Diabetic thoracic polyradiculopathy presenting as abdominal swelling

The 2017 Banting Memorial Lecture The diabetic lower limb - a forty year journey: from clinical observation to clinical science

A series of clinical research projects conducted over the past 40 years, all of which were informed by clinical observation or discussions with people with diabetes and staff colleagues are described in this review. A study of necrobiosis lipoidica diabeticorum confirmed that this rare skin complication occurs predominantly in young women with Type 1 diabetes and other microvascular complications. Biopsies of necrobiotic lesions showed destruction of superficial nerve fibres by inflammatory tissue, which likely causes the sensory loss in lesions that is pathognomonic of the condition. The development of corneal confocal microscopy as a new non-invasive surrogate marker of peripheral neuropathy in diabetes is described next and several small studies of the use of this new technique in clinical research are reported. The influence of blood glucose instability on the genesis of neuropathic pain is then explained, with results suggesting that the stability of glycaemic control may be more important than the level of control achieved. Lastly, in neuropathy, studies of gustatory sweating are discussed, including the observation that sweating in the head and neck region is more common in people with end-stage diabetic nephropathy than in those with neuropathy. The disappearance of gustatory sweating after renal transplantation suggests a metabolic cause and for those with troublesome sweating, use of the anticholinergic, anti-muscarinic, topical cream glycopyrrolate is confirmed in a randomized control trial. In the area of diabetic foot research, distended dorsal foot veins were observed to be a clinical sign of sympathetic autonomic neuropathy: raised venous Po₂ and Doppler abnormalities of blood flow are highly suggestive of arteriovenous shunting. A series of studies of the abnormalities of pressures and loads under the neuropathic diabetic foot are described: high dynamic plantar pressures are highly predictive of subsequent ulceration in the neuropathic foot. Lastly, a number of recent studies on unsteadiness and gait abnormalities when climbing and descending stairs are described. It is hoped that the art of clinical observation survives in the highly technological 21st century.

Diabetic neuropathy: achieving best practice

Peripheral neuropathy is one of the commonest complications of diabetes and the commonest form of neuropathy in the developed world.1 Diabetic polyneuropathy encompasses several neuropathic syndromes, and the commonest presentation is chronic distal symmetrical neuropathy (DSP). DSP, often associated with autonomic neuropathy, has two clinical consequences: namely neuropathic pain and foot ulceration. Both often occur in the same individual, and cause severe curtailment of quality of life. The other, less common presentations of diabetic polyneuropathy include acute painful neuropathies, and focal neuropathies (amyotrophy, pressure palsies, truncal radiculopathies, mononeuropathies and mononeuritis multiplex).2 Table 1 shows a recent classification of diabetic polyneuropathy based upon the natural history of the various syndromes.3

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.

Sensory manifestations of diabetic neuropathies: anatomical and clinical correlations

BACKGROUND

Diabetes mellitus is among the most common causes of peripheral neuropathy worldwide. Sensory impairment in diabetics is a major risk factor of plantar ulcers and neurogenic arthropathy (Charcot joints) causing severe morbidity and high health-care costs.

OBJECTIVE

To discuss the different patterns of sensory alterations in diabetic neuropathies and their anatomical basis.

STUDY DESIGN

Literature review.

METHODS

Review of the literature discussing different patterns of sensory impairment in diabetic neuropathies.

RESULTS

The different varieties of diabetic neuropathies include typical sensorimotor polyneuropathy (lower extremity predominant, length-dependent, symmetric, sensorimotor polyneuropathy presumably related to chronic hyperglycemic exposure, and related metabolic events), entrapment mononeuropathies, radiculoplexus neuropathies related to immune inflammatory ischemic events, cranial neuropathies, and treatment-related neuropathies (e.g. insulin neuritis). None of these patterns are unique for diabetes, and they can occur in nondiabetics. Sensory alterations are different among these prototypic varieties and are vital in diagnosis, following course, treatment options, and follow-up of treatment effects.

CONCLUSIONS

Diabetic neuropathies can involve any segment of peripheral nerves from nerve roots to the nerve endings giving different patterns of abnormal sensation. It is the involvement of small fibers that causes positive sensory symptoms like pain early during the course of disease, bringing subjects to physician's care.

CLINICAL RELEVANCE

This article emphasizes on the fact that diabetic neuropathies are not a single entity. They are rather different varieties of conditions with more or less separate pathophysiological mechanisms and anatomical localization. Clinicians should keep this in mind when assessing patients with diabetes on the first visit or follow-up.

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.

