summary Charcot-Marie-Tooth Disease, also known as peroneal muscular atrophy, is a common autosomal dominant hereditary motor sensory neuropathy, caused by abnormal peripheral myelin protein, that presents with muscles weakness and sensory changes which can lead to cavovarus feet, scoliosis, and claw foot deformities. Diagnosis is made with nerve conduction studies showing low nerve conduction velocities with prolonged distal latencies in the peroneal, ulnar, and median nerves. Treatment involves a multidisciplinary approach to address neuropathy, cavovarus and claw foot deformities, and scoliosis. Epidemiology Incidence most common inherited progressive peripheral neuropathy 40:100,000 Etiology Pathophysiology HMSN Type I abnormal myelin sheath protein is the basis of this degenerative neuropathy. results in a combination of motor and sensory disturbances. HSMN Type 2 intact myelin sheath with wallerian axonal degeneration that results in mild sensory and motor conduction velocities. pathoanatomy affected muscles become weak peroneus brevis peroneal involvement is typically first and most profound results in muscle imbalance and varus deformity tibialis anterior weakness results in dropfoot intrinsic muscles of hand and foot check for wasting of 1st dorsal interosseous in hands Genetics inheritance autosomal dominant duplication of chromosome 17 (most common) codes for peripheral myelin protein 22 (PMP 22) expressed in Schwann cells (most common) X-linked connexin 32 may also be autosomal recessive X-linked Orthopedic manifestations pes cavovarus claw toes hip dysplasia scoliosis hand muscle atrophy and weakness Classification The major categories of Charcot-Marie-Tooth are Types 1 through 7 an X-linked category Classification of CMT Type I A demyelinating condition that slows nerve conduction velocity Characteristics: 1. autosomal dominant 2. onset in first or second decade of life 3. most commonly leads to cavus foot 4. normal life expectancy 5. motor involvement more profound than sensory Type II Direct axonal death caused by Wallerian degeneration (not demyelination) Characteristics: 1. Usually less disabled than Type I 2. onset in second decade of life or later 3. most commonly leads to flaccid foot Presentation Symptoms motor deficits initial symptoms are distal weakness and atrophy of the distal muscles instability during gait clumsiness frequent ankle sprains difficulty climbing stairs lateral foot pain sensory sensory deficits are variable Physical exam lower extremity cavovarus foot (similar to Freidreich's ataxia) with hammer toes or clawing of toes usually bilaterally and symmetric. occurs due to unoposed pull of peroneus longus causing plantarflexion of the first ray and compensatory hindfoot varus. initially flexible, but progresses to a rigid deformity motor weakness peroneal weakness weakest muscles around foot and ankle anterior tibialis weakens next, but typically stronger than the peroneals can lead to drop foot in swing initially and later to a fixed equinus posterior tibialis stays strong for a prolonged period of time calf atrophy rarely significant present weak intrinsics including weak EDB and EHB clawtoes hyporeflexia or areflexia Coleman block test test to determine if hindfoot varus deformity is secondary to plantar-flexed first ray vs an independent component. If deformity corrects with Coleman block, this suggests a forefoot driven varus deformity. If deformity does not correct with Coleman block, this suggests hindfoot driven varus deformity. a rigid hindfoot will not correct into neutral upper extremity intrinsic wasting of hands weak pinch and grasp spine scoliosis may be evident on Adam's forward bend test Studies NCS low nerve conduction velocities with prolonged distal latencies are noted in peroneal, ulnar, and median nerves can also see low amplitude nerve potentials due to axonal loss Genetic Testing key component for diagnosis of CMT DNA analysis PCR analysis used to detect peripheral myelin protein 22 (PMP22) gene mutations chromosomal analysis duplication on chromosome 17 seen in autosomal dominant (most common) form Cavus Foot Deformity Introduction evaluation and treatment follows same principals for cavovarus foot pathophysiology plantar flexed 1st ray is initial deformity cavus caused by peroneus longus (more normal) overpowering weak tibialis anterior weak intrinsics and contracted plantar fascia varus caused by tibialis posterior (normal) overpowering weak peroneus brevis Treatment nonoperative accomodative shoe wear indications rarely sufficient except in mild deformity full-length semi-rigid insole orthotic with a depression for the first ray and a lateral wedge indications mild cavus foot deformity in adult (not indicated in children) supramalleolar orthosis (SMO) indications more severe cavovarus deformity recalcitrant to shoewear accomodations ankle foot orthosis (AFO) indications may be needed if equinus also present, resulting in equinocavovarus foot deformity works best if equinus is a dynamic defomrity (not rigid) lace-up ankle brace and/or high-top shoe or boots indications may consider in moderate deformities when patient does not tolerate the more rigid bracing with an SMO or AFO operative soft tissue reconstruction indications flexible deformity in adolescents with closed physes failed conservative management of fixed deformities performed with a combination of the following procedures plantar release (plantar fascia +/- Steindler stripping, i.e. release of short flexors off the calcaneus) indications cavus peroneus longus to brevis transfer indications plantar flexed first ray rationale decreases plantarflexion force on first ray without weakening eversion posterior tibial tendon transfer indications muscle imbalance: posterior tibialis typically is markedly stronger than evertors and maintains strength for a long time in most cavovarus feet may consider transfer of posterior tibialis to dorsum of foot if severe dorsiflexion weakness of anterior tibialis lengthening of gastrocnemius or tendoachilles (TAL) indications true ankle equinus outcomes gastrocnemius recession produces less calf weakness and can be combined with plantar release simultaneously (TAL should be staged several weeks after plantar release) Jones transfer(s) of EHL to neck of 1st MT and lesser toe extensors to 2nd-5th MT necks indications toe clawing combined with cavus foot performed if the indication is met and time permits 1st metatarsal dorsiflexion osteotomy indications flexible hindfoot cavus deformities (normal Coleman block test and/or passive hindfoot eversion past neutral) triple arthrodesis, lateral calcaneal slide or closed-wedge osteotomy indications performed if deformity does not correct with Coleman block test. 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, which becomes rigid with time Treatment operative Jones procedure indications for symptomatic claw toe deformity which has failed non-operative measures technique transfers extensor tendons of the great and lesser toes to 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 and the plantar aspect of the metatarsal heads Hip dysplasias Introduction hip dysplasia is sometimes associated with CMT (typically less than 10%) may present during adolescence in ambulatory patients Treatment pelvic osteotomy indications symptomatic hip dysplasia outcomes higher rate of sciatic nerve palsy after surgery Scoliosis Introduction often occurs in children with CMT ( ~ 10-20%) characteristic left thoracic and kyphotic curve distinguish from idiopathic scoliosis Treatment nonoperative bracing indications bracing rarely effective so not typically used operative fusion and instrumentation indications progressive deformity with scoliosis > 50 degrees