Faculty Bibliography

Perfusion computed tomography (CT) is a relatively new technique that allows rapid qualitative and quantitative evaluation of cerebral perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique is based on the central volume principle (CBF = CBV/MTT) and requires the use of commercially available software employing complex deconvolution algorithms to produce the perfusion maps. Some controversies exist regarding this technique, including which artery to use as input vessel, the accuracy of quantitative results, and the reproducibility of results. Despite these controversies, perfusion CT has been found to be useful for noninvasive diagnosis of cerebral ischemia and infarction and for evaluation of vasospasm after subarachnoid hemorrhage. Perfusion CT has also been used for assessment of cerebrovascular reserve by using acetazolamide challenge in patients with intracranial vascular stenoses who are potential candidates for bypass surgery or neuroendovascular treatment, for the evaluation of patients undergoing temporary balloon occlusion to assess collateral flow and cerebrovascular reserve, and for the assessment of microvascular permeability in patients with intracranial neoplasms. This article is a review of the technique, clinical applications, and controversies surrounding perfusion CT.

BACKGROUND AND PURPOSE: The incidence of poor-grade (Hunt and Hess grade IV and V) subarachnoid hemorrhage (SAH) is higher in elderly patients (>70 years) than in younger groups. The aim of this retrospective study was to analyze the outcome of these poor grade elderly patients after endovascular treatment. METHODS: We retrospectively reviewed the clinical records of 27 patients older than 70 years who underwent endovascular treatment for aneurysmal SAH between January 1996 and July 2002. Thirteen patients with SAH and a poor Hunt and Hess grade at initial presentation had been treated by endovascular means. Their outcomes were assessed by the using the Glasgow Outcome Scale (GOS). RESULTS: Two patients (15%) had a good outcome according to the GOS. Three patients (23%) were moderately disabled, two (15%) were severely disabled at the time of discharge from the hospital, and six (47%) died. Five patients (38%) developed clinical vasospasm and underwent balloon angioplasty. Three procedure-related deaths occurred (23%). CONCLUSION: Endovascular treatment has modified the management of poor-grade SAH in elderly patients, most of whom are high-risk surgical candidates. Endovascular treatment can be administered early after the initial ictus, reducing the risk of rebleeding and providing an option to pursue aggressive triple-H therapy. Symptomatic vasospasm can also be treated by endovascular means in the initial setting.

Cardiac complications are well known after aneurysmal subarachnoid hemorrhage. Electrocardiographic changes occur in 50% to 100% of such cases. Arrhythmias, left ventricular dysfunction, and frank myocardial infarction are infrequently observed. Myocardial infarction must be differentiated from neurogenic stunned myocardium, which is a reversible condition. From 1996 to 2001, 105 patients with aneurysmal subarachnoid hemorrhage underwent endovascular treatment at the University of Michigan. Of these, four patients with no history of cardiac disease experienced cardiac failure related to neurogenic stunned myocardium. All had signs of left ventricular dysfunction, electrocardiographic changes, and elevated cardiac enzymes. Three had pulmonary edema at presentation. All were diagnosed with myocardial infarction. One underwent coronary angiography, which was normal. All were considered poor surgical candidates and underwent endovascular treatment of the aneurysms. Three of four patients developed symptomatic vasospasm, and two required balloon angioplasty. Three patients achieved good outcomes. The eldest died from severe vasospasm that was unresponsive to angioplasty. Reversible cardiac failure associated with subarachnoid hemorrhage may be due the neurogenic stunned myocardium. Frequent symptomatic vasospasm occurs, possibly related to poor cardiac output and the inability to optimize hyperdynamic hypervolemic therapy, particularly with compromised volume status. These patients can be treated with endovascular therapy of the aneurysms and balloon angioplasty as needed. With aggressive management, patients can recover from these reversible cardiac complications.

Cerebral vasculitis presenting with intracranial hemorrhage is a rare but known entity. We discuss here the case of a 61-year-old woman presenting with subarachnoid hemorrhage. Cerebral angiography showed vasculitic changes involving the small and medium-sized vessels. She also had a concomitant herpes zoster rash on her back. A 3-month follow-up angiogram revealed partial resolution of the vasculitic changes.

Cochlear implant (CI) is an electronic device used to rehabilitate patients with sensorineural hearing loss. The intent of this review is to demonstrate the normal position of the electrode on computed tomography (CT) and contrast this with various examples of the electrode malpositioning. Post-implantation CT is performed to localize the cause of implant failure in patients in which radiographs suggest an anomalous course of the electrode. A common cause of device failure is extrusion or malpositioning of the electrode. It is important for the radiologists to recognize this important aspect of device failure. Post-implant CT can help identify patients with malpositioned electrode in whom another attempt can be made by correctly re-implanting the electrode.

A 5-year-old girl with no preexisting systemic or CNS neoplasm presented with a large right temporal mass lesion, the histopathology of which proved to be a poorly differentiated adenosquamous carcinoma, a highly unusual primary intracranial tumor. The tumor recurred despite radical resection, chemotherapy, and radiation therapy.

BACKGROUND: Neurenteric cysts are rare congenital lesions of the spine and are lined with entodermal epithelium. They result from anomalous endodermal-neuroectodermal adhesion in the 3rd week of embryonic life with persistence of canal of Kovalevsky. The nature of the eventual abnormality depends on the extent to which this adhesion subsequently disappears. Persistence of the entire tract results in the extreme form of combined anterior and posterior spina bifida with dorsal enteric fistula and persistence of only a part of the tract producing the isolated intraspinal cyst. The most common location is the cervico-dorsal region, and usually it lies ventral to the spinal cord. The lumbosacral location is uncommon. Associated vertebral anomalies, gut cysts, bowel duplication, the presence of keratin markers and mucin-secreting cuboidal or columnar intestinal epithelium in their walls confirm their entodermal origin. PATIENTS: We describe here three unusual cases of neurenteric cysts in patients aged 5-18 years who had already had symptoms for some time. One of these had a cyst sited predominantly in the sacral canal, another presented with a lumbar neurenteric cyst, and the third patient had an intradural extramedullary thoracic lesion. Two of these children had associated anomalies, the one with lumbar cyst also having a lipomeningomyelocele and spina bifida while the other also had deformed vertebrae. All three patients underwent laminectomy and gross excision of the cysts through a posterior approach. RESULTS AND CONCLUSION: The diagnosis of neurenteric cysts was confirmed by demonstrating mucin-producing cuboidal or columnar epithelium lining the cystic cavity.