Diabetic somatic neuropathy

Diabetic neuropathy (DN) is the most common, most neglected and difficult to treat diabetic complication. It affects the whole body, and presents with diverse clinical pictures. The most important outcome of somatic and autonomic DN are the development of diabetic foot followed by diabetic ulceration and possible amputation. In this chapter the definition, epidemiology, pathophysiology and classification of somatic DN will be discussed. Attention will be given to various practical aspects of somatic DN of different types with their specific clinical presentation, diagnostic approaches and treatment options, including the usually rarely discussed gender differences. DN remains a problem in diabetology, compared to other micro- and macrovascular complications. The disease is rarely investigated, although simple testing devices for somatic nerve impairment exist, and remains difficult to treat because ofthe complex pathogenetic mechanisms. The main prevention/progression delaying measure for the progression of DN is the tight glycaemic control. Painful DN is common and need appropriate symptomatic relieving drugs. Future investigations must be targeted on new treatment options.

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.

Chronic inflammatory demyelinating polyradiculoneuropathy in diabetes mellitus

There is a higher incidence of demyelinating peripheral neuropathy responsive to immunomodulating treatment in patients with diabetes mellitus. The diagnosis is often overlooked and the patients are given the label of "diabetic neuropathy." Progressive symmetric or asymmetric motor deficit, progressive sensory neuropathy in spite of optimal diabetic control, and unusually high cerebrospinal fluid protein level in "diabetic neuropathy" should alert the clinician to the possibility of an underlying treatable demyelinating peripheral neuropathy masquerading as "diabetic neuropathy."

Clinical presentations of peripheral neuropathies

This article addresses the clinical presentations of different peripheral neuropathies. The topic is discussed briefly with emphasis on the most important clinical features. MR imaging of the peripheral nerves is a rapidly advancing field, and it is hoped that the basic understanding of the clinical presentations of peripheral neuropathies will encourage radiologists to get more involved in MR imaging of the peripheral nerves.

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.

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.

Diabetic neuropathy: an update

Diabetic neuropathy is the most common neuropathy in industrialized countries, with a remarkable range of clinical manifestations. The usual pattern is a distal symmetrical sensory polyneuropathy, associated with autonomic disturbances. Less often, diabetes is responsible for a focal or multifocal neuropathy affecting cranial nerves, especially oculomotor nerves, and roots and nerves innervating proximal muscles of the lower limbs. Metabolic abnormalities due to hyperglycaemia, lack of insulin and their consequences and ischaemic phenomena secondary to diabetic microangiopathy account for nerve lesions.

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.

[Abdominal neuropathy of motor expression of diabetic origin. Apropos of a case]

Authors report a case of diabetic truncal neuropathy presenting as a painful abdominal swelling. This entity, which frequently is probably under estimated, may mimic abdominal visceral pathology and patients may be subjected unnecessary to extensive diagnosis procedures.

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.

Intercostal nerve conduction study in man

A new surface technique for the conduction study of the lower intercostal nerves has been developed and applied to 30 normal subjects. The problem of the short available nerve segment of the intercostal nerves and the bizzare compound motor action potential (CMAP) of inconsistent latency while recording over the intercostal muscles, is overcome by applying recording electrodes over the rectus abdominis muscle and stimulating the nerves at two points at a fair distance away. With the use of multiple recording sites over the rectus abdominis, the motor points for different intercostal nerves were delineated. CMAP of reproducible latencies and waveforms with sharp take-off points were obtained. Conduction velocity of the intercostal nerves could be determined.

Diabetic truncal neuropathy: topography of the sensory deficit

The distributions of sensory abnormalities in 17 episodes of diabetic truncal neuropathy among 7 patients with diabetes mellitus are described. The patterns are highly variable: the distribution of adjacent main spinal nerves may be involved, resulting in a complete dermatomal band of dysesthesia, but almost two-thirds of the episodes were restricted to the distribution of the ventral or dorsal rami of the spinal nerves or branches of these rami or varying combinations of these distributions.

Abdominal muscle paralysis from herpes zoster

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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.

Diabetic neuropathies and pain

Many of the diabetic neuropathic syndromes are characterized by painful symptoms with a sensation of burning and associated with troublesome hyperaesthesia. It is important to distinguish between the acute and chronic forms of peripheral sensory neuropathy; while the former carries an excellent prognosis for symptomatic improvement within one year, the latter may cause persistent symptoms for many years. In contrast to the acute form, in which symptoms are particularly severe but abnormal neurological signs are minimal, patchy stocking and glove sensory loss together with peripheral small muscle wasting are often present in chronic sensorimotor neuropathy. Peripheral polyneuropathies are more common in patients with poor metabolic control, although recent evidence implicates blood glucose flux as a possible contributory factor to neuropathic pain. It is possible that blood glucose flux or altered peripheral blood flow leads to increased spontaneous activity in nociceptive afferent fibres which are present in the axonal sprouts that characterize small fibre neuropathy. In the diagnosis of the neuropathies, exclusion of other aetiological factors is of paramount importance as there is no specific diagnostic test for diabetic nerve damage. If there is no symptomatic improvement after a period of stable and optimal metabolic control together with simple analgesics, then the tricyclic drugs should be regarded as first line therapy. The rapid effect of these drugs suggests a peripheral rather than central mode of action.