Polyneuropathy Flashcards
What are polyneuropathies?
Motor and/ or sensory disorders of multiple peripheral or cranial nerves.
Usually symmetrical and widespread
Are polyneuropathies usually worse distally or proximally?
Distally - glove and stocking distribution
How are they usually classed?
Chronicity
Function - sensory, motor, autonomic, mixed
Pathology - demyelination, axonal degeneration, both
What metabolic conditions can cause polyneuropathy?
DM
Hypothyroidism
Renal failure
Hypoglycaemia
What infections can cause polyneuropathy?
Leprosy
HIV
Syphilis
Lyme disease
What nutritional factors can cause polyneuropathy?
Low B1
Low B12/ folate
Low vit E
High B6
What inflammatory conditions can cause polyneuropathy?
Guillian Barre syndrome
Sarcoidosis
What inherited syndromes can cause polyneuropathy?
Charcot-Marie- Tooth
Porphyria
What types of malignancy can cause polyneuropathy?
Paraneoplastic syndromes
PV
What vasculitides can cause polyneuropathy?
RA
Polyarteritis nodosa
What drugs can cause polyneuropathy?
Vincristine Cisplatin Isoniazid Nitrofurantoin Phenytoin Metronidazole
If there is palpable nerve thickening, what should you think of?
Leprosy
Charcot-Marie-Tooth
What tests should be done?
FBC, ESR, glucose, U&E, TSH, B12, electrophoresis, ANA, ANCA, CXR, urinalysis
Consider LP and specific genetic testing
How do you distinguish demyelination from axonal causes?
Nerve conduction studies
What type of polyneuropathy is Guillian Barre syndrome?
Acute, predominantly motor demyelinating neuropathy
What type of polyneuropathy does chronic alcohol abuse lead to?
A chronic, initially sensory then mixed axonal neuropathy
What things should you ask in the history?
Time course Precise nature of symptoms Preceding or associated events e.g D&V before Guillian Barre, reduce weight in cancer, arthralgia from a connective tissue disease Travel Alcohol and drug use Sexual infections FH
What are some examples of conditions that cause sensory neuropathy?
DM
CKD
Leprosy
What symptoms are associated with sensory neuropathy?
Numbness
Pins and needles
Paraesthesia
Glove and stocking distribution
Difficulty handling small objects such as buttons
Signs of trauma - burns or joint deformity may indicate sensory loss
Diabetic and alcoholic neuropathies typically painful
What are some examples of conditions that cause motor neuropathy?
Guillian Barre
Lead poisoning
Charcot-Marie-Tooth syndrome
What character are associated with motor neuropathies?
Often progressive (may be rapid)
Weak, clumsy hands
Difficulty walking - falls, stumbling
Difficulty breathing - reduced vital capacity
Signs of LMN lesion - wasting, weakness, areflexia
In terms of sensory neuropathy management, what is important to minimise trauma?
Foot care
Show choice
All peripheral nerves are myelinated except…
C fibres which carry information about pain
Called slow fibres - signal travels slow due to lack of myelination
What mnemonic can be used to remember specific causes of peripheral neuropathies?
DAVID
Diabetes Alcoholism Vitamin deficiency e.g B12 Infective or inherited - Guillian Barre or CMT Drugs e.g isoniazid
What are the 6 main mechanisms of peripheral nerve degeneration?
Demyelination Axonal degeneration Wallerian - fibre cut or crushed Compression - not as severe as Wallerian Infarction Infiltration
What is an example of compressive degeneration?
Carpal tunnel syndrome
There is local demyelination at site of compression
What are examples of infiltrative degeneration?
Leprosy
Malignancy
Inflammation
Sarcoidosis
What are examples of degeneration due to infarction?
Diabetes
Polyarteritis nodosa
Chung-Strauss syndrome
There is also Wallerian degeneration distal to infarct
When does axonal degeneration typically occur?
In toxic neuropathies
What is leprosy?
An infection by the bacteria mycobacterium leprae or mycobacterium lepromatosis
Nerve damage - sensory, motor and autonomic
Skin lesions - red or hypopigmented patches with reduced sensation
Thickened peripheral nerves
Loss of sensation produces loss of protective reactions, which can lead to trauma and infections
The bacteria acts on Schwann cells producing a chronic granulomatous reaction - destruction of both myelin and underlying nerve cells
