Charcot-Marie-Tooth Disease 356.1

synonyms:HMSN, CMT, Hereditary Sensorimotor Neuropathy, HNPP, hereditary neuropathy with predisposition for pressure palsy

Charcot-Marie-Tooth Disease  ICD-9

• 356.1 Peroneal muscular atrophy; Charcot-Marie-Tooth disease, Neuropathic muscular atrophy

Charcot-Marie-Tooth Disease  Etiology / Epidemiology / Natural History

• most common Hereditary motor-sensory neuropathy (HMSN): Most-common inherited demyelinating neuropathy
• life expectancy, intellectual function are normal
• male > female, females more severe
• affects 1/2500 people
• 17 genetic vairiants have thus far been determined.  HMSN Type 1=AD form is a duplication of chromosome 17p11.2.  HMSN Type 2=AR, neuronal form
• Caused by chromosome 17 abnormalites which encode for peripheral myelin protein 22 (PMP-22). Which leads to dysfunciton in the compact myelin sheath laid down by Schwann cells.
• CMT is a duplication of the PMP-22 gene.
• HNPP = hereditary neuropathy with predisposition for pressure pasly = a CMT related disorder caused by deletion of PMP-22 gene.
• can be autosomal-dominant, autosomal-recessive or X-linked
• diagnosis is made based on clinical appearance of the foot and positive family history. There is no definitive diagnostic technique.

Charcot-Marie-Tooth Disease  Anatomy

•  intrinsic foot muscles affected first followed by peroneus brevis, >>anterior tibialis >> EDC
• Forefoot equinus develops as a result of an imbalance between the tibialis anterior muscle and the peroneus longus muscle.
• posterior compartment and peroneus longus pull foot into forefoot and ankle equinus
• The peroneus longus tendon courses from plantar lateral to medial and inserts into the base of the first metatarsal.  It opposes the action of the tibialis anterior muscle dorsally.  In CMT disease, the tibialis anterior and peroneus brevis muscles are weak.  The peroneus longus is unopposed and plantarflexes the first ray, creating forefoot equinus

Charcot-Marie-Tooth Disease  Clinical Evaluation

• present 1-3 decade, +family hx
• slowly progressive distal muscular weakness and atrophy with minor deficits in sensation
• c/o deformity and awkward gait, muscle cramping
• symmetric elevation of arches(pes cavus), plantar flexed first ray, hindfoot varus, claw toes, decreased ankle jerk, flatfoot or heal-toe gait.  May have callosities beneath MT heads
• Coleman Block test=plantar-flex first mt is allowed to hang free from block beneath foot.  If supple deformity the hindfoot corrects.
• evaluation for developmental hip dysplasia indicated(Van Erve J Pediatric Orthop 19:92;1999)
• HNPP symptoms are simlar to CTS, ulnar neuropathy, or peroneal nerve palsy often without high arched feet.
• Often have positive family history

Charcot-Marie-Tooth Disease  Xray / Diagnositc Tests

• EMG/NCV: nerve conduction slowing (20m/s), may show reinnervation in distal muscles. May be demyelinating or axonal.
• Consider genetic confirmation.

Charcot-Marie-Tooth Disease  Classification / Treatment

• fixed vs flexible
• Flexible=bracing vs plantar fascia release, closing wedge dorsiflexion osteotomy of 1st mt, calcaneal sliding and closing wedge osteotomy, transfer of peroneus longus into peroneus brevis a the level of the distal fibula, +/- TAL (Roper JBJS 71B:17;1989)
• Fixed=triple arthrodesis with transfer of posterir tib tendon throught the interosseous membrane and a TAL  (Wetmore JBJS 71A:417;1989)
• Foot drop with equinus contracture = gastrocnemius lengthening and transfer of the tibialis posterior tendon to the dorsum of the foot 

Charcot-Marie-Tooth Disease  Associated Injuries / Differential Diagnosis

• Amyotrophic lateral sclerosis (Lou Gerig's disease)
• Huntington's chorea
• Friedreich's ataxia
• Gullian-Barre syndrome
• Diabetic neuropathy
• Radiculopathy
• Cervical/lumbar stenosis
• also see Cavovarus foot

Charcot-Marie-Tooth Disease  Complications

Charcot-Marie-Tooth Disease  Follow-up Care

Charcot-Marie-Tooth Disease  Review References

• Guyton GP, Mann RA. The pathogenesis and surgical management of foot deformity in Charcot-Marie-Tooth disease. Foot Ankle Clin. 2000 Jun;5(2):317-26. 
• Beals TC, Nickisch F. Charcot-Marie-Tooth disease and the cavovarus foot. Foot Ankle Clin. 2008 Jun;13(2):259-74.
• Alexander IJ, Johnson KA: Assessment and management of pes cavus in Charcot-Marie-Tooth disease.  Clin Orthop 1989;246:273-281.
• Wetmore RS, Drennan JC: Long-term results of triple arthrodesis in Charcot-Marie-Tooth disease.  J Bone Joint Surg 1989;71A:417-422.
• Holmes JR, Hansen ST Jr: Foot and ankle manifestations of Charcot-Marie-Tooth disease.  Foot Ankle 1993;14:476-486