Diabetic neuropathy

Nitric oxide-sensitive protein ADP-ribosylation is altered in rat diabetic neuropathy

Endogenous ADP-ribosylation of proteins was studied in retina crude extract, membrane and cytosolic fractions of control and diabetic rats. ADP-ribosyltransferase activity is present in all cellular fractions, but protein ADP-ribosylation is reduced in diabetic rat retina. At least 6 proteins are labelled in the crude extract fraction and a similar number in the membrane preparation of control animals. In these preparations from diabetic retina, only two bands were labelled, the 85 K and 36 K for the crude extract, and the 97 K and 39 K for membranes. Labelling of 36 K and 39 K proteins was much less than in controls. In the cytosolic preparations of controls, two proteins of 85 K and 39 K are ADP-ribosylated, while in diabetic rat retina cytosol, only the 85 K is labelled. Treatment of diabetic rats with insulin normalized plasma glucose levels and prevented the alterations of the extent of ADP-ribosylation for the 38 K cytosolic, 39 K membrane and 36 K crude extracts proteins, but it failed to affect the other bands. These results suggest a hyperactivity of endogenous ADP-ribosylases in diabetic rat retina, so that the protein sites for ADP-ribosylation are no longer available. Since insulin treatment prevents the onset of neuropathy and of retinal G protein impairment (Abbracchio et al., J Neurosci Res 29:196-220, 1991) in diabetic rats and, in this study, normalizes ADP-ribosylation of 39 K, 38 K and 36 K proteins, we suggest that the abnormal endogenous ADP-ribosylation of these proteins might play a role in the onset of diabetic neuropathy.

The efficacy of aldose reductase inhibitors in the management of diabetic complications. Comparison with intensive insulin treatment and pancreatic transplantation

Recently, aldose reductase inhibitors (ARIs) have been registered in several countries for the improvement of glycaemic control. However, their efficacy is still controversial. ARIs inhibit the enhanced flux of glucose through the polyol pathway. As such, they can never be more effective than normoglycaemia, and so their potential benefits and limitations should be considered relative to the effects of prolonged euglycaemia. The clinical effects of ARIs can be put into perspective by assessing the effects of improved glycaemic control attained in randomised trials of intensive insulin treatment [such as the Diabetes Control and Complications Trial (DCCT)] and after pancreatic transplantation. Although direct comparison of these 3 interventions is hampered by differences in patient populations, duration and methods of follow-up and in the potency of ARIs, the effects of these 3 metabolic interventions and their course in time appear remarkably similar. For neuropathy, all 3 interventions induce an increase in average motor nerve conduction velocity of approximately 1 m/sec during the first months of treatment. At the same time, improvement of painful symptoms may occur. These changes probably largely represent a metabolic amelioration of the condition of the nerves. Around the second year of treatment with all 3 forms of metabolic improvement, an acceleration of nerve conduction of a similar magnitude occurs, with signs of structural nerve regeneration and some sensory recuperation. Experience with ARIs in nephropathy is still limited, but similar improvements in glomerular filtration rate and, less consistently, in urinary albumin excretion were found during short term normoglycaemia produced by all 3 forms of treatment. Comparison of a small number of studies, however, shows differences between intensive insulin regimens, pancreatic transplantation and ARIs in effects on retinopathy. Retinopathy often temporarily deteriorates in the early phases of improved glycaemic control, but this is not noted with ARIs. New microaneurysm formation was slightly reduced in a single long term study with the ARI sorbinil, but the preventive effects on the overall levels of retinopathy seemed less strong than in normoglycaemia trials of similar duration. However, the pharmacodynamic effects on inhibiting the polyol pathway differ among ARIs, and the half-life of the inhibiting effect of sorbinil may have been too short for a complete reduction of polyol pathway activity. The trials of prolonged intensive insulin therapy and pancreatic transplantation have demonstrated that very strict metabolic control must be maintained continuously for many years before a significant reduction of complications can be demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)

Dorsal root ganglia microenvironment of female BB Wistar diabetic rats with mild neuropathy

Abnormalities in the microenvironment of dorsal root ganglia (DRG) might play a role in the pathogenesis of sensory abnormalities in human diabetic neuropathy. We examined aspects of DRG microenvironment by measuring local blood flow and oxygen tension in the L4 dorsal root ganglia of female BB Wistar (BBW) diabetic rats with mild neuropathy. The findings were compared with concurrent measurements of local sciatic endoneurial blood flow and oxygen tension. Diabetic rats were treated with insulin and underwent electrophysiological, blood flow and oxygen tension measurements at either 7-11 or 17-23 weeks after the development of glycosuria. Nondiabetic female BB Wistar rats from the same colony served as controls. At both ages, BBW diabetic rats had significant abnormalities in sensory, but not motor conduction compared to nondiabetic controls. Sciatic endoneurial blood flow in the diabetic rats of both ages was similar to control values, but the older (17-23 week diabetic) BBW diabetic rats had a selective reduction in DRG blood flow. Sciatic endoneurial oxygen tensions were not significantly altered in the diabetic rats. DRG oxygen tension appeared lowered in younger (7-11 week diabetic) but not older (17-23 week diabetic) BBW rats. Our findings indicate that there are important changes in the DRG microenvironment of diabetic rats with selective sensory neuropathy.

Complaints of neuropathy related to the clinical and neurophysiological assessment of nerve function in patients with diabetes mellitus

To determine the value of a detailed evaluation of neuropathic sensory complaints in assessing diabetic polyneuropathy, a questionnaire listing different sensory symptoms was compared with a clinical and neurophysiological examination of the peripheral nerves. Thirty-seven insulin dependent and thirty-one non-insulin dependent diabetic patients who were consecutively referred because of suspected polyneuropathy were investigated. In all patients both clinical and neurophysiological examination confirmed the diagnosis of polyneuropathy. Only the scores of the clinical examination were significantly correlated with the scores of the sensory symptoms (r = 0.31, P < 0.01). Using a factor analysis, a dimension of complaints of sensory alteration could be distinguished from a dimension of complaints of neuropathic pain (alpha coefficients 0.88 and 0.86, respectively). Tingling sensations turned out to be an expression of the dimension of complaints of sensory alteration. The scores of clinical and neurophysiological examinations were only significantly correlated with the dimension of sensory alteration (r = 0.38, P < 0.002; r = 0.37, P < 0.02, respectively). We conclude that only symptoms of numbness and tingling sensations in hand and feet are associated with objectively assessed diabetic polyneuropathy.

