Usefulness of flat detector CT (FD-CT) with biplane fluoroscopy for complication avoidance during radiofrequency thermal rhizotomy for trigeminal neuralgia.

INTRODUCTION: Trigeminal neuralgia (TN) is characterized by episodes of shooting pain in the areas innervated by one or more divisions of the trigeminal nerve. The initial treatment of TN is with drugs but the increased frequency and intensity of the neuralgic episodes often force the patient to seek alternative therapies. Microvascular decompression (MVD) and radiofrequency thermal lesioning of trigeminal rootlets (RFTR) offer close to the best results for TN. MVD has the disadvantage of being an open surgical procedure with its attendant risks and longer hospital stay, whereas RFTR is a short, 'day-care' procedure. However this latter procedure involves positioning of the RF needle in the area behind the trigeminal ganglion through the foramen ovale, which can pose significant challenges. OBJECTIVE: To use the fluoroscopic support of a biplane catheter laboratory to access the foramen, and flat detector CT to confirm the location of the tip of the RF needle in the optimal position. METHODS: Fifty-three patients with TN underwent RFTR under local anesthesia with conscious sedation. RESULTS: All patients reported pain relief with hypesthesia over the offending trigeminal division. In seven patients the needle tip required repositioning according to the CT images. Two patients each had loss of corneal reflex and abducens nerve palsy after the procedure. No other complications were seen. CONCLUSIONS: The superior view in two planes coupled with the anatomical confirmation of the position of the needle tip in the Meckel's cave during the rhizotomy reduces the need for multiple passages of the needle to access the foramen ovale and achieves accurate needle tip positioning. The technique increases the safety and precision of such treatments and helps to manage potential complications.

Fluoroscopy assisted tracheal intubation in a case of anticipated difficult airway: Fail safe devices can also fail.

Difficulty in airway management is the most important cause of major anesthesia-related morbidity and mortality. Unexpected difficulties may arise even with proper preanesthesia planning. Here, we report a case of anticipated difficult airway primarily planned for flexible fibreoptic bronchoscope assisted intubation, but due to unexpected failure of light source, fluoroscopy was used, and the airway was successfully secured.

Current status of stenting in intracranial atherosclerotic disease: the story thus far and the way ahead.

Despite medical management, symptomatic intracranial atherosclerotic disease has a high risk of stroke and death. This unacceptably high rate has provided the impetus for development and continuous advancements in the field of endovascular revascularization. From early attempts at angioplasty alone to state-of-the art stents including self-expanding and drug-eluting stents specially designed for the cerebral vessels, developments in this field has come a long way. As we stand today, however, there are still mixed views on the use of these endovascular techniques vs aggressive medical management. In this article, we review the mechanisms of stroke in patients with intracranial atherosclerotic disease and review the current status of stenting in this condition. A brief discussion of the important clinical and procedural considerations is also provided along with a mention of the ongoing trials likely to provide valuable information on the future of stenting.

Susceptibility weighted imaging in cerebral hypoperfusion-can we predict increased oxygen extraction fraction?

INTRODUCTION: Increased concentrations of deoxyhemoglobin within veins can induce susceptibility changes resulting in increased conspicuity in susceptibility weighted imaging (SWI). Compensatory mechanisms following reduced cerebral perfusion due to carotid occlusive disease may not be sufficient to meet demands of ischemic tissue and increased tissue oxygen extraction ratio results in relative increase in deoxyhemoglobin levels in the venous blood draining affected hemisphere. We assessed whether patients with carotid disease display prominence of veins over affected cerebral hemisphere. METHODS: Eighteen patients with unilateral carotid occlusion or critical carotid stenosis proven by magnetic resonance angiography (MRA) were selected. The medical records and MRI findings including SWI and MRA were reviewed. The SWI images were studied for the presence of asymmetry of veins over the cerebral hemispheres and were correlated with the site and severity of stenosis or occlusion. The veins were assumed to be conspicuous and asymmetric if there were more numerous veins and/or large veins with greater signal loss observed compared with opposite normal hemisphere. RESULTS: In about half of patients, prominence of veins was noted in the cerebral hemisphere ipsilateral to side of occlusion. This was not observed in patients with significant extracranial carotid stenosis. The SWI abnormalities were seen extending beyond the boundaries of occluded vascular territory. There was good agreement between two observers in all the patients who showed positive finding. Also there was no interobserver variation in patients with negative findings. CONCLUSION: The increased susceptibility arising out of increased deoxyhemoglobin to oxyhemoglobin ratio leads to visualization of prominent veins over the affected cerebral hemisphere on SWI.

Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts.

PURPOSE: To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in characterizing the structural pathology of epidermoid cysts. DTI gives information about the tissue structure; a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight into the orientation of structures than FA. MATERIALS AND METHODS: DTI was performed in three patients with epidermoid cysts. FA, directionally-averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal-appearing white matter. Histopathological correlation was obtained. RESULTS: Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions. CONCLUSION: High CP values suggest preferential diffusion of water molecules along a two-dimensional geometry, which could be attributed to the well-structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.

Signal changes in cortical laminar necrosis-evidence from susceptibility-weighted magnetic resonance imaging.

INTRODUCTION: Two types of infarcts can be identified depending on the circumstances leading to its generation-infarcts with pannecrosis and infarcts with selective neuronal loss. Cortical laminar necrosis (CLN) can occur due to various etiologies of which infarctions and hypoxia are the commonest. Infarction results in pannecrosis whereas hypoxia and incomplete infarction result in selective neuronal loss with the presence of viable cells, glial proliferations, and deposition of paramagnetic substances. We investigated patients with CLN with susceptibility-weighted imaging (SWI), a technique highly sensitive to even traces of paramagnetic agents or hemorrhagic components. METHODS: We retrospectively reviewed medical records of patients diagnosed with CLN as per standard criterion. Demographic characteristics and etiologies were recorded. Findings in magnetic resonance images including SWI were analyzed. RESULTS: We identified 11 patients with CLN, six males and five females with age range of 4-64 years. Etiologies included hypoxia in two patients and infarction in the nine patients. SWI detected diffuse linear hypointensities along the gyral margins in CLN due to hypoxic ischemic encephalopathy. Linear dot like hypointensities were identified in one patient with infarction. CONCLUSION: CLN due to hypoxic ischemic encephalopathy display linear gyral hypointensities and basal ganglia hypointensities that are identifiable in SWI and may represent mineralization. This might be related to iron transport across the surviving neurons from basal ganglia to the cortex, which is not possible in complete infarction. SWI may be helpful in understanding the pathophysiological aspects of CLN due to complete infarction and hypoxia.

Metabolite signature of developmental foregut cyst on in vivo and in vitro (1)H MR spectroscopy.

Foregut duplication cysts are developmental anomalies of the bronchopulmonary foregut and are common cystic lesions of the mediastinum. We describe a case of mediastinal foregut duplication cyst with in vivo (1)H MR spectroscopy on a 1.5T magnet showing a large metabolite peak at 2.02 ppm, attributable to N-acetylated compounds, in addition to a smaller peak at 1.33 ppm, considered to represent lipids. In vitro NMR spectroscopy (7.05T) of cyst fluid confirmed the presence of these peaks. In addition, a broad multiplet centered at 3.7 ppm, possibly from various protons of the hexose ring system, was also noted. Chemical analysis of the cyst fluid demonstrated the presence of N-acetylhexosamines, proteins, and lipids. Again, in vitro spectra of pure samples of N-acetylglucosamine and N-acetylgalactosamine were obtained for comparison, which better resolved the N-acetyl peak and the peaks at 3.7 ppm. The mucus secreted by respiratory epithelium and the mucous glands of the foregut cysts contains glycoproteins that have N-acetylhexosamines as components and lipid breakdown products that are thought to contribute to the observed spectrum. This information might be useful in predicting the cyst content and, in turn, the lining of the epithelium and the glandular elements.