Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) as rare differential diagnosis of a dropped head syndrome

We report a 63 year-old patient with slowly progressive weakness of the neck extensor muscles developing a dropped head syndrome over a 12 months period. Clinical examination also revealed atrophic paresis of the shoulder and proximal upper limb muscles, weakness of the orofacial muscles, dysarthria and dysphagia. Tendon reflexes of the lower limbs were bilaterally exaggerated with bilaterally extensor plantar responses. Concentric needle electromyography (EMG) revealed denervation in the tongue, paravertebral and sternocleidomastoid muscles and chronic neurogenic changes of the motor unit potentials of the upper limbs. Motor nerve conduction studies were completely normal, including F-wave responses. Transcranial magnetic stimulation studies to the tongue and limbs showed also normal responses. However, sensory nerve action potentials (SNAPs) were generalized amplitude reduced und somatosensory evoked potentials after electrical stimulation of the median and tibial nerves were bilaterally absent. The examination of the CSF was normal, but serology and CSF demonstrated an abnormal CSF/serum index for treponemal antibodies, indicating an elapsed or moderately active neurosyphilis, correlating to a syphilis infection 40 years ago. MRI of the brain was normal, but MRI of the cervival spine revealed a moderate stenosis with subtle signs of myelopathy. Apart from neurosyphilis, a motoneuron disease like amyotrophic lateral sclerosis was considered as additional differential diagnosis. Under symptomatic treatment with antibiotics and riluzole the disease gradually progressed. Two years later the patient presented with generalized fasciculations and atrophic paresis of the limb muscles also involving the respiratory muscles with consecutive respiratory failure. The postmortem neuropathological examination revealed a chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with involvement of the autonomic ganglia and the intramural plexus. Histologically, there was no evidence for either neurosyphilis nor motoneuron disease. In our opinion and considering the complexity of the case the clinical diagnosis of a CIDP as cause of the dropped head syndrome was not possible during lifetime.