Diabetic Neuropathy Flashcards
Proposed mechanisms of diabetic neuropathy.
Occlusion of the vasa nervorum (more likely in isolated mononeuropathies)
Due to the more diffuse symmetrical nature, a metabolic cause is more likely.
Hyperglycaemia leads to increased formation of sorbitol and fructose in Schwann cells. The accumulation of these sugars may cause disruption and damage to the nerves.
Earliest histological change in diabetic neuropathy.
Segmental demyelination caused by damage to Schwann cells.
Peripheral neuropathy is often unrecognised by the person with diabetes in its early stages.
What early clinical signs might manifest?
Mainly sensory loss such as vibration, pain sensation and temperature sensation in the feet.
Does deep sensation or superficial sensation disappear first?
Deep sensation is lost before superficial.
In later stages of Symmetrical distal polyneuropathy, what might the patient complain about?
A feeling of walking on cotton wool.
They might lose balance when washing their face, or lose balance when walking in the dark.
Early stages => Glove & stocking, numbness, tingling and pain. This pain is particularly worse at night.
What does early involvment of neuropathy in the hands suggest?
It is uncommon and should prompt a search for non-diabetic causes.
Complications of symmetrical distal polyneuropathy.
Unrecognised trauma because of the loss of pain sensation.
Falls.
What abnormalities of the foot might be present in symmetrical distal polyneuropathy?
Interosseous wasting
High arch
Clawing of the toes
Callus formation under first metatarsal head or on the tips of the toes.
Explain interosseous wasting of the feet.
Due to damage of the motor nerves to the small muscles of the feet.
Explain clawing of the toes and high arch of the feet.
Unbalanced traction by the long flexor muscles.
Explain callus formation under the first metatarsal head or on the tips of the toes.
Du to the high arch and clawing leading to abnormal distribution of pressure on walking.
Complications of symmetrical distal polyneuropathy of the hands.
Small muscle wasting and sensory changes.
Why is it important to exclude other causes of in neuropathy of the hands?
E.g. carpal tunnel syndrome is more frequent in diabetes.
Other conditions might be reversible.
What is acute painful neuropathy?
A less common feature of diabetic neuropathy where the symptoms are typically worse at night even pressure from bedclothes may be intolerable.
This condition may present at diagnosis and after sudden improvement of the glycaemic control it may resolve.
Where is the pain typically in acute painful neuropathy?
Burning and crawling pains in the feet, shins and anterior thighs.
When might you see a chronic form of acute painful neuropathy?
Later in the course of diabetes.
It is sometimes resistant to almost all forms of therapy.
Why is neurological assessment difficult in acute painful neuropathy?
Because of the hyperaesthesia.
Differences between acute painful neuropathy and symmetrical distal polyneuropathy in neurological assessment.
Muscle wasting is not a feature of APN.
First line therapies of acute painful neuropathy.
Paracetamol
Duloxetine, tricyclics, gabapentin or pregabalin.
After that can also try mexiletine, valproate and carbamazepine.
They all reduce the perception of neuritic pain.
However usually not as much as patients hope for.
What non-medical treatment can be used?
Transepidermal nerve stimulation (TENS)
What is mononeuritis and mononeuritis multiplex?
Any nerve in the body can be involved in diabetic mononeuritis.
It has an abrupt onset and can sometimes also be painful.
Radiculopathy might also occur.
Give examples of mononeuritis.
Isolated palsies of nerves such as external eye muscles (CN III, CN VI)
Lesions commonly occur in:
Nerves at common sites for external pressure.
Nerve entrapment such as carpal tunnel.
Characteristics of diabetic third nerve lesions.
Painless
Pupillary reflexes are retained owing to sparing of pupillomotor fibres.
This means that the pupil will not be dilated.
Remission of mononeuritis.
Full spontaneous recovery usually occur over 3-6 months.
What is diabetic amyotrophy.
Painful usually asymmetrical wasting of the quadriceps muscles.
Clinical presentation of diabetic amyotrophy.
Painful wasting of the quadriceps.
The wasting may be very marked.
Knee reflexes are diminished or absent.
Affected area is often very tender.
Extensor plantar responses sometimes develop.
Elevated CSF protein.
When does diabetic amyotrophy occur?
In older men with diabetes.
Periods of more severe hyperglycaemia (may present at diagnosis)
Outcome of diabetic neuropathy.
Often resolves over time with improved glycaemic control.
Features of somatic neuropathy.
