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1
Neuropathic Case Studies
1.1 Introduction
In the past we have often described the neuropathic foot as a ‘forgiving’ foot, and there is little doubt that of the four main categories of patients – neuropaths, neuroischaemics, renals and Charcots – described in this book it is the neuropathic patients who do the best. It is, however, important never to underestimate the problems of the diabetic patient with neuropathy, which is a devastating deficit. In many of these patients, neuropathy affects other anatomical systems such as the cardiovascular, gastrointestinal and urogenital systems, and not just their feet and legs, and as a result they are incredibly frail and vulnerable, with greatly increased susceptibility to infections and other insults. When managing the neuropathic patient with foot problems, particular regard must be paid to all these susceptibilities and vulnerabilities. It is often said of these patients with neuropathic feet “Good pulses, not ischaemic, not in trouble” – but the neuropathic patient is actually very fragile and may rapidly develop severe problems and therefore can get into trouble very quickly.
In choosing sections for this chapter, we have included those that substantially affect the patient with diabetic neuropathic feet: highlighting first the role of infection, the “great destroyer”, which is a real mask of Janus, putting on so many different and deceptive faces in the diabetic patient (a theme that is repeated in every chapter). Second comes the effect of neuropathy in conjunction with other co-morbidities that are present in the neuropathic patient. Third, we look at the effect of reconstruction of the deformed or unstable neuropathic foot. Fourth, we consider the significance of psychological factors, and finally, the importance of long term care.
The diabetic foot with neuropathy is very susceptible to traumatic damage, leading to a break in the skin, which then acts as a portal of entry of infection. Colleagues from Africa and India have frequently described devastating infections that rapidly destroy the neuropathic foot. Now that London is an international city we too now see patients with horrendous infections, including those who have travelled from Africa and India, and this type of rapidly destructive infection is described in this section. In temperate climes as well as tropical ones, there is increased susceptibility of the diabetic neuropathic foot to infection, and we see very severe infections where the serum C-reactive protein (CRP) can be above 400 mg/l. Furthermore, when a neuropathic patient becomes systemically unwell then almost certainly the infection is very severe. We have also learnt that diabetic neuropathic patients are prone not only to foot infections but also to devastating infections elsewhere in the body.
Aggressive treatment of infection is important, starting with wide spectrum antibiotic therapy and then targeting therapy according to bacteria isolated. It is important to have a working knowledge of the principal bacteria and their local antibiotic sensitivities, including awareness of the prevalence of resistant organisms. However, in every patient, individual sensitivities of each organism isolated on culture should be sought to guide rational antibiotic therapy. There should be close co-operation between the microbiology laboratory and the diabetic foot service. Furthermore, antibiotic therapy should be accompanied by debridement of infective and necrotic tissue. When patients present with severe infection they need expert medical treatment including careful fluid replacement. Perioperative problems are common: in the early days of the Diabetic Foot Clinic we saw a patient who suffered respiratory arrest on codeine tablets and had to be temporarily ventilated.
We have also come to learn that diabetic neuropathic patients are frail vulnerable patients and we have also considered the impact that neuropathy and also co-morbidities can have on the diabetic patient. Peripheral neuropathy itself produces a major deficit of sensation in the lower limbs. It impairs proprioception and patients with neuropathy become very unsteady, and falls and associated traumatic lesions are common. Other complications, including postural hypotension and hypoglycaemic episodes without any warnings, make accidents even more likely. Neuropathy is a devastating deficit, and it is not just the feet and legs that are affected. The diabetic patient with a neuropathic ulcer will usually have evidence of nerve damage elsewhere. Autonomic neuropathy may affect the heart, gastrointestinal system and bladder. Damage to the nerve supply of the heart can lead to silent ischaemia and silent myocardial infarction. We have seen cases of sudden death in young, apparently robust neuropathic patients who had no peripheral vascular disease. There may be poor neurological control of ventilation leading to sleep apnoea and also susceptibility to pulmonary infections. In addition to neuropathy, co-morbidities may include poor vision through diabetic retinopathy and cataract.
Key principles to remember are that neuropathic patients may become destabilised by ulceration and sepsis and that neuropathic ulcers may present in various ways, often as medical emergencies with not only severe, rapidly progressing infections but also considerable metabolic upset.
Diabetic neuropathic patients who present with ulceration and infection often have deformity of the foot that has precipitated the initial ulceration. Such patients often need surgical debridement and in addition can benefit at the same time from surgical correction. If our early neuropathic patients seen in the 1980s and 90s developed severe deformity of the feet, the standard approach was to accommodate such deformity with appropriate footwear, but it is now possible to correct the deformity surgically as well as heal the ulcers.
