Charcot-Marie-Tooth Disease

Question 1

Charcot-Marie-Tooth Disease

Answer 1

also known as hereditary motor and sensory neuropathy (HMSN) or peroneal muscular atrophy, is the most common inherited disorder affecting motor and sensory nerves.
Initially the disorder involves the fibular (peroneal) nerve and affects muscles in the foot and lower leg.
It later progresses to the muscles of the forearms and hands, making activities like buttoning or writing difficult.

Question 2

Incidence

Answer 2

CMT is relatively common; it is estimated that 1 in 2 5 0 0 persons in the United States has some form of CMT. Onset may occur in childhood or adulthood.

Question 3

Etiology

Answer 3

genetically heterogenous neuropathy that is inherited as autosomal dominant, autosomal recessive, or X-linked pattern. 1 7 0 Chromosomal defects create either duplication, deletion, or point mutations in the genetic code for proteins that are involved in the process of myelination

Question 4

CMT1 is

Answer 4

most common; subdivided into three forms CMT1A, CMT1B, CMT1C
CMT1A accounts for 70% of all CMT1 cases (chromosome 17)
Creates segmental demyelination of the fibular nerve
Slowly progressive and begins in childhood
Hypertrophic onion bulb formation – creates palpable, enlarged peripheral nerves

Question 5

CMT2

Answer 5

less common, (chromosomes 1, 8 and X)
Creates axonal degeneration
Onset varies between second and seventh decades
Less involvement of small muscles of hands

Question 6

Clinical signs

Answer 6

Distally symmetric muscle weakness, atrophy and diminished DTRs
Pes cavus deformities and hammer toes
Weakness of dorsiflexors and evertors
Causes footdrop (steppage) gait
With progression, involvement will be seen distally in U.E.
Weakness and wasting of intrinsic muscles of hand followed by wasting in forearms
Because CMT1 demyelinates peripheral nerves, proprioception is lost in foot and ankles
Cutaneous sensation is diminished in foot and lower legs
Sensory loss is minimal in CMT2
With progression of muscle atrophy of the muscles below the knees, the legs take on the shape of an inverted champa

Question 7

Prognosis and Management

Answer 7

Is a slowly progressive disorder
If unmanaged, contracture formation resulting from weakness will create further gait abnormalities which leads to an increase in number of falls
In the U.E., may develop problems with writing and handling objects
The goal is to minimize deformity and maximize function
With imbalance in tibialis anterior and peroneus longus and tibialis posterior and peroneus brevis, leads to a pes cavus and varus deformity
This combined with a loss of proprioception and some degree of cutaneous involvement can lead to unsteady gait
These problems should be addressed with stretching, ROM exercises and bracing