Charcot-Marie Tooth Disease Flashcards
What is Charcot-Marie Tooth Disease
A form of hereditary motor and sensory neuropathy
What is the most common gene affected in Charcot-Marie Tooth
Chromosome 17- PMP22 gene
What is the method of inheritance of Charcot-Marie Tooth
Autosomal Dominant most commonly. Can also be autosomal recessive
When does CMT usually present
Puberty - most commonly
What is the pathophysiology of CMT
Peripheral neuropathy affecting both motor and sensory nerves
What are some of the signs of CMT
Distal limb weakness - pes cavus, toe clawing, contracture of achilles tendon, claw hand (if upper limb affected) Wasting of small muscles of the hand Sensory loss in stocking distribution Hyporeflexia - absent ankle jerks Champagne bottle legs - advanced cases High stepping gait - bilateral foot drop Well preserved thigh musculature
How do you differentiate CMT from MND or muscular dystrophy
Muscular atrophy begins in distal portions of affected muscles, unlike global atrophy of MND or muscular dystrophy
The degree of disability is minimal despite marked deformity
What are other causes bilateral of pes cavus?
Friedreich's ataxia Muscular dystrophies Spinal muscular atrophy Cerebral palsy Hereditary spastic paraparesis Spinal cord tumours
What are unilateral causes of pes cavus?
Fracture malunion- calcaneus or talus Burns Compartment syndrome sequelae Poliomyelitis Spinal trauma/tumour
How would you manage a patient with CMT?
No specific treatment- MDT approach including neurologists, orthopaedic surgeons, physios, OTs
Conservative: Patient education and advice
Physio to maintain limb function
Walking aids +/- AFOs
OT
Medical: Analgesia for MSK/neuropathic pain
Surgical: Orthopaedic surgery to correct deformities
Where would you be most likely to feel thickened nerves in CMT?
Common peroneal (around fibula)
In HSMN1 (most common), what is the mechanism of nerve damage?
Demyelination
AD inheritance
In HSMN2 (2nd most common), what is the mechanism of nerve damage?
Axon degeneration
AD inheritance
How would you investigate a patient with suspected CMT?
Nerve conduction studies- differentiate HSMN1 from 2 (reduced conduction velocity in demyelination vs reduced amplitude in axon degeneration)
Genetic testing
