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.
