How Common Is Diabetic Neuropathy Or Is It A Rare Disease?
Diabetic neuropathy is very common sequelae of diabetes, which is characterized by clinical manifestations of peripheral nerve dysfunction in diabetics after ruling out other causes of neuropathy. It is also the commonest cause of peripheral neuropathy. It is estimated the diabetic neuropathy is present, either as clinical or subclinical form, in about two-thirds of all patients with diabetes, which increases with the duration of diabetes mellitus. A study estimated that the incidence of diabetic neuropathy increased from 7.5% on diagnosis to 50% after 25 years of follow up.(1)
Diabetes mellitus is more common in Indians than the Western world with a prevalence of 4.3% and 1-2%, respectively. Although the incidence of diabetic neuropathy is not known, a study from South India estimated it to affect 19.1% of individuals with type 2 diabetes. Diabetic neuropathy is the most common cause of hospitalizations than other complications of diabetes and is more frequently associated with non-traumatic amputation. Diabetic autonomic neuropathy is also associated with silent attacks of myocardial infarction and shortening the life span of patients that results in death in 25-50% of patients within 5-10 years.(1)
Classification Of Diabetic Neuropathy
There are various types of diabetic neuropathies, which can be subdivided into symmetrical and asymmetrical diabetic neuropathy. Symmetrical diabetic neuropathy includes diabetic polyneuropathy, painful autonomic neuropathy, painful distal neuropathy with weight loss “diabetic cachexia”, insulin neuritis, polyneuropathy after ketoacidosis, polyneuropathy with glucose impairment, and chronic inflammatory demyelinating polyneuropathy with diabetes mellitus. Asymmetrical diabetic neuropathy consists of radiculoplexoneuropathies (lumbosacral, thoracic, cervical), mononeuropathies, median neuropathy at the wrist, ulnar neuropathy at the elbow, peroneal neuropathy at the fibular head, and cranial neuropathy.(1)
Accounting for 75% of all diabetic neuropathy, distal symmetrical polyneuropathy is the most common type of diabetic neuropathy. It can involve sensory or motor branches or may involve both of them. It can be further classified into large fiber neuropathy and small fiber neuropathy. In large fiber neuropathy, there is no pain and paresthesia is accompanied by vibration impairment, joint position, touch and pressure sensations, and loss of ankle reflex. Finally, sensory ataxia may occur when the disease in its advanced stage. Large fiber neuropathy leads to nerve conduction abnormality and slowing that disrupts the daily activities while impacting the quality of life. Small fiber neuropathy is associated with pain, burning and there is disruption in pain and temperature sensations with normal nerve conduction that is mostly associated with autonomic neuropathy. Small fiber neuropathy is mostly associated with increased morbidity and mortality.(1)
Nearly 10% of patients with diabetes constantly have pain that may be associated with other symptoms such as burning, pins and needles, tingling, cold, shooting, aching, sharp, cramping or allodynia. Feet are more commonly affected than hands and the symptoms are worsened at night. In some patients, the pain lasts for more than 6 months known as chronic painful diabetic neuropathy. Small fibers are mostly affected and they may be affected even before the clinical diagnosis of diabetes mellitus and this is termed as ‘impaired glucose tolerance neuropathy’. Some patients with recently diagnosed diabetes mellitus may experience intermittent pain and paresthesia in their lower extremity, which improves as glucose level is controlled.(1)
Diabetic autonomic neuropathy can range from being asymptomatic to having severe cardiovascular, sudomotor, gastrointestinal, genitourinary and endocrine abnormalities. Orthostatic hypotension, resting tachycardia and heart rate unresponsiveness are common features of diabetic autonomic neuropathy. It mostly goes undiagnosed for a very long time due to the varied nature of its symptoms.(1)
Diabetic proximal neuropathy can lead to weakness in the proximal diffuse lower extremity or thoracic radiculopathy. The weakness of pelvifemoral muscles is seen along with pain in the hip, low back, hip, anterior thigh that is mostly unilateral. Wasting of thigh and leg muscles along of reduced or absent knee reflex pursue. Multiple neuropathies may also exist at a given time that may affect more than one nerve.(1)
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