The 4th IEEE International Conference on E-Health and Bioengineering - EHB 2013 Grigore T Popa University o{Medicine and Pharmacy, ia:ji, Romania, November 21-23,2013

Nerve Conduction Studies in Peripheral Arterial

Disease With and Without Type 2 Diabetes Mellitus Daniela Matei1, CHin Corciova1, Radu Matei3, Bogdan Ignat2, Orest Bolbocean2, Daniel Alexa2,

Cristian Dinu Popescu2 lUniversity of Medicine and Pharmacy "Grigore T. Popa" Iasi, Romania, Faculty of Biomedical Engineering,

Department of Biomedical Sciences 2University of Medicine and Pharmacy "Grigore T. Popa" lasi, Romania, Faculty of General Medicine,

Department of Neurology 3Technical University "Gh. Asachi" oflasi, Romania, Faculty of Electronics, Telecommunications and

Information Technology

Abstract-This article aims at assessing the involvement of

the peripheral nervous system for patients with ischemic

pathology of the lower limbs. We studied relationships between

the ankle brachial index and peripheral nerve function among

60 male patients with peripheral arterial disease (PAD). The

ankle brachial index was measured using a handheld Doppler

probe. Nerve function was measured in the motor fibres of the

peroneal and tibial nerves and the sensitive fibres of sural nerve.

Our study has shown in patients with peripheral arterial disease

without diabetes mellitus (DM) an axonal degeneration,

resulting in axonal polyneuropathy. In patients with PAD and

type 2 diabetes mellitus the demyelination signs were

predominant. The secondary impairment of peripheral nerves in

PAD is frequently encountered in current clinical practice. The

data resulted from our study highlight the fact that PAD cause

nerve damage, mainly affected being the patients with PAD and

DM.

Keywords-ankle brachial index, peripheral arterial disease,

nerve conduction studies, diabetes mellitus.

I. INTRODUCTION

Peripheral arterial disease (PAD) is defined as a narrowing or occlusion of the arteries supplying the lower extremities [I]. The major cause of PAD is atherosclerosis. The

prevalence of PAD increases from the age of 50 onwards and is in the range of 3% to 18%, increasing to 25% to 30% in persons over 75 years [2]. PAD is associated with a high incidence of cardiovascular events such as stroke, myocardial

infarction (MI) and vascular death [ 1], [2]. In the REACH

registry, by one year, 2 1% of patients with PAD had developed MI, stroke, cardiovascular death or hospitalization compared with 15% of patients with coronary artery disease [3]. Risk factors for PAD are cigarette smoking, diabetes mellitus (DM), hypertension, dyslipidemia, renal insufficiency, inflammation and age [I]. The risk of PAD doubles in the setting of impaired glucose tolerance and increases by 2 to 4 fold in patients with overt diabetes mellitus [4]. PAD in diabetes tends to have more severe

degrees of stenosis as compared to non-diabetic patients with

PAD [5]. Also poor glycemic control is associated with more rapid PAD progression, increased risk of amputation and mortality [I], [4].

Several non-invasive tests have been proposed for the detection of PAD. These tests include digital subtraction angiography, color duplex ultrasound, and ankle-brachial

index (ABI). The measurement of the ABI is accepted as standard for the initial diagnostic evaluation of patients with suspected PAD and for high risk asymptomatic patients [6]. The ABI is the first-line test for screening PAD; it is

inexpensive to obtain and noninvasive and has a high

sensitivity (79% to 95%) and specificity (95% to 96%) compared with angiography as the gold standard [7]. A low ankle-brachial index correlates with subsequent development of angina, MI, cardiac failure, and stroke [8]. The severity of PAD in DM correlates with the duration and severity of the disease [9]. DM may also lead to peripheral neuropathy but the extent of nervous impairment in PAD is still unknown.

This paper aims to assess the damage of the peripheral nervous system among patients with PAD with and without DM using the nerve conduction studies for the detection and characterization of peripheral neuropathy, and also to find out if the degree of peripheral vascular impairment is consistent with the extent of nervous impairment.

II. MATERIALS AND METHOD

The study analyzed from clinical and paraclinical point of

view 60 patients with PAD and 25 age related subjects

without PAD. According to IDF - International Diabetes

Federation 2005 guide criteria, the patients were divided into

type 2 diabetes mellitus (30 patients) and non-diabetics (30

patients) [ 10]. All patients with diabetes had type 2 DM and

they were treated with diet and oral hypoglycaemic agents.

