Anne G. Osborn

Stereotaxic frame and computer software for CT-directed neurosurgical localization.

A clinical stereotaxic head frame designed for use with computed tomography (CT) body scanners is described. Frame geometry and a CT localization system provide an accuracy and versatility that should lead to optimal clinical usefulness. Initial phantom and clinical studies are presented.

Extensive experience with dural sinus thrombosis

OBJECTIVEDural sinus thrombosis (DST) is an uncommon cause of stroke. The safest and most effective therapy for DST has not been conclusively identified. METHODSA retrospective chart review of data for 31 patients who were treated for DST at our institution between 1992 and 2001 was performed. Four treatment strategies were identified, i.e., 1) medical observation only, 2) systemic anticoagulation (AC) therapy with heparin, 3) endovascular chemical thrombolysis with urokinase or tissue plasminogen activator and concurrent systemic AC therapy, and 4) mechanical endovascular clot thrombolysis with concurrent systemic AC therapy. Complications and clinical outcomes were assessed for each group. RESULTSPatients treated solely with medical observation fared the worst; four of five patients experienced intracranial hemorrhagic complications, and only two of five exhibited clinical improvement. Patients who received systemic AC therapy experienced no hemorrhagic complications, even when pretreatment hemorrhage was present; 75% (six of eight patients) exhibited improvement with AC therapy alone. Chemical thrombolysis was very effective in restoring sinus patency (90% of patients); however, 30% of patients (3 of 10 patients) experienced hemorrhagic complications. Sixty percent of patients (6 of 10 patients) who underwent chemical thrombolysis exhibited clinical improvement. Patients who underwent mechanical thrombectomies demonstrated a low hemorrhagic complication rate, and most (88%) made good recoveries. CONCLUSIONTherapy directed at the underlying clot in DST must begin without delay. Our results suggest that supportive medical management of DST, without therapy directed at the clot or clotting process, is not effective. Systemic AC therapy, even in the presence of intracerebral hemorrhage, seems to be safe. Heparin can be safely titrated to yield partial thromboplastin times of 60 to 70 seconds. Chemical clot thrombolysis is efficacious in opening occluded sinuses but may cause intracranial hemorrhage. We currently recommend either systemic AC therapy or systemic AC therapy in conjunction with mechanical clot thrombectomy as a safe effective treatment for DST.

Subependymomas: An analysis of clinical and imaging features

OBJECTIVE:Subependymomas are slow-growing, benign tumors usually found incidentally in the fourth ventricle at autopsy. They are typically associated with the ventricular system and become apparent clinically only when symptoms of hydrocephalus or mass effect develop. We review clinical, histological, and contemporary radiographic presentations of 16 subependymomas, including 2 intraparenchymal tumors. METHODS:We retrospectively evaluated eight patients with pathologically proven subependymomas. Initial magnetic resonance imaging and magnetic resonance spectroscopy were reviewed when available. Imaging was also available on eight outside subependymoma cases reviewed by our radiology department. RESULTS:Twelve of these subependymomas were intraventricular, one was in the posterior fossa, two were intraparenchymal, and one was an intramedullary spinal cord tumor. These lesions were hypo- to hyperintense on T1- and T2-weighted magnetic resonance imaging, with minimal to moderate enhancement. Initial complaints included headache, seizures, tingling sensations, and weakness. Among our eight patients who underwent gross total resection with no adjuvant therapy, no recurrences have been noted on follow-up magnetic resonance imaging. CONCLUSION:Subependymomas are rare, representing only 0.51% of all central nervous system tumors operated on during an 8-year period at the University of Utah. Clinical symptoms were associated with tumor location: intracranial masses caused headaches, seizures, and neurological complaints, and spinal cord locations resulted in neurological deficit. The authors review the clinical presentation, management, and contemporary radiographic appearance of this rare tumor.

