The 2021 World Health Organization Classification of Tumors of the Central Nervous System: What Neuroradiologists Need to Know

Neuroradiologists play a key role in brain tumor diagnosis and management. Staying current with the latest classification systems and diagnostic markers is important to provide optimal patient care. Publication of the 2016 World Health Organization Classification of Tumors of the Central Nervous System introduced a paradigm shift in the diagnosis of CNS neoplasms. For the first time, both histologic features and genetic alterations were incorporated into the diagnostic framework, classifying and grading brain tumors. The newly published 2021 World Health Organization Classification of Tumors of the Central Nervous System, May 2021, 5th edition, has added even more molecular features and updated pathologic diagnoses. We present, summarize, and illustrate the most salient aspects of the new 5th edition. We have selected the key "must know" topics for practicing neuroradiologists.

Tumefactive Primary Central Nervous System Vasculitis: Imaging Findings of a Rare and Underrecognized Neuroinflammatory Disease

Primary central nervous system vasculitis (PCNSV) is a poorly understood neuroinflammatory disease of the CNS affecting the intracranial vasculature. Although PCNSV classically manifests as a multifocal beaded narrowing of the intracranial vessels, some patients may not have angiographic abnormalities. A rare subset of patients with PCNSV present with masslike brain lesions mimicking a neoplasm. In this article, we retrospectively review 10 biopsy-confirmed cases of tumefactive PCNSV (t-PCNSV). All cases of t-PCNSV in our series that underwent CTA or MRA were found to have normal large and medium-sized vessels. T-PCNSV had a variable MR imaging appearance with most cases showing cortical/subcortical enhancing masslike lesion (70%), often with microhemorrhages (80%). Diffusion restriction was absent in all lesions. In summary, normal vascular imaging does not exclude the diagnosis of t-PCNSV. Advanced imaging techniques including MR perfusion and MR spectroscopy failed to demonstrate specific findings for t-PCNSV but assisted in excluding neoplasm in the differential diagnosis. Biopsy remains mandatory for definitive diagnosis.

Multinodular and Vacuolating Neuronal Tumor of the Cerebrum: A New "Leave Me Alone" Lesion with a Characteristic Imaging Pattern

Multinodular and vacuolating neuronal tumor of the cerebrum is a recently reported benign, mixed glial neuronal lesion that is included in the 2016 updated World Health Organization classification of brain neoplasms as a unique cytoarchitectural pattern of gangliocytoma. We report 33 cases of presumed multinodular and vacuolating neuronal tumor of the cerebrum that exhibit a remarkably similar pattern of imaging findings consisting of a subcortical cluster of nodular lesions located on the inner surface of an otherwise normal-appearing cortex, principally within the deep cortical ribbon and superficial subcortical white matter, which is hyperintense on FLAIR. Only 4 of our cases are biopsy-proven because most were asymptomatic and incidentally discovered. The remaining were followed for a minimum of 24 months (mean, 3 years) without interval change. We demonstrate that these are benign, nonaggressive lesions that do not require biopsy in asymptomatic patients and behave more like a malformative process than a true neoplasm.

Calcified cerebral emboli, a "do not miss" imaging diagnosis: 22 new cases and review of the literature

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.

Pituicytoma, spindle cell oncocytoma, and granular cell tumor: clarification and meta-analysis of the world literature since 1893

BACKGROUND AND PURPOSE

Pituicytoma, SCO, and GCT are poorly understood entities with confusing nomenclature and undetermined imaging characteristics. Our purpose was to confirm published cases of pituicytoma, SCO, and GCT with the newest 2007 World Health Organization criteria and elucidate imaging findings that distinguish these tumors from common entities such as pituitary adenoma.

MATERIALS AND METHODS

A literature search identified 145 published cases (81 GCTs, 48 pituicytomas, and 16 SCOs). Case diagnoses were blindly reviewed by a neuropathologist according to the latest WHO criteria, resulting in 112 pathologically documented cases (64 GCTs, 35 pituicytomas, and 13 SCOs). Imaging illustrations from proved cases were reviewed to determine location, configuration, attenuation and signal intensity, and enhancement characteristics.

