Foot & Ankle Institute

Monday, January 05th, 2009

Diabetic Peripheral Neuropathy

Etiology | Nerves affected | Diagnosing Peripheral Neuropathy

Autonomic Neuropathy

Name: Autonomic Neuropathy
Effects: Decrease in perspiration, dry skin, cracks, fissures
Results: Infection

This form of neuropathy occurs in up to 70% of diabetics. The autonomic component of the peripheral neuropathy may precede the onset of either sensory or motor involvement. Sympathetic fibers supply the small arteries and arterioles of the lower extremity, the sweat glands and the arrectores pilaris muscles. The effects of the autonomic neuropathy presents itself in the lower extremities in the following ways:

Vascular:
Vascular calcification resembling Monckeberg's medial calcific sclerosis as well as a vasodilation of the vessels. This latter results in an increased blood flow to the skin, subcutaneous tissues, and bone. The foot is extremly well perfused. The hyperemia weakens the bone and with continual forces on the foot leads to a Charcot collapse of the foot. The calcification of the vessels may make palpation of the pulses impossible.

Sweat Glands:
The anhidrotic skin found the the foot results in severe dryness, cracking and fissuring.

Arrectores Pilaris muscles:

Gastrointestinal:
May demonstrate as abdominal fullness, nausea, and vomiting.

Urinary System:
Bladder disturbances are occasionally present and may result in incomplete voiding, decreased frequency of voiding, incontinence, and impotence.

Sensory Neuropathy

Name: Sensory Neuropathy
Effects: Loss of Sensation/Painless trauma (Mechanical, Chemical, Thermal)
Results: Ulceration, Infection, Amputation


Normal Healthy Nerves		With nerve damage (neuropathy), pain messages are not transmitted to the brain.

Lack of protective threshold caused by sensory neuropathy allows tissue damage to go unhealed. Even if the foot demonstrates normal structure, presence of sensory neuropathy places the foot at an increased risk of ulceration from shoe wear, foreign objects in the shoe, wrinkles in the sock or from natural elliments such as heat and cold.

Motor Neuropathy

Name: Motor Neuropathy
Effects: Muscle atrophy, Change in gait, New pressure Points
Results: Foot Deformities, Ulceration, Infection, Amputation

"Muscle weakness almost invariably accompanies the sensory loss. The motor neuropathy usually involves the following muscles: "

Interosseous muscles:
The motor neurophathy involves the interosseous muscles of the feet and results in claw toe or hammertoe contractures resulting in increased pressure beneath the metatarsal heads. The claw toe deformity leaves the foot at risk for corns, callus and ulcer to develop over the high pressure areas.

Anterior Tibial Muscle:
The weakness involving the anterior tibial muscle may be profound enough to cause a dropfoot. Milder forms may still lead to a distinct dynamic imbalance which creates or exacerbates an ankle equinus deformity increasing even more the forces affecting the metatarsal, mid or rearfoot which may cause Charcot collapse.

Charcot Foot deformity is a result of the involvement of 3 nerves.