Neuropathy Flashcards
Describe how peripheral neuropathies can be categorised based on the pathophysiology?
Axonal degeneration (diabetes/alcoholic)
OR
Demyelination (diptheria/chronic immune demyelinating polyneuropathy)
OR
Axonal destruction and demyelinaton
Clinically axonal degeneartion tends to affect motor neurons predominantly at first.
In demyelinating conditions both sensory and motor nerves are affected.
List some of the common causes of neuropathies to be aware of and categorise them based on symptoms.
Metabolic/endocrine:
- Diabetes mellitus
- Chronic renal failure
Toxic:
- Alcohol
- Drugs – amiodarone, hydralazine, chemotherapy agents
Autoimmune/inflammatory:
- Guillan Barre Syndrome
- RA
- Mixed connective tissue disorders
Infective:
-Lyme disease
Neoplastic:
- Lymphoma/myeloma
- Paraneoplastic
Deficiency:
- B12 and Folate
- Vitamin E
Hereditary:
- Charcot-Marie-Tooth
- Other hereditary sensorimotor neuropathies
Describe some clinical patterns of peripheral nerve damage?
Sensory neuropathy:
- Often glove and stocking distribution*
- Paraesthesiae, numbness, burning pain, and loss of vibration sense and proprioception
- May present with ataxia due to loss of proprioception
Motor neuropathy:
-Presents as weakness usually starts distally extending proximally
Autonomic neuropathy:
- Polyneuropathy often affects the autonomic nerves
- Constipation
- Urinary/faecal incontinence
- Orthostatic hypotension
Hereditary neuropathy:
-May present with hammer toes, high arches, scoliosis etc.
*Depending on the cause can have different patterns e.g porphyria = swimming trunk pattern
Describe the presentation of diabetic peripheral sensory neuropathy?
Touch, pain and temperature sensation and proprioception in lower limbs in a glove and stocking distribution.
Loss of ankle jerks and, later, knee jerks.
Hands only affected in severe longstanding neuropathy
What is Charcot Marie Tooth disease?
It is a set of inherited neuropathies in which neuropathy is the sole or main component.
It is most commonly an autosomal dominant condition but recessive and x linked forms have also been identified.
Which genes are responsible in Charcot Marie Tooth?
CMT1 (most common)
CMT2/3/4/X
Describe the presentation of CMT?
Depending on which type presents differently (aka may present at different ages)
Most common type CMT1:
- Onset usually by 10yo
- Onset is insidious and slowly progressive
- Muscle weakness and wasting starting from the intrinsic muscles of the feet.
- Gradually affecting the lower leg and lower thigh.
Inverted champagne bottle leg
Hammer Toes
What is the typical history in Charcot Marie Tooth?
Significant family history
Onset is within the first two decades
Slowly progressing weakness in the distal limbs
Frequent tripping and ankle drop. Leads to high steppage gait
Describe the presentation of alcoholic neuropathy?
Usually affects sensory before motor but can affect both.
Insidious onset of lower limb distal paresthesias progressing proximally and symmetrically.
Note: alcoholic neuropathy and Folate/B12 deficiency neuropathy are separate entities however may co-exist
What is a nerve conduction study?
A nerve conduction study (nerve conduction velocity test)
-is a measurement of the speed of conduction of an electrical impulse through a nerve.
Two electrodes are placed on the skin over the nerve. One electrode stimulates the nerve with a very mild electrical impulse and the other electrode records it.
Slowed velocities may indicate nerve damage.
What is Guillan Barre Syndrome?
It is an autoimmune condition causing demyelination and axonal degeneration resulting in:
Acute, ascending and progressive neuropathy, characterised by weakness, paraesthesiae and hyporeflexia.
GBS is usually preceded by infection (many infectious agents have been indicated) campylobacter and viruses specifically.
Describe the presentation of GBS?
Ascending pattern of progressive symmetrical weakness, starting in the lower extremities.
Often occurring several weeks after an infective illness.
Maximum severity is usually reached 2 weeks after onset of symptoms.
In severe cases muscle weakness can cause respiratory failure.
Other signs and symptoms include:
- Loss of reflexes
- Neuropathic pain in the legs
- Paraesthesiae in the legs
- Urinary retention
How is GBS diagnosed?
Diagnosis established on clinical grounds and confirmed by nerve conduction studies showing slowing of motor conduction.
On CSF studies there will be a non specific raised protein.
May be antibodies present.
How is GBS managed?
Vital capacity monitored 4hrly to recognise respiratory muscle weakness.
A fall <80% of predicted or 20ml/kg is an indication for transfer to ITU and possible invasive ventilation.
There is assisted ECG monitoring to document cardiac arrhythmias associated with autonomic dysfunction.
IV IG daily for 5 days is standard treatment reduces severity and duration of paralysis and has fewer S/E than plasma exchange.
What are the complications of GBS?
20% have a neurological deficit of these 50% are severe
Roughly 10% of people die due to complications of respiratory failure, PE or infection.