RESULTS

Only pituicytomas presented as purely intrasellar lesions (7/33). Most GCTs were purely suprasellar (28/45). All SCOs were both intra- and suprasellar (13/13). Twenty-five percent of pituicytomas (6/22) and GCTs (7/30) appeared separate from the pituitary gland. All SCOs were infiltrating. Seventy-nine percent of entities appeared isointense to brain on T1-weighted image (34/43). Seventy-four percent of pituicytomas enhanced homogeneously (14/19). Twelve of 23 GCTs and 5/7 SCOs enhanced heterogeneously. Most GCTs were hyperattenuated to brain on CT (18/20). Eleven of 13 cases enhanced homogeneously. Visual disturbances were common symptoms for all entities (67/112). Diabetes insipidus was rare (4/112).

CONCLUSIONS

Pituicytoma may be considered for purely intrasellar masses that are clearly separate from the pituitary gland. GCT should receive consideration for purely suprasellar lesions that are hyperattenuated to brain on CT. SCO should be considered for infiltrating pituitary masses with a mixed intra- and suprasellar location. A history of diabetes insipidus helps to exclude these tumors.

The new World Health Organization Classification of Central Nervous System Tumors: what can the neuroradiologist really say?

The WHO Classification of Tumors of the Central Nervous System has become the worldwide standard for classifying and grading brain neoplasms. The most recent edition (WHO 2007) introduced a number of significant changes that include both additions and redefinitions or clarifications of existing entities. Eight new neoplasms and 4 new variants were introduced. This article reviews these entities, summarizing both their histology and imaging appearance. Now with more than 3 years of clinical experience following publication of the newest revision, we also ask, "What can the neuroradiologist really say?" Are there imaging findings that could suggest the preoperative diagnosis of a new tumor entity or variant?

Suspicious neuroimaging pattern of thrombotic microangiopathy

The TMAs are a group of microvascular occlusive disorders characterized by thrombocytopenia and intravascular hemolysis. Literature review reveals a spectrum of neuroimaging findings, including a single case report of multifocal hemorrhagic infarctions. We present a series of 12 patients with TMA demonstrating a similar pattern of multifocal cortical and subcortical hemorrhagic infarctions.

"Giant" arachnoid granulations just like CSF?: NOT!!

"Giant" AGs (>1 cm) are uncommon and can be misdiagnosed as venous sinus pathology such as a neoplasm or thrombosis. Seventeen patients with a total of 19 venous sinus AGs of >1 cm were collected from contributing authors. MR imaging was available for all AGs; CT, for 5/19; and DSA, for 7/19. Intra-AG fluid was compared with CSF in subarachnoid spaces. Nonfluid AG tissue was compared with gray matter. Diagnosis was based on imaging findings. Fluid within giant AGs did not follow CSF signal intensity on at least 1 MR image in nearly 80% (15/19) of AGs. Nine of these 15 AGs had CSF-incongruent signal intensity on ≥2 MR images. CSF-incongruent signal intensity was seen in 8/8 AGs on FLAIR, 7/10 on precontrast T1WI, 13/19 on T2WI, and 8/14 on contrast-enhanced T1WI. Nonfluid signal intensity was present in 18/19 AGs and varied from absent/hypointense (intra-AG flow voids) to gray matter isointense (stromal tissue).

Artery of percheron infarction: imaging patterns and clinical spectrum

BACKGROUND AND PURPOSE

Occlusion of the AOP results in a characteristic pattern of ischemia: bilateral paramedian thalamus with or without midbrain involvement. Although the classic imaging findings are often recognized, only a few small case series and isolated cases of AOP infarction have been reported. The purpose of this study was to characterize the complete imaging spectrum of AOP infarction on the basis of a large series of cases obtained from multiple institutions.

MATERIALS AND METHODS

Imaging and clinical data of 37 patients with AOP infarction from 2000 to 2009 were reviewed retrospectively. The primary imaging criterion for inclusion was an abnormal signal intensity on MR imaging and/or hypoattenuation on CT involving distinct arterial zones of the bilateral paramedian thalami with or without rostral midbrain involvement. Patients were excluded if there was a neoplastic, infectious, or inflammatory etiology.

RESULTS

We identified 4 ischemic patterns of AOP infarction: 1) bilateral paramedian thalamic with midbrain (43%), 2) bilateral paramedian thalamic without midbrain (38%), 3) bilateral paramedian thalamic with anterior thalamus and midbrain (14%), and 4) bilateral paramedian thalamic with anterior thalamus without midbrain (5%). A previously unreported finding (the "V" sign) on FLAIR and DWI sequences was identified in 67% of cases of AOP infarction with midbrain involvement and supports the diagnosis when present.