Somatosensory evoked potentials in non-insulin-dependent diabetics with different degrees of neuropathy

Changes in median nerve somatosensory evoked potential (SEP) in diabetic patients have amply been reported. However the relationships between the diabetic polyneuropathy and the abnormalities of SEPs are still a matter of discussion. To elucidate these relationships, we have studied SEPs in 38 non-insulin-dependent diabetics with mild or severe degree of peripheral neuropathy. Our principal findings are as follows. (i) The wrist-Erb point (EP) conduction velocity (WECV) and the EP-N13 interpeak latency are significantly altered in diabetics. The N11-N13, N13-N20 and N13-P22, interpeak latencies are within the normal range. (ii) The WECV is more reduced in patients with severe neuropathy than in those with mild neuropathy, whereas the degrees of neuropathy have no influence on the alterations of EP-N13 interpeak latency. (iii) No significant correlation is found between the WECV and the EP-N13 interpeak latency. (iv) The WE conduction velocity was significantly correlated with both motor and sensory peripheral nerve conduction velocities. On the contrary, no correlation is found between these latter peripheral parameters and the EP-N13 interpeak latency. These findings indicate that the alteration in the tract from brachial plexus to the posterior column could not be a parallel process of distal neuropathy of non-insulin-dependent diabetic patients.

Comparison of prostaglandin E1- and prostaglandin E2-induced hyperalgesia in the rat

We have studied prostaglandin E1-induced mechanical hyperalgesia in the rat hindpaw, by assessing paw-withdrawal thresholds, before and after injecting prostaglandin E1 alone or with other agents, in normal and streptozotocin-induced diabetic rats. In normal and diabetic rats, prostaglandin E1 (1-1000 ng) produced a dose-dependent decrease in mechanical nociceptive threshold. In diabetic rats, prostaglandin E1 was more potent than in normal rats, in producing hyperalgesia, whereas prostaglandin E2 hyperalgesia was not changed in normal and diabetic rats. Prostaglandin E1-induced hyperalgesia was not inhibited by E-type 1 prostaglandin receptor antagonists, SC19220 or SC51089, either in normal or diabetic rats. In fact, in the presence of SC19220, prostaglandin E1 produced enhanced hyperalgesia, in normal rats. Prostaglandin E1 hyperalgesia was not significantly modified by sympathectomy or indomethacin. Unlike prostaglandin E2, prostaglandin E1 hyperalgesia was not blocked by the inhibitor of the stimulatory guanine nucleotide-binding regulatory protein, guanosine 5'-O-(2-thiodiphosphate). It is suggested that prostaglandin E1 decreases primary afferent nociceptive threshold directly, by activating a prostaglandin receptor other than the E-type 1 prostaglandin receptor, and that this receptor is not coupled to a stimulatory guanine nucleotide-binding regulatory protein.

Aldose reductase inhibitors and their potential for the treatment of diabetic complications

Aldose reductase converts glucose to sorbitol, which is further processed to fructose. The enzyme is present in most tissues and its possible physiological role is to produce an electrically neutral, non-diffusible osmolyte in cells exposed to hypertonicity, as typified by the renal medullary cells of the loop of Henlé. The enzyme has a low affinity for glucose, and under normal conditions it processes little substrate. However, in diabetes mellitus, the marked rise in intracellular glucose that occurs in some cells causes marked production of sorbitol. The increased flux and accumulation of sorbitol is damaging to cells and may result in some of the long-term complications of diabetes. In this review, David Tomlinson, Elizabeth Stevens and Lara Diemel discuss the role of aldose reductase and the potential of its inhibitors as therapeutic agents targeted at chronic diabetic complications.

Cerebral function in diabetes mellitus

Diabetes mellitus is a common metabolic disorder associated with chronic complications such as nephropathy, angiopathy, retinopathy and peripheral neuropathy. Diabetes is not often considered to have deleterious effects on the brain. However, long-term diabetes results in a variety of subtle cerebral disorders, which occur more frequently than is commonly believed. Diabetic cerebral disorders have been demonstrated at a neurochemical, electrophysiological, structural and cognitive level; however, the pathogenesis is still not clear. Probably alterations in cerebral blood supply and metabolic derangements play a role, as they do in the pathogenesis of diabetic neuropathy. Furthermore, the brain is also affected by recurrent episodes of hypoglycaemia and poor metabolic control. We describe herein the cerebral manifestations of diabetes and discuss the putative pathogenetic mechanisms.

The effect of 8 years of strict glycaemic control on peripheral nerve function in IDDM patients: the Oslo Study

We have investigated the effect of long-term strict glycaemic control on peripheral and autonomic nerve function in 45 IDDM patients (age 18-42 years, diabetes duration 7-23 years) without clinical signs of neuropathy or other neurological disease. They were randomly assigned to treatment either with continuous insulin infusion, multiple injections (4-6 times daily), or conventional treatment (twice daily) for 4 years and followed prospectively for 8 years. Motor and sensory nerve conduction velocities were measured at the start and after 8 years. Autonomic nerve function tests were performed only once, after 8 years. A significant reduction of nerve conduction velocity was observed during 8 years in patients with mean HbA1 more than 10% (n = 12, group mean 10.9%, range 10.1-13.2%) compared to patients with HbA1 less than 10% (n = 33, group mean 9.0%, range 7.5-9.9%). Change of motor nerve conduction velocity in the peroneal nerve was: -4.8 +/- 4.9 (SD) vs -2.2 +/- 5.3 m/s (p < 0.01). Change of motor nerve conduction velocity in the posterior tibial nerve was: -6.8 +/- 5.7 vs- 3.9 +/- 5.1 m/s (p < 0.05). No significant changes were observed in the ulnar nerve. Change of sensoric nerve conduction velocity in the sural nerve was: -8.9 +/- 8.0 vs -4.6 +/- 5.3 m/s (p < 0.05). Multiple regression analysis showed that a change in HbA1 of 1% resulted in a 1.3 m/s change in nerve conduction velocity during 8 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Randomized double-blind placebo-controlled trial to evaluate the effect of the ACTH4-9 analogue ORG 2766 in IDDM patients with neuropathy

