Charcot-Marie-Tooth Disease (peroneal muscular atrophy)

Topic updated on 04/30/16 2:00pm
  • A hereditary motor sensory neuropathy (HMSN) that has two forms resulting in muscles weakness and sensory changes
  • Epidemiology
    • most common inherited neurological disease
    • 1:2,500
  • Pathophysiology
    • combination of motor and sensory disturbances as a result of nerve damage
      • motor involvement more profound than sensory
    • affected muscles become weak 
      • peroneus brevis
      • tibialis anterior
      • intrinsic muscles of hand and foot
  • Genetics
    • inheritance
      • autosomal dominant (most common)
      • may also be
        • autosomal recessive
        • X-linked
    • mutations
      • duplication on chromosome 17 
        • codes for peripheral myelin protein 22 (PMP 22
        • X-linked connexin 32
  • Orthopedic manifestations  
    • pes cavus 
    • hammer toes 
    • hip dysplasia 
    • scoliosis
 Classification of CMT
Type I demyelinating condition that slows nerve conduction velocity 
   1. autosomal dominant
   2. onset in first or second decade of life
   3. most commonly leads to cavus foot
Type II Direct axonal death caused by Wallerian degeneration (not demyelination) 
   1. Usually less disabled than Type I
   2. onset in second decade of life or later
   3. most commonly leads to flaccid foot
  • Symptoms
    • lateral foot pain 
    • sensory deficits are variable
    • clumsiness
    • frequent ankle sprains
    • difficulty climbing stairs
  • Physical exam
    • lower extremity
      • rigid cavovarus foot (similar to Freidreich's ataxia) with hammer toes or clawing of toes 
      • atrophied EDB and EHB
      • calf atrophy
      • weak dorsiflexion and eversion due to weak tib ant and peroneals (foot drop during swing phase)
      • lower limb areflexia
      • Coleman block test
        • test to evaluate flexibility of hindfoot
          • flexible hindfoot will correct to neutral when block placed under lateral aspect of foot
          • a rigid hindfoot will not correct into neutral
    • upper extremity
      • intrinsic wasting of hands
  • EMG
    • low nerve conduction velocities with prolonged distal latencies are noted in peroneal, ulnar, and median nerves
  • Genetic Testing
    • DNA analysis
      • PCR analysis used to detect peripheral myelin protien 22 (PMP22) gene mutations
    • chromosomal analysis
      • duplication on chromosome 17 seen in autosomal dominant (most common) form
Cavus Foot Deformity
  • Introduction
    • plantar flexed 1st ray is initial deformity 
    • cavus caused by peroneus longus (normal) overpower weak tibialis anterior  
    • varus caused by tibialis posterior (normal) overpowering weak peroneus brevis
  • Treatment
    • follows similar treatment principals to cavovarus foot
    • nonoperative
      • stretching, strengthening, and orthotics
        • indications
          • as initial management of a young patient
        • modalities
          • stretching & strengthening
            • should focus on mobilization and strengthening of the weakening muscular units (peroneals, tibialis anterior)
          • orthotics 
            • includes accommodative inserts and orthotic devices for flexible deformity
            • in a flexible deformity the orthosis should post lateral forefoot and the lateral heel   
            • AFOs for foot drop
    • operative
      • plantar fascia release, tibialis posterior or peroneus longus tendon transfer, (+/-) TAL, (+/-) 1st metatarsal dorsiflexion osteotomy
        • indications
          • flexible hindfoot cavus deformities (normal Coleman block test)
          • surgical intervention should be delayed until progression of the deformity begins to cause symptoms and/or weakness of the muscular units, resulting in contractures of the antagonistic muscle units.
        • technique
          • tendon transfer (two method depending on involved muscels)
            • posterior tibialis transfer to dorsum of foot to improve foot drop (augment weak tibialis anterior)   
            • peronues longus transfer to peroneus brevis (if peroneus longus is normal)
      • calcaneal valgus producing osteotomy
        • indications 
          • rigid hindfoot cavus deformities (abnormal Coleman block test)
        • technique
          • combine with soft tissue procedure discussed above, and dorsiflexion 1st metatarsal osteotomy
      • triple arthrodesis 
        • indications
          • severe rigid deformities
          • may be helpful in select cases but is falling out of favor
      • 1st metatarsal osteotomy and transfer of EHL to neck of 1st MT 
        • indications
          • if there is hallux clawing combined with cavus foot
Claw Toes Deformity
  • Introduction
    • ankle dorsiflexion weakness may result in the recruitment of toe extensors for assistance
      • in the setting of intrinsic muscle weakness, increased toe extensor activity can lead to claw toe deformity
  • Treatment
    • operative
      • Jones procedure 
        • indications
          •  for symptomatic claw toe deformity which has failed non-operative measures
        • technique
          • transfers the extensor tendons of the great and lesser toes through the bone into the metatarsal neck
          • goal is to increase contributions to ankle dorsiflexion and decrease clawing in order to relieve pain on the dorsum of the toes
Hip dysplasias
  • Introduction
    • hip dysplasia is sometimes associated with CMT
      • may present during adolescence in ambulatory patients
  • Treatment
    • pelvic osteotomy
      • indications
        • end-stage osteoarthritis
      • outcomes
        • higher rate of sciatic nerve palsy after surgery
  • Introduction
    • often occurs in children with CMT
    • characteristic left thoracic and kyphotic curve distinguish from idiopathic scoliosis
  • Treatment
    • nonoperative
      • bracing
        • indications
          • bracing rarely effective
    • operative
      • fusion and instrumentation
        • indications
          • progressive deformity


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Qbank (14 Questions)

