Paraspinal ultrasonography: lack of accuracy in evaluating patients with cervical or lumbar back pain.

This study evaluates the ability of paraspinal ultrasonography to identify abnormal echogenicity in patients with cervical or lumbar back pain, or both. Paraspinal ultrasonography was performed on 82 subjects, including 23 asymptomatic controls. Echogenicity in the region of nerve roots and facets was assessed. Readings were correlated with location of patients' symptoms, if any. Receiver operating characteristic analysis demonstrated that evaluation of nerve roots by all four readers did not differ significantly from chance (0.07 < P < 0.99). Specificities ranged from 0 to 0.68. Kappa values were 0.06 for cervical and -0.06 for lumbar spine. Ultrasonography was unable to demonstrate abnormal echogenicity adjacent to facets in symptomatic patients. Paraspinal ultrasonography is neither accurate nor reproducible in evaluating patients with cervical and lumbar back pain.

Brainstem auditory evoked potentials: intraoperative monitoring technique in surgery of posterior fossa tumors.

Brainstem auditory evoked potentials (BAEPs) were used to monitor eight neurosurgical procedures involving posterior fossa tumors to assist the neurosurgeon in preservation of hearing postoperatively. The technique included placement of recording electrodes over the Cz (vertex) and both earlobes. Stimulation was accomplished intraoperatively with a specifically designed intraauricular click stimulator that did not interfere with surgical access to the suboccipital region. Continuous BAEP recording was performed with particular attention to the sequence of preincision, opening of the dura, tumor mobilization, tumor excision, and closure. Absolute latencies and interpeak latencies of all five waves were recorded when possible. In three patients BAEPs were not significantly altered intraoperatively, and hearing was preserved postoperatively. In another three patients the acoustic nerve was severed during surgery and intraoperative monitoring was discontinued. In the remaining two patients medical complications arose intraoperatively, and significant irreversible changes in BAEP were observed despite no gross anatomical damage to the acoustic nerve. Both of these patients experienced postoperative hearing loss. These two cases illustrated some of the BAEP abnormalities that occurred during surgery. Difficulties during the procedures included electrical noise and interference, use of a bipolar cautery device, and unclear wave forms. Solutions for these difficulties were braiding the electrodes and using extra ground electrodes and a spike suppressor; switching off the evoked potential equipment when the bipolar cautery device was in use; and increasing repetitions and changing click intensity and polarity, respectively. Monitoring BAEPs in posterior fossa surgery can be accomplished with presently available equipment and may aid the neurosurgeon in preserving or minimizing injury to auditory pathways and adjacent structures.(ABSTRACT TRUNCATED AT 250 WORDS)