In this study we report a randomized double-blind, placebo-controlled trial to evaluate the effect of ORG 2766 in IDDM patients with peripheral neuropathy. Sixty-two patients were selected based on the following criteria: abnormal vibration perception threshold above the 95th-percentile adjusted for age and/or abnormal warm temperature threshold, both measured in the right hand. The patients were randomized into two treatment groups after baseline studies: Group 1 was treated with placebo and Group 2 was treated with 3 mg of the ACTH4-9 analogue ORG 2766 every 24 h. The total study period was 1 year. After 1 year of treatment there was a significant improvement in vibration threshold in Group 1 compared to Group 2. No other parameters improved in the study period. The number of patients selected may have been too small to detect a more important treatment effect. We conclude from this study that ORG 2766 can improve vibration threshold, indicating large myelinated fibre function, but does not affect any of the other neurophysiological function tests.

Microvascular and acute complications in IDDM patients: the EURODIAB IDDM Complications Study

The prevalence of microvascular and acute diabetic complications, and their relation to duration of diabetes and glycaemic control were examined in a cross-sectional study of 3250 IDDM patients in Europe (EURODIAB IDDM Complications Study). Mean (SD) duration of diabetes was 14.7 (9.3) years. HbA1c and AER were measured centrally. Retinopathy was assessed by centrally graded retinal photography. Autonomic neuropathy was measured by heart rate and blood pressure responses to standing up. Sensory neuropathy was measured by biothesiometry. Normal HbA1c was found in 16% of patients. An AER of 20 micrograms/min or higher was found in 30.6% (95% CI 29.0%, 32.2%) of all patients, and 19.3% (15.6%, 23.0%) of those with diabetes for 1 to 5 years. The prevalence of retinopathy (46% in all patients; 82% after 20 or more years) was substantially lower than in comparable studies. Of all patients 5.9% (5.1%, 6.7%) had postural hypotension, 19.3% (17.9%, 20.7%) had abnormal heart rate variability, 32.2% (30.6%, 33.8%) reported one or more severe hypoglycaemic attacks during the last 12 months and 8.6% (7.6%, 9.6%) reported hospital admission for ketosis over the same period. Microvascular and acute complications were clearly related to duration of diabetes and to glycaemic control. However, the relation of glycaemic control to raised albuminuria differed qualitatively from its relation to retinopathy.

Low contents of nerve growth factor in serum and submaxillary gland of diabetic mice. A possible etiological element of diabetic neuropathy

Insulin and nerve growth factor are peptides that share several chemical and functional properties. While the total or relative deficiency of insulin causes diabetes, the possible disorders due to deficiency of nerve growth factor have not been clearly defined. However, the intense biological actions of nerve growth factor in the maintenance and growth of several neural cells make feasible its participation in the physiopathology of some diseases of the peripheral nervous system. We measured the contents of nerve growth factor in serum, submaxillary gland and sciatic nerve of mice with streptozotocin-induced diabetes. Nerve growth factor in diabetic mice was diminished in serum and submaxillary gland when compared with matched controls (P < 0.01). This finding further supports a similar observation in diabetic patients and suggests a possible etiological involvement of neural growth factor in the development of diabetic neuropathy.

Innervation of normal human sural and optic nerves by noradrenaline- and peptide-containing nervi vasorum and nervorum: effect of diabetes and alcoholism

Histochemical, immunohistochemical and neurochemical techniques were used to examine the innervation of epineurial nerve sheaths and fascicular nerve bundles of human sural and optic nerves from controls and patients with peripheral neuropathy due to diabetes or alcoholism. The normal distribution of autonomic nerves in both nerve trunk sheaths consisted of a dense innervation by noradrenaline (NA)-containing nerves of the vasa nervorum, together with some fibres in the nervi nervorum. Intrafascicular NA-containing nerves were only present in the sural nerve. Vasoactive intestinal polypeptide (VIP)- and neuropeptide Y (NPY)-containing nerves also innervated the vasa nervorum and nervi nervorum of the nerve sheaths, although their density was considerably less. Substance P (SP)-containing nerves were sparse and primarily intrafascicular. Neurochemical assays for NA, VIP, NPY and SP in fascicular and epineurial preparations from the sural and optic nerves confirmed the light microscopical observations. Post mortem delay significantly affected the NA levels in the sural nerve but not in the optic nerve while the NA fascicular/epineurial ratio for the sural nerve was independent of this factor. Age, sex and the presence of alcohol at time of death had no effect on transmitter levels in normal sural nerves. In the optic nerve fascicles NA levels were higher in females than in males. In patients with peripheral neuropathy there was a significant reduction in the SP fascicular/epineurial ratio in both the optic nerve, which was histologically normal, and in the sural nerve, where there was evidence of neuropathy. The NA fascicular/epineurial ratio was also significantly reduced in the sural nerve from patients with peripheral neuropathy with a possible greater effect in diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetic rats show more resistance to neuromuscular blockade induced by aminoglycoside antibiotics

1. Neuromuscular blocking effect of gentamicin and neomycin evaluated in phrenic-nerve hemidiaphragm preparation in normal and diabetic rats and IC50 of both drugs determined from LDR curves. 2. IC50 of gentamicin was 0.91 +/- 0.05 and 1.67 +/- 0.08 mmol.l-1 for normal and diabetic rats respectively. 3. IC50 of neomycin was 0.42 +/- 0.02 and 0.61 +/- 0.06 mmol.l-1 for normal and diabetic rats respectively. 4. The results show diabetic rats are more resistant to neuromuscular blocking action of aminoglycoside antibiotics (AGs). 5. Replacement of sodium by lithium (1.5 and 5 mmol.l-1) in the media, reduced this effect of aminoglycosides (AGs) significantly. 6. It appears that the prevention of AGs induced-neuromuscular blockade by lithium is not significantly different in both groups.

