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Cytotoxic lesions of the corpus callosum (CLOCCs) are secondary lesions associated with various entities. CLOCCs have been found in association with drug therapy, malignancy, infection, subarachnoid hemorrhage, metabolic disorders, trauma, and other entities. In all of these conditions, cell-cytokine interactions lead to markedly increased levels of cytokines and extracellular glutamate. Ultimately, this cascade can lead to dysfunction of the callosal neurons and microglia. Cytotoxic edema develops as water becomes trapped in these cells. On diffusion-weighted magnetic resonance (MR) images, CLOCCs manifest as areas of low diffusion. CLOCCs lack enhancement on contrast material-enhanced images, tend to be midline, and are relatively symmetric. The involvement of the corpus callosum typically shows one of three patterns: (a) a small round or oval lesion located in the center of the splenium, (b) a lesion centered in the splenium but extending through the callosal fibers laterally into the adjacent white matter, or (c) a lesion centered posteriorly but extending into the anterior corpus callosum. CLOCCs are frequently but not invariably reversible. Their pathologic mechanisms are discussed, the typical MR imaging findings are described, and typical cases of CLOCCs are presented. Although CLOCCs are nonspecific with regard to the underlying cause, additional imaging findings and the clinical findings can aid in making a specific diagnosis. Radiologists should be familiar with the imaging appearance of CLOCCs to avoid a misdiagnosis of ischemia. When CLOCCs are found, the underlying cause of the lesion should be sought and addressed. RSNA, 2017 An earlier incorrect version of this article appeared online. This article was corrected on February 13, 2017.

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Background and Purpose Transcranial Doppler sonography is of established value in the detection and monitoring of middle cerebral artery vasospasm. Little information exists on the utility of transcranial Doppler for detection of posterior circulation vasospasm.Methods Cerebral angiography and conventional handheld transcranial Doppler sonography were compared to determine sensitivity and specificity of transcranial Doppler for detection of vertebral and basilar artery vasospasm.Results Of 59 consecutive subarachnoid hemorrhage patients with transcranial Doppler angiogram correlations, 42 underwent posterior circulation angiography to evaluate 64 vertebral arteries and 42 basilar arteries during the period of risk for vasospasm and had technically adequate transcranial Doppler examinations within 24 hours of the angiogram. A mean flow velocity of 60 cm/s and above was indicative of both vertebral and basilar artery vasospasm. For the vertebral artery, there were 7 true-positive test results, 42 true-negatives, 6 false-positives (unknown cause in 3, increased collateral flow in 1, adjacent vessel vasospasm in 1, hyperperfusion V asospasm is a common occurrence after aneurysmal subarachnoid hemorrhage (SAH); it is detectable angiographically in 21% to 70% of patients with this disorder. "4 Angiographic vasospasm tends to occur between days 2 and 17 after SAH, with its maximal severity between days 7 and 12.' 3 Rarely, vasospasm may last for 3 to 4 weeks or even longer. The overall rate of focal neurological deficits in the 2-week period after initial SAH is 30%, with the etiologic fraction attributable to vasospasm ("clinical vasospasm") being 80%, yielding a cumulative rate of 24% by 14 days. 56 Recent data confirm that vasospasm is the leading cause of mortality (7.2%) and morbidity (6.3%) in survivors of aneurysmal SAH.7 -8 Transcranial Doppler sonography (TCD) has demonstrated value in the detection of middle cerebral artery vasospasm, 919 with an overall sensitivity of 68% to 94%, specificity of Received January 27,1994; final revision received Jury 28, 1994; accepted Jury 28, 1994. © 1994 American Heart Association, Inc.in 1), and 9 false-negatives (anatomic in 7, operator error in 2). Sensitivity was 44% and specificity was 87.5%. For the basilar artery, there were 10 true-positives, 23 true-negatives, 6 falsepositives (unknown cause in 4, hyperemia/hyperperfusion in 1, increased collateral flow in 1), and 3 false-negatives (operator error in 2, tortuous vessel course in 1). Sensitivity was 76.9% and specificity was 79.3%. When the diagnostic criterion was changed to ^80 cm/s (vertebral artery) and £95 cm/s (basilar artery), all false-positive results were eliminated (specificity and positive predictive value, 100%). Conclusions Our data suggest that transcranial Doppler has good specificity for the detection of vertebral artery vasospasm and good sensitivity and specificity for the detection of basilar artery vasospasm. Transcranial Doppler is highly specific (100%) for vertebra] and basilar artery vas...

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Preoperative embolization of vascular metastatic tumors of the spine, particularly carcinomas of renal and thyroid origin, is an adjuvant technique that significantly decreases the intraoperative blood loss and resultant surgical morbidity. Surgical decompression was achieved in 24 spinal vascular metastatic lesions, 20 of which were treated with preoperative embolization and four of which were not. The embolic materials used were gelatin sponge, polyvinyl alcohol foams, and metallic coils. In patients who underwent adequate embolization, an average of 1,850 mL of estimated blood loss was reported; in those who underwent inadequate or no embolization, greater than 3,500 mL of estimated blood loss occurred. When gelatin sponge is used, surgery should be performed within 24 hours to prevent preoperative recanalization.

To seek neural sources of endogenous event-related potentials, brain activations related to rare target stimuli detection in auditory and visual oddball tasks were imaged using a high temporal resolution functional MRI technique. There were multiple modality specific and modality non-specific activations. Auditory specific activations were seen in the bilateral transverse temporal gyri and posterior superior temporal planes while visual specific activations were seen in the bilateral occipital lobes and their junctions with the temporal lobes. Modality non-specific activations were seen in multiple areas including the bilateral parietal and temporal association areas, bilateral prefrontal cortex, bilateral premotor areas, bilateral supplementary motor areas and anterior cingulate gyrus. Results were consistent with previous intracranial evoked potential recording studies, and supported the multiple generator theory of the endogenous event-related potentials.

SUMMARY:IgG4-related disease is characterized by histologic fibrosis with IgG4-positive plasma cell infiltration. Our study evaluated MR imaging features of IgG4-related disease in the head and neck and brain. Images from 15 patients were retrospectively evaluated for the location, signal intensity, and enhancement patterns of lesions. Lacrimal gland enlargement was observed in 8 cases. Other lesions included orbital pseudotumor in 5, pituitary enlargement in 5, and cranial nerve enlargement in 7; the infraorbital nerve was involved in 4. All lesions were hypointense on T2-weighted images, which is typical for IgG4-related lesions. Multiple sites were involved in the head and neck and brain in 11 patients. The diagnosis of IgG4-related disease should be considered in a patient presenting with T2 hypointense lacrimal gland, pituitary, or cranial nerve enlargement, or a T2 hypointense orbital mass, especially if multiple sites in the head and neck are involved in the presence of elevated serum IgG4.ABBREVIATIONS: AIP ϭ autoimmune pancreatitis; HN ϭ head and neck; IgG4 ϭ immunoglobulin G4; IgG4-RD ϭ IgG4-related disease; IPT ϭ inflammatory pseudotumor; MD ϭ Mikulicz disease; SS ϭ Sjö gren syndrome; V1 ϭ first division of the trigeminal nerve (CN V); V2 ϭ second division of the trigeminal nerve