The differential diagnosis includes the various causes of motor neuron disease, chronic inflammatory demyelinating neuropathy, motor neuropathies, and mononeuritis multiplex. Despite his original diagnosis, ALS is not a strong clinical consideration in this patient as there is no evidence of upper motor neuron involvement. The duration of the disease process and lack of proximal involvement also argue against ALS as a diagnostic consideration. One of the spinal muscular atrophies could be considered, but the patient's age argues against even late onset cases. Adult onset hexosaminidase deficiency causes an upper and lower motor neuron syndrome, not consistent with the clinical presentation in this case.
Sensory symptoms are extremely common, and sensory signs are almost universal.
However, rare cases of motor involvement without significant sensory signs have been described. In most cases, however, the motor involvement is symmetrical at onset and throughout the course of the disease. The clinical course is progressive with episodes of relapse. Reflexes are universally decreased and often absent. These features argue against CIDP as the cause of neuropathy in this case.