men; median age 62.2 years (range 36-78); median weight loss 30 pounds (range 0-100). Overall, the clinical features were similar to DLRPN except painless patients had more symmetrical and upper limb involvement, with slower progression and more severe impairment. Physiological testing demonstrated pan-modality sensory loss, autonomic abnormalities and axonal polyradiculoneuropathies. Nerve biopsies were similar to DLPRN showing ischemic injury (multifocal fiber loss [11/23], perineural thickening [18/23], injury neuroma [11/23], neovascularization [17/23]) and evidence of altered immunity and microvasculitis (epineurial perivascular inflammation [23/23], prior bleeding [11/23], vessel wall inflammation [15/23], and microvasculitis [3/23]). In contrast, CIDP biopsies did not show ischemic injury or microvasculitis but revealed demyelination and onion-bulbs.

INTERPRETATION

1) Painless diabetic motor neuropathy is painless DLRPN and not CIDP and is caused by ischemic injury and microvasculitis. 2) The clinical features of painless DLRPN are different from typical DLPRN being more insidious and symmetrical with slower evolution. 3) The slower evolution may explain the lack of pain.

Immunotherapy for diabetic amyotrophy

BACKGROUND

People with diabetes mellitus (DM) sometimes present with acute or subacute, progressive, asymmetrical pain and weakness of the proximal lower limb muscles. The various names for the condition include diabetic amyotrophy, or diabetic lumbosacral radiculoplexus neuropathies. Some studies suggest that it may be due to immune-mediated inflammatory microvasculitis causing ischaemic damage of the nerves. Immunotherapies would therefore be expected to be beneficial.

OBJECTIVES

We aimed to review the evidence from randomised trials for the efficacy of any form of immunotherapy in the treatment of diabetic amyotrophy.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (searched April 2 2009), MEDLINE (searched January 1966 to April 2 2009), EMBASE (searched January 1980 to April 2 2009) and contacted authors of relevant publications and other experts to obtain additional references, unpublished trials, and ongoing trials.

SELECTION CRITERIA

We intended to include all randomised and quasi-randomised trials of any immunotherapy in participants with the condition fulfilling all the following: diabetes mellitus as defined by internationally recognised criteria, acute or subacute onset of pain and lower motor neuron weakness involving predominantly the proximal muscles of the lower limbs, weakness that is not confined to one nerve or nerve root distribution and exclusion of other causes of lumbosacral radiculopathies and plexopathy.

DATA COLLECTION AND ANALYSIS

Two authors independently examined all references retrieved by the search to select those meeting the inclusion criteria.

MAIN RESULTS

We found only one completed controlled trial using intravenous methylprednisolone in diabetic amyotrophy (Dyck 2006). The results have not been fully published and were not available for analyses.

AUTHORS' CONCLUSIONS

There is presently no evidence from randomised trials to support any recommendation on the use of any immunotherapy treatment in diabetic amyotrophy.

The natural history of chronic painful peripheral neuropathy in a community diabetes population

AIMS

To examine the natural history of chronic painful diabetic neuropathy (CPDN).

METHODS

A cross-sectional study of 350 people with diabetes was performed during 1998-1999 to assess the prevalence of CPDN in the community. Fifty-six patients with CPDN were identified and were followed up an average of 5 years later.

RESULTS

From the original cohort, 12 patients had died and 14 had moved away or were unable to participate in the follow-up study. Thus 30 patients with CPDN [21 male, mean (SD) age 68.6 years (9.4), mean (SD) duration of diabetes 15.4 years (8.7)] were re-assessed. Seven (23%) had been pain free for at least 12 months and 23 continued to report neuropathic pain of similar quality and severity [total McGill Pain Questionnaire Score median (interquartile range) at follow-up 22 (16-39) vs. 20 (16-33) at baseline, P = 0.3; mean (SD) visual analogue scale (VAS) score for pain over the preceding 24 h 5.3 cm (2.9) vs. 4.6 cm (2.5) at baseline, P = 0.1]. Only 65% had ever received treatment for CPDN despite 96% (22/23) reporting pain to their physician; 43.5% had received antidepressants, 17.4% anticonvulsants, 39% opiates and 30% had tried complementary therapies.