In addition to the impact of other co-morbidities, psychological problems are also very important. Many diabetic foot patients, when they are first referred to us, are deeply fearful, believing that they face inevitable amputation. The majority of patients rapidly gain confidence once they feel that they have found a safe haven where rapid and appropriate treatment will always be available. Patients build up relationships with the staff of the Diabetic Foot Clinic over many years, and even patients who do not always follow advice or do not always accept treatment are still cared for. However, some patients have concurrent psychological problems and remain deeply suspicious and often unwilling to accept care. Furthermore, there may be problems of self-delusion, when patients convince themselves that devastating foot infections are trivial.
We emphasize the need for long term management in a specialist Diabetic Foot Clinic for these patients.
Each diabetic neuropathic patient is unique, always beginning with the assumption that any person with diabetic neuropathy is a very vulnerable patient. It is important to have a thorough long term knowledge and understanding of the patient in order to apply effectively modern techniques for optimal diagnosis and treatment. Although we have always emphasized the need to make a clear distinction between the well perfused neuropathic foot and the neuroischaemic foot, it should never be forgotten that if a classical neuropathic patient lives long enough he is likely eventually to develop ischaemia. All the patients described in the neuroischaemic chapter will have started their diabetic foot lives as neuropathic patients. The diabetic foot is a moving target!
In this chapter we describe 36 cases of neuropathic foot disease. They fall into five main groups.
- Patients with differing presentations of infection and complications of infection.
- Patients with co-morbidities in addition to diabetes and neuropathy impacting on neuropathic foot presentations.
- Patients presenting with neuropathic foot deformity, ulceration and infection, when reconstruction to correct the deformity is carried out as well as surgical debridement for the infection.
- Patients with neuropathic feet in whom psychological factors have impacted on their management.
- Long term patients followed in the Diabetic Foot Clinic with neuropathic foot problems.
1.2 Differing presentations of infection and complications of infection
The first series ofcases in this chapter are different presentations ofinfection because these are the most serious and dramatic problems in the diabetic neuropathic foot. Even a slightly raised body temperature can mark a severe infection with the capacity to deteriorate with alarming rapidity.
Case 1.1 A slightly raised body temperature can be a marker of severe infection, which can lead to collapse within hours
A 40 year old man with Type 2 diabetes for 6 years had proliferative retinopathy and peripheral and autonomic neuropathy. Vibration sensation was absent at both great toes. He sustained plantar blisters on both his feet after walking around the house barefooted on a nylon carpet after soaking in a long hot bath (Figure 1.1a). On the first occasion he was encouraged to rest and take time off work so that the blisters would heal quickly. He did not follow this advice and developed a large neuropathic ulcer on the left forefoot (Stage 3 foot), after which he agreed to rest as much as possible and the ulcer quickly began to heal (Figure 1.1b) and was completely healed in two months. He was reluctant to wear bespoke shoes but agreed to wear trainers. Two further episodes of blistering healed quickly.
However, five years later he developed another large blister on the right foot and attended the Foot Clinic. There was no obvious spreading infection but he had local cellulitis and a body temperature of 37.7 °C and it was decided to admit him (Stage 4 foot). He insisted on going home first because he wished to take his car home as it was parked in a hospital car park. He said that he would leave his car at home and ask his brother to bring him to the hospital. He was brought back by his brother later that afternoon. In two hours he had become extremely ill, with a body temperature of 40.2 °C. He was very drowsy and shivering and had a spreading cellulitis. Blood pressure was 90/60 mm Hg. He was admitted at once. He was immediately given quadruple IV antibiotics according to our usual regime of amoxicillin 500 mg tds, flucloxacillin 500 mg qds, metronidazole 500 mg tds and ceftazidime 1 g tds. He was started on IV insulin sliding scale. Blood cultures grew Staphylococcus aureus and Group G Streptococcus and his IV antibiotics were then rationalised to amoxicillin and flucloxacillin. He was also treated with clindamycin 450 mg qds IV. The CRP on admission was 166.5 mg/l, falling to 104.2 mg/l the next day, 41.8 mg/l after two days and 19.1 mg/l after four days. On admission the white blood count (WBC) was 12.77 x 109/l, with a neutrophilia of 10.66 x 109/l, falling after four days to a WBC of 4.64 x 109/l and neutrophils normal at 2.79 x 109/l. Glycated haemoglobin was 11.7%. The blister developed into an area of necrosis (Figure 1.1c) but this gradually improved. He was discharged after 10 days. After this episode he agreed to check his feet every day and come to the Diabetic Foot Clinic regularly and he has not relapsed.
Learning points
- Systemic symptoms and bacteraemia can develop rapidly from diabetic foot infections. It is very risky to allow any delays in admission, for example when patients wish to go home to collect possessions.