(SBQ04.2) A 14-year-old male child presents with the increasing foot deformity shown in Figure A. On physical exam, it is noted that he is unable to walk on his heels and has decreased Achilles reflexes bilaterally. Coleman block testing reveals correctable hindfoot deformity. Which procedure is associated with improved clinical outcomes in patients with the above described condition? Topic Review Topic
FIGURES: A          

1. Transfer of peroneus brevis to peroneus longus
2. Split anterior tibial tendon transfer to lateral column
3. Triple arthrodesis
4. Posterior tibial tendon transfer through the interosseous membrane to dorsum of the foot
5. Lateral column lengthening calcaneal osteotomy

(OBQ12.248) A mutation of PMP22 located at chromosome 17p12 most likely leads to an initial presentation highlighted by a: Topic Review Topic

1. Weak tibialis posterior
2. Weak peroneus longus
3. Strong peroneus brevis
4. Strong peroneus tertius
5. Weak tibialis anterior

(OBQ10.56) A 32 year-old male complains of lateral foot pain and a progressively awkward gait. He has a family history of "foot problems" and reports some minor burning and numbness in both feet. He has no other medical problems, and takes no medications. Physical exam reveals bilateral cavus feet with clawing of the toes and intrinsic muscle wasting of the hands. A clinical photograph is shown in Figure A. Which of the following is responsible for the patients initial symptoms and awkward gait? Topic Review Topic
FIGURES: A          

1. Weak gastrocnemius-soleus complex
2. Peroneus brevis overpowering the posterior tibial tendon
3. Tibialis anterior overpowering the peroneus longus
4. Plantar flexion of the first ray
5. Clawing of the toes

(OBQ10.129) The PMP22 (peripheral myelin protein 22) is found at the cytogenetic location found in Figure A. What pediatric congenital disorder is associated with a mutation of this gene?

Topic Review Topic
FIGURES: A          

1. Duchenne's/Becker's muscular dystrophies
2. Limb-girdle dystrophies
3. Myotonic dystrophy
4. Charcot-Marie-Tooth disease
5. Spinal muscular atrophy

(OBQ10.224) A 22-year-old woman is concerned about frequent ankle sprains and an awkward gait. Lower extremity nerve conduction velocities show prolonged distal latencies in the peroneal nerves. DNA testing shows a duplication on chromosome 17. Which of the following images is most likely the radiograph of this patient? Topic Review Topic
FIGURES: A   B   C   D   E  

1. Image A
2. Image B
3. Image C
4. Image D
5. Image E

(OBQ08.29) A 5-year-old boy has bilateral cavus feet and genetic testing reveals duplication of the PMP (peripheral myelin protein) gene on chromosome 17. What is the most likely diagnosis? Topic Review Topic

1. Myelodysplasia
2. Ewings Sarcoma
3. Charcot-Marie-Tooth Disease
4. Cerebral Palsy
5. Poliomyelitis

(OBQ06.75) Plantar flexion of the first ray is the initial deformity seen in which condition? Topic Review Topic

1. Oblique talus
2. Kohler's disease
3. Charcot-Marie-Tooth
4. Calcaneovalgus foot
5. Juvenile hallux valgus

(OBQ06.83) A 42-year-old woman with Charcot-Marie-Tooth disease complains of longstanding foot pain. Orthotics, bracing, and NSAIDs no longer provide relief. She has cavovarus hindfoot deformity that does not correct with Coleman block testing. Radiographs are notable for degenerative changes within the talocalcaneal and calcaneocuboid joints. Which of the following is the most appropriate treatment? Topic Review Topic

1. Split tibialis posterior transfer
2. Triple arthrodesis
3. Lateral closing wedge calcaneal osteotomy with peroneus longus to brevis transfer
4. First metatarsal dorsal closing wedge osteotomy
5. Achilles tendon lengthening

(OBQ05.47) Lateral forefoot and heel posts would be the appropriate orthotic for the foot deformities associated with which of the following conditions? Topic Review Topic

1. Charcot-Marie-Tooth disease
2. Stage II posterior tibial tendon insufficiency
3. Stage III posterior tibial tendon insufficiency
4. Charcot arthropathy
5. Hallux rigidus

(OBQ05.87) The cavus deformity in Charcot-Marie-Tooth disease is caused by what muscular imbalance? Topic Review Topic

1. Peroneus brevis overpowering peroneus longus
2. Tibialis anterior overpowering tibialis posterior
3. Achilles overpowering tibialis anterior
4. Extrinsic toe flexors overpowering intrinsics
5. Peroneus longus overpowering tibialis anterior

(OBQ05.254) A 17-year-old male complains of a foot deformity that has progressed over the past 1 year. He has pain along the lateral border of his foot with walking. His father has had similar problems with both feet throughout his life. A clinical photograph of the foot is provided in Figure A. Proper management of this patient should include evaluation for which of the following findings? Topic Review Topic
FIGURES: A          

1. Acetabular dysplasia
2. Cervical stenosis
3. Uveitis
4. Hypoplastic thumb
5. Thrombocytopenia

(OBQ04.211) A 24-year-old male with hereditary motor sensory neuropathy complains of worsening bilateral foot pain with ambulation and limited walking tolerance. Clinical photographs are shown in Figures A and B. The deformity corrects with Coleman block testing. Radiographs of the left foot are provided in Figures C-E. Which of the following is the best initial management for this patient? Topic Review Topic
FIGURES: A   B   C   D   E  

1. Custom orthotics with posting of the lateral forefoot and lateral heel
2. Custom orthotics with posting of the medial forefoot and medial heel
3. Custom orthotics with medial heel posting and lateral forefoot recession
4. Gastrocnemius slide followed by dorsiflexion casting
5. Dorsal first metatarsal osteotomy with calcaneal slide osteotomy

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