CONCLUSIONS

The neuropathic pain of CPDN can resolve completely over time in a minority (23%). In those in whom painful neuropathic symptoms had persisted over 5 years, no significant improvement in pain intensity was observed. Despite the improvement in treatment modalities for chronic pain in recent years, patients with CPDN continue to be inadequately treated.

Mononeuropathy multiplex (AAEE case report #11)

Mononeuropathy multiplex is a syndrome of diverse causes, the most common of which is nerve ischemia due to microangiopathy associated with diabetes or the collagen-vascular diseases. The acquired inflammatory demyelinating neuropathies invariably are multifocal, although the clinical manifestations of these and other multifocal neuropathies may appear symmetrical. The identification of multifocal neuropathies is important because of the frequent therapeutic implications. A case of mononeuropathy multiplex associated with polyarteritis nodosa is described.

Diabetic amyotrophy progressing to severe quadriparesis

Diabetic amyotrophy is a distinctive form of diabetic neuropathy usually characterized by the abrupt onset of pain and asymmetric proximal leg weakness and wasting. Involvement of the upper limbs is unusual, and prognosis is said to be good. We describe two patients, each with type II diabetes mellitus, who presented with diabetic amyotrophy progressing to severe quadriparesis. One patient remains severely disabled. The clinical spectrum of diabetic amyotrophy includes progression to severe quadriparesis.

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.

Microvasculitis in non-diabetic lumbosacral radiculoplexus neuropathy (LSRPN): similarity to the diabetic variety (DLSRPN)

Diabetic lumbosacral radiculoplexus neuropathy (DLSRPN) has been shown to be due to ischemic injury from microvasculitis. The present study tests whether ischemic injury and microvasculitis are the pathologic cause of non-diabetic lumbosacral radiculoplexus neuropathy (LSRPN), and whether the pathologic alterations are different between LSRPN and DLSRPN. We studied distal cutaneous nerve biopsies of 47 patients with LSRPN and compared findings with those of 14 age-matched healthy controls and 33 DLSRPN patients. In both disease conditions, we found evidence of ischemic injury (multifocal fiber degeneration and loss, perineurial degeneration and scarring, characteristic fiber alterations, neovascularization, and injury neuroma) that we attribute to microvasculitis (mural and perivascular mononuclear inflammation of microvessels, inflammatory separation, fragmentation and destruction of mural smooth muscle, and previous microscopic bleeding [hemosiderin]). Teased nerve fibers in LSRPN showed significantly increased frequencies of axonal degeneration, segmental demyelination, and empty nerve strands. The segmental demyelination appeared to be clustered on fibers with axonal dystrophy. The nerves with abnormal frequencies of demyelination were significantly associated with nerves showing multifocal fiber loss. We reached the following conclusions: 1) LSRPN is a serious condition with much morbidity that mirrors DLSRPN. 2) Ischemic injury from microvasculitis appears to be the cause of LSRPN. 3) Axonal degeneration and segmental demyelination appear to be linked and due to ischemia. 4) The pathologic alterations in LSRPN and DLSRPN are indistinguishable, raising the question whether these 2 conditions have a common underlying mechanism, and whether diabetes mellitus contributes to the pathology or is a risk factor in DLSRPN. 5) Both LSRPN and DLSRPN are potentially treatable conditions.

Oxidative damage to mitochondrial DNA and its relationship to diabetic complications

Increased oxidative stress induced by hyperglycemia may contribute to the pathogenesis of diabetic complications. Oxidative stress is known to increase the conversion of deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OHdG) in DNA, which is linked to increased mitochondrial DNA (mtDNA) deletions. We investigated mtDNA deletions and 8-OHdG in the muscle DNA of non-insulin-dependent diabetes mellitus (NIDDM) patients. mtDNA deletion of 4977 bp (delta mtDNA4977) and the content of 8-OHdG in the muscle DNA of the NIDDM patients were much higher than those of the control subjects. There was a significant correlation between delta mtDNA4977 and the 8-OHdG content (P < 0.0001). Both delta mtDNA4977 and the 8-OHdG content were also correlated with the duration of diabetes. Delta mtDNA4977 and the 8-OHdG content in muscle DNA increased in proportion to the severity of diabetic nephropathy and retinopathy. This is the first report that an increase in delta mtDNA4977 and 8-OHdG is proportional to the severity of diabetic complications. Oxidative mtDNA damage is speculated to contribute to the pathogenesis of diabetic complications though a defect in mitochondrial oxidative phosphorylation or other mechanisms. 8-OHdG and delta mtDNA4977 are useful markers to evaluate oxidative mtDNA damage in the diabetic patients.

