Understanding The Impact Of Diabetic Neuropathy On Gait
- Volume 21 - Issue 6 - June 2008
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Sensory neuropathy is the most common form of diabetic neuropathy. Nerve damage results from poorly managed and chronically high levels of blood sugar. In patients who have type 1 diabetes, which usually affects those 25 years and younger, there is insulin deficiency. In regard to people with type 2 diabetes, their insulin production inadequately meets the body’s daily need to metabolize sugar and starches found in such foods as bread, potatoes, rice and corn.
In sensory polyneuropathy, nerve damage occurs many years after the onset of type 1 diabetes and poor glycemic management whereas nerve dysfunction is more accelerated among those with type 2 diabetes.
Nerve damage may occur due to small nerve fiber compression by the Schwann cells. This compression occurs as enzymes in the Schwann cells catalyze sugar into a crystalline alcohol that absorbs water. Water saturation causes the cells to swell, compress and thereby strangle the nerve. Unless the process is reversed, both the Schwann cell and the small nerve fiber slowly die.
The end result of small nerve fiber compression commonly includes pain in the form of burning, prickling and/or shock-like sensation to the feet and/or to the extremities.
Nerve damage can also be caused by neuroischemia, a lack of adequate blood supply to maintain large nerve fiber vitality. By destroying large nerve fibers, neuroischemia can lead to a loss of balance and a deadening sensory loss in the extremities.
The inability of the distal or lower extremity small nerve fibers to distinguish coarse from smooth, temperature variations and other sensory stimuli aggravates anatomical deterioration.1 Accordingly, one may see the development of calluses, swelling (edema), foot ulcers and/or gangrene. The patient’s inability to distinguish changes in the body’s balance due to large nerve fiber demise leads to reduced proprioception and coordination. This may impair daily living activities and increase the risk of falls and fractures.2
Nerve damage from diabetic neuropathy also greatly increases the risks of joint dislocations and stress fractures to bone. In patients with diabetes, bone stress injuries of the foot due to polyneuropathy are atypical since these injuries present as load-related swelling rather than load-related pain. Delayed treatment or overuse may cause irreversible joint and bone damage.3
What You Should Know About Distal Neuropathy And Diabetic Drop Foot
Distal neuropathy, the most frequent type of sensory, peripheral nerve damage, may also involve the motor functions of the foot and ankle. Distal motor neuropathy progressively inhibits the muscle stretch reflexes of the ankle and knee, and results in muscle weakness. The deterioration of the peroneal nerve compromises the function of the foot and ankle muscles. It also creates a void that the Achilles tendon will fill by abnormally pronating the midtarsal joint of the midfoot.
These patients will subsequently have an equinovarus deformity of the hindfoot with ankle pronation of the forefoot. They will also have an inefficient gait characterized by the foot slapping the floor at the beginning and toe dragging at the end of a step. This is otherwise known as diabetic drop foot.
When Gait Is Affected By Sensorimotor Neuropathy