Peripheral Neuropathies
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Introduction
Peripheral neuropathies include some of the most common neurological conditions. They can be mild, as can occur with diabetes, or life-threatening, as with Guillain-Barre syndrome.
Mononeuropathies affect single nerves, while polyneuropathies affect multiples. This is a helpful way of grouping them.
The Case of Mr. Bob Parry
Mr Parry is a 46 year-old man who rarely goes to the doctor. He is unsure of any medical conditions he has. He has noticed a gradually worsening numbness and tingling in his feet which has been present for the past 8 months.
- What further questions should you ask?
- What investigations should be carried out?
Causes and Risk Factors
Mononeuropathies include the following:
- compression (carpal tunel syndrome)
- heriditary (inherited predisposition to pressure palsy)
- inflammation/infection (Herpes simplex, Bell's palsy)
- multiple mononeuropathies (vasculitis, diabetes, leprosy)
radial neuropathy at the humeral groove can cause wrist drop
thoracic outlet syndrome
peroneal neuropathy at the fibular head
Carpal Tunnel Syndrome
sensory symptoms
- median nerve distribution
- numbeness, paresthesia, pain
- nocturnal symptoms
Polyneuropathies
- heriditary: Carcot-Marie-Tooth disease, amyloid neuropathies
- metabolic: diabetes, uremia, porphyria
- immune-mediated: monoclonal gammopathies, Sjogren's syndrome, carcinomatous sensory neuropathy
- post-infectious: Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy
- toxins: lead, arsenic, toluene
- drugs: amiodarone, pyridoxine, chemotherapy
acute vs chronic
- Guillain Barre syndrome
- porphyria
- diphteria
- toxins - arsenic, lead, organophosphates, thallium
- Lyme disease
- tick paralysis
- metabolic - diabetes, chronic renal failure
- inherited
- autoimmune (conenctive tissue diseases, chronic inflammatory demyelinating polyneuropathy
- toxins (alcohol, medications
- paraneoplastic
- nutritional - vitamin deficiencies
- infections (HIV, leprosy, etc
demyelinating vs axonal
- Demyelination is responsible for Charcot-Marie-Tooth, GBS, diptheria, and rarely diabetic polydeuropathy
axonal degeneration is involved in most polyneuropathies, including:
- diabetes
- toxins
- paraneoplastic
- infections
- porphyria
- nutritional
Medication Induced Neuropathy
- Vitamin B6
- HIV drugs
- chemotherapy
- metronidazole
- lithium
- amiodarone
- colchicine
- phenytoin
Diabetic
- can be: asymptomatic, symmetric distal, mononeuropathy, or diabetic amyotrophy
- first complaint is usually neuropathic pain or paresthesias
- lack of sensation leads to increased susceptibility to injury
- prevention is the best way to go, primarily through effective glucose management
- most other ptreatments are for neuropathic pain
Pathophysiology
Signs and Symptoms
- history
- physical exam
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
- fasting serum glucose
- TSH
- B12
- CBC, ESR, CRP
- electrolytes
- creatine
- BUN
- liver function tests
- protein electrophoresis
- ANA, ENA
- electromyography
Diagnostic Imaging
Evaluating mononeuropathy
- demonstrate motor/sensory abnormality in the affected nerve
- demonstrate normality in adjacent similar nerves
- use EMG
- MRI is best for determining cervical radiculopathy
Differential Diagnosis
Treatments
Consequences and Course
Resources and References
Topic Development
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