Peripheral neuropathies in diabetes

Peripheral neuropathy in diabetes remains a difficult management dilemma. The clinical manifestations may vary widely. Polyneuropathies develop with increasing duration of disease, and a thorough understanding of the clinical manifestations, including sensory, motor, and autonomic deficiencies, helps guide diagnosis and treatment. A multidisciplinary approach emphasizing preventive care and timely intervention can decrease morbidity significantly and improve the quality of life for the patient. Properly fitting shoes and avoidance of foot trauma are cornerstones of preventive management. Strict control of serum glucose can alter the course of peripheral neuropathies. This control can be accomplished with a strict insulin regimen or pancreatic transplant. Further research is needed to increase knowledge about peripheral neuropathies in diabetes and aid the physician with new treatment options.

Autoimmune diabetic neuropathy

Recent work has shown that inflammatory vasculopathy is commonly seen in biopsies of diabetic patients with neuropathy. Most of these patients have had syndromes consistent with proximal diabetic neuropathy or amyotrophy. This suggests that inflammatory vasculopathy is important in the pathogenesis of these disorders. Immunosuppressive therapy may benefit many of these patients.

Diabetic neuropathy

The most common form of diabetic neuropathy is chronic, distal symmetrical sensorimotor, or predominantly sensory neuropathy; the latter is invariably associated with some degree of autonomic dysfunction. There are, however, other neuropathic patterns in diabetes mellitus that are uncommon but are important to recognize, since they may mimic many other non-neurologic diseases. This article discusses a variety of forms of mononeuropathies and diabetic proximal motor neuropathy, commonly known as diabetic amyotropy.

AAEM case report #13: diabetic amyotrophy

A case fulfilling the criteria for the diagnosis of diabetic amyotrophy is reported. Based on the clinical and electrodiagnostic features, it is concluded that diabetic amyotrophy is a recognizable clinical entity that can be differentiated from other diabetic neuropathies. The site of the lesion and the pathogenesis in diabetic amyotrophy remain controversial. The course of the illness is variable with gradual, but often incomplete, improvement.

A new mitochondrial DNA deletion associated with diabetic amyotrophy, diabetic myoatrophy and diabetic fatty liver

Mitochondrial dysfunctions of the muscle in diabetic amyotrophy and of the liver in diabetic fatty liver have been reported. We investigated mitochondrial gene mutations in three cases: (1) a patient with diabetic amyotrophy in the muscles of the lower extremities, and neuropathy; (2) 5 diabetics with myoatrophy, diabetic nephropathy, and chronic renal failure; and (3) an IDDM patient with a diabetic fatty liver. We identified a 5778-bp deletion (8214-13991) in mitochondrial DNA from the muscle and liver biopsy specimens by the primer shift PCR and PCR-direct sequence methods. It is speculated that 5778-bp deletion is due to homogeneous recombination in the 7-bp repeat sequence of TCCTAGA flanking the region deleted in the mitochondrial DNA. Determination of respiratory chain enzyme activities in fresh muscle mitochondria demonstrated the defect in complex I activity. The deletion covers areas coding ND3, ND4, ND4L, and ND5 in complex I. The 5778-bp deletion might cause a defect in mitochondrial oxidative phosphorylation and contribute to the pathogenesis of diabetic amyotrophy, myoatrophy with diabetic nephropathy, and chronic renal failure, as well as diabetic fatty liver in IDDM.

Sixteenth annual AAEM Edward H. Lambert Lecture. Electrodiagnostic aspects of diabetic neuropathies: entrapments. American Association of Electrodiagnostic Medicine

A MEDLINE review suggested a lack of recent studies about the entrapments seen with underlying diabetic neuropathy. Suggested protocols for research in diabetic peripheral neuropathy have not included the concepts of entrapments as an early--indeed, first manifestation of the neuropathy. Carpal tunnel syndrome is a frequent accompaniment of diabetic peripheral neuropathy. Assessment of the degree of entrapment superimposed on the generalized peripheral neuropathy can be clarified by analysis of the CMAP and the SNAP--particularly with respect to duration of the negative spike of the action potential. Also, analysis of the action potentials elicited by stimulation of the ulnar and radial nerves and their comparison with the median nerve is often helpful. Finally careful inspection of the action potential when stimulating proximal and distal to the entrapment will establish the degree of nerve compromise relative to the underlying diabetic neuropathy.