Correlation of preoperative urodynamic findings to postoperative complications following pancreas transplantation

Urological complications are common following pancreas transplantation with bladder drainage. Some investigators have excluded patients from pancreas transplantation because of abnormal preoperative urodynamics. To determine the risk of an abnormal bladder in bladder-drained pancreas transplantation, we prospectively evaluated 23 type I diabetic patients undergoing pancreas transplantation with preoperative urodynamics. For study purposes, criteria for an abnormal urodynamic evaluation were a bladder capacity of greater than 1,000 cc, absence of normal detrusor contractility and an abnormal voiding pattern. In addition, an abnormal study was defined by the presence of 2 or more of the following: 1) suppressed proprioception at 250 cc or at a volume of greater than 50% of bladder capacity, 2) peak flow of less than 10 cc per second, 3) interval to peak flow of greater than 30 seconds or 4) post-void residual of greater than 150 cc. Of the 23 patients 10 (43%) had abnormal preoperative urodynamic studies. All 23 patients underwent pancreas transplantation with bladder drainage, alone or in combination with a kidney transplant. The incidence of urological complications was 3.1 and 3.4 per patient, respectively, in the normal and abnormal groups (p = 0.126). Patient and graft survival rates were similar between the 2 groups (p > 0.5). We were unable to show that abnormal preoperative urodynamic studies preclude successful pancreas transplantation with bladder drainage or predict an increase in postoperative complications.

Treatment of diabetic autonomic neuropathy with an aldose reductase inhibitor

To evaluate the effects of the aldose reductase inhibitor Ponalrestat (Statil) on diabetic autonomic neuropathy, a double-blind placebo controlled trial was carried out on a group of 34 diabetic patients with documented cardiac autonomic neuropathy. After a 4-week, placebo run-in period, patients were randomised for treatment with 600 mg Statil or placebo for another 24 weeks. Moreover, the reliability of the autonomic nerve function tests was investigated by comparing the results at onset and at week 4. Fifteen patients treated with Statil and 12 with placebo completed the study. Neither symptom scores nor cardiovascular reflexes, pupil reflexes and skin vasomotor reflexes improved after Statil therapy, which led us to conclude that Statil is not effective in the treatment of diabetic autonomic neuropathy. Reliability coefficients for cardiovascular reflexes and pupil reflex showed high values, ranging from 60% to 80%. Therefore these methods are recommended in future therapy trials.

Patterns of sensory nerve conduction abnormalities in demyelinating and axonal peripheral nerve disorders

The pattern of an abnormal median-normal sural (AMNS) sensory response is associated with acute and chronic inflammatory demyelinating polyradiculoneuropathy (AIDP and CIDP) and considered unusual in other types of neuropathy, although specificity and sensitivity of this pattern have not been evaluated. We compared sensory responses (patterns and absolute values) in patients with AIDP, CIDP, diabetic polyneuropathy (DP), and motor neuron disease (MND). Using strict criteria, the AMNS pattern occurred more frequently in recent onset AIDP (39%) compared with CIDP (28%), DP (14%-23%), or MND (22%) patients. This pattern was found in 3% of control subjects. The extreme pattern of an absent median-present sural response occurred only in AIDP and CIDP patients and in no other groups. Abnormalities of both nerves were more common in long-standing polyneuropathies such as CIDP and DP compared with AIDP or MND. Median nerve amplitudes were reduced significantly in AIDP, CIDP, and DP patients compared with MND patients, whereas sural nerve amplitudes were significantly reduced only in DP and CIDP patients. These findings may reflect early distal nerve involvement particularly in AIDP patients which is highlighted by differences in median and sural nerve recording electrode placement. We conclude that, in the appropriate clinical setting, the AMNS pattern, an absent median-present sural response pattern, or a reduced median amplitude compared with the sural amplitude supports a diagnosis of a primary demyelinating polyneuropathy.

Mechanical hyperalgesia in streptozotocin-diabetic rats

Recent evidence strongly suggests that the hyperalgesia induced by agents acting directly on the primary afferent is mediated by stimulatory G-proteins and the cAMP second messenger system. In this study, we used the Randall-Selitto paw-pressure device to study hyperalgesia that develops in the streptozotocin-diabetic rat. Subcutaneous injection of streptozotocin in male Sprague-Dawley rats induced hyperglycemia and glucosuria detectable within 24 h of injection. A decrease in mechanical nociceptive threshold in the hindpaw was detected after one week. Intradermal injection of indomethacin, a cyclooxygenase inhibitor, had no significant effect on nociceptive threshold; and prostaglandin E2, which produces hyperalgesia by a direct action on the primary afferent, decreased nociceptive threshold similarly in streptozotocin-diabetic and control rats. Guanosine 5'-O-(2-thiodiphosphate), which blocks stimulatory G-proteins, attenuated the prostaglandin E2-hyperalgesia in both streptozotocin-diabetic and control rats, but had no effect on baseline nociceptive threshold in either group. Intradermal injection of either 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, or phosphodiesterase, which degrades cAMP, increased mechanical nociceptive threshold in streptozotocin-diabetic rats whilst not affecting mechanical nociceptive threshold in the control rats. Intradermal injection of 8-bromo cAMP, a membrane-permeable analog of cAMP, produced hyperalgesia of significantly greater magnitude in the streptozotocin-diabetic rats than the control rats. Intradermal injection of N6-cyclopentyl adenosine, an A1-type adenosine agonist, which can activate an inhibitory G-protein and decrease cAMP production, also increased nociceptive thresholds in streptozotocin-diabetic rats. This effect was blocked by pertussis toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Ulceration, unsteadiness, and uncertainty: the biomechanical consequences of diabetes mellitus

