Lin Xiong

EVALUATION OF GADOPENTETATE DIMEGLUMINE MAGNETIC RESONANCE CISTERNOGRAPHY IN AN ANIMAL MODEL : PRELIMINARY REPORT

RATIONALE AND OBJECTIVES To evaluate magnetic resonance (MR) imaging characteristics of the cisternal administration of gadopentetate dimeglumine (gadolinium) in a small experimental animal. METHODS Four female New Zealand White rabbits were used for this experiment. Each rabbit received a single dose of intrathecal gadolinium (doses ranged from 75-100 micromol) via a cisternal puncture. Immediate and delayed sagittal and axial T1-weighted images of the brain and cervical spinal cord were acquired on a 2 Tesla CSI magnet. RESULTS All the rabbits tolerated the experiment well, without significant alterations in behavior or seizure activity. During the early phase of imaging, subarachnoid space enhancement was observed over the surface of the brain parenchyma and spinal cord on T1-weighted images. Gradual diffusion of the gadolinium into the cranial parenchyma was seen on the delayed MR studies (45 minutes-6 hours), as revealed by progressive generalized enhancement of the brain. Sustained enhancement of gray matter of the spinal cord was observed. CONCLUSION This study illustrates that there is no barrier between the cerebrospinal fluid (CSF) and the brain-spinal cord with regard to gadolinium. Possible practical applications for gadolinium-enhanced MR myelography or cisternography include the assessment of communication or obstruction of CSF pathways, subarachnoid space CSF flow pattern analysis, spontaneous or acquired CSF fistula evaluation, evaluation of the intercommunication of central nervous system cystic structures bordering on CSF pathways, and the study of the dynamics of gadolinium diffusion in the central nervous system parenchyma.

CT and MRI characteristics of ossification of the ligamenta flava in the thoracic spine.

Abstract. The purpose of this study was to compare MRI findings with CT findings of mass-forming calcification/ossification of the thoracic ligamenta flava (OTLF). Twenty-one Chinese patients presented with clinical evidence of chronic and progressive thoracic spinal cord compression which included: difficulty in walking; weakness; and/or numbness of the extremities, back pain, and lower extremity paresthesias. Axial and sagittal T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) were performed through the thoracic spine on a 1.0-T Impact unit (Siemens, Erlangen, Germany). Axial CT was obtained with 5-mm contiguous sections through the thoracic region. Decompressive surgery with resection of the OTLF were carried out in all patients. Low signal intensity of the mass-forming OTLF was demonstrated at a single level (n=1) or at multiple levels (n=20) on both T1WI and T2WI. The distribution of OTLF was bilateral at all levels identified in 6 cases, unilateral at all levels in 5 patients, and both unilateral and bilateral at different levels in 10 cases. Ossification of the thoracic ligamenta flava involved the upper thoracic spine (T1–4) in 3 cases, midthoracic spine (T5–8) in 3 cases, lower thoracic spine (T9–12) in 10 cases, and more than one thoracic spinal subregion in 5 cases. Computed tomography confirmed the MR findings regarding the location and distribution of OTLF in all cases, as well as the associated evidence of central spinal canal stenosis. In addition, 5 patients revealed associated ossification of the posterior longitudinal ligament. All patients demonstrated gradual, but incomplete, clinical improvement of the radiculomyelopathy following decompressive surgery. Ossification of the posterior longitudinal ligament resulting in thoracic central spinal canal stenosis and clinical radiculomyelopathy is not uncommon in the Asian people. Ossification of the thoracic ligamenta flava can be accurately evaluated equally well by CT and MR with regard to level(s) and side(s) of involvement, as well as to the relative degree of central spinal canal stenosis and the associated compression of the thoracic spinal cord.

Evaluation of intrathecal gadolinium-enhanced MR cisternography in a rabbit model of traumatic nasoethmoidal CSF fistula.

This pilot study details the feasibility of intrathecal gadopentetate dimeglumine (Gd) administration in the detection of posttraumatic cerebrospinal fluid (CSF) fistula in an animal model. Five rabbits were used in this study. An attempt was made to create a traumatic CSF fistula surgically via a nasal approach. Seven days following the procedure, images of the cranium in sagittal and coronal planes were obtained utilizing a 1.9 T magnetic resonance (MR) imaging scanner before and after intrathecal injection of 16 μmol Gd. Following the imaging study, the animals were euthanized and grossly sectioned coronally to search for fistula formation. One animal died on the third day following the surgical procedure. The other four rabbits underwent the MR and gross pathologic study. Diagnosis of the fistula by intrathecal Gd‐enhanced MR imaging was successful in two rabbits; this finding was confirmed by gross pathologic examination. No fistula was detected on either intrathecal Gd‐enhanced MR imaging or on pathologic study in the remaining two rabbits. Intrathecal enhanced MR cisternography is a potentially promising technique for the evaluation of posttraumatic CSF fistulae. J. Magn. Reson. Imaging 2000;11:20–24.