CONCLUSIONS

The 4 distinct patterns of ischemia identified in our large case series, along with the midbrain V sign, should improve recognition of AOP infarction and assist with the neurologic evaluation and management of patients with thalamic strokes.

[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.

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.

The oculomotor cistern: anatomy and high-resolution imaging

BACKGROUND AND PURPOSE

The oculomotor cistern (OMC) is a small CSF-filled dural cuff that invaginates into the cavernous sinus, surrounding the third cranial nerve (CNIII). It is used by neurosurgeons to mobilize CNIII during cavernous sinus surgery. In this article, we present the OMC imaging spectrum as delineated on 1.5T and 3T MR images and demonstrate its involvement in cavernous sinus pathology.

MATERIALS AND METHODS

We examined 78 high-resolution screening MR images of the internal auditory canals (IAC) obtained for sensorineural hearing loss. Cistern length and diameter were measured. Fifty randomly selected whole-brain MR images were evaluated to determine how often the OMC can be visualized on routine scans. Three volunteers underwent dedicated noncontrast high-resolution MR imaging for optimal OMC visualization.

RESULTS

One or both OMCs were visualized on 75% of IAC screening studies. The right cistern length averaged 4.2 +/- 3.2 mm; the opening diameter (the porus) averaged 2.2 +/- 0.8 mm. The maximal length observed was 13.1 mm. The left cistern length averaged 3.0 +/- 1.7 mm; the porus diameter averaged 2.1 +/-1.0 mm, with a maximal length of 5.9 mm. The OMC was visualized on 64% of routine axial T2-weighted brain scans.

CONCLUSION

The OMC is an important neuroradiologic and surgical landmark, which can be routinely identified on dedicated thin-section high-resolution MR images. It can also be identified on nearly two thirds of standard whole-brain MR images.

Intracranial neurenteric cysts: imaging and pathology spectrum

BACKGROUND AND PURPOSE

Intracranial neurenteric (NE) cysts are rare congenital lesions that may be mistaken for other, more common non-neoplastic cysts as well as cystic neoplasms. We delineate the imaging spectrum, pathologic findings, and differential diagnosis of NE cysts.

METHODS

History, imaging, surgical and pathologic findings were analyzed retrospectively in 18 patients with intracranial NE cysts. Fifteen were surgically proved cases; 3 exhibited classic imaging findings and are being followed clinically.

RESULTS

Thirteen cysts were located in the posterior fossa; 12 of 13 were extra-axial. Size varied from 1.2 x 0.8 x 0.6 cm to 3.4 x 3 x 2.5 cm. Five were supratentorial, measuring from 7 x 5 x 3 to 9 x 6 x 7 cm. All were frontal and off the midline. Seven of 18 patients had CT scans. Cysts varied widely in attenuation. None enhanced. Eighteen of 18 had MR images. Sixteen of 18 were hyperintense, and 2 were isointense to CSF on T1-weighted imaging. Sixteen of 18 were hyperintense on T2-weighted imaging. All cysts were hyperintense to CSF on fluid-attenuated inversion recovery (FLAIR) sequences. Diffusion imaging was performed on 2 patients. One case showed mild restriction. Mild posterior rim enhancement was seen in 5 cases at the site where the cyst adhered to brain parenchyma.

CONCLUSION

The imaging spectrum for NE cysts is broader than previously reported. Intracranial NE cysts should be considered in the differential diagnosis for intracranial extra axial cystic lesions both above and below the tentorium.

Remote cerebellar hemorrhage

Remote cerebellar hemorrhage (RCH) is a rare but benign, self-limited complication of supratentorial craniotomies that, to the best of our knowledge, has not been described in the imaging literature. RCH can be an unexpected finding on routine postoperative imaging studies and should not be mistaken for more ominous causes of bleeding such as coagulopathy, hemorrhagic infarction, or cortical vein occlusion. Cerebellar hemorrhage in the typical setting can be identified as RCH and does not require more extensive or invasive evaluation.

Transdural spinal cord herniation: imaging and clinical spectra

PURPOSE

Transdural herniation of the spinal cord is a rarely reported clinical entity, and many of the existing reports were published before the advent of MR imaging. We describe five current cases and compare them with findings in 25 cases reported in the literature to delineate the clinical and imaging spectra of transdural spinal cord herniation.

METHODS

MR imaging, CT myelography, and conventional myelography were performed in five patients with transdural herniation of the spinal cord. These studies, along with clinical findings, are described. Intraoperative photographs are included for one case. The salient features of both the current and previously reported cases are summarized in tabular form.

