Peripheral and autonomic nerve function in diabetic ketoacidosis

Permanent damage of the sciatic nerve in an 8-year-old girl with newly diagnosed type 1 diabetes

Neuropathy, a complication of type 1 diabetes (T1D), is a heterogeneous group, and chronic polyneuropathy is the most common form in adults. Αn 8-year-old girl admitted with severe diabetic ketoacidosis was diagnosed with T1D. She was managed with intravenous fluids and insulin and was subsequently commenced on multiple daily subcutaneous injections of insulin. On the 7th day of hospitalisation, a right foot drop with sensory loss on the dorsal surface and cellulitis were detected and the latter responded to intravenous antibiotics. Electrophysiology demonstrated reduced nerve conduction velocity indicative of severe axonal damage of the sciatic nerve (SN). Physiotherapy along with vitamins B₆ and B₁₂ and magnesium were prescribed. Twelve months later there was no sign of clinical improvement and the selective damage of the SN was deemed to be permanent. Peripheral neuropathy can occur in children with newly diagnosed T1D.Abbreviations: DKA: diabetic ketoacidosis; DN: diabetic neuropathy; HbA1c: glycated haemoglobin; MRC: Medical Research Council; MRI: magnetic resonance imaging; PICU: paediatric intensive care unit; SN: sciatic nerve; T1D: type 1 diabetes.

Bilateral optic atrophy following diabetic ketoacidosis

Diabetic ketoacidosis (DKA) can result in neuropathic abnormalities of the somatic and the autonomous nervous systems. We report the case of a 50-year-old man with Type 1 diabetes of 20-year duration who after severe DKA lost vision in his right eye and only retain partial vision in his left. This case demonstrates that optic neural tissue is vulnerable to haemodynamic and metabolic complications of DKA.

Prospective study of autonomic nerve function in type 1 and type 2 diabetic patients: 24 hour heart rate variation and plasma motilin levels disturbed in parasympathetic neuropathy

To clarify the impact of autonomic neuropathy in diabetic patients, we have conducted a prospective study of 58 Type 1 and 51 Type 2 diabetic patients (investigated at baseline, after 4, and after 7 years). In Type 1 diabetic patients, the sympathetic nerve function (orthostatic acceleration and brake indices) and in Type 2 patients, parasympathetic nerve function (R-R interval variation; E/l ratio) deteriorated during 7 years of prospective observation. Symptoms of autonomic neuropathy were associated with signs of autonomic neuropathy (low brake indices) in Type 1 but not in Type 2 diabetic patients. In the latest assessment 24 h ECG recording was performed and blood samples assayed for neuropeptide Y (NPY) and motilin were obtained. Type 1 diabetic patients with parasympathetic neuropathy (abnormal E/l ratio) showed significantly lower SD value (less variation in the R-R intervals; 29 [17] vs 50 [16], [mean (interquartile range)]; p = 0.001) and higher postprandial plasma motilin values (70 [20] pmol l-1 vs 50 [15] pmol l-1; p < 0.01) than patients with normal parasympathetic nerve function. In Type 2 diabetic patients, sympathetic neuropathy (low brake indices) was associated with an increased frequency of ventricular extra systolic beats during 24 h ECG recording (rs = 0.65; p < 0.01). Postprandial plasma NPY levels were not associated with disturbed autonomic nerve function.

The natural history of somatosensory and autonomic nerve dysfunction in relation to glycaemic control during the first 5 years after diagnosis of type 1 (insulin-dependent) diabetes mellitus

The natural evolution of neural dysfunction was studied prospectively over 5 years following diagnosis of Type 1 (insulin-dependent) diabetes in 32 patients aged 12-36 years. Motor and sensory nerve conduction velocities, heart rate variation at rest and during deep breathing, and pupillary function were measured at diagnosis and after 3, 12, 24, 48, and 60 months. Thermal and vibration sensation thresholds were determined after 24, 48, and 60 months of diabetes. Mean HbA1 levels of months 3-60 within the normal range of less than 8.3% (7.3 +/- 0.2%) were observed in 13 patients (Group 1), while a mean HbA1 of months 3-60 greater than or equal to 8.3% (10.0 +/- 0.3%) was found in 19 patients (Group 2). Mean nerve conduction was significantly diminished in Group 2 as compared with Group 1 in at least 4 out of 6 nerves tested during months 12-60 (p less than 0.05). Both tests of heart rate variation were significantly impaired in Group 2 as compared with Group 1 after 24 and 60 months (p less than 0.05), but no differences in pupillary function were observed between the groups. Thermal discrimination but not vibration perception thresholds on the foot were significantly higher in Group 2 than in Group 1 at 40 and 60 months (p less than 0.05). Abnormalities in nerve conduction, thermal discrimination, and heart rate variation, but not vibration perception threshold and the pupillary function tests were significantly more frequent in Group 2 than in Group 1 at 60 months (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of Na+, K(+)-ATPase to delayed motor nerve conduction velocity: effect of aldose reductase inhibitor, ADN-138, on Na+, K(+)-ATPase activity