Ocular palsies
Carpal tunnel syndrome
Small muscle wasting of the hands
Amyotrophy
Painful neuropathy
Neuropathic foot.
Systems invovled in autonomic neuropathy.
Cardiovascular system
GI tract
Bladder
Sexual dysfunction
Features of autonomic neuropathy.
Gustatory sweating
Cardiac denervation
Postural hypotension
Gastroparesis
Diarrhoea
Atonic bladder
ED
Arteriovenous shunting
Features of cardiovascular neuropathy.
Vagal neuropathy.
Denervation of the heart.
Loss of cardiovascular reflexes.
Postural hypotension
Warm foot
What does vagal neuropathy result in?
Tachycardia at rest and loss of sinus arrhythmia due to the loss of vagal innervation.
What does a denervated heart resemble?
A transplanted heart.
Give an example of a cardiovascular reflex lost in diabetic neuropathy.
Valsalva manoeuvre
Why might postural hypotension occur in diabetic neuropathy?
Loss of sympathetic tone to peripheral arterioles.
Why might a warm foot with a bounding pulse happen in neuropathy?
Often seen in polyneuropathy due to peripheral vasodilation.
Bedside testing of autonomic function.
Supine to erect blood pressure. (>30 fall is abnormal)
Heart rate responses to deep breathing (< 10 is abnormal)
Valsalva manoeuvre and then the ratio of longest to shortest R-R interval (< 1.20 is abnormal)
Lying to standing ratio of R-R interval of 30th to 15th beats. (< 1.00 is abnormal)
Briefly explain supine to erect blood pressure.
Measure supine BP
Make patient stand up and measure it again.
A normal fall of SBP would be 10.
An abnormal fall of SBP would be over 30
Explain deep breathing test for autonomic function.
Deep breathing where patient takes 6 breaths over 1 min.
You measure the max to min heart rate. ( A drop of heart rate )
> 15 is normal
< 10 is abnormal
Explain the valsalva maneuvre to test autonomic function.
Valsalva manoeuvre is performed for 15 seconds.
The ratio of longest to shortest R-R interval are then measured.
Normal is >1.21
Abnormal is < 1.20
Valsalva increases ICP and should cause bradycardia due to vagal stimulation.
What can vagal damage in GI tract lead to?
Gastroparesis which can cause intractable vomiting.
Symptoms of altered gastrointestinal motility.
Dysphagia
Dyspepsia
Abdo pain
Constipation
Diarrhoea
Faecal incontinence
Vomiting
When does the autonomic diarrhoea commonly occur?
At night
Treatment of gastroparesis.
Implantable devices that stimulate gastric emptying,
Injection of botulinum toxin into the pylorus.
Complications of neuropathic gastroparesis.
Presdisposes bacterial overgrowth leading to bile salt deconjugation, fat malabsorption and diarrhoea. Can also lead to anaemia and macrocytosis.
Explain the bladder complications in diabetic neuropathy.
Loss of tone
Incomplete emptying and stasis.
Can ultimately result in an atonic, painless and distended bladder.
Treatment of bladder neuropathy.
Intermittent self-catherisation or permanent if intermittent fails.
Overall prevalence of sexual dysfunction in men with diabetes.
35-40%
First manifestation of sexual dysfunction in men.
Incomplete erection
Later presentation of sexual dysfunction in diabetes.
Total failure leading to retrograde ejaculation.
(This can also happen in autonomic neuropathy)
Explain the causes of erectile dysfunction in diabetes.
Inadequate vascular supply due to atheroma in pudendal arteries.
Primary or secondary gonadal failure.
Hypothyroidism
Anxiety
Depression
Alcohol excess
Drugs like thiazides and b-blockers
What is needed to be done when a man present with ED?
Detailed history and examination.
Bloods.
What are you looking for in bloods of ED?
LH
FSH
Testosterone
Prolactin
Thyroid function
First line treatment of ED.
Phosphodiesterase type 5 inhibitors such as sildenafil, tadalafil, vardenafil and avanfil.
They enhance the effects of nitric oxide on smooth muscle and increase penile blood flow.
When should sildenafil and etc.. not be given?
When patient are treated with nitrates for angina as well.
Alternative treatments for ED.
Apomorphine - 2 or 3 mg sublingually 20 minutes before sex
Alprostadil (Partner needs to use barrier contraception if pregnant)
Intracavernosal injection of alprostadil
Vacuum devices
Penile prostheses.
What should be done if the foot pulses are not felt anymore?
Doppler pressure measurements.
