Banting memorial lecture: from clinical observation to improved care in diabetic neuropathy
Friday 10th March
medwireNews: In the final named lecture of the conference – the Banting memorial lecture – Andrew Boulton outlined 40 years of research leading to our current understanding of diabetic neuropathy.
Boulton, who is Consultant Physician at Manchester Royal Infirmary and Professor of Medicine at the University of Manchester, began by emphasizing the importance of listening to patients.
“Each of the research projects was informed by interaction, not only with colleagues, but also with patients, through listening to what they were saying, observing, looking, and seeing the problems,” he said.
The first part of Boulton’s lecture covered necrobiosis lipoidica diabeticorum, a rare complication of diabetes affecting approximately 0.3% of patients. He explained that the condition is most commonly seen in patients with type 1 diabetes, and involves destruction of the superficial nerves by necrobiotic tissue, manifesting as skin lesions occurring mainly on the lower part of the legs.
In an analysis of 25 patients with necrobiosis lipoidica in Miami in the 1980s – 24 of whom had type 1 diabetes – Boulton and colleagues observed that necrotic tissue lesions occurred primarily under the apparently normal skin surrounding the visible lesions, and all patients had no sensation in the lesions due to destruction of superficial nerves by the necrobiotic tissue. This loss of sensation “is helpful in the differential diagnosis from other conditions,” he said. In terms of managing the condition, Boulton remarked that “there will never be any randomized controlled trials of treatments because it is so rare.” However, he suggested that injecting steroids into the perilesional skin – where the lesion is most active – may be beneficial.
Boulton discussed the importance of establishing a full clinical history to identify diabetes complications, giving the example of a patient who was admitted to hospital for a week’s worth of tests, before being diagnosed with thoracic neuropathy after Boulton established the patient was experiencing allodynia. “The moral of this story is to always take a history and look at your patient,” he said.
He then described the current standards for assessing diabetic neuropathy – clinical neurologic examination, followed by electrophysiology, sensory testing, and skin/nerve biopsy – and outlined the evidence supporting the use of corneal confocal microscopy as a marker of neuropathy. Nerve fiber length, branching density, and fiber density as measured by this technique are progressively reduced among patients with mild, moderate, and severe neuropathy, he said. “Therefore, corneal confocal microscopy is a useful surrogate that can be used non-invasively and potentially for the assessment of new treatments.”
In the last part of his presentation, Boulton outlined the results of foot pressure studies and discussed the impact of diabetes on gait and steadiness.
“The warm but insensate foot is the at-risk foot in diabetes,” he said, describing studies showing that foot pressure abnormalities – sometimes linked to wearing ill-fitting shoes – precede the development of neuropathy, and that high foot pressures predict ulcers.
An investigation comparing the incidence of neuropathy among a group of patients with diabetes and a group of patients with rheumatoid arthritis who had similarly elevated foot pressures found that 32% of the patients with diabetes had a history of foot ulcers, compared with none of the patients with rheumatoid arthritis. Furthermore, the patients with diabetes had severe neuropathy, whereas patients in the rheumatoid arthritis group had mild or no neuropathy. Together, these findings indicate that high pressures alone do not cause foot ulceration, Boulton concluded.
He explained that unsteadiness is a very common symptom of neuropathy, and patient perception of unsteadiness correlates strongly with lab tests of imbalance. He also highlighted study results from a gait laboratory with a staircase showing that patients with diabetes have less accurate stepping than those without.
“Diabetic peripheral neuropathy has a huge increased risk of falls and trips compared with age-matched controls,” he said. “The next question is: can we do something about this?”
In a 16-week pilot study in which patients were allocated to an exercise training intervention or a control group, muscle strength in the ankles and knees when ascending and descending stairs significantly improved as a result of the intervention, suggesting that exercise training “may help balance and reduce falls,” he said.
To round off his lecture, Boulton reiterated the importance of “clinical observation, of listening to patients, looking, and observing.” Quoting Sir Dominic Corrigan, he said: “The trouble with most doctors is not that they don’t know enough, but they don’t see enough.”
And according to Professor James Lindsay, “for one mistake made for not knowing, 10 mistakes are made for not looking.”
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