Inclusion criteria for the controls were the absence of any

history of diabetes, normal levels of fasting serum glucose

and with normal values of the neurophysiologic protocol (the

978-1-4799-2373-1/13/$31.00 ©2013 IEEE

protocol includes bilateral studies of sural sensory nerves,

peroneal and tibial motor nerves). Subjects were excluded from the study if they had an active

foot ulcer or an amputation of any part of the lower limb, or if they had any major disability due to other disorders (stroke,

myocardial infarction, severe congestive heart failure etc.). All subjects participated voluntarily after being given a detailed explanation of the purpose of the study.

Body mass index (BMI, kg/m2- was calculated as weight divided by height squared), systolic (SBP) and diastolic (DBP) blood pressure were measured. In all patients there were measured bioumoral parameters.

A comprehensive vascular history and physical exam

(examination of peripheral pulses: femoral, popliteal, foot; abdominal palpation for aneurysm) were performed for all patients.

For highlighting the PAD, the ankle-brachial index was

determined using the portable Doppler device. The ABI was

calculated by dividing the highest value of systolic blood

pressure measured at ankle level, to the highest value

measured at arm level [6].

The interpretation of data obtained at ABI measurement is

the following: 0.9 - l.3 - normal values; 0.7 - 0.9 - mild

PAD; O.S - 0.7 - moderate PAD; under O.S - severe PAD;

over 1.3 - suggests calcifications and severe atherosclerotic

processes [6]. Patients with an ABI higher than l.30 were

excluded from the study. Also vascular Doppler and duplex

ultrasound was performed.

Nerve conduction studies (NCS) are non-invasive,

standardized, and provide a sensitive measure of the

functional status of nerves. NCS can determine the presence,

severity, the distribution of abnormality and whether the

pathophysiology is predominantly segmental demyelination

or axonal degeneration [ 1 1]. For electrophysiological investigations the electromyograph

Neuro-MEP Micro was used. The stimulodetection examination was realized in the motor fibers of peroneal and tibial nerves, and in the sensitive fibers of sural nerve according to the standard procedures [ 1 1]. The investigations were carried out in a warm room, the temperature of the

patient's skin being at least 32°C. The muscular response was registered with surface electrodes according to the principle

"belly-tendon", in which the active electrode is placed on the muscle belly and the reference electrode on its tendon [II].

For each motor nerve the following electro-physiological indices were studied: motor distal latency (MDL - ms), compound motor action potential (CMAP - mY), motor

nerve conduction velocity (mNCV - m/s). At the examination

of sensitive nerves the following parameters were measured: sensitive latency (SL - ms), sensory nerve action potential

(SNAP - micro V), sensory nerve conduction velocity (sNCV - m/s).

The statistical processing of data was done using the program Epilnfo 6.0. The results were expressed as mean ± standard deviation. The comparison of results was realized

using variance analysis (ANOV A). The values p < O.OS were considered statistically significant.

III. RESULTS

The data obtained from 60 patients with PAD and 2S

healthy subjects were analyzed. In patients with PAD

analyses were performed separately among participants with

and without type 2 diabetes. The three groups had no

significant differences regarding age (F=O.2, p=O.SI). The

average age was 6 1.4±S. 1 years in the control group and

62.S±7 years in patients with PAD. The anthropometric

parameters and biochemical profile of the patients from the

study groups are given in Table I. The duration of diabetes

ranged from S to IS years with a mean of 8.2 years. Most DM

patients had poor glycaemic control (mean HbA I c 8.2 ± 2. 1

%). The values of triglyceride (p<O.OI), SBP (p<O.OOI), DBP

(p<O.OI) for the PAD without DM patients were much

elevated compared with control group. Also they had HDL­

cholesterol (p<O.OI) reduced compared with control group

(Table I).

TABLE I CHARACTERISTIC OF STUDY GROUPS ACCORDING TO MORPHOMETRIC AND

B10UMORAL DATA

Parameter Control PAD without PAD with OM (n=25) OM (n=30) (n=30)

Age (years) 61.4±5.1 62.5±7 61.7±5.2 BMI (Kg/m2) 26.7±2.1 26.3±2.7 2S.1±2.06· Fasting blood

90.7±11.2··· 92.4±1l.9 12S.6±32.14·· sugar (mg/dl) HbAlc (%) 5.S±2.1··· 6.02±2.1 S.2 ± 2.1 ••

Cholesterol IS I.7±25.S·· 21 I.9±74.02 232.4±7I.9

(mg/dl) HOLcholesterol

49.7±3.3··· 44.7±4.6S** 41.27±2.71·· (mg/dl)

Triglyceride 155.2±16.S··· I 92.3±44.2** 221.2±6S.I·

(mg/dl)

