Nonconvulsive status epilepticus following cerebral angiography

The role of magnetic resonance angiography in head and neck surgery

Magnetic resonance angiography (MRA) is a recently developed, noninvasive vascular imaging technique. The authors of this investigation assessed the diagnostic value of MRA, along with its influence on therapeutic decisions, in 11 patients with a variety of head and neck disorders. In 5 patients, MRA diagnosed or ruled out an intrinsic vascular lesion. MRA was used to evaluate 5 of 8 patients with cancer for evidence of direct tumor involvement of vascular structures. Other uses of MRA included preoperative determination of tumor vascularity and delineation of anatomic relationships between normal vessels and head and neck pathology. Overall, MRA results guided management in 10 patients, and in some cases it determined the extent of surgical intervention. Because MRA is safer and more practical than traditional angiography, the authors recommend more frequent use of this imaging technique in the practice of head and neck surgery.

EEG detection of nontonic-clonic status epilepticus in patients with altered consciousness

Subtypes of status epilepticus (SE) without tonic-clonic convulsions (nontonic-clonic SE) present as altered consciousness sometimes with subtle motor activity and are important to consider in the differential diagnosis of patients with unexplained altered consciousness. Other patients may have altered consciousness with intermittent ictal activity on electroencephalography (EEG) that represents probable SE, but have other medical conditions that may be contributing to altered consciousness. EEG is the only reliable way to make the diagnosis of nontonic-clonic SE and we make emergency EEG available on a 24-h basis at our hospital. To determine how often definite or probable nontonic-clonic SE was detected by EEG we prospectively collected data on all cases where physicians ordered EEG to evaluate altered consciousness or possible SE. Out of 198 cases with altered consciousness but no clinical convulsions, 74 (37%) showed EEG and clinical evidence of definite or probable nontonic-clonic SE. Forty-two episodes (57%) were probable or definite complex partial SE, 29 (39%) were probable or definite subtle generalized SE, and three (4%) were myoclonic SE. In 23 SE cases altered consciousness was the only clinical sign at the time of diagnosis; subtle motor activity was present in 36 others. Neither clinical signs nor prior history predicted which patients showed SE on EEG. Nontonic-clonic SE followed a cerebral infarction in 16 cases. Contrary to other reports, we found no relationship between duration of SE and EEG pattern. Subtle generalized SE occurred most commonly in the setting of a diffuse brain injury rather than evolving from convulsive SE. This study demonstrates that nontonic-clonic SE is a common finding in patients with unexplained altered consciousness and EEG is necessary in the evaluation of these patients.

Variables affecting the accuracy of stereotactic localization using computerized tomography

Stereotactic localization using computerized tomography (CT) is increasingly employed to guide neurosurgical procedures in crucial areas of the brain such as the brain stem. This technique allows the surgeon to resect a lesion in its entirety while sparing critical areas of the brain. Thus, the parameters used for scanning should be selected for maximum accuracy. While the small pixel size of CT scanners suggests a high degree of precision in localization, there have been few systematic studies of this accuracy. The authors have studied the amount of error in localization created by variables such as CT scan thickness, interscan spacing, size of lesion, and method of computation when using the Brown-Roberts-Wells (BRW) stereotactic system. Over 1000 CT scans were made of a phantom composed of spheres of differing diameter and location. The CT slice thickness was varied from 1.5 to 5.0 mm, and interscan spacing was varied from 0.5 to 3.0 mm. The coordinates of the center of the spheres were calculated independently using the laptop computer supplied with the unit and also by a stereotactic computer which automatically calculates the center of the fiducials. The actual BRW coordinates of the sphere center were obtained using the phantom base and were then compared to the computer-calculated coordinates to determine error in localization. Variables with a significant effect on error included the scan thickness, interscan spacing, and sphere size. The mean error decreased 23% as the scan thickness decreased from 5.0 to 1.5 mm and 45% as the interscan spacing decreased from 3.0 to 0.5 mm. Mean error was greatest for the smallest sphere sizes. The two computational methods did not differ in error. This study suggests that, for critical areas of the brain or for small lesions, a scan thickness of 1.5 mm and interscan spacing of 0.5 mm should be employed.

[Prolonged confusion syndrome in the course of cyclosporine treatment: a state of confusion?]

Cyclosporine is a potent immunosuppressant that is more and more widely used, particularly after organ transplantations. Many neurological side effects, including convulsions, that could be related to this drug, have been previously observed, most often with high blood concentrations. We report, for the first time, a case of prolonged confusion where a non convulsive status epilepticus may be discussed. It occurred in a 64-year-old woman, 17 days after a liver transplantation. The whole blood cyclosporine value was 230 micrograms/l (normal range: 100-200 micrograms/l) at the beginning of the status epilepticus. The cyclosporine imputability and the part of other factors that could have facilite are discussed.