Diabetic truncal neuropathy: topography of the sensory deficit

Truncal sensory polyneuropathy in light-chain amyloidosis

We describe a case of truncal sensory polyneuropathy in a patient with light-chain amyloidosis. We highlight the clinical signs and differential diagnoses related to the presentation.

Inflammatory biomarkers as a part of diagnosis in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN), a chronic neurological complication of diabetes mellitus, remains scantily addressed area of research. Many lacunae in the temporal sequence between cause and effect of DPN still remain unfilled and therefore treatment of DPN remains unsatisfactory. This is largely due to the conventional glucocentric focus to resolve the problem. This focus over hyperglycemia should be shifted to consider, chronic low grade inflammation as the major determinant in DPN. Rapidly emerging evidences from recent studies suggest that chronic low grade inflammation leads to the activation of innate immune system response, loss of insulin signaling and insulin resistance, endoplasmic reticulum stress, mitochondrial stress, leading to production of kinases like protein kinase C, mitogen activated protein kinase and jun-N-terminal kinase, pro-inflammatory cytokines and inter leukins-1b, 2, 6 and 8, tumour necrosis factor-alpha and other chemokines, leading to DPN. These biomarkers can be early predictors of DPN and therefore should be the focus of work testing their clinical utility to identify high-risk individuals as well as perhaps to target interventions. In this paper, we would like to review all the aspects of DPN, laying greater emphasis on inflammatory biomarkers as a tool for early diagnosis of DPN and the possible research approaches to address it satisfactorily.

Focal and entrapment neuropathies

Of the many patterns of peripheral nerve disorders in diabetes mellitus (DM), isolated clinical involvement of single nerves, though less common than distal symmetric polyneuropathy and perhaps polyradiculoneuropathy, constitute an important collection of characteristic syndromes. These fall into four anatomical regions of the body: cranial, upper limb, truncal, and lower limb territories. Each of these groups of mononeuropathies has its own ensemble of epidemiologic patterns, clinical presentations, laboratory and radiologic findings, differential diagnosis, management principles and prognosis.

Diabetic neuropathy

Neuropathies related to diabetes mellitus can affect 60-70% of patients with diabetes. These can include peripheral polyneuropathies, mononeuropathies, and autonomic neuropathies. Control of glucose, lipids, and hypertension and cessation of smoking can limit onset and progression of these neuropathies. Besides control of the above listed risk factors, we do not have effective medications to treat the pathophysiologic mechanisms of diabetic neuropathies. Treatment is limited to ameliorating pain and correcting the end organ consequences of the neuropathic processes.

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.

Diabetic neuropathy

PURPOSE OF REVIEW

Diabetes is the most common cause of peripheral neuropathy in the world. More than half of patients with diabetes have neuropathy, and half of patients with neuropathy have diabetes. Diabetic neuropathy is a major cause of disability and health care expense. This article reviews the various forms of diabetic neuropathy with a focus on diagnosis and treatment.

RECENT FINDINGS

Diabetes causes a wide variety of peripheral nerve problems. These can be divided into chronic neuropathies, of which distal symmetric polyneuropathy is the most common, and acute neuropathies, such as diabetic amyotrophy. There is growing evidence suggesting that prediabetic levels of hyperglycemia and other consequences of obesity and dyslipidemia contribute to neuropathy risk. Evolving literature suggests that many of the acute diabetic neuropathies are related to inflammatory mechanisms. An important exception is treatment-related neuropathy, previously known as "insulin neuritis".

SUMMARY

While disease-altering therapy continues to prove elusive, our understanding of basic disease mechanisms is improving, and new diagnostic and research tools will hopefully lead to novel therapies for distal symmetric diabetic polyneuropathy.

Truncal polyradiculopathy due to sarcoidosis

We report the case of a 43-year-old woman who developed multiple cranial nerve palsy, the symptoms of which included hyposmia, visual loss, facial hypoesthesia, facial weakness, dysphagia, gustatory disturbance, and sensory disturbance of the trunk and ulnar side of the bilateral arms. The clinical features included swelling of the bilateral hilar lymph nodes, uveitis, an elevated serum angiotensin-converting enzyme level, and negative tuberculin reactions, which led to a diagnosis of neurosarcoidosis. Her symptoms improved after administration of steroids. An elevated cerebrospinal fluid cell count and protein level, a low-frequency F-wave and slightly decreased sensory nerve action potentials in bilateral ulnar nerves by nerve conduction studies, and normal findings in the spine by magnetic resonance imaging suggested that truncal hypoesthesia was caused by polyradiculopathy. Although rare, in patients with neurosarcoidosis, truncal polyradiculopathy is noteworthy findings in addition to cranial nerve palsy.