Pilomyxoid Astrocytoma: Expanding the Imaging Spectrum

BACKGROUND AND PURPOSE: Pilomyxoid astrocytoma (PMA) is a recently described variant of pilocytic astrocytoma (PA) with unique clinical and histopathologic characteristics. Because the histopathology of PMA is distinct from that of PA, we hypothesized that PMAs would display distinctive imaging characteristics. We retrospectively reviewed the imaging findings in a large number of patients with PMA to identify these characteristics. MATERIALS AND METHODS: CT and MR images, pathology reports, and clinical information from 21 patients with pathology-confirmed PMA from 7 institutions were retrospectively reviewed. CT and MR imaging findings, including location, size, signal intensity, hemorrhage, and enhancement pattern, were tabulated. RESULTS: Patients ranged in age from 9 months to 46 years at initial diagnosis. Sex ratio was 12:9 (M/F). Twelve of 21 (57%) tumors were located in the hypothalamic/chiasmatic/third ventricular region. Nine (43%) occurred in other locations, including the parietal lobe (2/21), temporal lobe (2/21), cerebellum (2/21), basal ganglia (2/21), and fourth ventricle (1/21). Ten (48%) tumors showed heterogeneous rim enhancement, 9 (43%) showed uniform enhancement, and 2 (9%) showed no enhancement. Five (24%) masses demonstrated intratumoral hemorrhage. CONCLUSION: This series expands the clinical and imaging spectrum of PMA and identifies characteristics that should suggest consideration of this uncommon diagnosis. One third of patients were older children and adults. Almost half of all tumors were located outside the typical hypothalamic/chiasmatic region. Intratumoral hemorrhage occurred in one quarter of patients. PMA remains a histologic diagnosis without definitive imaging findings that distinguish it from PA.

Hemorrhagic and nonhemorrhagic Rathke cleft cysts mimicking pituitary apoplexy

OBJECTIVES Rathke cleft cysts (RCCs) are infrequently symptomatic, and apoplexy is one of the most unusual presentations. Only a few cases of apoplexy associated with RCCs have been reported, and their clinical, imaging, surgical, and pathological features are poorly understood. In the cases that have been reported, intracystic hemorrhage has been a consistent finding. The authors report 6 cases of RCCs in which the presenting clinical and imaging features indicated pituitary apoplexy, both with and without intracystic hemorrhage. METHODS The authors retrospectively reviewed charts and magnetic resonance (MR) imaging studies obtained in patients who underwent transsphenoidal surgery for RCC. Six patients were identified who presented with symptoms and MR imaging characteristics consistent with pituitary apoplexy but were found intraoperatively to have an RCC. All 6 patients presented with a sudden headache, 2 with visual loss, and 1 with diplopia. Review of the preoperative MR images demonstrated mixed signal intensities in the sellar masses suggestive of a hemorrhagic pituitary tumor. In all patients there was a presumed clinical diagnosis of pituitary tumor apoplexy and an imaging-documented diagnosis of hemorrhagic pituitary tumor. RESULTS All 6 patients underwent transsphenoidal resection to treat the suspected pituitary apoplexy. Intraoperative and histopathological findings were consistent with the diagnosis of an RCC in all cases. Only 2 cases showed evidence of hemorrhage intraoperatively. In all cases, an intracystic nodule was found within the RCC at surgery, and this intracystic nodule was present on the initial MR imaging when retrospectively reviewed. The imaging characteristics of the intracystic nodules were similar to those of acute hemorrhage seen in cases of pituitary apoplexy. CONCLUSIONS The clinical and imaging features of RCCs appear similar to those of hemorrhagic pituitary tumors, making them often indistinguishable from pituitary apoplexy.

Computed Tomography and Differential Diagnosis of the Extruded Lumbar Disc

Herniated lumbar discs may infrequently extrude through or around the posterior longitudinal ligament and migrate within the epidural space either as a contiguous mass with or as a free fragment of the parent nucleus pulposus. Recognition of this entity may obviate the use of chymopapain or may otherwise alter the surgeons approach to the disc herniation. The CT scans of 40 surgically confirmed cases of lumbar disc extrusion were reviewed. In 36 cases CT identified the extruded disc material as a lobulated soft tissue mass of similar attenuation to the disc space, migrating either superiorly or inferiorly from the parent disc interspace. In 34 cases the extrusion was 6 mm or more from the center of the parent disc. Calcification of the disc extrusion occurred in five cases. In six cases an extruded free fragment of disc material was associated with a normal-appearing parent disc interspace at CT. In one such case gas bubbles occurred within a degenerating extruded fragment which had eroded through the dura. The differential diagnosis of lumbar disc extrusion is also discussed.

Anatomic and Pathologic Spectrum of Pituitary Infundibulum Lesions

OBJECTIVE The pathologic spectrum of pituitary infundibulum disease is diverse. We reviewed 65 infundibular lesions in 44 adult and 21 pediatric patients, and summarized their imaging features and clinical presentation. CONCLUSION The spectrum of pathology involving the pituitary infundibulum is broad yet distinct from other pathology in the sella and parasellar region. Pituitary stalk lesions can be grouped into three categories: congenital and developmental, inflammatory and infectious, and neoplastic. Knowledge of the imaging appearance of diseases specific to adults and to children is important for accurate diagnosis and treatment.

