Glenn S. Forbes

Orbital volume measurements in enophthalmos using three-dimensional CT imaging.

The purpose of this study was to investigate enophthalmos by measuring the volume of various orbital structures using off-line computer techniques on images generated by a CT scanner. Eleven patients with enophthalmos had CT scans of the orbits consisting of 30 to 40 adjacent 1.5-mm slices. The data from the scans were analyzed on a Nova 830 stand-alone computer system using software programs that allowed measurement of total bony orbital volume, total soft-tissue volume, globe volume, orbital fat volume, neuromuscular tissue volume, and apex-to-globe distance in the horizontal plane. These data were analyzed comparing the volumes in the normal eye with the volumes in the enophthalmic eye in each patient. The analysis demonstrated a statistically significant increase in bony orbital volume in the enophthalmic eye, but the total soft-tissue volume, fat volume, neuromuscular tissue volume, and globe volume were the same as in the normal eye. The apex-to-globe distance, a measure of the degree of enophthalmos, was less in the enophthalmic eye than in the normal eye. These results suggest that in the majority of patients, the cause of posttraumatic enophthalmos is increased bony orbital volume rather than by soft-tissue loss or fat necrosis. (Several patients showed no volume discrepancies, and it is likely that cicatricial contracture is responsible for the enophthalmos in these cases.) This study suggests that the objective of surgery for correction of enophthalmos in patients with a volume discrepancy should be to decrease the volume of the bony orbit and to increase the anterior projection of the globe.

Persistent chorea triggered by hyperglycemic crisis in diabetics

Five female patients developed chorea concurrent with, or shortly after a hyperglycemic episode (admission glucose values 500–1,000 mg/dL). In four of these five patients, there was no prior history of diabetes mellitus. The chorea continued despite correction of blood glucose and persisted to the time of last follow‐up, 6 months to 5 years later. The chorea developed subacutely over 2 days to 1 month and was generalized in one, unilateral in three, and involved right > left lower extremity in the other; the severity initially reached ballistic proportions in two. Associated clinical features were nil in four of these patients, but cognitive impairment and personality change occurred in one. The histories and laboratory studies identified no predisposing factors other than the hyperglycemia. The chorea was sufficiently troublesome to require administration of neuroleptic medication in all five cases. Four of the five cases had high signal intensity within basal ganglia on T1‐weighted magnetic resonance (MR) imaging, as has previously been described; however, this was not seen in one case (who had the most severe clinical condition). Most previously described cases have involved a reversible clinical syndrome, in contrast to our patients. The pathogenic mechanisms remain uncertain.

Rathke cleft cyst: CT, MR, and pathology of 23 cases

Objective We report the radiologic findings in 23 cases of Rathke cleft cyst (RCC) and correlate them with the histopathology. Materials and Methods We reviewed the radiology and pathology of 23 cases of surgically treated RCC operated upon at our institution or referred in consultation. Results There appears to be a correlation between the MR and CT appearance of the cyst, the gross appearance of the cyst contents, and the histopathologic characteristics of the cyst lining. Some of the lesions demonstrated peripheral enhancement, which in two cases was clearly due to a peripherally displaced rim of pituitary tissue. Conclusion The appearance of RCC with CT and MRI is variable, and radiologic diagnosis can be difficult. Imaging features such as a sellar epicenter, smooth contour, absence of calciflcation, absence of internal enhancement, and homogeneous attenuation or signal intensity within the lesion suggest the diagnosis of RCC. Rim enhancement does not correlate with the presence of squamous metaplasia, hemosiderin, or cholesterol within the cyst wall and is not consistently seen in cases with changes of mild, chronic inflammation. In some cases, rim enhancement is due to a peripherally displaced rim of pituitary tissue.

Computed tomography in the evaluation of subdural hematomas.

Computed tomographic (CT) scans used in the diagnosis and management of subdural hematomas were analyzed with respect to their contribution to angiography and surgery. There has been a progressive increase in the use of CT in evaluating post-traumatic and postoperative subdural hematomas at the Mayo Clinic. At present, 40% of all patients undergo operation on the basis of the CT findings alone. False-positive diagnoses revealed at surgery have decreased to less than 4%. Erroneous negative interpretations have involved 10% of all patients whose diagnosis was subdural hematoma. Criteria for the interpretation of scans have been established.

Pilocytic Astrocytomas: Well-Demarcated Magnetic Resonance Appearance Despite Frequent Infiltration Histologically

OBJECTIVE To determine the magnetic resonance imaging (MRI) characteristics of pilocytic astrocytomas and to correlate them with the histopathologic findings. MATERIAL AND METHODS MRI examinations and histopathologic findings in 56 patients with pilocytic astrocytomas were retrospectively reviewed. In 38 patients, findings on MRI were compared with those on computed tomography. RESULTS The tumors occurred at all levels of the central nervous system, including the spinal cord. The intracranial tumors were periventricular (73%) or periaqueductal (9%). All tumors were typical pilocytic astrocytomas and were grade 1 on the basis of the World Health Organization classification. At operation, they were often circumscribed and cystic. Radiologically, the tumors were well demarcated (96%), had benign morphologic features, and almost always showed enhancement (94%). CONCLUSION MRI of pilocytic astrocytomas typically demonstrated a relatively large, sharply demarcated periventricular mass with pronounced contrast enhancement but minimal or no associated edema. Often, the tumors were cystic on MRI. Despite the well-demarcated appearance grossly and on MRI, pathologic review showed that many of these tumors (64%) infiltrated the surrounding parenchyma, particularly the white matter.

