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Detailed information of CHARCOT-MARIE-TOOTH DISEASE
CHARCOT-MARIE-TOOTH DISEASE
DEFINITION:
A hereditary neurological disorder characterized by demyelination
of motor nerves resulting in progressive distal muscle weakness.
EPIDEMIOLOGY:
- incidence: 3.8/100,000 (prevalence)
- age of onset:
- usually begins in adolescence but variable from childhood to
the end of the 5th decade
- risk factors:
- familial - autosomal dominant with 82% expressivity
- M = F
PATHOGENESIS:
- a group of hereditary disorders characterized by progressive
distal muscle weakness
- also called Peroneal Muscular Atrophy
- motor nerves are predominantly affected with sensory and
autonomic nerve involvement occurring later
- there are 3 clinical variants:
- can be subdivided into demyelinating (Types I + III) and
non-demyelinating or neuronal (Type II)
2. Genetic Defect
- genetic defect -> demyelination of peripheral motor nerves
-> peroneal and tibial nerves most severely affected ->
progressive atrophy of the muscles of the anterior compartment
of the lower legs -> progressive weakness of the distal muscles
of the lower limb with gait disturbances
- proximal muscle weakness is mild and a late manifestation
with no involvement of the axial muscles
CLINICAL FEATURES:
- distal muscle weakness
- clumsiness, frequent falls, tripping over feet
- atrophy of the anterior compartment muscles (anterior
tibialis, peroneal) producing a characteristic "stork-like"
contour of the legs
- bilateral progressive weakness of ankle dorsiflexion ->
eventual foot drop
- pes cavus deformity due to denervation of the intrinsic
foot muscles
- loss of distal deep tendon reflexes -> areflexia
2. Upper Limbs
- distal muscle weakness
- atrophy of muscles in the forearm and hands may occur
but is usually a late finding
- contractures of the wrists and fingers may produce a
"claw hand"
2. Sensory Nerves
- progressive loss of proprioception and vibration sense
with involvement of large myelinated nerve fibres - may also
loose sensation to pain and temperature - tingling or burning
sensations of the feet (rarely pain)
3. Autonomic Nerves
- cold feet with blotching or pallor of the skin of the feet
due to poor vasomotor control
- normal sphincter control with no involvement of the heart,
gastrointestinal tract, or bladder
4. Others
- kyphoscoliosis
- normal cranial nerves
INVESTIGATIONS:
- decreased motor and sensory NCV (may be as slow as 20% of
normal)
- usually present in one parent who has a symptom-free
demyelinating neuropathy
2. Nerve Biopsy (Sural Nerve)
- extensive segmental demyelination and remyelination
- reduction in the number of large- and medium-sized
myelinated fibres
- increased collagen
2. Hypertrophic Neuropathy
- characteristic "onion-bulb formations" of proliferated
Schwann cell cytoplasm surrounding axons -> affected nerves
become palpably enlarged
- axonal changes (i.e., degeneration) may also be a part of
the disease process
3. EMG/Muscle Biopsy
- cycles of denervation/reinnervation
4. Cerebral Spinal Fluid
- CPK may be elevated but usually normal protein
- normal serum CPK
MANAGEMENT:
- no treatment for underlying disease
- multidisciplinary approach
- Paediatrics, Neurology, Orthopedics, Physiotherapy
- genetic counselling
2. Physiotherapy
- strengthening exercises to the feet and legs
- active stretching of the feet
- polypropylene ankle-foot orthoses to stabilize feet and
reduce falling
- special adaptive devices for hands if affected - utensils,
writing
3. Prognosis
- normal life span with most patients remaining ambulatory
(except those with onset in early childhood)
INTERNET LINKS:
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Pediatric Database - CHARCOT-MARIE-TOOTH DISEASE
Pediatric Organization - Pedbase [at] Gmail.com