Peripheral Neuropathy Flashcards
Describe the mechanism of peripheral nerve degeneration.
Infarction- diabetes mellitus
Infiltration- leprosy and granulomas
Demyelination- Guillain-Barre Syndrome
Axonal degeneration- toxic neuropathies
Wallerian degeneration
Compression- carpal tunnel syndrome
Classify peripheral neuropathy.
Number and distribution of nerves affected- mononeuropathy, mononeuritis multiplex, polyneuropathy
Type of nerve fibre affected- motor, sensory, autonomic
Mechanism/process of nerves affectation- Diabetic neuropathy, neuritis, compression neuropathy, chemotherapy-induced peripheral neuropathy
Describe the clinical features of sensory neuropathy.
Large fibre:
Negative symptom:
Loss of vibration
loss of proprioception
hyporeflexia
sensory ataxia
positive:
paraesthesia
Small fibre:
negative:
Loss of pain
Loss of temperature
Postive:
Dysesthesias
Allodynia
Describe the clinical features of motor neuropathy.
Wasting, hypotonia, muscle weakness, hyporeflexia, fasciculation, deformity (claw deformity, wrist drop, foot drop)
Describe the clinical features of autonomic.
Postural hypotension, urinary retention, erectile dysfunction, diarrhea/constipation, diminished sweating, cardiac arrhythmias, gustatory sweating
Discuss diabetic neuropathies.
Duration of DM and Degree of Hyperglycaemia correlate to the neuropathy
Occlusion of the vasa nervorum: Vascular hypothesis (e.g isolated mononeuropathy)
Sorbitol and fructose accumulation in Schwann cells due to chronic hyperglycaemia disrupt function and structure of peripheral nerves: Metabolic cause
features:
Delayed nerve conduction velocity is the earliest functional change in diabetic nerve
Segmental demyelination is the earliest histological change due to Schwann cells damage: reversible
Axonal degeneration occurs at later stage: irreversible
Test:
10 gram monofilament
tuning fork 128 Hz
Patella hammer
Biothesiometer
What are the types of diabetic neuropathy?
Distal symmetrical polyneuropathy (stockings and gloves pattern)
Acute painful neuropathy
Mononeuropathy
Mononeuritis multiplex
Diabetic amyotrophy
Autonomic neuropathy
What is the autonomic neuropathy of diabetes?
Gustatory
cardiac denervation
postural hypotension
diarrhea
atonic bladder
erectile dysfunction
arteriovenous shunting
What is the somatic neuropathy of diabetes?
Ocular palsies
Carpal tunnel syndrome
Small muscle wasting
amytrophy
Painful neuropathy
Neuropathic foot
Discuss Carpal tunnel Syndrome.
Due to median nerve entrapment
Clinical presentation:
- Pain, tingling and paraesthesia on palmar aspect of hand and fingers
- Thenar muscles weakness and wasting of abductor pollicis brevis
- Symptoms are usually nocturnal
- Pain may extend to arm and shoulder
- Tinel’s and Phalen’s signs are present
Discuss Guillain- Barre Syndrome
acute inflammatory demyelinating polyneuropathy (AIDP)
Characterised by symmetrical ascending muscle weakness 1-3 weeks after infection
Trigger infections include Campylobacter jejuni, CMV, Mycoplasma, HIV, EBV
Leading to formation of antibodies against peripheral nerves
Proximal muscle are more affected- respiratory, trunk, and cranial nerves
Sensory signs may be absent, while autonomic dysfunction is uncommon
Spontaneous recovery may occur after several weeks
What are the investigations for Peripheral neuropathy?
Urinalysis- glucose, protein
Haematology- FBC, ESR, vitamin B12, folate
Biochemistry- HbA1c, fasting glucose, E/U/Cr, LFT, TSH
CSF- protein elevated with normal cell count (albuminocytologic dissociation) in GBS
Nerve conduction studies (NCS)
Electromyography (EMG)
Nerve biopsy: most useful in inflammatory disorders such as vasculitis, sarcoidosis, CIDP, infectious diseases such as leprosy, or infiltrative disorders such as amyloidosis or tumour
What is the treatment for peripheral neuropathy?
Treatment of the underlying cause is key.
Adequate metabolic control (in diabetes mellitus)- may lead to recovery particularly in early stage
Treatment of neuropathic pain:
1. Anticonvulsants- Gabapentin, pregabalin, sodium valproate
2. Antidepressants- Amitriptyline, duloxetine, venlafaxine
3. Opioids- tramadol, morphine, tapentadol
4. Capsaicin cream
Transcutaneous electrical nerve stimulation
Foot care
Weight reduction
Walking aids: for those with severe lower limbs weakness
Occupational therapy
Physiotherapy
Outline the aetiology of peripheral neuropathy.
Diabetes mellitus
Nutritional deficiencies- Vitamin B1 deficiency, vitamin B12 deficiency, pyridoxine deficiency (impaired sphingosine synthesis)
Alcohol
Infection – HIV, leprosy, diphtheria, tetanus, botulism
Heavy metal poisoning- Lead and mercury
Malignancy
Metabolic and endocrine – hypothyroidism, liver failure, renal failure
Postinfective polyneuritis – Guillain-Barre Syndrome
Sarcoidosis
Drugs – isoniazid, vincristine, phenytoin, gold
Genetic diseases – Charcot-Marie Tooth syndrome
Vasculitis - polyarteritis nodosa (PAN), Churg-Strauss syndrome (CSS), cryoglobulinaemia
