European Journal of Cardiovascular Medicine

Diabetes mellitus is a global problem. The prevalence of diabetes mellitus is growing rapidly worldwide and is reaching epidemic proportions. It is estimated to increase from 4% in 1995 to 5.4% by the year 2025.According to the International Diabetes Federation (IDF) 2013 there are 67.1 million diabetics in India. WHO studies reported total diabetics in India in 2000 was 31.7 million, likely to increase to 79.4 million by 2030.[1] Type 2 Diabetes mellitus is characterized by variable degree of insulin resistance. Both type 1 and type 2 diabetes (T2DM) may occur at any age, but type-2 diabetes is mainly diagnosed after the age of 40 years .[2] So the present study is done in diabetics aged 40-50 yrs. According to the American Diabetes Association (ADA), Type 2 diabetes accounts for at least 90% of all cases of diabetes.[3] Diabetic neuropathy (DN) is one of the most commonly occurring microvascular complications accounting for 28% of all the complications in diabetics.[4] It is a progressive process that has a long asymptomatic stage. The clinical impact of diabetes is mainly manifest on the peripheral nervous system. The most common pattern of diabetic neuropathy is a Distal symmetric polyneuropathy (DSP) in which sensory symptoms and deficits predominate sensory symptoms and deficits predominate, weakness is minimal (or) absent until much later.[5] Distal symmetric polyneuropathy (DSP) is the most common form of nerve injury in diabetes, with an estimated prevalence of 50%.[6]Nerve conduction study (NCS) is the gold standard for measurement of diabetic neuropathy. It is non–invasive, least subjective single criterion.[7] Nerve damages caused by diabetes can be categorized into two groups; myelin and axonal damages categories. The nerve conduction velocity mainly reflects the myelin changes, while the action potential amplitude indicates the axonal changes and the state of the nerve fibers. The action potential amplitude is an estimate of the number of neural fibers activated by electrical stimulation, and its reduction implies an axonal damage. According to studies conducted in this field by researchers and experts, it was found that the nerve conduction velocity is more variable than the action potential amplitude and is more affected by interventions [8]Nerve conduction studies (NCS) are considered to be the most sensitive, reliable, non-invasive, and objective means of investigating diabetic neuropathy.[9-10] Routine NCS include evaluation of motor function of the median, ulnar, peroneal and tibial nerves, and sensory function of median, ulnar and sural nerves in terms of onset latency, amplitude, and conduction velocity. F waves are motor responses produced by antidromic activation of motor neurons following stimulation of motor axons peripherally. Various F-wave parameters such as minimal F-wave latency and persistence have been reported to a have a very high diagnostic reliability in diabetic patients.

The present study was undertaken for a period of   subjects, both males and females aged between 40-50 years , informed written consent was taken from the subjects. The study group consisted of 30 diabetic patients, with history of diabetes for 1-10 years and controls (Non Diabetics) were 30 age and sex matched healthy individuals. 

Criteria For Inclusion: Controls included 40-50 years aged 30 normal healthy individuals without diabetes. Subjects included 40-50 years aged 30 type 2 diabetics under control without complications on oral hypoglycemic drugs with Duration of diabetes 1-10years. 

Exclusion Criteria:

 The following criteria were excluded from the study:

1. Patients with established diabetic neuropathy, inflammatory demyelinating neuropathies, lumbar or cervical radiculopathies or any other neurologic illness which could affect peripheral nerve conduction.
2. Chronic alcoholics, smokers, and patients with a history of occupational or environmental heavy metal exposure.
3. Patients with vitamin B12, B6 deficiency, thyroid disorders, and on medication known to cause neuropathies

Nerve Conduction Study (Ncs): Nerve conduction study was done . For motor & sensory nerve study, output range was 20mA,max repeat rate 1Hz,pulse width 0.05ms stimulation with current ranging between 10-20mA was applied with increasing strength until desired response was obtained. Sensory nerves tested were Median, and Ulnar nerve. 

Stimulation And Recording Sites Of Sensory Nerves: 

Sensory nerve: Median, Method of stimulation: Orthodromic, Stimulation site : Index finger Recording site : Middle of the wrist .