Diabetes mellitus, which results from a failure of the endocrine system to control blood glucose levels within normal limits, affects approximately 15% of the population over the age of 65 in developed countries. Between 20-50% of people with diabetes for more than 10 years will experience symmetrical distal sensory neuropathy resulting in a progressive, distal to proximal, loss of sensation in the lower extremities. The most common consequence is plantar ulceration that too often results in partial or total amputation of the foot. While neuropathy is a major permissive factor, plantar ulcers occur at locations of high plantar pressures. The measurement of pressure using tools developed and refined in the field of biomechanics has been shown to be a valuable asset to the management of the foot at risk for ulceration. In particular, the use of in-shoe measuring techniques has the potential to revolutionize the prescription of therapeutic footwear. Biomechanical techniques have also helped to evaluate other consequences of diabetic neuropathy on the foot such as callus formation, foot deformity, limited joint mobility and bony abnormalities. The reduction of afferent information from the lower extremities implies a lack of active feedback thought to be necessary for the control of human movements such as posture and gait. Our results show that diabetic neuropathy results in a significant increase in sway during standing that is not compensated for by other sensory systems. The study of the sagittal plane movements of the same individuals walking on a treadmill showed little effect on the kinematic control of gait when compared to age matched nonneuropathic control groups. This may indicate the dominance of efferent input over afferent feedback during gait. We believe that the study of the biomechanical consequences of diabetes can act as a model for many other diseases that have yet to come under the scrutiny of a multidisciplinary team.

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.

Diagnóstico das neuropatias periféricas diagnósticos sindrômicos, topográficos e etiológicos: syndromic, topographic and etiological diagnoses

Por avaliação retrospectiva, discriminam-se no presente estudo os diagnósticos sindrômicos topográficos e etiológicos aos quais se conseguiu chegar em 209 casos de neuropatias periféricas. A anamnese e o exame clínico-neurológico foram fundamentais para a realização dos diagnósticos sindrômicos e topográficos. A eletromiografia teve papel relevante, particularmente no que se refere aos diagnósticos topográficos. Os diagnósticos etiológicos dependeram, adicionalmente, de outros exames complementares, dentre os quais se destacam: glicemia e curva glicêmica; avaliação nutricional; avaliação familiar; biópsias de nervo, pele, faringe e seio maxilar; teste qualitativo para a presença de porfirinas na urina; ácido delta-aminolevulínico e porfobilinogênio urinários; exames radiológicos. As polineuropatias mais frequentemente encontradas foram as: etílico-carenciais, diabéticas, inflamatórias desmielinizantes agudas e hereditárias. As síndromes do túnel do carpo, as lesões traumáticas do VII nervo craniano e as neuralgias do trigêmeo foram os diagnósticos mais frequentes entre os de mono-neuropatias. A hanseníase, as lesões traumáticas! do plexo braquial e a síndrome do desfiladeiro torácico predominaram entre as multineuropatias.

Antihypoxic treatment at an early stage of diabetic neuropathy: an electrophysiological study with sabeluzole

Thirty-seven non-IDDM patients at an early stage of polyneuropathy, defined as the presence of symptoms for less than two years, as well as an abnormal perception threshold and/or abnormal thermal discrimination threshold, were treated with sabeluzole, a new antihypoxic drug, or placebo for 1 year in a double-blind, placebo-controlled study. They were examined neurophysiologically every 3 months, when motor (tibial, ulnar) nerve and sensory (sural, ulnar) nerve conduction velocities, H-reflex of the soleus muscle, SF-EMG of the anterior tibial muscle, static and dynamic pupillometry were measured. Statistical analysis did not show significant differences in nerve function between the sabeluzole group and the placebo group. There were also no significant changes within each group over the 1-year period. The results of the present study show no beneficial effect of sabeluzole on peripheral nerve function in patients at an early stage of diabetic polyneuropathy.

Clinical examination versus neurophysiological examination in the diagnosis of diabetic polyneuropathy

Several methods have been used to diagnose diabetic polyneuropathy and to quantitate the degree of affection of peripheral nerves. Using a newly developed scoring system we compared bedside clinical examination with neurophysiological examination in a group of 78 diabetic patients. Individual scores for clinical examination were significantly correlated with scores for neurophysiological examination (r = 0.7, p < 0.0005). All 78 patients had at least one clinical symptom or sign of polyneuropathy. Clinical examination indicated polyneuropathy in three patients with neuropathic complaints, while neurophysiological examination in these patients showed no abnormalities. In 12 out of 14 patients with normal neurophysiological sensory nerve function, clinical examination showed at least one abnormal sensory modality. Comparing the four different sensory modalities, light touch sense and pinprick sense indicated polyneuropathy better than vibration or position senses. An abnormal Hoffmann reflex of the soleus muscle was always associated with a decreased or absent ankle jerk. The scoring system for the clinical examination proved useful for diagnosing and quantitating the severity of diabetic polyneuropathy. Clinical sensory deficits could not be inferred from the results of neurophysiological testing of sensory nerve function. Pinprick sense, light touch sense, and ankle jerks were the most important parameters in the clinical diagnosis of diabetic polyneuropathy.

Nonenzymatic incorporation of glucose and galactose into brain cytoskeletal proteins in vitro

Initial studies demonstrated the loss of lysine and simultaneous appearance of glucitollysine in intracellular proteins following incubation with sugar. For example, when a crude nervous tissue cytoskeletal preparation was incubated in 100 mM glucose for 10 days, > 60% of the lysine residues were modified. Over 20% of the lysyl residues in a spinal cord neurofilament preparation are susceptible to Schiff base formation after one day and over 30% following five days of incubation with 100 mM glucose. When incubated with 100 mM galactose, F- and G-actin were found to be significantly modified in as few as 15 h, with > 70% of the lysyl residues lost. After 45 h of incubation, > 90% of the residues had been modified. These data also indicate that many of the lysyl residues in F- and G-actin are exposed and very susceptible to modification by sugar. This rapid and extensive modification of lysine in actin in vitro suggest that it may be modified in diabetic nervous tissue.