RESULTS

In three cases, transdural spinal cord herniation occurred posttraumatically, in one case the cause was iatrogenic and in the others the herniation occurred spontaneously. Imaging features not previously reported include dorsally directed herniations at thoracolumbar levels (two patients), apparent (lacking surgical confirmation) syringomeyelia (one case), a vertebral body nuclear trail sign (one case), and intramedullary hyperintensities on MR images (two cases). Clinical features not previously reported include unilateral pyramidal-sensory deficits (one case) and isolated unilateral pyramidal signs (one case). Clinical findings similar to previous reports include progressive paraparesis (two cases) and progressive Brown-Séquard syndrome (one case).

CONCLUSION

Our five cases illustrate certain clinical and imaging findings not previously reported, and, together with the established features of the 25 cases in the literature, delineate the spectra of transdural spinal cord herniation.

Imaging of sella and parasellar disease

The sella and parasellar region may be affected by a variety of disease states. Diseases of this region often result in visual disturbances because of the proximity of the sella to the optic pathways and cranial nerves. Knowledge of the pathological conditions affecting the sella and surrounding structures is important for the orbital imager.

Thrombosis of the deep venous drainage of the brain in adults. Analysis of seven cases with review of the literature

OBJECTIVES

To characterize the clinical, radiographic, and pathologic findings in thrombosis of the deep venous drainage of the brain. To highlight clinical and radiographic findings that may lead to the diagnosis of disease and distinguish it from dural sinus thrombosis. To review the published literature on this disorder.

DESIGN

Retrospective review of the medical and radiographic records of seven patients from three institutions over the past 10 years. Review of the English language literature from 1971 to the present.

RESULTS

All seven patients had risk factors for cerebral venous thrombosis. Five patients presented with a short, rapidly progressing course characterized by headache, nausea and vomiting, and decline in level of consciousness. All five patients died or were rendered severely disabled. Computed tomographic scans, magnetic resonance imaging, and magnetic resonance angiography showed findings associated with deep cerebral vein thrombosis in three of four, in five of five, and in three of three patients, respectively. Transfemoral catheter angiography was diagnostic in two of two patients. Twenty-one reported cases of deep cerebral venous thrombosis were identified in the literature.

CONCLUSIONS

When the two populations are combined and compared with large series of patients with dural sinus thrombosis, patients with deep venous system thrombosis are more commonly women, tend to present with a more rapidly declining time course, altered consciousness, and long tract signs. Death or long-term sequelae are far more likely to occur in internal cerebral vein thrombosis than with dural sinus thrombosis. Unenhanced computed tomography can demonstrate findings that are strongly suggestive of the diagnosis. Magnetic resonance imaging and magnetic resonance angiography are confirmatory. Angiography may still be necessary when the diagnosis is not clear.

The cerebral ventricles: a computer-based interactive tutorial

The computer-based tutorial, "The Cerebral Ventricles," enables the user to review the anatomy, imaging, and common pathologic conditions of the human cerebral ventricular system. The program runs on a workstation that includes a laser videodisk player and a videodisk with 21,000 still images plus motion sequences. By using a mouse to select specific portions of the anatomic diagram depicting the ventricles, the user can review different planes of normal gross anatomy, corresponding computed tomographic and magnetic resonance images of normal anatomy, images of gross specimens of different pathologic entities, and corresponding radiologic images. The motion sequences portion of the program shows reconstructed three-dimensional images of ventricular anatomy and helps the user gain a greater understanding of the complex anatomy as seen from all angles. Subprograms provide more detailed information about anatomic relationships, disease entities, and bibliographic references. "The Cerebral Ventricles" assists radiologists in gaining a greater understanding of the ventricles so that an appropriate differential diagnosis of an intraventricular lesion can be offered when such masses are encountered in clinical practice.

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography

PURPOSE

To determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis.

METHODS

A retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast.

RESULTS

Three cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous).

CONCLUSION

MR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.

Safety and efficacy of iopromide in cerebral arteriography

RATIONALE AND OBJECTIVES

Iopromide is a new nonionic monomeric contrast medium for cerebral arteriography. This agent has been approved for sale in over 45 countries; however, it is still undergoing clinical review in the United States. This study evaluated the safety and efficacy of iopromide in comparison with two other nonionic contrast media.

