Expert Pearls For Treating Charcot-Marie-Tooth Disease
- Volume 27 - Issue 1 - January 2014
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These authors detail the treatment of a 35-year-old patient who presented with chronic pain, longstanding high arches and ankles that “give way” easily.
Charcot-Marie-Tooth (CMT) disease is a genetically and clinically heterogeneous group of inherited disorders of the peripheral nervous system. The etiology of CMT is caused by mutations in neuronal proteins governed by various inherited patterns. The most common cause (70 to 80 percent) is the duplication on the short arm of chromosome 17 that includes the PMP22 gene. This affects mitochondrial protein coding for neuronal proteins.1 One can diagnose CMT through clinical symptoms, electromyography (EMG) and nerve conduction velocity (NCV), peripheral nerve biopsy, and DNA testing.
Clinical symptoms usually begin in late childhood or early adulthood depending on patterns of inheritance and gene mutation. The X-linked dominant and recessive patterns account for severe clinical forms at earlier ages. Most commonly, autosomal dominant inheritance accounts for adulthood onset. Those affected may not experience symptoms until their early 30s or 40s. Wasting of muscle tissue of the lower leg due to denervation gives rise to “stork legs” (see Figure 1) and an “inverted champagne bottle” appearance due to preservation of the proximal thigh musculature. Stumbling and frequent ankle sprains with the presence of “high arches” (pes cavus) are classically associated with this disorder. Sensory and proprioceptive function of the hands and feet are often damaged. Due to muscle imbalance, overuse of the affected limb can activate symptoms of numbness, spasm and cramping.
The clinical classification of CMT was originally described by Dyck and colleagues.2 This involves hereditary and sensory neuropathies of which CMT encompasses hereditary motor and sensory neuropathy (HMSN) I and II.3
HMSN I occurs in 75 percent of patients and is referred to as the myelinated type of CMT. Peripheral nerve biopsy will reveal hypertrophied demyelination with reactive fibrosis, often referred to as “onion bulb” due to increased thickness of the nerve. The NCV will reveal decreased conduction velocities of affected motor and sensory nerves. The onset usually occurs between the ages of 10 and 20.
HMSN II, which occurs in 25 percent of patients with CMT, is referred to as the axonal type. There are decreased numbers of axons with relative sparing of the myelin. The NCV will reveal normal conduction velocities but decreased amplitudes. The onset of HMSN II usually occurs between the ages of 20 and 30.