SBP (mmHg) 116.5± II.S· 132.6±13.75**

129.31±16.53 *

OBP (mmHg) 66.2±9.71·· 76.6±9.36** 76.24±10.6 ABI 1.03±0.09··· 0.62±0.12*** 0.66±0.14

Data are expressed as % or means ± standard deviation; *- P< 0.05; ** - P< 0.01; *** - P< 0.001 for diflerence between controls and PAD without OM; .- P< 0.05; •• - P< 0.01; ••• - P< 0.001 for difference between PAD without and with OM • - P< 0.05; •• - P< 0.01; ••• - P< 0.001 for diflerence between controls and PAD with OM

The ABI value was decreased in PAD without DM patients

0.62±0. 12 vs 1.03±0.09 in control group with p<O.OO I.

PAD with DM patients had reduced HDL-cholesterol

(p<O.OI), pulse pressure (p<O.OS) and had triglyceride

(p<O.OS) more elevated compared with PAD without DM.

The ABT value were decreased in PAD with DM patients

0.66±0. 14 vs 1.03±0.09 in control group with p<O.OOl.

The analysis of the results of nerve conduction studies

shows that both for sensitive and motor nerves in patients

with PAD, the parameters are much reduced as compared to

the control group (Table II). The results of sural nerve

exploration show that the sensitive potential amplitude at

PAD with DM is 3.7±2.2 IlV vs 7.S±3.3 IlV for the control

group, difference with high statistical significance (p<O.O I).

The same difference with p<O.OI was found between PAD

without DM and controls (Fig. I ). Also with high statistical

significance was the difference between the sensitive

conduction velocity in sural nerve for PAD with DM

38.3±3. 1 m/s vs 45.7±5.3 m/s control group with (p<O.OI)

(Table II). Sensitive latency of sural nerve was increased in

PAD with DM (4.2±0.06 ms) vs control group (3.1±0, 1 ms)

with p<O.O \.

The peroneal nerves show signs of impairment in the sense

of mNCV decreasing in diabetics PAD (p<0.05) compared to

PAD patients without DM (Table II). Also the other

parameters such us motor action potential amplitude (p<0.05)

and the distal motor latency (p<O.O I) were neatly different in

diabetics with PAD compared to control group (Fig.2).

TABLE II RESULTS OF NERVE CONDUCTION STUDIES IN THE STUDY GROUPS

Parameter Control PAD without DM PAD with DM

n=25 n=30 n=30 Sural

SNAP (IlV) 7.5±3.3- - 5.2±3.5** 3.7±2.2-SL (ms) 3.1±0.1" 3.4±0.11 4.2±0.06"

sNCV (m/s) 45.7±5.3- - 44.5±5.3 38.3±3.1" Tibial

CMAP ( mY) 4.3±2.6- 3. 7± 1.9* 3.4±1.3" mNCV (mls) 44.1±4.27- 42.03±4.7 38.2±4.8

MDL (ms) 4.9±0.8- 5.1±1.2 5.7±1.4 Peroneal

CMAP (mV) 4.7±1.04- 2.5± 1.2* 2.8±2.2 mNCV (mls) 45.6±4-- 44.7±5.6 40.1±4.2"

MDL (ms) 3.8±2.3- - 4.7±0.7* 5.2±0.6"

Data: expressed as means ± standard deviation; *- P< 0.05; ** - P< 0.01 for difference between controls and PAD without DM; "- P< 0.05; "" - P< 0.01 for difference between PAD without and with DM - - P< 0.05; -- - P< 0.01 for difference between controls and PAD with DM

The tibial nerves show CMAP at PAD with DM is 3.4±1.3

mV vs 3.7±\.9 mV for PAD without DM, difference with

high statistical significance (p<0.05).

MDL was increased (p<0.05) and mNCV was reduced in

PAD with DM patients when we compared to the control

group (38.2±4.8 m/s vs 44. 1±4.2 m/s with p<0.05) (Fig.3). The results of Pearson correlation test, for a confidence

interval of 95% indicate a significant inverse corelation between age and the mNCV value of the peroneal nerve (r= -0.344, p<0.05); the correlation coefficients indicate a decrease in the values of conduction velocity with age.

The glycemia negatively correlated with sNCV value of the

sural nerve (r=-O.4, p<O.O I). HDL cholesterol negatively correlated with CMAP in the

peroneal nerve (r= -0.62, p<O.OOOI) and with peroneal mNCV (r= -0.48, p<O.OI).