Focal and multifocal diabetic neuropathies

Diabetic neuropathy is the most common neuropathy in industrialized countries, with a remarkable range of clinical manifestations. The vast majority of the patients with clinical diabetic neuropathy have a distal symmetrical form that progress following a fiber-length dependent pattern, with predominant sensory and autonomic manifestations. This pattern of neuropathy is associated with a progressive distal axonopathy. Patients are exposed to trophic changes in the feet, pains and autonomic disturbances. Less often, diabetic patients may develop focal and multifocal neuropathy that includes cranial nerve involvement, limb and truncal neuropathies. This neuropathic pattern tends to occur after 50 years of age, mostly in patients with longstanding diabetes mellitus. The LDDP does not show any trend to improvement and either relentlessly progresses or remain relatively stable over years. Conversely the focal diabetic neuropathies, which are often associated with inflammatory vasculopathy on nerve biopsies, remain self limited, sometimes after a relapsing course.

Diabetes mellitus and the peripheral nervous system: manifestations and mechanisms

Diabetes targets the peripheral nervous system with several different patterns of damage and several mechanisms of disease. Diabetic polyneuropathy (DPN) is a common disorder involving a large proportion of diabetic patients, yet its pathophysiology is controversial. Mechanisms considered have included polyol flux, microangiopathy, oxidative stress, abnormal signaling from advanced glycation endproducts and growth factor deficiency. Although some clinical trials have demonstrated modest benefits in disease stabilization or pain therapy in DPN, robust therapy capable of reversing the disease is unavailable. In this review, general aspects of DPN and other diabetic neuropathies are examined, including a summary of recent therapeutic trials. A particular emphasis is placed on the evidence that the neurobiology of DPN reflects a unique yet common and disabling neurodegenerative disorder.

Diabetic neuropathy--a review

Diabetic neuropathy is the most common neuropathy in industrialized countries, and it is associated with a wide range of clinical manifestations. The vast majority of patients with clinical diabetic neuropathy have a distal symmetrical form of the disorder that progresses following a fiber-length-dependent pattern, with sensory and autonomic manifestations predominating. This pattern of neuropathy is associated with a progressive distal axonopathy. Patients experience pain, trophic changes in the feet, and autonomic disturbances. Occasionally, patients with diabetes can develop focal and multifocal neuropathies that include cranial nerve involvement and limb and truncal neuropathies. This neuropathic pattern tends to occur after 50 years of age, and mostly in patients with long-standing diabetes mellitus. Length-dependent diabetic polyneuropathy does not show any trend towards improvement, and either relentlessly progresses or remains relatively stable over a number of years. Conversely, the focal diabetic neuropathies, which are often associated with inflammatory vasculopathy on nerve biopsies, remain self-limited, sometimes after a relapsing course.

Abdominal wall protrusion following herpes zoster

We present the case of a 62-year-old woman with abdominal segmental paresis consequent to radiculopathy caused by zoster, which was confirmed by electroneuromyography. The paresis resolved completely within three months. Recognition of this complication caused by zoster, which is easily misdiagnosed as abdominal herniation, is important for diagnosing this self-limited condition and avoiding unnecessary procedures.

Diabetic thoracic polyradiculopathy

Diabetic thoracic polyradiculopathy usually causes severe, chronic abdominal pain in patients with type 2 diabetes of variable duration. Other diabetic complications, weight loss and paretic abdominal wall protrusion are common. Sensory, motor and autonomic functions are affected. The diagnosis can be made from the characteristic history, physical examination findings, paraspinal electromyography, and other procedures. The differential diagnosis includes postherpetic neuralgia, abdominal wall pain, malignancy, and other spinal disorders. The pathology appears to be immune-mediated neurovasculitis resulting in ischemic injury. Traditional therapy is symptomatic, but recent pathological findings and clinical experience suggest that immunotherapy may be effective.