Clinical observations and experiments in diabetic neuropathy

Diabetic neuropathies form a group of diverse conditions, which can be distinguished between those which recover (acute painful neuropathies, radiculopathies, mononeuropathies) and those which progress (sensory and autonomic neuropathies). These two main groups can be distinguished in several ways: sensory and autonomic neuropathies are classic diabetic complications progressing gradually in patients with long-standing diabetes who often have other specific complications, while the reversible neuropathies do not have these features. The latter are characterised by their occurrence at any stage of diabetes, often at diagnosis, they may be precipitated on starting insulin treatment, and they are more common in men; they can occur at any age, though more often in older patients, and are unrelated to other diabetic complications. The two groups of neuropathies also show differences in nerve structural abnormalities and with regard to distinctive blood flow responses. The underlying mechanisms responsible for these very different forms of neuropathy remain speculative, but evidence for an immunological basis for the development of severe symptomatic autonomic neuropathy is presented.

Proximal skeletal muscle alterations in streptozotocin-diabetic rats: a histochemical and morphometric analysis

The response of rat quadriceps muscle fibers to chronic streptozotocin (STZ) diabetes was studied. Transverse sections of rectus femoris muscle from diabetic and weight-matched control rats were assayed for myofibrilar adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR). A quantitative analysis was carried out by an automatic interactive analysis system focused on the fiber type size and distribution. STZ-induced diabetes caused important effects in this muscle, with changes in the distribution of oxidative enzyme reactions, type I fiber hypertrophy, and type II fiber atrophy, which was greater in type IIB than in type IIA. It is concluded that hypoinsulinism produces morphological alterations in proximal skeletal muscle fibers that are similar to those of neurogenic myopathy. Thus the pathological changes in these mammalian muscle fibers could explain the clinical syndrome seen in diabetic patients called "diabetic symmetrical proximal motor neuropathy," perhaps the least understood of the major neuropathic complications of diabetes.

Expression of heat shock protein epitopes in tubular aggregates

Tubular aggregates may be found in a variety of conditions and have been associated with a wide range of chemical and ischemic insults. We report clinical and histological features in a case of myopathy with tubular aggregates. The structure of these tubular aggregates was examined using antibodies to cytoskeletal proteins and heat shock proteins. Epitopes of the 72 kD heat shock protein were expressed in the areas of abnormality in this case and in a case of hypokalemic periodic paralysis with tubular aggregates. Heat shock proteins have a role in the modulation of the tertiary structure of proteins and may be involved in the pathogenesis of tubular aggregates and other microtubular abnormalities in muscle.

Diabetic amyotrophy without pain. A puzzling clinical picture

A patient with weight loss and weakness presents a diagnostic challenge. Drs Moeser and Kent describe an unusual case of diabetic amyotrophy that required extensive workup to arrive at the diagnosis and rule out more serious disease. Symptoms were dramatic, and recovery was spontaneous following conservative treatment.

Aldose reductase in the etiology of diabetic complications. 3. Neuropathy

Aldose reductase has been shown to be present in both autonomic and somatic nerves. Activation of this enzyme and the polyol pathway has been demonstrated in diabetic animal models to cause a range of biochemical, functional, and structural consequences that include the accumulation of sorbitol and fructose; axoglial dysjunction; paranodal demyelination; abnormalities in axonal transport, blood flow, and vascular permeability; and resistance to ischemic transmission of action potentials. These data provide an insight into the range of processes that if activated may either singly or in combination result in altered patterns of nerve function and structural alterations in diabetic neuropathy. In animal models of diabetes, it has been shown that inhibition of aldose reductase can modify these diabetes-induced changes. It is hoped that the results of large-scale controlled trials will provide clinical evidence to support these data.