The role of sorbitol, myo-inositol, and Na+, K(+)-adenosine triphosphatase (ATPase) activity on motor nerve conduction velocity (MNCV) in streptozotocin (STZ)-diabetic rats was studied. Reduction of MNCV and Na+, K(+)-ATPase in caudal nerves appeared after 3 weeks of diabetes, and at this time treatment with aldose reductase inhibitor (ARI), ADN-138 and 1% myo-inositol supplement was begun. One percent myo-inositol supplement for 3 weeks resulted in a significant increase in myo-inositol levels in diabetic nerves, but left MNCV and sorbitol levels unchanged. In contrast, treatment with ADN-138 for 3 weeks reduced sorbitol levels in diabetic nerves and resulted in significant increases in MNCV and Na+, K(+)-ATPase in the nerves. Since ADN-138 did not restore myo-inositol levels, the increase in Na+, K(+)-ATPase levels by ADN-138 treatment was independent of myo-inositol levels. Also, nerve Na+ levels in ADN-138-treated rats were reduced and the ratio of K+ to Na+ was raised, while 1% myo-inositol supplement did not affect them. These results suggest that treatment with ADN-138 elevates MNCV through a series of processes: ARI----reduction of sorbitol level----increase in Na+, K(+)-ATPase activity----correction of K+, Na+ imbalance----increase in MNCV.

Adolescent diabetic amyotrophy

A 16-year-old boy with insulin-dependent diabetes mellitus since age five years was admitted with severe ketoacidosis, and suffered a cardiorespiratory arrest from which he made a full recovery. He subsequently developed the typical clinical picture of diabetic amyotrophy with painful asymmetrical weakness and wasting of proximal lower limb muscles. Cerebrospinal fluid protein was elevated, and electromyography showed typical changes. Diabetic amyotrophy has not previously been reported in this age group.

Effects of one year of near-normoglycemia on peripheral nerve function in type 1 (insulin-dependent) diabetic patients

Ninety poorly controlled C-peptide negative type 1 (insulin-dependent) diabetic patients with chronic complications were allocated to intensified insulin treatment with either continuous subcutaneous insulin infusion or multiple insulin injections; 83 were studied over 1 year (seven patients dropped out of the study). Peripheral nerve function was assessed by clinical examination, malleolar vibration perception threshold, and motor and sensory nerve conduction velocities (MNCV; SNCV) in the median, ulnar, peroneal, and sural nerves. In order to assess the effect of metabolic control on peripheral nerve function, the results in patients with normal mean HbA1 levels during months 3-12 of the study less than 8.6% (tight control (tc); n = 50) were compared with those with abnormal mean HbA1 greater than or equal to 8.6% (poor control (pc); n = 33). Mean blood glucose was significantly higher in pc than in tc at months 2-9 and 11 (P less than 0.05). In pc median and ulnar SNCV were significantly lower at 6 and 12 months, and ulnar and peroneal MNCV at 12 months than in tc (P less than 0.05). No significant differences between the groups were observed for median MNCV, sural SNCV, and vibration sensation. Further analysis revealed that in well-controlled patients who showed abnormal peripheral nerve tests at baseline, median, and ulnar MNCV and SNCV but not peroneal MNCV, sural SNCV, and vibration sensation were significantly improved after 12 months as compared with poorly controlled patients with initially abnormal tests (P less than 0.05). There were no differences in nerve function between well- and poorly-controlled patients who had normal nerve tests at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of diabetic neuropathy with pentoxifylline: case report

Diabetic neuropathy includes a heterogenous group of neuropathic syndromes associated with diabetes mellitus. One form of diabetic neuropathy is distal symmetric polyneuropathy, which is characterized at a late stage by intractable pain. This pain is generally refractory to present modalities of therapy except for narcotics. Pentoxifylline offers a new approach to therapy, reducing the blood viscosity and improving perfusion of ischemic microcirculation. A case report will be presented of intractable painful peripheral neuropathy responding dramatically to pentoxifylline therapy.

Treatment of peripheral neuropathies

There are three general approaches to treatment of peripheral neuropathy. First, an attempt should be made to reverse the pathophysiological process if its nature can be elucidated. Second, nerve metabolism can be stimulated and regeneration encouraged. Third, even if the neuropathy itself cannot be improved, symptomatic therapy can be employed. This review outlines the options available for each approach.

