Neuropathy Flashcards
What is polyneuropathy?
-A generalized disease of peripheral nerves [+/- cranial nerves]
=May be predominantly/only motor
=May be predominantly/only sensory
=May be mixed sensori-motor
Pathophysiological processes of polyneuropathy
-Mainly demyelination (of peripheral NS)
-Mainly axonal
Causes of polyneuropathy
-Genetic
-Toxic (alcohol, drugs, other toxins)
-Metabolic (DM, vitamin deficiencies)
-Auto-immune/Inflammatory (GBS)
-Paraneoplastic
-Infections (HIV, Leprosy)
Clinical picture of polyneuropathy
-Weakness (LMN character)- wasting, normal/reduced tone
-Sensory loss
-Reduced or absent tendon reflexes
=Distribution depends on cause
-Classical sensory polyneuropathy picture
[for example, related to DM]
=Glove and Stocking Pattern with Areflexia
Investigations for polyneuropathy diagnosis
-Nerve conduction studies
=Demyelination= slowing
=Axonal= reduced amplitude
Presentation of Guillian-Barre syndrome
-Back/leg pain
-Progressive, symmetrical, ascending weakness of limbs (4 weeks)
-Reflexes reduced or absent
-Mild distal paraesthesia
-History of gastroenteritis
-Respiratory muscle weakness
-Cranial nerve involvement (diplopia, bilateral facial palsy, oropharyngeal weakness)
-Autonomic (urinary retention, diarrhoea)
Investigation of Guillian-Barre syndrome
-Immune-mediated demyelination of PNS triggered by infection
-LP (rise in protein with a normal white blood cell count)
-Nerve conduction: decreased motor nerve conduction velocity, prolonged distal motor latency, increased F wave latency, ganglioside GM1
-Contrast enhanced MRI spine
Management of Guillian-Barre syndrome
IV immunoglobulin, plasma exchange, DVT prophylaxis
Describe diabetic neuropathy
-Presentation: glove and stocking, burning/ shooting pain, numbness, paraesthesia, painless injuries, gastroparesis
-Diagnosis: 10G monofilament for sensation, reduced/ absent ankle reflexes
-Management: pregabalin/ gabapentin/ duloxetine/ amitriptyline, tramadol as rescue therapy for exacerbations of neuropathic pain/ topical capsaicin for localised neuropathic pain
Describe B12 deficiency
-Presentation: megaloblastic anaemia, sore tongue and mouth, mood disturbances, joint position and vibration affected before distal parenthesis. Pernicious anaemia: lethargy, pallor, dyspnoea, mild jaundice, subacute combined degeneration of spinal cord.
-Investigation: blood test, low WCC and platelets, low vitamin B12, anti-intrinsic factor antibodies/ anti gastric parietal cell antibodies
-Management: 1 mg of IM hydroxocobalamin x3 for 2 weeks then once every 3 months
Describe folate deficiency
-Megaloblastic anaemia, neural tube defect.
-400mcg folic acid until 12th week of pregnancy/ at higher risk of neural tube defect= 5mg folic acid from before conception until 12th week of pregnancy.
-Treat B12 first to avoid precipitating subacute combined degeneration of cord.
Describe thiamine deficiency
-Wernicke-Korsakoff syndrome (nystagmus, ophthalmoplegia- failure of lateral gaze, ataxia, amnesia, confabulation), heart failure (wet beriberi= dilated cardiomyopathy), dry beriberi (peripheral neuropathy).
-Investigation: erythrocyte thiamine pyrophosphate, ABG (raised anion gap metabolic acidosis), lactate (elevated), thyroid function tests (rule out thyrotoxicosis)
-Management: IV thiamine (hospitalised), magnesium, potassium, phosphate replacement, oral thiamine (community alcohol withdrawal)
Describe alcoholic neuropathy
-Presentation: history of alcohol abuse, gait instability, paraesthesia in the distal lower extremities progressing proximally, paraesthesia of the fingers and hands appear once symptoms extend above ankle level, sensory symptoms typically present prior to motor symptoms
-Signs: loss of sensation and deep tendon reflexes in the lower extremities, sensory ataxia, positive Romberg’s sign; signs of alcoholic liver disease: ascites, splenomegaly, cutaneous telangiectasias, palmar erythema, finger clubbing, Dupuytren’s contractures
-Investigation: EMG and nerve conduction studies (axonal Sensori-motor peripheral neuropathy, LFTs
-Management: intervention, pain relief, vitamin supplement, physiotherapy
Describe Charcot-Marie-Tooth disease
-MOTOR LOSS, abnormal gait due to foot drop, toe-walking as a child, paraesthesia minimal: length-dependent, symmetric glove and stocking distribution of abnormalities, distal muscle atrophy, inverted champagne bottle legs, frequently sprained ankles, hyporeflexia.
-Investigation: EMG and nerve conducting studies (demyelinating, low nerve amplitude), genetic testing
-Management: physical and occupational therapy, bracing, orthopaedic surgery, exercise.
Drug causes of neuropathy
-Amiodarone, isoniazid, vincristine, nitrofurantoin, metronidazole, colchicine, phenytoin, statins, thalidomide