METHODS

A total of 173 patients participated in the study, which was prospective, double-blind, and randomized. In two centers, patients received iopromide or iohexol; in the other three centers, patients received iopromide or iopamidol. Adverse events were monitored by investigators, and efficacy was evaluated by grading the radiographic images.

RESULTS

Most adverse events were mild or moderate in severity; all resolved completely. Twenty-one percent of patients given iopromide were reported to have a drug-related adverse event, versus 44% of patients given a comparator. No statistically significant difference emerged between iopromide and the comparators with regard to efficacy.

CONCLUSIONS

These study results indicate that iopromide is a safe and effective contrast medium for cerebral angiography.

Cranial magnetic resonance imaging in severe preeclampsia vs eclampsia

OBJECTIVE

This study was undertaken to evaluate the hypothesis that severe preeclampsia and eclampsia are associated with unique cranial magnetic resonance images.

DESIGN

Case series of women with severe preeclampsia and eclampsia.

SETTING

Referral center.

PATIENTS

Sixteen women with severe preeclampsia and 10 women with eclampsia.

RESULTS

Half of the women with severe preeclampsia had abnormal scans with nonspecific foci of increased signal in the deep cerebral white matter on T2-weighted images. However, women with eclampsia had either a multifocal area of increased signal at the gray-white matter junction on T2-weighted images or cortical edema and hemorrhage. These findings are consistent with necropsy descriptions of cortical edema and petechial hemorrhage. Basal ganglion lesions were also common.

CONCLUSIONS

These findings appear to be unique to eclamptic women and should be considered of diagnostic significance in contrast to the nonspecific changes in patients with severe preeclampsia. Cranial magnetic resonance imaging may, thus, be of value in cases with diagnostic uncertainty, atypical presentation, or focal neurologic deficit.

Overview of MR imaging modalities

Practical approaches to optimization of the use of gadolinium in MR imaging comprise a range of advances in data-acquisition techniques and pulse sequences that augment tissue contrast and reduce scanning times, increasing throughput and patient comfort. In addition to the effects of magnetic field strengths and manipulation of contrast doses for routine spin-echo (SE) imaging, several approaches are reviewed. These include: fat suppression, which helps to resolve enhancing lesions from tissues with inherently high signal on post-gadolinium T1-weighted imaging; gradient-echo (GRE) and partial radio-frequency (RF) echoplanar techniques, which tend to reduce data acquisition times; MR angiography, which enables elucidation of slow-flow vessels and mass-vessel relationships; and three-dimensional GRE scan displays, which relate lesion location to regional and surface anatomy.

Ocular melanoma

Uveal melanoma is the second most frequent ocular malignancy after metastasis and the most common primary ocular malignant neoplasm in adults. The diagnosis is usually made from clinical examination and ocular ultrasound. CT and MR may be helpful for further evaluation.

Spinal nerve enhancement with Gd-DTPA: MR correlation with the postoperative lumbosacral spine

PURPOSE

To search for a probable source of the recurrent signs and symptoms associated with lumbosacral postsurgical syndrome on intravenous gadolinium-enhanced MR.

METHODS

A retrospective study of 120 patients with recurrent symptomatology following lumbar disk surgery was carried out with spin-echo MR pre- and postenhancement with gadopentetate dimeglumine (0.1 mmol/kg). In addition, 10 asymptomatic subjects were evaluated at least 6 months postoperatively using the same imaging protocol.

RESULTS

21.6% of the symptomatic subjects (N = 26) had enhancement of one or more spinal nerve root. This enhancement was focal or multisegmental, and involved single or multiple nerve roots. The abnormal neural enhancement was associated with otherwise isolated epidural fibrosis in 88.5%, and with herniated nucleus pulposus in the remaining 11.5%. The overall clinical correlation of single root enhancement with a monoradiculopathy and multiroot enhancement with a polyradiculopathy was 95.7%. However, 21.7% of these same cases also showed additional nerve root enhancement that did not have an overt clinical correlation. All of these latter patients were imaged relatively early in the postoperative period (5 days to 8 months). The 10 patients in the asymptomatic group all manifested degrees of postoperative epidural scarring on MR, but no abnormal radicular enhancement or other associated pathology.

CONCLUSION

In the chronic postoperative phase (more than 6 to 8 months), the presence of radicular enhancement on MR imaging in symptomatic individuals, and its absence in asymptomatic subjects, suggests that neural enhancement serves as a marker for active neural pathology that may in certain individuals be related temporally to the signs and symptoms associated with the lumbosacral postsurgical syndrome.

