Peripheral Neuropathy Flashcards
Peripheral neuropathy (polyneuropathy) can be caused by many diseases.
The 4 categories are:
Guillian-Barre syndrome
Chronic inflammatory demyelinating polyradioneuropathy
Idiopathic, sensorimotor neuropathy
Metabolic, toxic, vitamin deficiency neuropathies
INFO CARD
What is Guillian-Barrè syndrome (GBS)?
Guillian-Barrè syndrome = most common acute polyneuropathy
=> inflammatory demyelinating disorder as a result of infection
=> Campylobacter jejuni and CMV infections cause severe GBS
=> Infecting organisms cause an antibody response against peripheral nerves
What are the symptoms of Guillian-Barrè syndrome?
Weakness of distal limb muscles / distal numbess
Foot-drop, weak hand
Low back pain = early feature
Weakness and sensory loss progress proximally over several days to 6wks
Loss of tendon reflexes
Respiratory & facial muscle weakness (20%)
How is Guillian-Barrè syndrome diagnosed?
What are the differential diagnosis?
Clinical diagnosis confirmed by nerve conduction studies
Nerve conduction studies shows:
=> slowing of conduction in common demyelinating form
=> prolonged distal motor latency
=> conduction block
CSF protein may be raised
Differential diagnosis:
=> Acute paralytic illnesses i.e. botulism, cord compression, muscle disease and myasthenia gravis
What are the initial investigations for peripheral neuropathy?
Blood tests: => FBC, ESR, Vit. B12 => Renal, liver, thyroid function => Glucose => Protein electrophoresis, immunoglobulins, immunofixation => Anti-Nuclear antibodies (ANA)
Chest Xray
Urine: Bence Jones proteins
How do you manage Guillian-Barrè syndrome?
Monitor ventilation + ventilation support if required
Low molecular weight heparin + compression stocking to reduce risk of venous thrombus
Immunoglobulin IV within first 2wks => reduces duration and severity of paralysis
=> patients should be screened for IgA deficiency (because congenital deficiency can lead to IgG led allergic reaction upon administering immunoglobulins)
Chronic inflammatory demyelinating polyradiculoneuropathy:
=> develops over months
=> progressive or relapsing proximal and distal limb weakness with sensory loss
=> Immunosuppression with steroids to manage
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Paraproteinaemic neuropathies:
=> 70% of patients with a serum paraprotein have neuropathy
=> Assoc. with monoclonal gammopathy of unknown significance (MGUS)
=> Also seen in myeloma
Paraproteinaemic neuropathies:
IgM paraproteins:
=> demyelinating neuropathy
=> directed against myelin assoc. glycoprotein (anti-MAG)
=> Anti-MAG phenotype = slowly progressive distal neuropathy with ataxia and prominent tremor
Chronic sensorimotor neuropathy has no known cause.
How does it present?
What does nerve conduction studies show?
=> Progressive symmetrical numbness & tingling
=> In hands & feet spreading in a glove and stocking distribution
=> Distal weakness ascends
=> Tendon reflexes are lost
Nerve conduction studies show axonal degeneration
What are the metabolic causes of peripheral neuropathy?
Diabetes
Uraemia
Hepatic disease
Thyroid disease
Porphyria
Amyloid disease
Malignancy
What are the toxic causes of peripheral neuropathy?
Drugs i.e. phenytoin, chloramphenicol, metronidazole, isoniazid, nitrofurantoin, disulfiram, amiodarone, chloroquine, anti-retroviral drugs, vincristine
Alcohol
Industrial toxins i.e. lead
What are the vitamin deficiency causes of peripheral neuropathy?
B1 (thiamine) deficiency
B6 (pyridoxine) deficiency
Nicotinic acid
B12
What is the most common cause of peripheral neuropathy in developed countries?
Diabetes => 50% of patients with diabetes have neuropathy after 25 years
What types of neuropathy occurs in diabetes?
Good glycemic control is protective against this microvascular complication
- Distal symmetrical sensory neuropathy
=> glove & stocking distribution, numbness, tingling and pain e.g. worse at night
=> reduced sensation - Acute painful sensory neuropathy
=> reversible with improved glycemic control - Mononeuropathy and multiple mononeuropathy
- Diabetic amyotrophy
=> painful wasting of quadriceps and other pelvifemoral muscles
=> reversible vasculitic plexopathy or femoral neuropathy
5. Autonomic neuropathy => postural BP drop => reduced cerebrovascular autoregulation => loss of respiratory sinus arrhythmia => gastroparesis => urine retention => erectile dysfunction => gustatory sweating => diarrhoea
Thiamine deficiency causes beri-beri.
Beri-beri key features are:
=> polyneuropathy
=> cardiac failure
Thiamine deficiency also leads to Wernicke’s encephalopathy & Korsakoff psychosis
=> Alcochol is the most common cause of Wernicke-Korsakoff syndrome
Wernicke’s encephalopathy due to damage in the brainstem + its connections
Wernicke-Korsakoff syndrome signs:
- Eye signs i.e. nystagmus, bilateral lateral rectus palsies, conjugate eye palsies
- Ataxia i.e. broad based gait, cerebellar signs and vestibular paralysis
- Cognitive changes i.e. stupor, coma leading to irreversible amnestic state
Vitamin B12 deficiency causes damage to the spinal cord, peripheral nerves and brain.
It also causes subacute combined degeneration of the cord (SACD).
What is subacute degeneration of the cord (SACD)?
Initial stages:
=> numbness and tingling of fingers & toes
=> distal sensory loss
=> absent ankle jerks
=> with cord involvement - exaggerated knee jerks + extensor planters
=> optic atrophy & retinal haemorrhage
Later stages:
=> sphincter disturbances
=> severe generalised weakness
=> dementia
*parenteral B12 reverses nerve damage but no affect on cord and brain
Genetic neuropathies:
What is Charcot-Marie-Tooth disease?
Charcot-Marie-Tooth disease is a group of heterogenous hereditary motor and sensory neuropathies.
=> Distal limb wasting and weakness esp legs
=> Progress slowly over many years
=> Variable loss of sensation and reflexes
=> Advanced disease = severe foot drop
=> Mild disease = per cavus (higher than normal arch) and toe clawing
Other peripheral neuropathies:
=> neuropathy in cancer
=> neuropathy in systemic diseases i.e. SLE, Polyarteritis nodosa, Granulomatosis with eosinophilia, Rheumatoid disease
INFO CARD
Autonomic neuropathy may develop in diabetes, amyloidosi, Guillian-Barrè syndrome and Parkinson’s.
What are the signs of autonomic neuropathy?
Postural hypertension
Urinary rentention
Erectile dysfunction
Nocturnal diarrhoea
Diminished sweating
Impaired pupillary responses
Cardiac arrhythmia
