Assessment of zero drift in the Codman intracranial pressure monitor: a study from 2 neurointensive care units.

OBJECTIVE: Intraparenchymal monitoring devices play an important role in the daily management of head injury and other critically ill neurosurgical patients. Although zero drift data exist for the Camino system (Camino Laboratories, San Diego, CA), only in vitro data exist for the Codman system (Codman and Shurtleff, Inc., Raynham, MA). The aim of this study was to assess the extent of zero drift for the Codman intracranial pressure (ICP) monitor in patients being monitored in 2 neurointensive care units. METHODS: This was a prospective study conducted at 2 neurointensive care units. Eighty-eight patients who required ICP monitoring and who presented to the 2 neurosurgical departments, Center 1 (n = 48) and Center 2 (n = 40), were recruited for participation. The duration of ICP monitoring was noted, as was the resultant pressure reading in normal saline on removing the ICP monitor (zero drift). RESULTS: The median absolute zero drift for the group was 2.0 mm Hg (interquartile range, 1-3 mm Hg). The median time in situ was 108 hours (interquartile range, 69-201 hours). There was a positive correlation between the drift and time of the probe spent in situ (Spearman's correlation coefficient = 0.342; P = 0.001). Of the readings, 20 and 2% showed a drift greater than 5 and 10 mm Hg in magnitude, respectively. CONCLUSION: These data demonstrate that a small amount of zero drift exists in ICP monitors and that this drift increases with time. The wide range in the data demonstrates that some drift readings are quite excessive. This reinforces the school of thought that, although ICP readings contribute significantly to the management of neurosurgical patients, they should be interpreted carefully and in conjunction with clinical and radiological assessment of patients.

Spontaneous hemorrhage of a spinal ependymoma: a rare cause of acute cauda equina syndrome: a case report.

STUDY DESIGN: An interesting case of spontaneous bleeding from an ependymoma of the filum terminale is presented. OBJECTIVES: To document a rare case of rapid neurologic deterioration as a consequence of spinal tumoral hemorrhage and to highlight important issues regarding tumor histologic subtype and the impact of anticoagulation that have emerged from an illuminating review of the literature. SUMMARY OF BACKGROUND DATA: To our knowledge, there have been only 8 reported cases of hemorrhage from an ependymoma of the filum terminale or conus medullaris causing acute cauda equina syndrome. Bleeding is described in the pathology texts as being a consequence of the vascular architecture of the myxopapillary subtype and so postulated to be more common in this group. Anticoagulation is recognized to increase the frequency of tumoral bleeding, but no studies report its effect of severity of clinical presentation. METHODS: We report the case of a 57-year-old woman who developed nontraumatic acute cauda equina syndrome, including sphincter compromise. She underwent a lumbosacral laminectomy for evacuation of a hematoma, at which stage a filum terminale ependymoma was excised. Histopathologic analysis demonstrated it to be of a nonmyxopapillary subtype. RESULTS: The patient demonstrated gradual improvement of the neurologic deficit. At 12-month follow-up, her saddle area sensory deficit has resolved, her right lower limb is much stronger allowing her to walk long distances, and she is successfully performing intermittent self-catheterization of her bladder. CONCLUSIONS: The possibility of an underlying tumor should always be borne in mind so that adequate preoperative planning can be undertaken. The presence of the myxopapillary subtype should not prevent a clinician from excluding other reasons for hemorrhage, and counseling when reinstituting anticoagulation must include warning against a worse prognosis from any future hemorrhage.