Diffusion-weighted MRI as a screening tool for hepatocellular carcinoma in cirrhotic livers: correlation with explant data-a pilot study.

OBJECTIVE: The purpose of this study was to compare the sensitivity and specificity of diffusion-weighted liver MRI alone with complete, multiphasic gadoteridol-enhanced MRI for the detection of hepatocellular carcinoma in cirrhotic patients before liver transplant. MATERIALS AND METHODS: This single institution retrospective study was performed after IRB approval and was HIPAA compliant. MRI scans of 37 patients who underwent liver transplant were evaluated and findings correlated with liver explant (36) or biopsy (1). All MRI scans were obtained within six months of explant. MRI from 17 patients with liver lesions by report at imaging subsequently proven to be HCC at pathology and 20 controls without liver lesions by imaging and pathology were reviewed in random order on the radiology PACS by three independent readers blinded to the MRI reports and pathology reports in two separate sittings. First, only the diffusion-weighted images (DWI) were interpreted. Second, the complete multiphasic MRI exam with DWI was reviewed. A consensus read was obtained by two separate radiologists who had access to the patients' explant data in order to map lesions. Reader-specific and pooled classification was assessed using sensitivity, specificity, positive predictive value, and negative predictive values and corresponding 95% confidence intervals (CI) for both DWI and complete MRI examination readings compared to pathology. McNemar's test and Kappa coefficient were used to assess differences (agreement) in DWI and complete examination readings. RESULTS: A total of 37 patients have been studied (25M 12F age range 21-70). Averaged results of the three independent readers demonstrated a sensitivity of 78% (95% CI 65-89%) and specificity of 88% (95% CI 77-95%) for DWI alone for detection of liver lesions, with a positive predictive value of 85% (95% CI 72-94%) and a negative predictive value of 83% (95% CI 71-91%). Review of the complete MRI exam showed a sensitivity of 90% (95% CI 76-97%) and a specificity of 82% (95% CI 66-92%) with a positive predictive value of 83% (95% CI 69-93%) and a negative predictive value of 89% (95% CI 74-97%). McNemar's agreement test revealed no significant difference between the DWI and complete multiphasic interpretations (p = 0.3458), with simple Kappa coefficient of 0.6716 (95% CI 0.5332-0.8110). Lesions identified on DWI ranged in size from 1.5 to 5 cm. Detection of lesions was decreased in the presence of artifact from motion, large ascites, and technical issues. CONCLUSION: Diffusion-weighted MRI has NPV and PPV comparable to complete multiphasic MRI examination for liver lesion detection in cirrhotic patients and may have a role in screening.

Cryptic vicariance in the historical assembly of a Baja California peninsular desert biota.

We use analyses of phylogeographic population structure across a suite of 12 mammalian, avian, amphibian, and reptilian species and species-groups to assess the role of Late Miocene to Pleistocene geological history in the evolution of a distinct Baja California Peninsular Desert biota. Comparative examination of phylogroup distributions provides support for previously hypothesized vicariant events produced by: a middle Pleistocene midpeninsular seaway, a late Pliocene northward transgression of the Sea of Cortéz, and a Pliocene seaway across the southern peninsular Isthmus of La Paz. Most of this phylogeographic architecture is cryptically embedded within widespread taxonomic species and species-groups, such that the unique evolutionary history of the Peninsular Desert has been obscured and ignored. The Peninsular Desert can no longer be considered a subset of the Sonoran Desert-it is a separate regional desert with its own unique evolutionary history, ecological arena, and conservation value.

Phylogeography and systematics of the Peromyscus eremicus species group and the historical biogeography of North American warm regional deserts.

Phylogeographic relationships among 26 populations from throughout the geographic range of the Peromyscus eremicus species group are described based on sequence data for a 699-bp fragment of the mitochondrial DNA COIII gene. Distance, maximum-likelihood, and maximum-parsimony analyses of phylogenetic trees generated under four separate character-weighting strategies and representing five alternative biogeographic hypotheses revealed the existence of a cryptic species (Peromyscus fraterculus, previously included under P. eremicus) on the Baja California Peninsula and adjacent southwestern California and two distinct forms of P. eremicus, one from the Mojave, Sonoran, and northwestern Chihuahuan regional deserts (West) and one from the remainder of the Chihuahuan Desert (East). Distinctiveness of P. fraterculus is supported by previous morphometric and allozyme analyses, including comparisons with neighboring P. eremicus and parapatric P. eva, with which P. fraterculus shares a sister taxon relationship. Divergence of the eva + fraterculus, West + East eremicus, and P. merriami haplotype lineages likely occurred in the late Neogene (3 Ma), in response to northern extension of the Sea of Cortéz and elevation of the Sierra Madre Occidental; divergence of eva from fraterculus is concordant with the existence of a trans-Peninsular seaway during the Pleistocene (1 Ma); and divergence of West from East eremicus occurred during the Pleistocene pluvial-interpluvial cycles, but well before the Wisconsinan glacial interval. The sequence of divergence within the eremicus species group and causal association of geological events of the Neogene and Holocene provide a working hypothesis against which phylogeographic patterns among other arid-adapted species of the warm regional deserts of North America may be compared.

Comparative phylogeography of Baileys' pocket mouse (Chaetodipus baileyi) and the Peromyscus eremicus species group: historical vicariance of the Baja California Peninsular Desert.

