Long lists of causes of peripheral neuropathy make peripheral nerve disease a dry and uninspiring subjectOverell JR Peripheral neuropathy: pattern recognition for the pragmatist Practical Neurology 2011;11:62-70
This page examines sensory changes caused by involvement of multiple nerves = polyneuropathy.
Pathophysiology
- Axonal polyneuropathy (most common)
- Axons degenerate in distal-to-proximal pattern.
- Axonal vulnerability is correlated with length; longer axons are the first to be affected, producing LL symptoms/signs, sensory > motor
- Progresses to weakness of the LL and UL producing a “glove and stocking” sensory loss
- Can progress to intercostal nerves and sternal sensory loss
- Causes include:
- Diabetes
- Alcohol
- Amyloidosis
- Hypothyroidism
- Vitamin deficiencies (B12, folate)
- Lyme disease
- Hereditary Motor and Sensory Neuropathy Type II
- Demyelinating polyneuropathy
- Causes include:
- Guillain-Bare syndrome
- Chronic inflammatory demyelinating polyneuropathy (CIDP)
- Hereditary Motor and Sensory Neuropathy Types I & III (e.g. Charcot-Marie-Tooth)
- Myeloma
- Refsum’s = AR peroxisomal disorder leading to an accumulation of phytanic acid
- POEMS paraneoplastic syndrome = Polyneuropathy, Organomegaly, Endocrinopathy, Myeloma protein, Skin changes
- HIV
- Causes include:
Symptoms
- Classically the glove and stocking distribution
- Symmetrical distal sensory loss, burning, with varying degrees of reflex loss or weakness, most commonly LL>UL.
- Border between normal and absent sensation is usually gradual (in contrast to functional sensory loss)
- Demyelinating sensory neuropathies tend to produce parasthesia.
- The figure below summarises modalities commonly affected:
On examination
- Skin: shiny, dry, hair loss, ulcers (autonomic neuropathy)
- Skin can appear red, warm and swollen, or pale and cool with autonomic dysfunction.
- If chronic – Charcot’s joints (loss of pain and proprioception)
- Ataxia (loss of proprioception)
- Romberg sign +ve (indicating a sensory ataxia vs. cerebellar ataxia)
- Painful neuropathy? Likely alcohol related
- If motor:
- Wasting, weakness, fasciculations, loss of reflex
- Plantars downgoing
- Check postural BP/HR if suspicion of autonomic failure
Often all modalities will be affected. If certain modalities are affected, consider if it is predominantly large fibre or small fibre:
- Large: loss of vibration/proprioception
- Small: loss of temperature/pain/autonomic
- Diabetes, alcohol, amyloid, leprosy, heavy metals, hypothyroid
Diagnosis
- Bloods
- FBC, U&E
- HbA1c, Glucose
- ESR, CRP
- LFT
- TFT
- B12/folate
- Serum electrophoresis
- Autoimmune screen
- Syphilis, Lyme, HIV
- CSF
- Raised protein in CIDP/GBS
- Nerve conduction
- Axonal
- Mostly preserved conduction velocity, CMAP small, distal motor latency normal
- Demyelinating
- Reduced conduction velocity, conduction block, CMAP normal, distal motor latency prolonged
- Axonal
Treatments
- Treat cause
- Axonal
- Generally speaking, try to minimise exposure to offending agent
- Demyelinating
- Refer to management of CIDP/GBS: intravenous immune globulin, glucocorticoids, and plasma exchange
- Painful neuropathy
- Consider trial of gabapentin/carbamazepine/TCA