Subclinical diabetic neuropathy: similarities between electrophysiological results of patients with type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus

Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic patients share many clinical and biochemical characteristics. However, sural nerve biopsies from patients with advanced and chronic neuropathy show ultrastructural differences between these two groups. We investigated whether at a subclinical stage of the illness, when Type 1 and Type 2 diabetic patients are clinically uniform and the histopathological nerve alterations are not advanced, comparison between the two diabetes groups might show differences in nerve fibre involvement related to the different pathogeneses of the neuropathies. A total of 88 diabetic patients (52 Type 1 and 36 Type 2), with a subclinical form of polyneuropathy were selected. The clinical neurophysiological examination consisted of motor and sensory nerve conduction studies, Hoffmann (H)-reflex, single fibre electromyography and static as well as dynamic pupillometry. With regard to clinical neurophysiological abnormalities, the severity of the polyneuropathy appeared to be equal in both groups. Despite the absence of clinical symptoms the neurophysiological abnormalities were pronounced and it was impossible to differentiate Type 1 diabetic patients from Type 2 diabetic patients on a clinical neurophysiology basis when correcting for differences in age, height, and duration of illness. In the Type 1 diabetic group as well as in the Type 2 diabetic group the autonomic nerve fibres and nerves in the legs were more frequently affected than the thick myelinated nerves in the arms. These findings do not support the assumption that there is a difference in the manifestation of polyneuropathy between Type 1 and Type 2 diabetic patients.

Effects of uridine in the treatment of diabetic neuropathy: an electrophysiological study

The authors performed a controlled double-blind neurophysiological study (uridine vs placebo) in 40 diabetic patients with peripheral neuropathy. Twenty subjects were treated with uridine and 20 with placebo. The neurophysiological evaluation consisted of a study of the MCV of the median nerve, the common Peroneal, the posterior Tibial, the SCV of the radial nerve, the median and the sural as well as the amplitudes of the motor and sensory responses. The nerves examined were on the dominant side. The evaluations were performed at baseline and after 60, 120, 180 days of therapy with a follow up control after 90 days from the completion of therapy. No statistically significant modifications were observed in the placebo group. In the drug group, the neurophysiological parameters improved significantly from the 120th day post therapy compared with baseline and were maintained through to follow up. The authors discuss the results which demonstrated that treatment with uridine can bring about a neurophysiological improvement in peripheral nerves.

Effects of methylcobalamin on diabetic neuropathy

We studied the clinical and neurophysiological effects of methylcobalamin on patients with diabetic neuropathy. In a double-blind study, the active group showed statistical improvement in the somatic and autonomic symptoms with regression of signs of diabetic neuropathy. Motor and sensory nerve conduction studies showed no statistical improvement after 4 months. The drug was easily tolerated by the patients and no side effects were encountered.

Alteration in the levels of 1,25-(OH)2D3 and corticosterone found in experimental diabetes reduces nerve growth factor (NGF) gene expression in vitro

Circulating concentrations of corticosterone and 1,25-(OH)2D3 have been reported to be respectively increased and decreased in the streptozotocin-treated rats. Using the cell line L929 cultured in a steroid-free medium, we show that the alteration in the levels of corticosterone and 1,25-(OH)2D3 found in vivo in experimental diabetes is able to decrease the synthesis of NGF by these cells. This finding raises a possible relationship between the balance in the concentration of these steroids and some aspects of the neuropathic complications found in experimental diabetes.

Comparison of electrodiagnostic criteria for primary demyelination in chronic polyneuropathy

Three sets of electrodiagnostic criteria for establishing primary demyelination in chronic polyneuropathy are evaluated. Sensitivity is assessed in 70 patients with clinically established chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The criteria use different abnormal values, one adjusts for the effects of axonal loss, while another relies only on conduction velocity. However, even when consideration is given to sufficient number of nerves tested, there is no significant difference (P = 0.37) in diagnostic sensitivity among them, with 48% to 64% of CIDP patients fulfilling criteria for primary demyelination. Specificity is assessed by applying the criteria to 47 patients with motor neuron disease and 63 patients with diabetic polyneuropathy. No patients meet any of the criteria. Further analysis shows that as sensitivity increases specificity decreases, because of overlapping distributions of nerve conduction abnormalities in these neuropathic disorders. A sensitivity of approximately 66% is a practical limit for electrodiagnostic criteria in CIDP.

Conduction block in diabetic neuropathy

Symmetric sensorimotor polyneuropathy is a common complication of diabetes. Sensory and motor evoked amplitudes and conduction velocities are reduced. Both demyelination and axon loss have been reported in pathologic studies. Conduction block (CB), a manifestation of segmental demyelination, has not been previously studied in diabetic neuropathy. We determined the prevalence of conduction block in patients with diabetes by analyzing electrodiagnostic data from 24 diabetics. Conduction block was defined as a greater than 20% drop in peak-to-peak amplitude, and a less than 15% change in negative-peak duration between proximal and distal stimulation sites. A total of 76 nerve segments were studied. The criteria for conduction block were met in only 6 segments in 6 patients. The mean decrease in peak-to-peak amplitude between stimulation sites was 28% (range 21% to 40%). We conclude that conduction block over long nerve segments is uncommon in diabetic neuropathy, and, if present, suggests that other causes for neuropathy in diabetic patients should be sought.

Pentoxifylline in the treatment of distal diabetic neuropathy

Painful diabetic distal sensory neuropathy is a disabling and common complication of diabetes mellitus. There is evidence that microvascular changes resulting in ischemia to the vasa nervorum may contribute to this problem. Pentoxifylline has been shown to improve circulation through partially occluded peripheral vessels and has been postulated to be of potential benefit. Forty adult type II diabetics were enrolled in a double-blind, placebo-controlled study utilizing pentoxifylline for six months. Visual analog scores, nerve conduction studies, and physical examinations were used to evaluate response to treatment. At the end of the six-month trial, there was no significant difference in the patients' pain between the pentoxifylline- and placebo-treated groups. The authors conclude that pentoxifylline is not useful in the treatment of painful distal diabetic neuropathy.