Phylogenetic analysis of 699 bp of the mitochondrial DNA (mtDNA) COIII and 450 bp of the cytochrome b genes among 14 species of coarse-haired pocket mice (Heteromyidae: Chaetodipus) corroborated previous indications that genetic divergence between species and species groups within the genus is generally very high, suggesting old times of divergence, and that the nominal species C. baileyi represents a highly divergent lineage within the genus, with no closely related extant sister species. Analysis of phylogeographic structure among 51 individuals from 12 localities throughout the geographic range of C. baileyi revealed three geographically separate mtDNA haplotype lineages. The oldest split separates populations east and west of the Colorado River, a pattern that is congruent with chromosomal and allozyme electrophoretic evidence. We consider the western populations to represent a distinct species, C. rudinoris. Within C. rudinoris, mtDNA haplotypes are further subdivided into northern and southern lineages along the Baja California Peninsula. Comparison of phylogeographic structure in the baileyi species group and the codistributed Peromyscus eremicus species group implies two points of codivergence and thus supports two historical vicariance hypotheses proposed for biotas distributed across the peninsular and continental warm deserts: a late Neogene (3 Ma) northern extension of the Sea of Cortéz and a mid-Pleistocene (1 Ma) midpeninsular seaway across Baja California.

Experimental chronic compressive cervical myelopathy: effects of decompression.

Twelve dogs developed a delayed onset of neurological abnormalities from chronic cervical cord compression that was characteristic of myelopathy. The animals were divided into two groups and matched according to degree of neurological deficit. Six animals underwent decompression through removal of the anteriorly placed compressive device. Throughout the experiment, serial neurological examinations and somatosensory evoked potential studies were performed on each animal. Spinal cord blood flow measurements were obtained during each surgical procedure and at sacrifice. Magnetic resonance images were obtained after compression and before sacrifice. All animals in the decompressed group showed significant neurological improvement after decompression; no spontaneous improvement in neurological function was seen in the compressed group. On pathological examination, irreversible changes including large motor neuron loss, necrosis, and cavitation were seen in four of the animals in the decompressed group and five in the compressed group. Cervical spondylotic myelopathy in humans is known to respond to decompression; this study provides further evidence that this animal model for chronic compressive cervical myelopathy accurately reflects the disease process seen in humans.

The history of endovascular therapy.

The roots of endovascular therapy in both the United States and Russia are explored. Developments in selected areas of endovascular neurosurgery are recounted.

Angioplasty of vasospasm: is it reasonable?

Clinical and radiographic examinations indicate preliminarily indications that transluminal angioplasty may be effective in overall management of the patient with vasospasm. Many questions remain, including: How does it work?; Are the effects persistent?; Is the arterial wall injured by the process? Recent studies in several patients who died after angioplasty allow us to provide some answers. Undilated spastic arteries show proliferation of both cellular and connective tissue elements. There is good evidence that myofibroblasts have reorganized the collagen framework, increasing fibril density and thus thickness. Dilated vessels show thinning of the arterial wall without disruption but with compaction of the new collagen fibrils. Cellular nests are also compressed and stretched. The endothelial layers are undisturbed. The success of dilatation depends on the amount and location of proliferation present. The effect is usually permanent. Because our protocols call for dilatation no greater than 10% above normal diameter, the muscle layers have not been torn or stretched although focal areas of necrosis are sometimes seen. Understanding the constrictive process and its relief through dilatation, allows us to formulate a therapeutic plan. Our experience in treating 89 patients with vasospasm after SAH suggests that, for best results, angioplasty should be performed before the angiopathic features become florid. This helps to preserve flow through the short arteries to the brain stem and deep brain nuclei, which may be involved indirectly in the vasospastic process.

Thrombosis of a giant aneurysm after extracranial-intracranial bypass.

A patient presenting with a giant, fusiform middle cerebral artery aneurysm underwent extracranial to intracranial bypass grafting before permanent occlusion of the aneurysm. The patient was to return 4 months later for endovascular treatment. Arteriography obtained before obliteration revealed complete aneurysmal thrombosis. No further treatment was deemed necessary. Factors predisposing to thrombosis are discussed.

Coexistent hemangioblastoma and arteriovenous malformation of the cerebellum. Case report.

A case of cerebellar hemangioblastoma and coexistent arteriovenous malformation (AVM) is presented. Angiography displayed the AVM, but histological examination revealed a coexisting hemangioblastoma. Various theories concerning the etiology of this condition are discussed.

Efficacy of tissue plasminogen activator in the lysis of thrombosis of the cerebral venous sinus.

Therapy for thrombo-occlusive disease of the cerebral venous sinuses remains controversial. Although several thrombolytic agents, such as urokinase and anticoagulants, are recommended for treatment, major significant risks include cerebral hemorrhage, especially in patients with venous infarction. Tissue plasminogen activator (tPA) has shown a high affinity for fibrin-bound plasminogen, while exhibiting a low affinity for circulating plasminogen. The purpose of this study was to evaluate this drug for use in cerebral sinus thrombo-occlusive disease. Eleven adult male rabbits were chosen as experimental animals. All animals underwent microsurgical dissection of their major dural venous sinuses. Direct compression was used to form a thrombus within the sinus. The presence of significant venous thrombosis was confirmed radiographically by iohexol sinography. Subsequently, tPA was delivered systemically via the marginal ear vein at a dose of 3000 units/h; the result was total lysis of the clot documented by a sinogram 1 hour after the drug was administered. Postmortem pathological examination confirmed total lysis in seven of eight animals. One animal showed partial retained clot fragments. No significant coagulopathic state was observed. In three control animals, saline was infused without clot lysis. We conclude that tPA is a highly effective agent for the lysis of acute induced venous sinus thrombosis in an experimental model.