 Sensory nerve : Ulnar , Method of stimulation: Orthodromic ,Stimulation site :  Little finger , Recording site :  Medial wrist 

Sensory nerve conduction study was done:

Parameters Assessed:

1. Sensory nerve action potential (SNAP) Amplitude.
2. Sensory nerve conduction velocity.

Statistical Analysis: Statistical analysis was done using SPSS version18 (software statistical package social science).students unpaired t test was used to compare Nerve conduction parameters between the study and control groups . p value was calculated.

P Value <0.001 - Highly Significant.

P Value <0.05 – Significant.

 P Value >0.05 - Not Significant.

Table 1 : Comparison of Blood Sugar Levels in Study and Control Group subjects

Table-1 depict FBS and PPBS levels in controls and diabetics. FBS, PPBS was significantly higher in diabetics (P<0.001) than controls.

Table 2: Comparison of Sensory Nerve conduction parameters in Controls and Diabetics subjects

AMP -amplitude, SNCV-sensory nerve conduction velocity.

Table-2 shows  Comparison of sensory nerve parameters in Control Group(non diabetics) and diabetics there is highly significant slowing of sensory nerves median & ulnar (p<0.001) and decrease in amplitude of Median nerve(p<0.05) in diabetics compared to controls.

Diabetic peripheral neuropathy (DPN) is an important complication and contributes to the morbidity of diabetes mellitus. Evidence indicates early detection of DPN results in fewer foot ulcers and amputations. DPN is a complex disease of progressive nerve fiber loss. A need exists for objective, simple, and reproducible assessment tools like NCS that can be readily used in clinical practice in asymptomatic stage so NCS is employed for screening diabetics for neuropathy in subclinical stage. There is a progressive neuronal involvement in diabetics which is accelerated by poor glycaemic control. The estimation of both nerve conduction velocity and the HbA1c levels in diabetics is helpful in identifying the risk category for diabetic neuropathy, which is one of the main causes for severe morbidity among the diabetes mellitus patients. The present study is done to study the neuropathy changes in diabetics and correlate it with glycemic control.[11] The present study is similar to study by Munisekhar13 et al, Hussain Gauher et al14 who found FBS, PPPS & HbA1c levels to be higher in diabetics compared to control and the values were statistically significant.[12]The neuropathy is caused by the presence of signs and symptoms of peripheral nerve disorders in diabetic patients. Nerve damage in diabetic patients has various features and the change in nerve conduction velocity is one of its symptoms. The position and characteristics of the nerve fibers, the severity of diabetes and demographic characteristics (such as age, duration of disease, and gender) are of the factors playing a key role in the severity of sensorimotor neuropathy. As mentioned earlier, such complications are common in diabetics, and somewhat predictable, but they have a wide range of changes and potency, which have been the subject of research by researchers. For example, Soivers et al (2004) have conducted a research in order to perform the clinical and electroneurographic study of peripheral nerve involvement in diabetic patients. Nerve conduction changes associated with diabetic neuropathy include declining response amplitude and conduction velocity. In the present study, a significant difference was found between the NCS parameters of cases and controls. Smaller amplitude and slower conduction velocity was found in all the nerves in both sensory and motor NCS of neurologically asymptomatic diabetic patients. Smaller amplitude reflects axonal loss and slowing of conduction velocity could be the result of a combination of segmental demyelination, loss of fastest conducting axons, and metabolic alterations.[13-14] Diabetic neuropathy is a common complication of diabetes mellitus with severe morbidity, compromising the quality of life.

Although this study was conducted on a relatively small group of patients, it provides an evidence of association between hyperglycaemia and neuropathy. Our findings propose early management of hyperglycaemia in order to prevent neuropathy in type 2 diabetes.  We observed progressive decline in sensory conduction velocity with the duration of the disease. This shows that poor metabolic control causes early onset and rapid progression of neuropathy. We conclude the study with the observation that nerve conduction study can be used as a screening tool to diagnose neuropathy in subclinical stages and overweight diabetics should be considered at risk category for aggressive glycemic control by diet, drugs and life style modification to prevent progression of neuropathy.

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