Antagonistic effects of dexamethasone and 1,25-dihydroxyvitamin D3 on the synthesis of nerve growth factor

Dexamethasone is known to decrease the pool of nerve growth factor (NGF) mRNA in various experimental systems. The negative regulatory effect of the glucocorticoid was first observed in mouse fibroblast-like L929 cells, and was subsequently reported to take place in many experimental systems, including in vivo following sciatic nerve injury. Conversely, another steroid hormone, 1,25-dihydroxy-vitamin D3 (1,25-(OH)2D3) was recently reported to promote NGF synthesis in mouse L929 cells. The present work was undertaken to investigate the effect of the concomitant addition of both steroids to L929 cells. Measurements of NGF mRNA and assays of the mature protein secreted by the cells provide evidence that the negative regulation exerted by dexamethasone may be counteracted in a dose-dependent manner by the positive action of 1,25-(OH)2D3, and vice versa. Therefore, the expression of the NGF gene can be regulated in a subtle way by the balance between the two steroids. It may be expected on the basis of these observations that in tissues that are responsive to both hormones, administration of 1,25-(OH)2D3 should be able to reverse the down-regulation of NGF synthesis elicited by glucocorticoids.

Prevention and management of drug-induced peripheral neuropathy

When symptoms of peripheral neuropathy appear, the possibility that they have been induced by drugs should be considered. A large number of drugs of all kinds, several of which are considered indispensable, have been implicated in peripheral neuropathy. A list of some of these drugs is provided. Neuropathy is a universal and dose-limiting factor during treatment with vinca alkaloids, but is otherwise a rare complication of drug therapy. Drug-induced peripheral neuropathy is almost always due to a dose-dependent primary axonal degeneration caused either by toxic reactions or by metabolic changes in neurons or their surroundings. The use of drugs should be restricted, especially in patients with a risk for development of neuropathy or with already existing neuropathy, e.g. patients with hepatic or renal failure, diabetes mellitus, or malnutrition. Patients should be given vitamins, prophylactically or therapeutically, which will sometimes allow a treatment to be continued. In other cases of drug-induced neuropathy the drug should be stopped. Reversal depends on the severity of the neuropathy, intensity and duration of the treatment and existence of causative cofactors, but generally the prognosis is good. While waiting for recovery physiotherapy is of importance, and when paraesthesia and pain are troublesome the patient should be treated with carbamazepine, imipramine or lidocaine (lignocaine).

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.

Do rheological variables play a role in diabetic peripheral neuropathy?

Whole blood viscosity and its determinants were measured in diabetic patients with and without peripheral neuropathy to assess whether these variables could have a role in the microvascular aetiology of diabetic peripheral neuropathy. Although corrected whole blood viscosity at high and low shear rates (5.29 +/- 0.51 and 21.10 +/- 3.03 mPa s), plasma viscosity (1.41 +/- 0.13 mPa s), and red cell filtration ratio (0.49 +/- 0.04) in diabetic patients were significantly different from non-diabetic control subjects (high shear rate 4.83 +/- 0.54, low shear rate 17.36 +/- 2.78, plasma 1.29 +/- 0.09 mPa s, all p less than 0.001, and red cell filtration ratio 0.55 +/- 0.03, p less than 0.001) there were no significant differences between diabetic patients with neuropathy and those without. Blood rheology is altered to a similar extent in diabetic patients with and without neuropathy.

Ischaemic lumbosacral plexopathy in acute vascular compromise: case report

Anterior spinal artery syndrome (ASAS) is a well reported cause of spinal cord injury (SCI) following thoracoabdominal aortic surgery. The resultant deficits are often incomplete, typically attributed to the variable nature of the vascular distribution. Our Physical Medicine and Rehabilitation (PM and Rehabilitation) service was consulted about a 36-year-old patient with generalised deconditioning, 3 months after a stab wound to the left ventricle. Physical examination revealed marked lower extremity weakness, hypotonia, hyporeflexia, and a functioning bowel and bladder. Further questioning disclosed lower extremity dysesthesias. Nerve conduction studies showed slowed velocities, prolonged distal latencies and decreased amplitudes of all lower extremity nerves. Electromyography revealed denervation of all proximal and distal lower extremity musculature, with normal paraspinalis. Upper extremity studies were normal. Recently, 3 cases of ischaemic lumbosacral plexopathy, mimicking an incomplete SCI, have been reported. This distinction is particularly difficult in the polytrauma patient with multiple musculoskeletal injuries or prolonged recuperation time, in addition to a vascular insult, as in this patient. The involved anatomical considerations will be discussed. A review of the electrodiagnostic data from 30 patients, with lower extremity weakness following acute ischaemia, revealed a 20% incidence of spinal cord compromise, but no evidence of a plexopathy.

Increased capillary permeability to albumin and diabetic neuropathy

An increase in the capillary permeability to albumin (CPA) has been reported in diabetic patients. We observed this frequently with a non-invasive isotopic test derived from the Landis method, using 99mTc-albumin and measuring residual radioactivity externally after removal of forearm venous compression. Evidence of the independent effects of hypertension and microangiopathy on CPA has already been found. The present work was designed to investigate CPA using the same test on diabetic patients without retinopathy and clinical proteinuria. Some of these patients had objective clinical distal and symmetrical polyneuropathy. Neuropathy was clearly present in 10 of the 11 patients with an abnormal test unexplained by causes other than diabetes and in only one of the 17 patients with a normal test. The most frequent abnormality affected the late radioactivity disappearance curve, which probably reflects an impaired lymphatic wash-out of interstitial albumin. These results strongly suggest a link between peripheral neuropathy and diabetic functional microangiopathy. An elevated blood flow secondary to sympathetic nerve failure may induce an increase in CPA and a saturation of lymphatic pumping which could also be deficient due to impaired lymphatic innervation.

