Neuromuscular

Hereditary neuropathies - CMT, peroneal atrophy, Friedreich's

Inherited peripheral neuropathies and ataxias: diagnosis, nerve conduction findings, deformity and surgery

17 questions 3 source pages

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Q1What is CMT/hereditary motor sensory neuropathy and how is it inherited?▸

Q2Compare CMT type 1 and type 2.▸

Type 1: AD, demyelinating, onset 10-20 y.o., cavus foot
Type 2: most AD, some AR, direct axonal death, onset >20 y.o., flaccid foot

Q3What is the differential diagnosis of pes cavus?▸

Unilateral: polio, post-ischaemia contracture, Charcot
Bilateral: CP, syringomyelia, Friedrich ataxia, spinal bifida, CMT

Q4What muscle imbalances cause cavus, varus, claw toe and big toe plantarflexion?▸

Q5What is the management goal and conservative management of CMT?▸

Investigation: EMG, DNA test
Goal: stable, plantigrade, shoeable, painless foot best with mobility
Prefer bony procedures as the disease is progressive
Conservative: lateral wedge insole to correct hindfoot varus; AFO if footdrop

Q6What are the operative options in CMT?▸

Varus: PL to PB transfer, lateral sliding osteotomy
Cavus: Steindler procedure, Jone’s procedure, dorsal closing wedge osteotomy
Planter flexed big toe: Jone’s procedure
Claw toes: EDL lengthening, EDB tenotomy, PP excisional arthroplasty, TA lengthening

Q7What is the epidemiology and genetics of hereditary motor sensory neuropathy?▸

Q8What are the three main types of hereditary motor sensory neuropathy?▸

Q9How does peroneal muscle atrophy present?▸

Motor deficits: weakness, instability, clumsiness, frequent ankle sprains, difficulty with stairs
Lateral foot pain
Sensory deficit

Q10What are the examination findings in peroneal muscle atrophy?▸

Cavovarus +/- rigid hindfoot
Weakened tibialis anterior and peroneal muscles (foot drop during swing phase)
Hyporeflexia or areflexia

Q11What other orthopaedic manifestations are associated with peroneal muscle atrophy?▸

Q12How is peroneal muscle atrophy diagnosed?▸

Q13What is the inheritance, genetics and neuroanatomical involvement of Friedreich's ataxia?▸

Commonest spinocerebellar degenerative disease
Autosomal recessive (frataxin mutation affecting mitochondria production)
Affects the cerebellar system, dorsal root ganglia, corticospinal tract and sensory peripheral nerve

Q14What is the classic triad and gait finding of Friedreich's ataxia?▸

Q15What conditions are associated with Friedreich's ataxia?▸

Q16How is Friedreich's ataxia diagnosed?▸

Q17At what age does loss of ambulation (LOC) occur and what is the life expectancy in Friedreich's ataxia?▸

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