The purpose of this study was to define as a distinct clinical entity the syndrome of neurapraxia of the cervical spinal cord with transient quadriplegia. The sensory changes include burning pain, numbness, tingling, and loss of sensation, while the motor changes range from weakness to complete paralysis. The episodes are transient and complete recovery usually occurs in ten to fifteen minutes, although in some patients gradual resolution occurs over a period of thirty-six to forty-eight hours. Except for burning paresthesia, pain in the neck is not present at the time of injury and there is complete return of motor function and full, pain-free motion of the cervical spine. In our series, routine roentgenograms of the cervical spine were negative for fractures or dislocations in all patients. However, the roentgenographic findings did include developmental spinal stenosis in seventeen patients, congenital fusion in five patients, cervical instability in four patients, and intervertebral disc disease in six patients. Spinal stenosis was determined by two different roentgenographic methods. The first was the standard method, and the second was a ratio method devised by us. Both measurements were made at the level of the third through the sixth vertebral body on a routine lateral roentgenogram of the cervical spine that was available for twenty-four of the thirty-two patients and for a control group of forty-nine male subjects of similar age who did not have any neurological complaints. Using the ratio method, a measurement of less than 0.80 indicated significant spinal stenosis in the group of twenty-four patients for whom roentgenograms were available, as compared with a ratio of approximately 1.00 or more in the control group. There was statistically significant spinal stenosis (p less than 0.0001) in all of the patients as compared with the control subjects by both methods of determining spinal stenosis. A survey of 503 schools participating in National Collegiate Athletic Association (NCAA) football in the 1984 season found that 1.3 per 10,000 athletes had a history that was suggestive of neurapraxia of the cervical spinal cord. The phenomenon of neurapraxia of the cervical spinal cord occurs in individuals with developmental stenosis of the cervical spine, congenital fusion, cervical instability, or protrusion of an intervertebral disc in association with a decrease in the anteroposterior diameter of the spinal canal. We postulate that in athletes with diminution of the anteroposterior diameter of the spinal canal the spinal cord can, on forced hyperextension or hyperflexion, be compressed, causing transitory motor and sensory manifestations.(ABSTRACT TRUNCATED AT 400 WORDS)