Evaluation of thermal and pain sensitivity in type I diabetic patients

Thermal sensitivity was studied in 280 type I diabetic patients and in 75 control subjects. Warm and cool thresholds, temperature sensitivity limen (difference between warm and cold thresholds, TSL), and hot and cold pain thresholds were quantitated on the skin of the index finger, hand, foot and medial calf. The diabetic group had mean values that were significantly different from controls in all variables except the pain thresholds in the upper extremity. TSL was the most sensitive parameter, being abnormal in 57, 63, 79 and 78% of patients in the four skin sites tested. Hot pain sensitivity was abnormal in 37, 21, 39 and 26% of patients in the same sites. Thermal sensitivity abnormalities were more frequently observed than abnormalities in motor and sensory nerve conduction studies. Thermal tests correlated with the duration of the diabetes, although there were abnormalities at all stages of the disease. The results show that diabetic neuropathy has a variable presentation in different types of nerve fibres.

Patterns of contact phase proteins indicating neuropathy in diabetic patients

In 42 outpatients of the diabetology division, coagulation and fibrinolysis variables were determined in order to detect typical patterns of results with which it was possible to discriminate between three groups with different diabetic complications (17: no complication, 7: angiopathy alone, 18: neuropathy with or without other complications). There was a statistically significant discriminatory function involving C1-inhibitor concentration, high molecular weight kininogen coagulant activity and fibrinogen as the most decisive variables. The neuropathy group was appropriately separated from the others with an 81% correct reclassification. Heparin cofactor II, histidine-rich glycoprotein, alpha 2-macroglobulin, pre-kallikrein and factor XII had no discriminative power.

Endogenous levels of nerve growth factor (NGF) are altered in experimental diabetes mellitus: a possible role for NGF in the pathogenesis of diabetic neuropathy

Sympathetic and neural-crest derived sensory neurons consisting of unmyelinated and small myelinated fibers are known to be affected at an early stage in diabetes mellitus (DM). Since these peripheral neurons need nerve growth factor (NGF) for their development and maintenance of function in adulthood, changes in endogenous NGF levels could be of relevance for the pathogenesis of diabetic neuropathy (DNP). Using an improved two-site enzyme immunoassay for NGF, we have investigated whether endogenous NGF levels are altered in Sprague-Dawley rats with DM induced by a single injection of streptozotocin (STZ). STZ-treated rats are known to develop in many respects equivalents to neuropathic complications observed in human DM. We found in some sympathetically innervated target organs decreased NGF contents by maximally 56%: transiently in the iris 2 weeks and in the ventricle 12-24 weeks after DM induction and permanently in the submandibular gland already 3 days after DM induction. Several weeks after onset of DM, NGF content was increased by maximally 145-300% in most peripheral targets investigated, such as in iris, cardiac atrium and ventricle, spleen, prostate gland, and vas deferens. This is suggestive for an impaired NGF removal by NGF-sensitive neurons in diabetic rats. Moreover, NGF levels were decreased to minimally 42.6 +/- 4% of control in the NGF-transporting sciatic nerve. NGF levels began to decrease not before 3 weeks after DM induction and remained decreased with 54.0 +/- 5% of control even after 6 months duration of DM. About the same time (i.e., 2 weeks after induction of DM) NGF levels began to decrease in the superior cervical ganglion (where the sympathetic perikarya are located) to minimally 53.2 +/- 4% of control 12 weeks after DM induction. No altered NGF levels were observed during a 3-month duration of DM in the terminal ileum and sensory trigeminal ganglion. Since NGF exerts its neurotrophic action in the perikarya after its retrograde transport from the NGF-producing periphery, our results are consistent with the hypothesis that an alteration in NGF levels may play a role in the pathogenesis of DNP as far as sympathetic neurons are concerned. Thus, our results suggest that DM influences the production and/or transport of endogenous NGF and consequently, that a deprivation of this neurotrophic factor may account for some of the functional deficits known to occur in DNP, such as impaired catecholaminergic transmitter synthesis. This hypothesis possibly opens the way for new concepts in the therapy of DNP.

Further evidence for 'pain-related' behaviours in a model of unilateral peripheral mononeuropathy

A model of experimental peripheral neuropathy producing pain-related disorders has recently been described in the rat. The present study aimed to investigate, using a different and quantifiable behavioural approach, the abnormal pain-related sensations in the animals. The neuropathy was produced by 4 ligatures tied loosely around the common sciatic nerve. 6-8 days after surgery, most of the rats exhibited pain-related disorders ipsilateral to the sciatic ligation, which became maximal 2 weeks after surgery. Mechanical noxious stimulation (pinching of the hind paw) revealed hyperalgesia in all the animals. Rats also exhibited allodynia when tested with the vocalization threshold test to paw pressure (mean vocalization thresholds were 65.5 +/- 3.6% of the preoperative control, P less than 0.01, n = 95). Tests using heat (40, 42, 44, 46 degrees C) and cold (10 degrees C) stimulation (immersion of the rat's hind paw in a bath until it was observed to struggle) indicated hyperalgesia to noxious heat (decrease of 30% in the immersion duration (ID) at a temperature of 46 degrees C), and allodynia to non-noxious heat (decrease of 30% in the temperature of the struggle threshold) and to cold stimulation (decrease by 40% in the ID). In addition, the animals showed modifications in the spontaneous postures of the affected hind paw in a natural setting, suggesting a 'spontaneous' pain-related behaviour (the mean 'pain' rating, derived from the technique used for the formalin test and numbered 0-5, was 2.8 +/- 0.4, P less than 0.01, n = 12). Lastly, sensitized responses were observed to mechanical stimulation after thermal stimulation in the non-noxious range applied to the lesioned but not the non-lesioned paw. The time course of pain-related disorders was comparable whatever the behavioural test, with recovery 2 months after surgery. These results clearly show that the neuropathy produces abnormal pain-related disorders in the rat, which are reminiscent of those observed in some human neuropathies.