The increased values of fasting blood glucose represent a risk factors for peripheral arteriopathy, there is a statistically

significant, positive relationship between them (p< 0.001, RR=5.2).

IV. DISCUSSION

PAD is a manifestation of atherosclerosis characterized by atherosclerotic occlusive disease of the lower extremities and is a marker for other plaques of atherosclerosis in other vascular beds [ 1]. Diabetes is an independent risk factor for PAD and PAD occurs more frequently in diabetics than in non-diabetics [5]. In diabetes, the risk of PAD is increased by age, duration of diabetes, glycaemic control, and presence of peripheral neuropathy [ 10]. Risk factors like smoking and hypertension are associated with proximal impaired of the aorto-iliofemoral arteries.

).tV Sensory nerve action potential in sural nen'e

9 8 7 6 5 4 3 2 1 o

SNAP

• Controls

• PAD without OM

• PAD with OM

Fig. 1. Sensory nerve action potential in sural nerve in study groups (p expressed for difference between controls and PAD with and without DM)

mV

4,5 4

3,5 3

2,5 2

1,5 1

0,5 o

Compound motor action potential in peroneal and tibial nerves

CMAP peroneal

CMAPtibial

• Controls • PAD without DM • PAD with DM

Fig. 2. Compound motor action potential in peroneal and tibial nerves in

study groups (p expressed difference between controls and PAD without DM

for peroneal nerve and difference between controls and PAD with DM for

tibial nerve)

Nerve conduction velocity values in study groups

sNCV sural mNCV

peroneal

mNCVtibial

• Controls

• PAD without OM

• PAD with OM

Fig. 3. Sensitive nerve conduction velocity in sural nerve (sNCV), motor nerve conduction velocity (mNCV) in peroneal, tibial nerves in study groups

(p expressed for diflerence between controls and PAD with DM)

Diabetes is associated with femoral-popliteal and tibial

PAD, commonly affected are the small vessels [9]. Chronic hyperglycemia contribute to initiation of diabetic

complications like PAD and diabetic peripheral neuropathy (PN). Among pathophysiological mechanisms involved are: the polyol pathway [ 12]; nonenzymatic glycation of proteins which increases advanced glycation end-products (AGEs) [ 13]; hexosamine pathway [ 14]; protein kinase C pathway [ 15]; increased oxidative stress; overproduction of endothelial growth factors [ 16]; loss of neurovascular support [ 17].

Accumulation of sorbitol and fructose in nerve cells results in reduced nerve myoinositol, impaired membrane Na+!K+-ATPase activity, and axonal transport [ 12]. The

accumulation of AGE and free radicals can have toxic damages to Schwann cells [ 13]. Increased polyol synthesis reduces the bioavailability of nitric oxide (NO) which leads to decreased nerve blood flow [ 18]. Microangiopathy is considered to produce ischemia in diabetic nerves [ 17], [ 18].

Nerve conduction studies may be used in confirming the presence of neuropathy, evaluation of the underlying pathologic process: axonal loss or demyelination [ 19]. The

signs of demyelination are decrease of the nervous conduction velocities, decrease of the motor action potentials, and an extension of the distal latencies [20]. On the contrary, axonal neuropathies are characterized by a reduction in amplitude of the motor action potentials, with a relative conservation of the nervous conduction velocity [20].

Our study has shown by electroneurographic investigation, in case of nervous impairment associated with PAD without OM, reduced SNAP of sural nerve, decreased CAMP of peroneal nerve and increased MDL of peroneal nerve. Motor

nerve conduction showed only minor reductions in patients with PAD. Therefore we concluded that PAD causes axonal degeneration, resulting in axonal polyneuropathy. In patients with PAD and DM we found prolongation of distal motor latencies, decrease of motor and sensory nerve conduction velocities, and reduction in amplitude of the compound muscle action potential. A severe impairment of sural and peroneal nerve velocities was evident in OM patients. At these patients the demyelination signs were predominant.

A possible limitation of our study is the presence of a limited number of subjects. This decreases the statistical power of our study to detect differences between the groups.

Larger studies are needed to investigate the possible mechanisms linking PAD and PN and to determine whether PAD predicts the development and progression of PN.

V. CONCLUSION

The secondary impairment of peripheral nerves in PAD is frequently encountered in current clinical practice.

Our study has shown in patients with peripheral arterial disease without diabetes mellitus an axonal degeneration, resulting in axonal polyneuropathy. In patients with peripheral arterial disease and type 2 diabetes mellitus the demyelination signs were predominant. The data resulted from our study highlight the fact that PAD cause nerve damage, mainly affected being the patients with PAD and DM.

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