Acute Painful Neuropathy Restricted to the Abdomen following Rapid Glycaemic Control in Type 2 Diabetes

A 46-year-old Japanese man with type 2 diabetes mellitus, whose only diabetic complication was simple retinopathy, developed acute painful neuropathy. This presented as paresthesia and hyperesthesia restricted to the abdomen. The patient's haemoglobin A1c had dropped from 12% to 7.5% within 5 months, following a rapid improvement in glycaemic control. On investigation, there were no indications of disease in the intraabdominal area. Nerve conduction studies were consistent with mild sensorimotor peripheral and autonomic neuropathy. The patient required medication (mexiletine, sulpiride and imipramine hydrochloride) to control the pain. Four months after presentation, the symptoms showed a dramatic improvement and the treatment for pain relief was discontinued without any recurrence of paresthesia or hyperesthesia in the patient's abdomen. This was a very unusual case of diabetic post-treatment painful neuropathy in which the prominent features were severe pain, paresthesia and hyperesthesia restricted to the abdomen.

Focal and multifocal neuropathies

The focal and multifocal neuropathies affect only a minority of patients with diabetes; however, they form a major clinical problem in terms of diagnosis, development of significant symptoms and signs, and often inadequate therapy. Diagnosis requires accurate and detailed clinical history and neurologic examination combined with targeted neurophysiologic tests, which differ considerably from those carried out in day-to-day practice. Because of their relatively infrequent occurrence, treatment is not evidence based.

Diabetic Lumbosacral Polyradiculoneuropathies

The pathogenic basis and treatment of diabetic polyradiculoneuropathy is a source of recent controversy as there may be two or more distinct forms of diabetic polyradiculoplexopathy. We believe that the following two categories of diabetic polyradiculoneuropathy can be made on the basis of clinically differences: 1) the more common asymmetric, painful polyradiculoneuropathy; and 2) the rare symmetric, painless, polyradiculoneuropathy. The asymmetric, painful form (also known as diabetic amyotrophy) may have an autoimmune basis, but the etiology is not clear. The natural history for diabetic amyotrophy is spontaneous improvement. Nevertheless, various immunotherapies (eg, corticosteroids and intravenous immunoglobulin (IVIg) have been tried with subsequent improvement in symptoms. Treatment is reserved only for patients with severe ongoing pain, given the significant side effects of these medications in those patients with diabetes. Prednisone and IVIg may help alleviate the pain associated with diabetic amyotrophy. Relief of pain can help patients begin physical therapy earlier, however, there are no prospective, blinded, controlled studies that demonstrate that these treatments lead to an earlier and better recovery of muscle strength compared with the natural history of the disorder. The symmetric, painless form of diabetic polyradiculoneuropathy may in fact represent chronic inflammatory demyelinating polyneuropathy (CIDP) occurring in a patient with diabetes mellitus (DM). Patients with idiopathic CIDP may improve various immunomodulating therapies, including corticosteroid treatment, plasma exchange (PE), and IVIg. In this regard, patients with the symmetric, painless, proximal diabetic polyradiculoneuropathy may also respond to corticosteroids, plasma exchange, IVIg, azathioprine, or cyclophosphamide. However, as with diabetic amyotrophy, some patients improve spontaneously without treatment. In still other patients, the neuropathy appears unresponsive to immunotherapy. In such patients, this polyradiculoneuropathy might be caused by metabolic dysfunction associated with DM. Unfortunately, from a clinical, laboratory, and electrophysiologic standpoint, it is impossible to distinguish the patients with a symmetric, painless diabetic polyradiculoneuropathy who might respond to therapy. A trial of PE can be useful in identifying patients who might have a polyradiculoplexopathy that is responsive to immunotherapy. If patients respond to PE, they may continue to receive intermittent exchanges or be switched over to prednisone or IVIg.

Neuropathological alterations in diabetic truncal neuropathy: evaluation by skin biopsy

OBJECTIVES

To describe the neuropathological features in skin biopsies from patients with diabetic truncal neuropathy.

METHODS

Three patients with diabetic truncal neuropathy underwent skin biopsies from both symptomatic and asymptomatic regions of the chest and trunk. After local anaesthesia, biopsies were performed using a 3 mm diameter punch device (Acupunch). Intraepidermal nerve fibres (IENFs), the most distal processes of small myelinated and unmyelinated nerve fibres, were identified after staining with PGP 9.5 as previously described.

RESULTS

Diabetes was diagnosed at the time of the neurological presentation in two, and one was a known diabetic patient. All three had associated sensory-motor polyneuropathy. In all, skin biopsies showed a marked reduction of both epidermal and dermal nerve fibres in the symptomatic dermatomes, compared with skin from asymptomatic truncal areas. In one patient, a follow up skin biopsy when symptoms had improved showed a return of IENFs.