Complications of diabetes. Prevalence, detection, current treatment, and prognosis

The late complications associated with diabetes mellitus affect the eye (retinopathy and cataract), the kidney (diabetic glomerulosclerosis), the nerves (mononeuropathies, distal symmetric polyneuropathy, and autonomic neuropathy), and the large blood vessels (coronary artery, cerebrovascular, and peripheral vascular disease). With the exception of large blood vessel disease, evidence in animals and humans has suggested that the development of diabetes-associated complications is related to metabolic abnormalities associated with hyperglycemia. Although the exact mechanism by which hyperglycemia causes damage in individual tissues is unknown, a number of potentially pathogenic mechanisms have been proposed. These include increased activity of the polyol pathway, disturbance in the metabolism of myo-inositol and its phospholipid derivatives, abnormal permeability of the small blood vessels, and excessive glycosylation of various proteins. With the introduction of potent aldose reductase inhibitors, the role of increased activity of the polyol pathway (and related abnormalities in myo-inositol metabolism) in the pathogenesis of diabetes-associated complications can be clarified.

Experimental diabetic neuropathy: impairment of slow transport with changes in axon cross-sectional area

Analysis of slow axonal transport in the sciatic and primary visual systems of rats with streptozotocin-induced diabetes of 4-6 weeks duration showed impairment of the transport of neurofilament subunits, tubulin, actin, and a 30- and a 60-kDa polypeptide in both systems. The degree of impairment was not uniform. Transport of polypeptide constituents of the slow component b, such as the 30- and 60-kDa polypeptides, appeared to be more severely affected than the transport of constituents of the slow component a, such as neurofilaments. Morphometric analysis of sciatic axons revealed a proximal increase and a distal decrease of axonal cross-sectional area. It is proposed that impairment of axoplasmic transport and changes of axonal size are related. Transport impairment results in a larger number of neurofilaments, microtubules, and other polypeptides in the proximal region of the axon, which increases in size, whereas fewer neurofilaments, microtubules, and other polypeptides reach the distal axons that show a size decrease. Such changes in axonal transport and area are likely to occur in other diabetic animal models and in human diabetes.

Near normoglycaemia improved nerve conduction and vibration sensation in diabetic neuropathy

Twelve C-peptide deficient Type 1 (insulin-dependent) diabetic patients with abnormal peripheral nerve function were randomly assigned to continuation of conventional insulin therapy (CIT) or to continuous subcutaneous insulin infusion (CSII). There were no statistically significant differences at entry to the study between the two treatment groups in nerve function assessed by neurologic disability score, computer assisted sensation examination and measurements of amplitudes, distal latencies, F-wave latencies and somatosensory evoked potential latencies over the spine and conduction velocities of motor and sensory fibers of ulnar, median, peroneal, tibial, plantar and sural nerves. In addition, mean plasma glucose from 24 h profiles (12.5 vs 10.6 mmol/l, respectively) and HbA1 (11.0 vs 11.6%, respectively) did not differ significantly between the two treatment groups at entry. Despite improved glycaemia from CSII in 5 patients (one dropped out of the study after 2 months) contrasted to CIT in 6 patients (5.3 vs 9.9 mmol/l, respectively, p = 0.002) and HbA1 (8.5 vs 10.7%, respectively, p = 0.002), there were no significant differences in measurements of peripheral nerve function after 4 months. After 8 months of improved glycaemia (4.4 vs 10.2 mmol/l, p = 0.004) and improved HbA1 (8.3 vs 10.5%, p = 0.002), nerve conduction (p = 0.03) and vibratory sensation threshold (p = 0.002) were significantly better in patients treated with CSII than those who received CIT. The improvements in nerve function, although small, provide further evidence that some clinical endpoints of neuropathy are favorably influenced by improved control of glycaemia.

Stridor and parkinsonism

A patient is described with idiopathic Parkinson's disease and severe laryngeal stridor. Other than urinary frequency and urgency, not uncommon in this condition, and postoperative levodopa-sensitive postural hypotension, there were no features of generalized autonomic failure. The laryngeal stridor responded to levodopa therapy, and we are not aware that this has been reported previously.

