Phrenic paresis--a possible additional spinal cord dysfunction induced by neck manipulation in cervical spondylotic myelopathy (CSM): a report of two cases with anatomical and clinical considerations.

The clinical records of two male subjects with severe cervical spondylotic myelopathy (CSM) who developed respiratory insufficiency after the cervical manipulation involved in preoperative anesthetic intubation were examined. Their cervical imaging was analyzed with respect to the known anatomic relationships of the spinal phrenic nerve nuclei to the spondylotic compressive lesions in an attempt to provide the anatomic and pathologic rationales that may explain this phrenic paresis as a possible traumatic complication of severe CSM. Perusal of extant literature revealed extensive descriptions of CSM symptoms, but none had previously reported an associated neuromuscular weakness of the diaphragm. Magnetic resonance imaging analyses indicated that the existing degree of upper cervical cord compression, when reinforced by the additional posterior and anterior pressures consequent to cervical spinal extension and flexion, could readily account for the functional impairment of phrenic nerve neuron cells and/or their efferent fibers. Thus, the anatomic relations of the phrenic nerve nuclear columns and their efferent tracts predispose them to interference by compressive lesions found in CSM, and undue manipulation of the cervical spine when advanced stenosis is known to be present should be recognized as a possible cause of cervical spondylotic myelopathic-phrenic paresis.