Primary condition of the peripheral nerves causing symmetrical motor and/or sensory symptoms and signs in the limbs
Typically sensory change that is a symmetrical glove and stocking loss to all modalities. This is unlike an invidiual nerve or nerve root.
In demyelinating peripheral neuropathies such as Guillain Barre Syndrome, the weakness may be proximal and thus stimulates myopathic disease
Axonal degeneration - most common pathology
- Systemic, metabolic, toxic and Nutritional disorders
- Damaged axons degenerate distally
- Predilection for large diameter and long fibres
- EMG records show fibrillation potentials
- Within a week nerve becomes electrically inert
Segmental demyelination - destruction of the myelin sheath leaving the axon intact
- Slowing of nerve conduction - inflammatory process Multiple Sclerosis
- Electrophysiological studies helpful to differentiating
Neuronopathies - cell bodies of axons anterior horn cells or dorsal root ganglia are primarily affected
Causes/Factors
Acute onset:
- Guillain-Barre Syndrome
- Porphyria
- Toxic (for example, arsenic, nitrofurantoin)
- Serum sickness (postimmunisation)
- Diphtheria
- Malignancy
- Critical illness polyneuropathy
- Diabetes Mellitus, uraemia (rarely)
Predominantly motor:
- Guillain-Barre syndrome
- Porphyria
- Diphtheria
- Lead
- Charcot-Marie-Tooth disease
- Diabetes (diabetic amyotrophy)
Predominantly sensory:
- Leprosy Diabetes (distal sensory polyneuropathy)
- Vitamin B12 or thiamine deficiency (Nutritional disorders)
- Malignancy
- Hereditary sensory and autonomic neuropathy
- Primary of familial Amyloidosis
- Uraemia
- Lyme disease
- Sjogren’s syndrome
Radicular:
- Diabetic truncal neuropathy
- Lyme disease
- Sjogren’s syndrome
Painful neuropathies:
- Alcohol, Nutritional disorders
- Diabetes (acute painful neuropathy)
- Hereditary sensory and autonomic neuropathy (HSAN type 1)
- Arsenic
- Cryoglobulinaemia
- Lyme disease
- Paraneoplastic sensory neuropathy
- Vasculitic neuropathies
Symptoms
Sensory symptoms
- Numbness, tingling, pins and needles
- Burning sensations
- Pain
- “Walking on cotton wool”
- Band like sensation around wrists or ankles
Motor weakness
In early stages weakness is usually distal - early proximal weakness is a feature of inflammatory and porphyric neuropathy
Signs
- Unsteady on feet
Investigations
- FBC
- ESR, CRP
- LFTs, GGT
- TFTs
- glucose
- creatinine
- plasma B12 and folate
- serum protein electrophoresis and immunoelectrophoresis
- urinalysis
- CXR
Special tests:
- EEG
- EMG
- Specific antibody levels
Management
- Need to understand cause of pain
Pharmacological
- non-opiod analgesics and NSAIDS
- tricyclic antidepressants
- anti-epileptics
- capsaicin
- opioid analgesics
- serotonin-norepinephrine reuptake inhibitors (SNRIs) e.g. duloxetine, venlafaxine
- NMDA receptor antagonists such as ketamine
For all neuropathic pain (except trigeminal neuralgia) a choice of amitriptyline, duloxetine, gabapentin or pregabalin should be offered
Consider input from neurology