Magnetic resonance imaging in a routine clinical setting.

The results of magnetic resonance imaging (MRI) examinations in the first 1,000 consecutive patients who were studied by this technique at our institution were reviewed to determine the disease states encountered, the sensitivity and accuracy of results, and the value of the examination as compared with computed tomography and other imaging procedures. The MRI device was a 0.15-tesla resistive magnet that used a variety of saturation recovery, spin echo, and inversion recovery pulse sequences to produce images. MRI was found equal to or superior to other imaging techniques in most cases. Exceptions included organs or body regions that are prone to excessive respiratory or vascular motion, lesions that necessitate exquisite spatial resolution for diagnosis, and lesions in which angulation of the viewing plane is necessary for optimal depiction. Fresh blood and calcification within a lesion were also difficult to detect with use of MRI.

Relationship of the Optic Nerve to the Paranasal Sinuses as Shown by Computed Tomography

Restricted exposure and inconsistencies in sinus pneumatization place the optic nerve at risk during operations on the sphenoid sinus and posterior ethmoid cells. In this study, computed tomography was used to examine these relationships. We reviewed 80 patients who underwent high-resolution computed tomographic scanning for ophthalmologic complaints in which the scan was negative. Forty-eight percent of posterior ethmoid cells are separated from the optic nerve by the thin bony lamina of the optic canal. Nearly 90% of sphenoid sinuses contact the ipsilateral optic nerve and 10% contact both nerves. Eight percent of posterior ethmoid cells override the ipsilateral sphenoid sinus and contact the optic nerve on that side. Paraxial reformatted displays allowed estimation of the degree of projection of the optic nerve into adjacent sinus cavities. Three percent of optic nerves have significant projection into the posterior ethmoid cell, and 23% project significantly into the sphenoid sinus. The width of the bony plate that separates the optic nerve from the sinus cavity was the same for sphenoid and ethmoid sinuses. Although sinus pneumatization varies among individuals, right and left sides are generally similar within one person.

Intracranial Hypertension in Behçet's Disease: Demonstration of Sinus Occlusion With Use of Digital Subtraction Angiography

We describe two patients with Behçets disease who had symptomatic intracranial hypertension due to cerebral venous sinus thrombosis. The sinus thrombosis was demonstrated by digital subtraction angiography. In those patients with Behçets disease who have unexplained headaches, papilledema, and elevated cerebrospinal fluid pressure, venous digital subtraction angiography is an expedient, accurate, and safe procedure for demonstrating intracranial venous thrombosis.

Therapeutic Embolization Angiography for Extra-Axial Lesions in the Head

Percutaneous transcatheter arterial embolization has played an increasingly important role in the management of vascular lesions in the head. Embolization can promote thrombosis within vascular tumors and malformations, reduce bleeding and decrease the need for transfusion intraoperatively, and facilitate surgical approaches to otherwise unresectable lesions. It is important for the clinician to be aware of this interventional technique because many of the patients who are considered for embolization are triaged through several different clinical areas, and much can be gained from the collaboration of the clinician, the surgeon, and the angiographer. We performed 31 therapeutic particulate embolization procedures for extra-axial head lesions in 23 patients by using flow-directed techniques. Of these procedures, 11 resulted in vascular occlusion and 15 resulted in 80 to 95% obstruction, as demonstrated by angiography. In 14 patients, embolization was performed preoperatively both to decrease blood loss and to occlude inaccessible or unresectable portions of a lesion. In nine patients, embolization was the sole means of treatment for occluding an abnormal vascular shunt. Two patients (9%) experienced a minor transient neurologic change after the procedure.

Electronic Imaging Impact on Image and Report Turnaround Times

We prospectively compared image and report delivery times in our Urgent Care Center (UCC) during a film-based practice (1995) and after complete implementation of an electronic imaging practice in 1997. Before switching to a totally electronic and filmless practice, multiple time periods were consistently measured during a 1-week period in May 1995 and then again in a similar week in May 1997 after implementation of electronic imaging. All practice patterns were the same except for a film-based practice in 1995 versus a filmless practice in 1997. The following times were measured: (1) waiting room time, (2) technologist’s time of examination, (3) time to quality control, (4) radiology interpretation times, (5) radiology image and report delivery time, (6) total radiology turn-around time, (7) time to room the patient back in the UCC, and (8) time until the ordering physician views the film. Waiting room time was longer in 1997 (average time, 26∶47) versus 1995 (average time, 15∶54). The technologist’s examination completion time was approximately the same (1995 average time, 06∶12; 1997 average time, 05∶41). There was also a slight increase in the time of the technologist’s electronic verification or quality control in 1997 (average time, 7∶17) versus the film-based practice in 1995 (average time, 2∶35). However, radiology interpretation times dramatically improved (average time, 49∶38 in 1995 versus average time 13∶50 in 1997). There was also a decrease in image delivery times to the clinicians in 1997 (median, 53 minutes) versus the film based practice of 1995 (1 hour and 40 minutes). Reports were available with the images immediately upon completion by the radiologist in 1997, compared with a median time of 27 minutes in 1995. Importantly, patients were roomed back into the UCC examination rooms faster after the radiologic procedure in 1997 (average time, 13∶36) than they were in 1995 (29∶38). Finally, the ordering physicians viewed the diagnostic images and reports in dramatically less time in 1997 (median, 26 minutes) versus 1995 (median, 1 hour and 5 minutes). In conclusion, a filmless electronic imaging practice within our UCC greatly improved radiology image and report delivery times, as well as improved clinical efficiency.