Cowchock Syndrome

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.

Cowchock Fischbeck Syndrome; Charcot-Marie-Tooth Disease with Deafness and Mental Retardation; Hereditary Motor Sensory Neuropathy (HMSN) II.

Unknown. A few reports exist of familial series. Male offsprings are more severely affected.

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.

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.

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.

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.

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.

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.

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 reactions. However, this has not been confirmed by a larger, retrospective series of a total of 161 procedures in 86 patients, of whom 48% received succinylcholine and 90% received malignant hyperthermia triggering agents without significant adverse effects. It has been suggested, however, that individuals with acute exacerbations of the disease represent a subset of patients who have altered responses to muscle relaxants and that, in such a scenario, succinylcholine should be avoided and other muscle relaxants used in small incremental doses with neuromuscular monitoring only.

See Hereditary Motor and Sensory Neuropathies (HMSN) for an overview of the different types.

Charcot-Marie-Tooth Disease: A hereditary polyneuropathy condition presenting with distal weakness and muscular atrophy (myopathy).