Intracranial meningioma

This case shows many of the imaging features classically associated with meningiomas. The illustrations show common location, shape, and local effects as well as enhancement characteristics. Hyperostosis and bone destruction, a fluid "cleft" surrounding the extraaxial mass, gray-white interface displacement, and secondary intraparenchymal changes are correlated with gross pathology findings. These key features are summarized in Table 1 and the composite anatomic diagram (Fig. 6).

Radiologic-pathologic correlation. Epidermoid tumor of the cerebellopontine angle

This case demonstrated the classic gross pathologic, CT, and MR appearances of epidermoid tumors. The imaging features and differential diagnosis are summarized.

Multiple sclerosis in adolescents: CT and MR findings

The MR and CT findings in 12 adolescents with multiple sclerosis were compared with reported findings in adults. The adolescent group showed a more striking female predominance, more severe disease characteristics, and more frequent infratentorial involvement. Cortical atrophy and abnormal iron accumulation in the basal ganglia were uncommon in the adolescents. Neither group demonstrated a correlation between symptom severity and either extent or location of disease as delineated by MR imaging. MR was more sensitive than CT in detecting demyelinating plaques.

Multiple sclerosis in adolescents: CT and MR findings

The MR and CT findings in 12 adolescents with multiple sclerosis were compared with reported findings in adults. The adolescent group showed a more striking female predominance, more severe disease characteristics, and more frequent infratentorial involvement. Cortical atrophy and abnormal iron accumulation in the basal ganglia were uncommon in the adolescents. Neither group demonstrated a correlation between symptom severity and either extent or location of disease as delineated by MR imaging. MR was more sensitive than CT in detecting demyelinating plaques.

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.

Computed tomographic features of nonthyroid extraocular muscle enlargement

While Graves' disease is the most common cause of enlarged extraocular muscles, other disorders may masquerade as dysthyroid orbitopathy. The authors conducted a retrospective analysis of the computed tomographic (CT) scans of 60 patients with nonthyroid enlarged extraocular muscles to establish the differential radiographic features of these disorders. The diseases were classified as primary or local invasion of neoplasm (26%), inflammatory (25%), metastatic tumor (20%), vascular (13%), infection (12%), and acromegaly (3%). The inflammatory cases demonstrated more bilateral involvement (40%) and less involvement of the tendons (47%) than previously appreciated. The relatively high incidence of these features in the inflammatory group is important because both features have been considered pathognomonic for Graves' disease. Primary and metastatic tumors produced a nodular muscle enlargement with sharp borders and frequent bone changes. Certain tumors showed a predilection for certain muscle groups. Vascular cases involved multiple unilateral muscles and usually enlarged the superior ophthalmic vein. Infectious cases usually demonstrated fusiform muscle enlargement with blurred margins, whereas acromegaly caused moderate enlargement of all recti. Although certain diagnosis-specific radiographic patterns are described, no feature is pathognomonic for any disorder.

Efficacy, safety, and tolerability of ioversol in intra-arterial digital subtraction angiography

Twenty-two women and 18 men undergoing intra-arterial digital subtraction angiography were enrolled in an open-label, noncomparative study to assess the efficacy, safety, and patient tolerance of the contrast medium ioversol. The quality of radiographs generated was excellent in 60.0% of the studies, diagnostic in 37.5%, and nondiagnostic in 2.5%. There were no clinically significant drug-related changes in vital signs or laboratory tests among the patients, and no drug-related adverse effects were reported. Heat and pain related to injection of ioversol were graded on a four-point scale, with 0 indicating none and 3 indicating severe. The average scores were 1.3 for heat and 0.1 for pain. In this study, ioversol was a safe and effective contrast medium for angiography and was associated with a low incidence of patient discomfort.

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.

Disorders of histogenesis: the neurocutaneous syndromes

MRI is uniquely suited to demonstration of the wide array of brain abnormalities in the neurocutaneous syndromes, due to its ability to provide previously unattainable neuroanatomic information on T1-weighted images and its extreme sensitivity to changes in water content of brain structures on T2-weighted images. It therefore is assisting physicians in better understanding the full expression of these heritable disorders, such as the extent of optic pathway involvement in optic nerve glioma, the presence of hamartomas in TS, and abnormal myelination in Sturge-Weber syndrome. It may in the future have a role in genetic counseling in TS. CT provides complimentary information to MRI in the evaluation of intracranial pathology in the neurocutaneous syndromes. Bone abnormalities and abnormal states of calcification may at times still be better evaluated by CT. Additionally, CT is a less expensive means of following existent abnormalities over time.

