Peripheral Neuropathy
Types
Sensory neuropathies can be broadly divided into 2 subtypes:
| Type | Affected fibres | Clinical manifestation |
|---|---|---|
| Small-fibre predominant | Small-diameter nerve fibres mediate pain and temperature |
|
| Large-fibre predominant | Large-diameter nerve fibres mediate vibration, pressure and proprioception |
|
Causes and Clinical Features
Sensory-Predominant Peripheral Neuropathy
Up to 40% of cases are idiopathic
Most common causes (all cause a distal symmetrical polyneuropathy pattern):
- Diabetes (diabetic neuropathy) – most common overall
- Vitamin B12 deficiency
- Paraproteinaemias (e.g. multiple myeloma, MGUS, AL amyloidosis)
Other causes:
- Alcohol misuse (alcoholic neuropathy)
- Systemic disease
- Hypothyroidism
- Amyloidosis
- CKD
- Chronic liver disease
- Other nutritional deficiencies
- Vitamin B1 (thiamine)
- Vitamin B6 (pyridoxine)
- Vitamin B9 (folic acid)
- Copper
- Vitamin E
- Immune-mediated conditions (e.g. sarcoidosis, Sjogren’s syndrome, SLE, vasculitis)
- Infections (e.g. HIV, Lyme disease, leprosy, VZV / shingles)
- Drugs and toxins
- Medications include: metronidazole, fluoroquinolones, nitrofurantoin, leflunomide, reverse transcriptase inhibitors, phenytoin, levodopa, cytotoxic agents (e.g. cisplatin)
- Toxins include: lead, arsenic, mercury, organophosphates, thallium, nitrous oxide
- Environmental factors – prolonged exposure to cold, vibration or hypoxaemia
Distal symmetrical polyneuropathy is the most common clinical pattern
- This refers to a length-dependent peripheral nerve injury which results in bilateral symmetrical neuropathy affecting the longest nerve first
- Clinically, symptoms start distally (e.g. in the feet) and progress proximally in a stocking-glove distribution
Motor-Predominant Peripheral Neuropathy
Key causes:
| Cause | Clinical clues |
|---|---|
| Mononeuritis multiplex | Typically caused by vasculitis, such as in:
Clinically presents as patchy, asymmetrical neuropathy (often painful and non-length dependent) and weakness |
| GBS (AIDP) |
|
| CIDP |
|
| Charcot-Marie-Tooth disease (HMSN) |
|
| Diabetic lumbosacral radiculoplexus neuropathy |
|
| Acute porphyria |
|
| Lead poisoning |
|
| Motor neuron disease |
See the Motor Neurone Disease article for more information |
Assessment and Management
Initial investigations for sensory neuropathy:
- HbA1c + fasting glucose
- Vitamin B12 level
If other causes are suspected, investigate accordingly based on clinical judgement
Peripheral neuropathy with ANY of the following should be referred to a specialist:
- Asymmetrical
- Motor-predominant
- Rapidly progressing
- Non-length dependent
- Prominently autonomic
- Proximal
- Onset at a young age
Management involves identifying the underlying cause and treating accordingly.