The patient's thyroxine level may be slightly decreased and the thyroid stimulating hormone increased. Most patients, however, remain euthyroid but may develop a goiter. Alcohol is also a cause of myopathy. Differentiating between myopathies and neuropathies is possible on a clinical basis, but may be difficult. Toxic peripheral neuropathies are usually diffuse, and symmetric.
Most toxic neuropathies are axonopathies.
Sensory and motor fibers are involved and distal dysesthesias predominate on presentation. Pure motor axonopathies do exist but are rare. In axonopathies involvement is distal initially, rather than proximal as is seen in this myopathy. Neuronopathies where the body of the nerve cell is killed result in loss of sensation, or proprioception or at times autonomic responsiveness. Clinically the result is related to the specific neuron involved.