Polyneuropathies

Question 1

Define Polyneuropathy

Answer 1

Peripheral or cranial neuropathies

Distribution is usually symmetrical & widespread, often distal

Question 2

How are polyneuuropathies classified?

Answer 2

• Course: Acute/ chronic
• Function: Sensory/ Motor/ Autonomic/ Mixed
• Pathology: Demyelination/ Axonal damage/ both

Question 3

Outline the typical presentation of Sensory Polyneuropathy

Answer 3

• Distal feet affected first
• Paraesthesiae, numbness, burning pain, loss of vibration & position sense
• Signs of bumps/ burns/ bruising
• Pain: diabetic & alcohol neuropathies
• Muscle wasting may occur

Question 4

Outline the typical presentation of Autonomic Polyneuropathy

Answer 4

• Constipation
• Loss of bowel/ bladder control
• Orthostatic hypotension
• **Erectile dysfunction (point) **& Ejaculatory failure (& shoot)
• Skin; pale & dry
• Horner’s syndrome
• Holmes-Adie pupil

Question 5

Outline the typical presentation of Motor Polyneuropathy

Answer 5

• Often progressive
• Weak/ clumsy hands
• Difficulting walks (fall, stumbling)
• Difficulting breathing
• LMN Lesion signs;
  
  • Hand & Foot DROP
  • Reduced/ absent reflexes

Question 6

Outline the typical presentation of Cranial Nerve Polyneuropathy

Answer 6

• Swallowing/ speaking difficulty
• Diplopia

Question 7

Define Small Fiber Peripheral Neuropathy?

• Common presentation
• Diagnosis

Answer 7

Damage to small unmyelinated peripheral nerve fibers (C Fibers)

Present in;

• Skin (somatic fibers)
• Organs (autonomic fibers)

Presentation;

• Sensory symptoms (highly variable)
  
  • Paraesthesias, Dysaethesias

Diagnosis

• Quantitative Sensory Testing (QST) assess small fiber function by measuring temperature & vibratory sensory
  
  • May be attributed to CNS problems though
  • Limited by patients subjectivity
• Quantitative Sudomotor Axon Reflex Testing (QSART) measures sweating responce at local body sites
• Skin Biopsy to measure epidermal nerve fiber density

Question 8

What is Guillain-Barre Syndrome (GBS)?

Outline;

• Definition
• Pathogenesis

Answer 8

GBS is the most common acute neuropathy

aka Acute inflammatory demyelinating polyneuropathy

Definition

• Inflammatory demyelinating (occasionally axonal) polyneuropathy

Pathogenesis

• Usually triggered by infection:
  
  • Campylobacter jejuni
  • Epstein-Barr virus
  • Cytomegalovirus
• Infectious organism shares epitopes with an antigen in peripheral nerve tissue
  
  • Ganglioside GM₁ and GQ1b
  • ⇒ Autoantibody mediated nerve cell damage
• Reached pinicle in 4wks then recovery
• 10% mortality

Question 9

Outline the clinical features of Guillain-Barre Syndrome (GBS)

Answer 9

• Progressive onset of limb weakness (usually symmetrical)
  
  • Reaches nadir within 4 weeks → recovery
  • Disability ranges from mild to severe (facial & respiratory muscle involvement)
  • Proximal muscles affect (unlike other polyneuropathies)
• Reflexes lost early
• Pain common
• Rarer
  
  • Sensory symptoms: paraesthesias. (Few signs)
  • Autonomic symptoms

Question 10

What is Miller Fisher syndrome?

Answer 10

Variant of Guillain-Barre syndrome (GBS)

Affects **cranial nerves to eye muscle: **opthalmoplegia & ataxia

Question 11

What is Chronic Inflammatory Demyelinating Polyradiculopathy (CIDP)?

Answer 11

Guillain-Barre characterized by slow onset & recovery

Question 12

How do you investigate Guillain-Barre syndrome (GBS)?

Answer 12

• Clinical diagnosis
• Nerve conduction studies
  
  • Slow motor conduction
  • Prolonged distal motor latency
  • Conduction block
• CSF protein non-specifically elevated (+ normal sugar & cell count)

Question 13

How do you investigate Miller Fisher syndrome?

Answer 13

Autoantibodies again GQb1 have sensitivity of 90%

Question 14

Ouline the management of Guillain-Barre syndrome

Answer 14

• Monitoring
  
  • Vital capacity/ 4hr (resp weakness)
    
    • <80% predicted = ITU (/ mechanical ventilation)
  • ECG (arrythmias)
• Treatment
  
  • IV Immunogloblin for 5d
    
    • Contraindications: IgA deficiency
  • Plasma exchange
• Supportive treatment
  
  • Heparin (thrombosis)
  • Physio
  • Tube feeding (swallowing difficulty)

Question 15

Outline Thiamine deficiency neuropathy

Outline;

• Demographic
• Presentation
• Treatment

Answer 15

Thiamine aka Vitamin B₁ deficiency

• Demographic
  
  • Alcoholics
  • Starvation
  • Beriberi [milled rice]
• Presentation
  
  • Wernicke-Korsakoff syndrome
  • Cardiac failure
  • Polyneuropathy (sensory, occasionally motor)
• Treatment
  
  • Thiamine (250mg IM/IV/ 3d)
    
    • Not parenteral: Anaphylaxis occurs

Question 16

Outline Pyridoxine deficiency neuropathy

Outline;

• Demographic
• Presentation
• Treatment

Answer 16

Pyridoxine aka Vitamine E₆ deficiency

• Demographic
  
  • Insoniazid therapy (complexes with pyridoxal phosphate) for TB in those who acetylate the drug slowly
• Presentation
  
  • Mainly sensory neuropathy
• Treatment
  
  • Prophylactic pyridoxine (10mg/d) given with Isoniazid

Question 17

Outline Vitamine B₁₂ deficiency neuropathy

Outline;

• Demographic
• Presentation
• Treatment

Answer 17

Vitamine B12 deficiency

• Demographic (examples)
  
  • Dietary (vegans due to no animal products)
  • Intrinsic factor deficiency (atrophic gastritis, surgery)
  • Malabsorption
• Presentation
  
  1. Polyneuropathy
  2. Subacute combined degeneration of the cord
     
     • Distal sensory loss (particularly posterior collumn)
     • Absent ankle jerks
     • Evidence of ord disease (exag. knee jerk reflex, extensor plantar responses)
• Treatment
  
  • IM vit B12 (little effect on CNS

Question 18

Outline Hereditary sensorimotor neuropathy

Outline;

• Charcot-Marie-Tooth disease
  
  • Aetiology
  • Presentation

Answer 18

Hereditary sensorimotor neuropathy are alarge & complex group with variable genetic mutations

Most common of which is Charcot-Marie-Tooth disease;

• Autosomal dominant
• Presentation
  
  • Distal limb wasting & progressive weakness over many years
    
    • Inverted champagne bottles
  • Variable sensory loss & reflexes