Peripheral neuropathy Flashcards
What are the different types of neuropathy?
- Mononeuropathy (single nerve affected)
- Multiple mononeuropathies (mononeuritis multiplex)
- Symmetrical polyneuropathy
Name some genetic causes of polyneuropathy?
- Charcot-Marie-Tooth (CMT) disease
- Familial amyloid polyneuropathy
What drugs can cause a polyneuropathy?
- Amiodarone
- Antibiotics (dapsone, isoniazid, metronidazole, ethambutol)
- Chemotherapy (cisplatin, vincristine, thalidomide)
- Phenytoin
What toxins can cause a polyneuropathy?
- Alcohol
- Recreational use of nitrous oxide
What vitamin deficiencies can cause a polyneuropathy?
- Thiamine
- Pyridoxine
- Vitamin E
- Vitamin B12
What infections can cause a polyneuropathy?
- HIV
- Leprosy
- Brucellosis
Name some inflammatory causes of polyneuropathy?
- Vasculitis
- Guillain-Barre syndrome
- Chronic inflammatory demyelinating polyradiculoneuropathy
Systemical medical conditions which can cause a polyneuropathy?
- Diabetes
- Renal failure
- Sarcoidosis
What are the types of polyneuropathy and why is it important to make a distinction?
- Axonal
- Damage to the nerve cell body
- Demyelinating
- Damage to the myelin sheath
- * Only demyelinating neuropathies are susceptible to treatment
What does motor nerve involvement in neuropathies result in?
LMN lesions
What does autonomic nerve involvement in neuropathies result in?
- Usually complications other neuropathies
- Postural hypotension
- Disturbance of sweating
- GI, bladder and sexual dysfunction
Describe some investigations into peripheral neuropathy?
- Glucose (fasting)
- ESR, CRP, FBC, U&Es, LFTs
- Serum protein electrophoresis
- Vitamin B12, folate
- ANA, ANCA
- HIV testing
Describe entrapment neuropathies?
- Usually the cause of a mononeuropathy
- Predisposing factors: DM, excess alcohol, genetic syndromes
\Describe an entrapment neuropathy of the median nerve?
- At wrist, carpal tunnel syndrome
- Pain/paraesthesia on palmar aspect of hands and fingers
- Waking patient from sleep. Pain may extend to arm and shoulder.
- Motor loss:
- Abductor pollicis brevis
- Sensory loss:
- Lateral palm and thumb, index, middle and lateral half of fourth finger
Describe an entrapment neuropathy of the ulnar nerve?
- Entrapment at elbow
- Paraesthesia on medial border of hand, wasting and weakness of hand muscles
- Motor involvement:
- All small hand muscles, except abductor pollicis brevis
- Sensory involvement:
- Medial palm and little finger, and medial half fourth finger
Describe an entrapment neuropathy of the radial nerve?
- Weaknesss of extension of wrist and fingers, often precipitated by sleeping in abnormal posture eg arm over back of chair
- Motor involvement:
- Wrist and finger extensors, supinator
- Sensory involvement:
- Dorsum of thumb
Describe an entrapment neuropathy of the common peroneal nerve?
- Foot drop, trauma to head of fibula
- Motor involvement:
- Dorsiflexion and eversion of foot
- Sensory involvement:
- Nil or dorsum of foot
Describe an entrapment neuropathy of the lateral cutaneous nerve of the thigh?
- Meralgia paraesthetica
- Tingling and dysasthesia on lateral border of thigh
- Motor involvement:
- Nil
- Sensory involvement:
- Lateral border of thigh
Name some causes of Axonal multifocal mononeuropathy?
- Defined on nerve conduction studies
- DM
- Vasculitis
- Sarcoidosis
- Infec tion (HIV, HCV, Lyme disease, diphtheria)
Name some causes of Focal demyelination causes of multifocal mononeuropathy?
- Multifocal motor neropathy
- Multiple compression neuropathies
- Lymphoma
What is the most common polyneuropathy?
Length-dependent pattern
Describe Length dependent polyneuropathy?
- Occurs in the longest periphertal nerves first
- Affects the LLs before the ULs
- Develop in an ascending glove and stocking distribution
Describe Guillain-Barre syndrome?
- Immune mediated conditions
- Most common variant is an acute inflammatory demyelinated polyneuropathy (AIDP)
- Can be associated with Campylobacter jejuni
- Acute paralysis developing over days or weeks with a loss of tendon reflexes
What are the clinical features of Guillain-Barre?
- Distal paraesthesia and pain precede muscler weakness
- Ascends rapidly from lower to upper limbs
- Facial and bulbar weakness
- Respiratory weakness requiring ventilatory support in 20%
Describe the timing of the clinical features Guilain-Barre?
- Weakness can develop over 4 weeks
- Respiratory failure can develop within hours
Signs of Guillain-Barre on examination?
- Diffuse weakness
- Loss of reflexes
Describe Miller Fisher syndrome?
- Variant of Guillain-Barre Syndrome
- Involves anti-GQ1b anitbodies
- Internal and external opthalmoplegia
- Ataxia
- Areflexia
Describe the investigations into Guillain-Barre?
- Nerve conduction studies
- Slowing of nerve conduction velocity
- CSF
- Elevated protein
- LFTs
- Elevated AST/ALT
- Spirometry
- Reduced vital capacity
Describe the management of Guillain-Barre syndrome?
- Plasma exchange
- or
- IV immunoglobulin
- Supportive treatments
What is the most common cause of chronic neuropathy?
Diabetes mellitus
What is Charcot-Marie-Tooth disease (CMT)?
Umbrella term for the inherited neuropathies
Most common type of Charcot-Marie-Tooth (CMT) disease?
- Autosomal dominantly inherited CMT type 1
- Mutation of PMP-22 gene
What are the common signs of Charcot-Marie-Tooth disease?
- Distal wasting
- Inverted champagne bottle legs
- Pes cavus
- Predominantly motor involvement
Describe Brachial plexopathy?
Trauma damage to the upper or lower parts of the brachial plexus
Upper brachial plexus damage?
- Erb-Duchenne palsy
- Affected muscles:
- Biceps, deltoid, rhomboids, brachioradialis, triceps
- Sensory loss:
- Patch over deltoid
Describe lower brachial plexus damage?
- Affected muscles
- All small hand muscles, ‘claw hand’ (ulnar wrist flexors)
- Sensory loss
- Ulnar border of hand/forearm
Describe the symptoms of thoracic outlet syndrome?
- Affected muscles
- Small hand muscles, ulnar forearm
- Sensory loss
- Ulnar border of hand/forearm/upper arm
Describe Neuralgic amyotrophy?
- aka Brachial neuritis
- Presents as acute brachial plexopathy of inflammatory origin
- Severe shoulder pain -> patchy upper brachial plexus lesion
- Autosomal dominant form exists
Differential for Neuralgic amyotrophy?
- Motor herpes zoster
- Appearance of vesicles