Ganglioside treatment in diabetic peripheral neuropathy: a multicenter trial

Ganglioside treatment was evaluated with a multicenter, randomized, double-blind, controlled, cross-over vs placebo trial in 140 insulin-treated diabetic subjects with peripheral neuropathy. The patients entered the study when they showed an impairment in at least two of the electroneurographic parameters, and were assigned to two protocols according to the presence and severity of their neurological symptoms. Ninety-seven diabetic subjects with no or mild symptoms were assigned to protocol I, whereas 43 symptomatic patients were assigned to protocol II. the treatment periods lasted 6 weeks with an intermediate washout period of 4 weeks. The treatment consisted in the daily i.m. administration of 20 mg gangliosides or of placebo. Electroneurographic parameters were recorded at the beginning and at the end of each treatment period, whereas clinical and metabolic data (mean daily plasma glucose, glycosuria and glycosylated hemoglobin) were evaluated every three weeks in protocol I and every two weeks in protocol II. No change in the metabolic parameters was observed throughout the trial period. However, the treatment induced a statistically significant improvement of paresthesias (protocol II) and of some electrophysiological parameters; in particular, ganglioside treatment improved MCV of peroneal nerve (p less than 0.03) in patients of protocol I, MCV o ulnar nerve (p less than 0.002) and SCV of median nerve (p less than 0.06) in patients of protocol II. Furthermore, 22 subjects of protocol II showed a 'drug preference' while 10 preferred placebo and 9 had no preference. In conclusion, ganglioside treatment seems to have a positive effect on diabetic peripheral neuropathy, improving both some symptoms and some electrophysiological parameters.

Metabolism of phospholipids in peripheral nerve from rats with chronic streptozotocin-induced diabetes: increased turnover of phosphatidylinositol-4,5-bisphosphate

The effect of chronic streptozotocin-induced diabetes on phospholipid metabolism in rat sciatic nerve in vitro was investigated. In normal nerve incubated for 2 h in Krebs-Ringer-bicarbonate buffer containing [32P]orthophosphate, radioactivity was primarily incorporated into phosphatidylinositol-4,5-bisphosphate and phosphatidylcholine. Smaller amounts were present in phosphatidylinositol-4-phosphate, phosphatidylinositol, and phosphatidic acid. As compared to controls, phosphatidylinositol-4,5-bisphosphate in nerves from animals made diabetic 2, 10, and 20 weeks earlier accounted for 30-46% more of the isotope, expressed as a percentage, incorporated into all phospholipids. In contrast, the proportion of radioactivity in phosphatidylcholine decreased by 10-25%. When the results were expressed as the quantity of phosphorus incorporated into phospholipid, only phosphatidylinositol-4,5-bisphosphate displayed a change. The amount of isotope which entered this lipid increased 60% and 67% for 2- and 10-week diabetic animals, respectively. Increased phosphatidylinositol-4,5-bisphosphate labeling was observed when epineurial-free preparations were used or when the composition of the incubation medium was varied. Sciatic and caudal nerve conduction velocities were decreased after 10 and 20 weeks but were unchanged after 2 weeks. We conclude that an increase in the turnover of phosphatidylinositol-4,5-bisphosphate in sciatic nerve from streptozotocin-diabetic rats appears relatively early and persists throughout the course of the disease. This metabolic alteration may be related to a primary defect responsible for the accompanying deficient peripheral nerve function.

Diabetic autonomic neuropathy. The diagnostic value of heart rate monitoring

The use of heart rate monitoring in the diagnosis of diabetic autonomic neuropathy, and its value in observing the natural history of this disorder, has been assessed. Two tests were used: measurement of heart rate variation during deep breathing and of heart rate change on standing up. Two hundred and eighty seven diabetics aged between 20 and 49 years were studied, and 21 of them were observed repeatedly over 3 to 5 years. Heart rate variation (HRV) on deep breathing proved to be the more sensitive diagnostic index of autonomic neuropathy and was abnormal or borderline in 62 of 64 patients with established autonomic symptoms. Autonomic abnormalities were also detected in some diabetics without autonomic symptoms especially in those with peripheral neuropathy, 30% of whom had abnormal HRV on deep breathing. Abnormal tests appeared to represent permanent autonomic damage and may be present for years without the development of autonomic symptoms, occasionally (7%) preceding any other manifestation of diabetic neuropathy. Serial observations of HRV on deep breathing over 3 to 5 years showed little change, although overall there was a small deterioration of autonomic function, with a decrease of HRV score of 1.0 per year. The tests used are simple, and provide quantitative bedside measurements of autonomic function. When heart rate variation is normal, autonomic neuropathy is virtually excluded.

Painful myocardial infarction in severe diabetic autonomic neuropathy

Two cases are reported of painful myocardial infarction in diabetics with severe autonomic neuropathy confirmed by abnormal autonomic function tests. Painless myocardial infarction in diabetics has traditionally been attributed to damage of cardiac pain fibres by autonomic neuropathy but other factors such as microangiopathy in the myocardium may be responsible. It may simply be that diabetics come into hospital more often for other reasons and a silent myocardial infarction diagnosed incidentally.