Normal and diseased acoustic pathway: evaluation with MR imaging

To evaluate the use of magnetic resonance (MR) imaging in the assessment of the normal and diseased acoustic pathway, 176 patients with sensorineural hearing loss (SNHL) underwent MR imaging. In 65 patients an abnormality was detected at MR; in 50 of the 65, the abnormality was believed to be definitely or possibly responsible for the SNHL. In 47% of cases, the cochlea (3%) or vestibulocochlear nerve (44%) was involved by primary lesions. Computed tomography (CT) was performed, in addition to MR, in 25 patients in whom an abnormality was seen at MR; in 18 (72%), MR was believed to be superior to CT for lesion display. A review of 30 normal MR images of the cerebellopontine angle and brain disclosed that the cochlea was directly imaged in all cases with the use of short or long repetition times (TRs). The vestibulocochlear nerve was directly seen in 77% of cases with the use of short TR imaging. In conclusion, MR imaging delineates the acoustic pathway more clearly than does CT and is recommended for the examination of abnormalities in this region.

CT/MR spectrum of far lateral and anterior lumbosacral disk herniations

Forty-eight patients had 50 extraforaminal disk herniations (EFDHs) demonstrated on CT and/or MR by (1) presence of disk density or disk signal material lateral to the neural foramen, (2) displacement or obliteration of paravertebral fat, and (3) nerve root or ganglion compression or displacement. Forty-one of 50 EFDHs had a coexisting intraforaminal component; nine of 50 had an isolated far lateral herniated nucleus pulposus. EFDHs typically occurred in the absence of a coexisting intraspinal disk herniation. Migratory fragments were seen in 50% of all cases and were at or cephalad to the interspace of origin in all cases. Forty-six percent of EFDHs were at L2-L3 or L3-L4, although the most commonly affected level was L4-L5 (38%). EFDHs, which were often overlooked (15/50 scans reviewed), are an important preventable cause of failed intraspinal diskectomy. EFDHs can be readily identified on both CT and MR if appropriate scans are obtained from L2 through S1 and if the neural foramina and paravertebral spaces are carefully examined.

Non-Hodgkin's lymphoma of the head and neck: CT evaluation of nodal and extranodal sites

Forty-five patients with non-Hodgkin's lymphoma (NHL) of the extracranial head and neck who had undergone CT as part of their evaluation were reviewed to assess the impact of CT on clinical management. The sites of tumor deposition were subdivided by location: I, nodal; II, extranodal, lymphatic (Waldeyer's ring); and III, extranodal, extralymphatic (orbit, sinonasal, deep facial spaces, mandible, salivary gland, skin, and larynx). The CT appearance of NHL in each of the three locations was analyzed for characteristic CT signatures. Nodal NHL was suspected when CT showed multiple, large, homogeneous lymph nodes, often in unusual nodal chains of the head and neck. Extranodal, lymphatic NHL of Waldeyer's ring was indistinguishable from squamous cell carcinoma of this area unless synchronous tumor deposit in an extranodal, extralymphatic location was also present. When NHL was in nodes and/or Waldeyer's ring, CT-derived information was of limited clinical value since treatment was unfocused (chemotherapy and/or large-field radiotherapy). The CT appearances of extranodal, extralymphatic NHL was generally not distinguishable from other malignancies of these areas. However, CT-derived information regarding deep-tissue tumor size and extent was critical to planning the radiotherapy ports.

Vagal neuropathy: evaluation with CT and MR imaging

The vagus nerve, as a result of its protracted course from the brain stem to the abdomen, can present a difficult imaging problem when it is compromised by a clinically occult lesion. The clinical and radiologic records of 48 patients with suspected vagus nerve dysfunction were reviewed to derive an efficient and effective approach to imaging this patient population. An imaging algorithm is proposed in which vagal neuropathies are divided both clinically and radiologically into proximal and distal categories. Proximal vagal lesions are part of a cranial neuropathy complex and have associated oropharyngeal signs and symptoms (e.g., abnormal gag reflex, uvular deviation). Distal vagal lesions occur as an isolated paralysis of the vagus nerve with no symptoms or signs referable to the oropharynx. Either computed tomography (CT) or magnetic resonance imaging can be used to diagnose proximal or distal lesions. However, CT will be insensitive in the detection of the more cephalic proximal lesions, especially those in the brain stem, basal cisterns, and skull base.

