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An X-linked form of sensory and motor neuropathy
characterized by atrophy of the peroneal muscle, but also involving other
distal muscles of the legs and arms.
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Cowchock Fischbeck Syndrome; Charcot-Marie-Tooth Disease
with Deafness and Mental Retardation; Hereditary Motor Sensory Neuropathy
(HMSN) II.
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Unknown. A few reports exist of familial series. Male
offsprings are more severely affected.
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X-linked, with mapping to Xq24-q26. It may be
either allelic to X-linked Charcot-Marie-Tooth (CMT) disease or a contiguous
gene syndrome, with the features of Charcot-Marie-Tooth Syndrome
resulting from alterations in the CMTX1 gene or in one of the other two CMT
genes on the X chromosome.
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Consistent with hereditary motor sensory
neuropathy type II. Electromyography demonstrates widespread denervation and
occasional fibrillation. Motor nerve conduction velocities are normal to
moderately delayed, however, sensory conduction in the median and sural
nerves is markedly abnormal. Electron microscopy of sural nerve tissue
reveals a paucity of myelinated axons. Audiometry shows sensorineural
hearing loss.
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Based on the clinical findings in infants with foot
drop, clawing of fingers, and progressive atrophy and weakness of peroneal
and other distal foot muscles in combination with a positive family history.
Electrophysiology plus microscopy show reduced conduction velocity,
demyelination, and axonal degeneration.
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Presentation is usually in infancy with slowly
progressive distal or generalized muscle weakness and atrophy and diminished
or absent deep tendon reflexes. Motor development is delayed. Other clinical
features may include foot dropping (manifesting as frequent tripping), pes
cavus deformity, muscle cramping, steppage or equine gait, “champagne
bottle" or stork legs, hammertoes, and clawhand. Pain and temperature
sensation are normal. The diaphragm, phrenic nerve, and vocal cords are
occasionally involved. Frequently associated with mental retardation and
deafness. Moderate disability in adulthood.
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Assess the patient neurologically
and ask about respiratory and cardiac problems. Pulmonary function tests
including a chest radiograph and arterial blood gas analysis should be
performed if respiratory involvement (secondary to respiratory muscle
weakness) is suspected. An electrocardiogram is recommended for all
patients, and an echocardiogram may be indicated depending on the clinical
findings.
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Anesthesia may exacerbate preexisting
respiratory disease, and prolonged postoperative mechanical ventilation may
be required. A peripheral nerve stimulator should be used to monitor
neuromuscular blockade if muscle relaxants will be used. However, care
should be taken to place the electrodes on an unaffected nerve to prevent
erroneous results. Regional anesthesia has been used successfully in
multiple cases. Involvement of the autonomic nervous system may result in
abnormal temperature regulation. Mental retardation and deafness may affect
patient cooperation. Sedative and/or anxiolytic premedication and/or the
presence of the primary caregiver during induction of anesthesia may be
helpful.
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Specific experience is lacking,
however, the literature indicates that the induction dose of thiopentone may
need to be reduced in CMT disease. A small number of case reports indicate the
use of succinylcholine in CMT may result in hyperkalemia or malignant
hyperthermia-like ...