CONCLUSIONS

In diabetic truncal neuropathy, skin biopsies from symptomatic regions show a loss of IENFs. After clinical recovery, there is a return of the IENF population, suggesting that improvement occurs by nerve regeneration. These findings suggest that sensory nerve fibre injury in diabetic truncal neuropathy is distal to or within the sensory ganglia. Skin biopsy provides a possible tool for understanding the pathophysiology of the disease.

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.

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.

Diabetes and the nervous system

Hyperglycemia and its vascular complications affect the entire nervous system, contributing to increased morbidity and mortality. Chronic hyperglycemia is not only a known and major risk factor for cerebral vascular diseases but also the presence of hyperglycemia at the time of a cerebrovascular event may adversely influence the outcome. It also affects the treatment of some neurodegenerative disorders, and there are suggestions that diabetes may in fact suffer from a "chronic diabetic encephalopathy." Its varied effects on the peripheral nervous system result in several forms of diabetic neuropathies, the exact pathogenesis of which is still obscure. There is, however, some new information that may link metabolic and vascular hypotheses.

Investigation of peripheral neuropathy

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Prevalence and forms of neuropathic morbidity in 800 diabetics

We prospectively determined the prevalence of morbidity from the various forms of diabetic neuropathy over one year in a population of 800 patients with diabetes mellitus (336 type 1, 464 type 2 DM). Symptoms documented were: pain/paraesthesia in the feet, loss of feeling and the restless legs syndrome. We also documented the prevalence of: neuropathic ulcers, amyotrophy, foot drop, and oculomotor palsy. Autonomic symptoms documented were: impotence, postural hypotension and diarrhoea. The only symptoms reported by 100 non-diabetic control subjects were: loss of feeling in 2% and restless legs syndrome in 7%. In the diabetics; pain/paraesthesia was present in 13%, feeling loss in 7% and neuropathic ulcers in 2%. The prevalence of Diabetic amyotrophy (proximal femoral neuropathy) was 0.8%, oculomotor palsy 0.1% and peroneal nerve palsy 0.1%. Erectile impotence was present in 20%, symptomatic postural hypotension in 1% and diabetic diarrhoea in 1%. Overall; 22.9% of the population was afflicted by one or more problems resulting from neuropathy. Neuropathy was associated with older age (p < 0.001), and serious retinopathy (p < 0.001) in both groups of diabetics and with duration of diabetes, proteinuria (p < 0.02), hypertension (p < 0.01) and ischaemic heart disease (p < 0.02) in type 1 diabetics.

Neuropathies associated with diabetes

Diabetic neuropathy is the most frequent complication of diabetes and the leading cause of polyneuropathy in the Western world. A distal symmetric predominantly sensory polyneuropathy is the most common of the diverse neuropathies that occur secondary to diabetes. Pain is often the most bothersome and difficult to treat symptom of diabetic neuropathy. Autonomic neuropathy is a frequent feature of diabetic neuropathy and the source of many significant problems including postural hypotension, gastroparesis, diarrhea, constipation, neurogenic bladder, and male impotence. Physicians need to be familiar with the multiple, less common forms of diabetic neuropathy, as these often mimic other medical or neurologic conditions. The cause of diabetic neuropathy is not determined, but abundant evidence suggests that both metabolic and ischemic nerve injury are likely factors. These should not be considered mutually exclusive causes of diabetic neuropathy as both factors likely operate to different degrees to produce the clinical spectrum of neuropathies that are seen in diabetes. Although no effective treatment exists to cure diabetic neuropathy, improvement is possible with glycemic control and symptomatic therapy.

Endoneurial blood supply to peripheral nerves is not uniform

Peripheral nerves are not uniformly susceptible to the effects of ischemia in human and experimental ischemic neuropathies. Since endoneurial blood flow is directly proportional to the number of endoneurial capillaries, we studied endoneurial capillary density at multiple levels of the peripheral nerves of normal rats. Capillary density was lowest in the sciatic and proximal tibial nerves and significantly higher in dorsal and ventral roots and distal tibial and plantar nerves. Endoneurial capillary density corresponds to the hierarchy of susceptibility to ischemic nerve damage in human and experimental ischemic neuropathies. These findings suggest that susceptibility of peripheral nerves to ischemia is determined, at least in part, by the density of endoneurial capillaries.

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.