- A high fever, as in this case, is usually indicative of a very severe infection and is associated with a bacteraemia. Blood cultures should be carried out on all diabetic patients with foot infections and a fever, however mild this fever is.
- The clinician should beware of even mild fever as any fever is a sign of a serious infection. However, many diabetic patients do not develop fever even when they have a foot infection.
- Clindamycin was used because the patient had signs of toxicity with high fever and clindamycin is a powerful inhibitor of streptococcal toxin synthesis.
- When using clindamycin it is necessary to be aware of antibiotic-induced colitis, especially in elderly and postoperative patients.
- Serial measurements of falling serum CRP levels can confirm progress in resolving infection.
- Staphylococcus aureus is the commonest cause of infection in the diabetic foot and is often accompanied by a streptococcal infection of either Group B or Group G and rarely Group A. These organisms act in synergy and can lead to considerable tissue necrosis because hyaluronidase, produced by the Streptococcus, facilitates the spread of toxins produced by the Staphylococcus.
Case 1.2 Even if the pedal pulses are strong, necrosis develops when infection is severe
Another common presentation of infection in the neuropathic foot is of gangrene: the diabetic black toe. Previously, necrosis in a diabetic foot with palpable pedal pulses was deemed to be due to “small vessel disease”, and the unfortunate patient often found himself on the receiving end of a major amputation. The diabetic black toe with bounding pulses a few centimetres away is now well known to be a complication of infection, where septic vasculitis damages the digital vessels, which become occluded by septic thrombus. As they are end arteries, the result is gangrene of the area supplied by the affected arteries, as in this case.
The patient, a 74 year old retired builder with Type 2 diabetes of five years duration, presented as an emergency at Casualty with infection and necrosis of the second and third toes of the left foot (Stage 5 foot) (Figure 1.2a), and was referred to the Diabetic Foot Clinic. He had strong pedal pulses but absent vibration sense at the big toes. His X-ray was normal despite the full-thickness necrosis. He was admitted and treated with quadruple IV antibiotics, amoxicillin 500 mg tds, flucloxacillin 500 mg qds, metronidazole 500 mg tds and ceftazidime 1 g tds. His CRP was 155.2 mg/l and his WBC was 16.85 × 109/l, with neutrophils of 14.41 x 109/l. He had a double ray amputation within 24 hours of admission (Figure 1.2b). He grew Staphylococcus aureus from the wound swab and Proteus mirabilis and Group G Streptococcus from tissue samples taken in theatre. His antibiotics were focussed to amoxicillin, flucloxacillin and ceftazidime.
His recovery from the ray amputation was complicated by his development of frank painful haematuria. He had a past history of renal stones and had had a bladder stone removed in an open operation. His haemoglobin dropped from 11.3 g/dl to 8.2 g/dl and he underwent a blood transfusion. CT scan and ultrasound revealed a 5 mm calculus at the lower pole of the left kidney. MSU showed a heavy mixed growth and the patient was treated with ciprofloxacin 500 mg bd. His haematuria resolved and he was reviewed by the urologists, who felt that no further treatment was necessary. His Type 2 diabetes was usually treated with oral hypoglycaemics but on admission, because of hyperglycaemia (20.5 mmol/l), he was treated with IV insulin sliding scale, which after two days was changed to a basal bolus insulin regime. Later on in the admission his foot wound grew Enterococcus faecium sensitive to vancomycin and teicoplanin. A PICC line was inserted into an antecubital vein, and he was discharged home on teicoplanin 400 mg daily IV and ciprofloxacin 500 mg bd orally. His foot healed after six weeks and the orthotists made him two pairs of shoes with cradled insoles. After healing of the foot, his diabetic therapy returned to metformin and glargine insulin at bedtime. He attended the Diabetic Foot Clinic regularly for nail care and removal of callus and his foot did not relapse.
Learning points
- Diabetic patients with Type 2 diabetes often have evidence of complications at the time of diagnosis because of glucose intolerance that may have been present for some years. Thus it is not surprising for this patient, who has a known history of diabetes for five years, and probably had glucose intolerance for some years before that, to have profound neuropathy.
- This patient had a typical polymicrobial infection of the diabetic foot, with Staphylococcus aureus, Group G Streptococcus and Proteus mirabilis isolated. The latter two organisms were isolated from operative tissue samples, thus illustrating the critical importance of sending operative tissue for culture. All three organisms in this poly- microbial culture were important and each needed appropriate antibiotic therapy.
- Many patients with Type 2 diabetes and foot infections will need insulin during the period of foot sepsis and subsequently during wound healing.
- Patients with Type 2 diabetes often have multi-system disease. Recovery from diabetic foot infections can be complicated by other illnesses, which need prompt attention or else they may compromise healing of the foot.
- Diabetic pat...