The Radiologic Assessment of Trigeminal Neuropathy

The clinical and radiologic records of 76 patients with trigeminal neuropathy and an abnormal imaging study (CT and/or MR) were analyzed retrospectively. The trigeminal nerve (cranial nerve V) was divided into proximal (brainstem, preganglionic, gasserian ganglion, and cavernous sinus) and distal (extracranial V1, V2, and V3) segments. Lesions were organized according to segments and correlated with the type and distribution of clinical symptoms or signs. The purpose of the study was to (1) determine the efficacy of clinical localization of cranial nerve V lesions, (2) compare CT and MR for cranial nerve V imaging, (3) develop an MR protocol for effective cranial nerve V imaging, and (4) construct a differential diagnosis by anatomic segment for lesions of cranial nerve V. Clinical localization was found to be extremely inaccurate. CT was not as sensitive as MR for lesions involving the basal cisterns and skull base and will not detect the most common brainstem lesions (small infarcts and multiple sclerosis plaques). The MR protocol developed does not rely heavily on clinical localization. On the basis of lesions found in this series, a differential diagnosis by segment was developed. Patients with cranial nerve V symptoms should undergo MR imaging according to the protocol provided in this article. CT is not as effective as MR in imaging some cranial nerve V segments. Clinical localization is inaccurate.

Magnetic resonance imaging spectrum of medulloblastoma.

IntroductionTwo medulloblastoma variants were recently added to the WHO classification of CNS tumours. We retrospectively analysed the imaging findings of 37 classic and 27 cases of variant medulloblastomas to identify imaging characteristics that might suggest a particular MB subtype.MethodsSixty-four patients from three institutions were included. Location, tumour margins, signal intensities on conventional MRI, enhancement pattern, the presence of haemorrhage, calcifications and hydrocephalus were recorded and analysed. Signal characteristics on diffusion-weighted MR images and MR spectra were evaluated when available.ResultsThirty-seven classic type of MB (CMB), twelve cases of desmoplastic/nodular medulloblastoma (DMB), nine medulloblastomas with extensive nodularity (MB-EN), five cases of anaplastic and one of large-cell medulloblastoma were included. Fifty of 64 tumours were located in the 4th ventricle region. On T2WI, CMB were all hyperintense, whereas DMB and MB-EN showed isointensity in up to 66%. One third of the classic MB showed only subtle marginal or linear enhancement. All medulloblastoma variants showed marked enhancement.ConclusionThe results of our study suggest: (a) an age-dependent distribution of MB variants, with DMB and MB-EN more common in younger children; (b) a female predominance in DMB; (c) a more common off-midline location in DMB (50%) and MB-EN (33%) variants.

Calcified Cerebral Emboli, A “Do Not Miss” Imaging Diagnosis: 22 New Cases and Review of the Literature

The prevalence, imaging appearance, presumed source, treatment, and outcome of patients with calcified cerebral emboli on CT were assessed in 22 cases seen by the authors and in 48 from the literature. Most calcified emboli were found in the middle cerebral artery territory and were thought to arise from the heart, aortic arch, or carotid plaques. The overall prevalence of these emboli was 2.7% with 27% initially misdiagnosed and 9% overlooked on the first interpretation. BACKGROUND AND PURPOSE: Calcified cerebral emboli are a rarely reported but devastating cause of stroke and may be the first manifestation of vascular or cardiac disease. Our aim was to evaluate the diagnosis, prevalence, imaging appearance, presumed embolic source, treatment, and outcome of patients with calcified cerebral emboli. MATERIALS AND METHODS: Our radiology information system was searched for all CT scans by using keywords “calcified,” “emboli,” and their permutations. The radiology information system was also searched to identify all “stroke” CT reports to calculate the prevalence of calcified cerebral emboli. We also performed a MEDLINE search to identify all published case reports. RESULTS: Twenty-two cases were identified from our database, and 48 were cases reported from the literature. The middle cerebral artery was the site of 83% of calcified emboli. Presumed sources were calcific aortic stenosis (36%), carotid atherosclerotic plaque (30%), and mitral annular calcification (11%). Spontaneous embolism occurred in 86%. Surgical treatment was performed in 34% of patients. Sixty-four percent of the patients with calcified aortic stenosis underwent aortic valve replacement. Among those with identifiable arterial disease, 53% underwent endarterectomy. Forty-one percent of patients experienced at least 1 recurrent stroke. The prevalence of calcified cerebral emboli identified on stroke CT scans at our institution was 2.7%. Seventy-three percent of cases were correctly identified. Twenty-seven percent were misdiagnosed on initial interpretation, while 9% were overlooked on preliminary interpretation. CONCLUSIONS: Calcified cerebral emboli are more common than previously assumed, are frequently overlooked or misinterpreted, affect clinical course when diagnosed, and carry substantial risk for recurrent stroke.