Some people with diabetes lose their perception of feeling in their feet. This is called Diabetic Peripheral Neuropathy (DPN) and is defined as
“the presence of symptoms and/or signs of peripheral nerve dysfunction in people with diabetes after exclusion of other causes” (Bolton 1998).
Many people will be unaware that any such problems exist and up to 50 % of people at diagnosis may present with some signs of neurological changes.
DPN can lead to various problems.
- Lose of protective sensation resulting in the inability to feel pain
- Change of shape of the foot such as clawing of the toes resulting in areas of increased pressure which may cause areas of callus especially under the metatarsal heads.
The simplest and most evidence based way to determine if a patient is suffering from DPN is to test them with a 10g monofilament.
- Sensory examination should be carried out in a quiet and relaxed setting. First apply the monofilament on the patient’s hands (or elbow or forehead) so that he or she knows what to expect.
- The patient must not be able to see whether or where the examiner applies the monofilament. There are three sites to be tested on both feet are indicated. The 1st and 5th metatarsal heads and the plantar surface of the distal hallux.
- Apply the monofilament perpendicular to the skin surface.
- Apply sufficient force to cause the filament to bend or buckle.
- The total duration of the approach – skin contact and removal of the filament – should be approximately 2 seconds.
- Apply the filament along the perimeter of, not on, an ulcer site, callus, scar or necrotic tissue.
- Do not allow the filament to slide across the skin or make repetitive contact at the test site.
- Press the filament to the skin and ask the patient whether they feel the pressure applied (‘yes’/’no’) and next where they feel the pressure (‘left foot’/’right foot’).
- Repeat this application twice at the same site, but alternate this with at least one ‘mock’ application in which no filament is applied (total three questions per site).
- Protective sensation is present at each site if the patient correctly answers two out of three applications.
- Protective sensation is absent with two out of three incorrect answers – the patient is then considered to be at risk of ulceration.
- Encourage the patients during testing by giving positive feedback.
- The healthcare provider should be aware of the possible loss of buckling force of the monofilament if used for too long a period of time.
(Taken from the prevention and management of foot problems in diabetes: a summary guidance for daily practice 2015, based on the IWGDF Guidance documents)