Diabetic amyotrophy: reassessment of the clinical spectrum

Diabetic amyotrophy is a syndrome whose recognition may be difficult or delayed. We reviewed thirteen patients with this disorder, all of whom had significant proximal lower limb wasting and weakness as the predominant feature and eleven of whom had pain in the affected limbs. Significant weight loss was common. In nine patients the deficits were largely or totally reversible. Important variations from the classical features were observed. Only five patients displayed asymmetric proximal lower limb wasting, weakness and pain, motor deficits in the remainder being either unilateral or bilateral and symmetrical. The shoulder girdle and arms were also involved in two patients. Proximal limb pain was not invariable, a distal sensory peripheral neuropathy was common, and diabetic control at diagnosis was likely to be good. No prognostic factors were identified. Thus, not all patients with diabetic amyotrophy exhibit the classically-described features. Other than careful clinical examination, a thorough bilateral electromyographic and nerve conduction study remains the most helpful diagnostic test. Appreciation of the clinical spectrum and context of diabetic amyotrophy should facilitate its differentiation from other disorders, including other forms of diabetic neuropathy.

Distal axonopathy in streptozotocin diabetes in rats

We noted the earliest morphological changes in the motor endplates 8 weeks after the induction of streptozotocin diabetes in rats. Morphometric measurements showed reduced axonal areas of the lateral plantar and the sciatic nerves in the diabetic rats 28 but not 2 and 8 weeks after the experiment. These findings suggested distal axonopathy.

Clinical aspects of diabetic neuropathies

Diabetic neuropathy is a common complication of diabetes that may be associated both with considerable morbidity (painful polyneuropathy, neuropathic ulceration) and mortality (autonomic neuropathy). The epidemiology and natural history of diabetic neuropathy is clouded with uncertainty, largely due to confusion in the definition and measurement of this disorder. We have reviewed a variety of the clinical manifestations associated with somatic and autonomic neuropathy and discussed current views related to the management of the different abnormalities. Although unproven, the best evidence suggests that near normal control of blood glucose in the early years following onset of diabetes may help delay the development of clinically significant nerve impairment. Intensive therapy to achieve normalization of blood glucose may also lead to reversibility of early diabetic neuropathy, but again this is unproven. Our ability to manage successfully the many different manifestations of diabetic neuropathy depends ultimately on our success in uncovering the pathogenic processes underlying this disorder. The recent resurgence of interest in the vascular hypothesis, for example, has opened up new avenues of investigation for therapeutic intervention. Paralleling our increased understanding of the pathogenesis of diabetic neuropathy, there must be refinements in our ability to measure quantitatively the different types of defects that occur in this disorder. These tests must be validated and standardized to allow comparability between studies and more meaningful interpretation of study results.

AAEE case report #13: diabetic amyotrophy

A case fulfilling the criteria for the diagnosis of diabetic amyotrophy is reported. Based on the clinical and electrodiagnostic features, it is concluded that diabetic amyotrophy is a recognizable clinical entity that can be differentiated from other diabetic neuropathies. The site of the lesion and the pathogenesis in diabetic amyotrophy remain controversial. The usual course of the illness is one of gradual improvement over weeks to months.

Analysis of F-wave in metabolic neuropathies: a comparative study in uremic and diabetic patients

Motor nerve conduction study along the entire length of the ulnar and tibialis posterior nerves was carried out in 30 diabetics compared with 30 uremic patients and 30 control subjects. The conduction in the proximal and the distal nerve segments was evaluated by the determination of the M and F latencies, MNCV (between the stimulus sites), FWCV (between the spinal cord and the stimulus sites), and F-ratio (conduction time ratio of proximal to distal segment). In both groups of patients the lower limbs appear much more involved than the upper, where the ulnar nerve is more commonly affected in uremic than in diabetic patients. In diabetic neuropathy the motor conduction abnormalities are diffuse over the total length of the nerve, but more marked distally in the ulnar nerve.

Structural alterations of the intramuscular nerves and junctional region in extraocular muscles of C57BL/Ks (db/db) diabetic mice

The extraocular muscles of the C57BL/Ks (db/db) diabetic mutant mouse were examined by electron microscopy. The intramuscular myelinated nerves and the junctional apparatus of the singly and multiply innervated muscle fibers were found to exhibit various anomalies. Lamellated inclusion bodies were found in many of the Schwann cells of the myelinated nerve fibers; intra-axonal inclusion bodies resembling polyglucosan bodies were also observed. Junctional abnormalities consisted of various types of inclusion bodies within the junctional sarcoplasm and within sole-plate nuclei; in addition, hypertrophied endplates were observed and often penetrated by networks of axonal terminal branches. At times, pseudopod-like extensions of the junctional sarcoplasm encompassed and made protracted synaptic contacts with the incoming axons.