Diabetes might not even have been diagnosed when patients start to feel pain in their legs. Of course, they will not readily connect this pain with any internal disease such as diabetes, but will seek orthopaedic or other help which might lead to a long and painful medical history.
A neurologist would immediately know what is wrong because in about 50% of all patients, diabetes mellitus causes several clinical neuropathic (meaning affection of the nerves) syndromes which are the reason for this pain. Neurologists are trained to look out for certain typical pain patterns and are alarmed by them. Diabetic polyneuropathy progresses insidiously over five to ten years and can occur even long before the diagnosis Diabetes is confirmed.
There are different types of neuropathy with different typical patterns of pain distribution. For instance there is the:
Symmetric type of diabetic neuropathy
Characterized typically by sensory loss, weakness and painful burning of toes and feet. First symptoms of the symmetric polyneuropathy may appear in the sole of one foot or even involving half a toe, then gradually spreading circumferentially up both legs to the knees, then into thighs and finally the hands. The latter pattern is also termed as “stocking-glove” distribution. Neuropathy always is length-dependent, because the longest axons are the most vulnerable. Patients describe tingling, prickling, burning, numbness and a band like pressure.
Due to sensory deficits, small cuts and wounds will not be noticed by the patients at first thus causing seemingly inexplicable infections. Later, weakness of the muscles will develop, particularly expressed by the fact that patients cannot stand on their heels. With progressing sensory disturbances spreading up also into the tips of the fingers, patients will have difficulties holding objects. Most common is a painful burning in the feet which gets worse with high temperatures. Light stimuli applied to the numb areas may be experienced as extremely painful. Also an imbalance of the gait, getting worse in the dark, is a common symptom of patients with Diabetes.
When the onset of diabetes occurs at a juvenile age of the patients, neuropathies may be first noticed as late as in their thirties to fifties but when the onset takes place at an age over 50, they tend to occur readily with adult-onset. There is a known correlation between the occurrence of neuropathy, the duration and the severity of diabetes, body weight, body size and long-standing hyperglycaemia which must be investigated individually with each patient.
Apart from the above described symmetric form of neuropathy there are other diabetes related neuropathies in different classifications:
showing focal weakness or sensory loss of single nerves, mainly in one upper arm, one thigh or the cranial nerves.
Asymmetric focal and multifocal types
The distinction between the different kinds of neuropathy is crucial as far as the different approaches to diagnosis and management are concerned, but also regarding the prognosis.
The most essential part of the evaluation of diagnosis and therapy are – apart from an intensive neurological examination – the electro diagnostic studies of the nerves. The examination comprises Electromyography (EMG) and nerve conduction velocity (NCV). The EMG involves recording electrical potentials by an electrode placed into the muscle, both at rest and during voluntary contractions. The NCV is carried out by stimulating the motor and/or sensory nerves electrically. From the data recorded, informative characteristics of the recorded forms of waves can be determined, thus leading to a clear picture and appropriate treatment.
In the long-term, by way of Diabetes and Complications Control, trial patients who controlled their diabetes meticulously showed significantly less neuropathy. When symptoms of neuropathy occur in patients suffering from diabetes or early signs of polyneuropathic pain patterns as described above, occur, an early neurological examination is of the essence.
Dr. J. Marquardt, MD, PhD
German Senior Consultant in Neurology
GNC German Neuroscience Center, DHCC