Cochlear implant candidates: assessment with CT and MR imaging

Eighty-seven patients with severe to profound hearing loss were evaluated for possible placement of a multichannel cochlear implant hearing device. After initial clinical screening, 42 patients underwent computed tomographic (CT) examination. Five of these patients were also examined with magnetic resonance (MR) imaging. Twenty-two patients received implants. CT of the middle and inner ear was normal in 24 patients (57.1%) and showed labyrinthine ossification in 12 (28.6%), cochlear or fenestral otosclerosis (or both) in four (9.5%), and congenital cochlear malformation in two (4.8%). The information provided by CT was used to (a) exclude patients in whom multichannel cochlear implantation would most likely be unsuccessful (owing to obliterative labyrinthine ossification, or congenital cochlear malformation, severe cochlear, or fenestral otosclerosis), (b) help select the best ear for implantation, and (c) provide a preoperative picture of normal variants and avoidable surgical pitfalls. MR experience is limited but assessment of the size of the cochlear nerve and the membranous labyrinth is possible with this modality and may provide additional information in the evaluation of these patients.

Ranulas and their mimics: CT evaluation

The spectrum of computed tomographic (CT) findings in ten patients with pathologically proved simple and diving ranulas is reviewed. These retention cysts originate within the sublingual space from obstruction of the sublingual or minor salivary glands; when they enlarge, the cysts herniate to involve the submandibular and inferior parapharyngeal spaces (the so-called diving or plunging ranula). CT findings in 38 additional patients with a variety of cystic lesions in the floor of the mouth are contrasted with findings in cases of ranulas. The relevant anatomy is reviewed. This experience indicates that a unilocular, cystic mass emanating from the sublingual space and extending into the adjacent submandibular and/or inferior parapharyngeal spaces can be considered a diving ranula in virtually all cases. A unilocular, cystic mass entirely within the sublingual space can be considered a simple ranula in most instances, although absolute distinction between a simple ranula and an epidermoid cyst cannot be made radiographically.

CT patterns of facet fracture dislocations in the thoracolumbar region

Thoracolumbar facets are not as commonly dislocated as are those of the cervical spine. It is, however, crucial to make an early and accurate diagnosis of thoracolumbar facet dislocation since the injury may be unstable and require reduction and internal fixation. This paper presents three major CT patterns of thoracolumbar facet fracture dislocation. The first represents anterior subluxation of the vertebral body with anteriorly locked facets. The second is a lateral vertebral body subluxation with laterally locked facets. The third is an acute kyphosis with little vertebral body subluxation but superiorly dislocated facets. Since the vertebral body subluxation may be missed on axial CT images, these facet-dislocation patterns should be recognized by identifying the paired superior and inferior facets and establishing their congruency. Identification of the facets is accomplished by their orientation with respect to the vertebral body (superior facets are directed posteromedially and inferior facets are directed anterolaterally) as well as by the shape of the articular surface (superior facet articular surface is concave, inferior facet articular surface is flat or convex).

Radiographic evaluation of brachial plexopathy

Neurologic signs and symptoms of brachial plexopathy may be subtle or confusing, making clinical localization of disease along the length of the brachial plexus difficult. To determine the most direct radiographic approach to diagnosing and anatomically delineating the cause of brachial plexopathy, we reviewed the clinical and radiographic records of 43 patients presenting with signs and symptoms referable to the brachial plexus who received CT and/or myelography as part of their radiographic evaluation. The study population was divided into two groups, those with and those without trauma. Significant deficiencies were detected in the radiographic evaluation of the nontraumatic group, with 35% of these patients having an incomplete or inappropriate CT examination that failed to visualize the full extent of the brachial plexus. In four patients, this led to a significant (greater than 6 months) delay in diagnosis. It was concluded that trauma patients presenting with brachial plexus symptoms should have cervical myelography first, rather than CT. Patients without a history of trauma should be classified on the basis of clinical findings as having central (cord, epidural space, neural foramen) or peripheral (retroclavicular space, axillary apex) disease. If the abnormality is central, myelography should be the first technique used; if peripheral disease is present, CT should be the first study. If the disease extends beyond the confines of the anatomic compartment suggested clinically, the other technique should be used for further evaluation. CT scan protocols for brachial plexus evaluation should employ bolus/drip contrast enhancement to distinguish vascular structures from masses.(ABSTRACT TRUNCATED AT 250 WORDS)