MR of disc protrusion engendered by infectious spondylitis

PURPOSE The purpose of this study was to determine if infection-related disc protrusion formed a component of the perispinous/epidural mass in patients with intervertebral disc infection. METHOD A retrospective review was undertaken of 16 consecutive patients with intervertebral disc space infection who were referred for gadolinium-enhanced MRI. Possible correlation was sought between disc infection and the presence of associated posterior disc protrusion as determined by MRI. RESULTS Of the 16 infected discs, 10 cases were in the lumbosacral spine, 3 in the thoracic spine, and 3 in the cervical spine. Four cases had isolated posteriorly directed disc protrusion, and 12 showed both posterior and anterior disc protrusions. The infection in patients with disc protrusion was related to Staphylococcus aureus in 14 patients, Salmonella enteritidis in 1, and Streptococcus pneumoniae in 1. CONCLUSION This study showed that disc protrusion occurred in combination with disc space infections. Local factors such as the secretion by hyaluronidase from Staphylococcus aureus may play an important role in causing focal disc protrusion. The clinical importance of this finding is in the recognition that a significant part of the compromise of the spinal canal in cases of disc infection can be related to disc fragments engendered by the infectious process.

An Animal Model of Corpus Callosum Impingement as Seen in Patients with Normal Pressure Hydrocephalus

RATIONALE AND OBJECTIVES.Callosal impingement has been postulated to cause the symptoms associated with normal pressure hydrocephalus. The authors developed an animal model for the investigation of corpus callosum impingement by the falx cerebri METHODS.The corpus callosum was compressed from above by a plastic blade and surgically placed in the interhemispheric fissure in adult Sprague-Dawley rats. Magnetic resonance imaging (MRI) was performed both preoperatively and postoperatively. The brains of the rats also were examined grossly at the time of autopsy. RESULTS.All rats survived the surgical procedure. MRI proved to be a suitable method to image the corpus callosum, to confirm the location of the blade, and to demonstrate the corpus callosum impingement. MRI correlated well with necroscopy sections. CONCLUSIONS.It was possible to surgically produce callosal impingement in rats, and this impingement could be confirmed by MRI. In the future, this rat model of callosal impingement will be used to search for evidence of changes in metabolism, neuroelectrical activity, behavior, and neuronal anatomy which are known or are thought to be associated with hydrocephalus.

Evaluation of histopathologic changes in an animal model of mechanical corpus callosum impingement as seen in hydrocephalus

RATIONALE AND OBJECTIVES We evaluated histologic changes associated with chronic impingement of the corpus callosum. Similar callosal impingement has been postulated to be responsible for some of the symptoms in people who have hydrocephalus. METHODS Eight rats with callosal impingement produced by surgical implantation of a blunt blade in the interhemispheric fissure and four control animals with no callosal impingement were evaluated by magnetic resonance (MR) imaging and by direct histologic evaluation after autopsy. The histologic evaluations occurred 1 month after surgery in half the animals and 6 months after surgery in the other half. RESULTS MR imaging results showed that the implanted blade was in a good position in all animals. Histologically, the corpus callosum appeared normal 1 month after implantation of the impingement blade. Six months after surgery, the experimental group demonstrated decreased callosal thickness and a loss of axonal fibers in the corpus callosum both near and remote to the blade. CONCLUSION Chronic impingement of the corpus callosum was associated with callosal thinning and by loss of callosal axons. Further research will be required to investigate the possible relation of these histologic findings to the clinical findings in normal-pressure hydrocephalus.

Sterile, benign radiculitis associated with lumbosacral lateral recess spinal canal stenosis: evaluation with enhanced magnetic resonance imaging.

Two cases of symptomatic lumbar lateral recess stenosis are described in which the compressed nerve root became focally enhanced on magnetic resonance imaging (MRI) studies performed with gadolinium DTPA. Two men with low back pain and lumbar radiculopathy were examined with contrast-enhanced MRI studies, which showed intradural enhancement of the symptomatic nerve roots. In selected cases of lateral recess stenosis, focal radicular injury may be visualized on enhanced MRI as a result of a breakdown of the blood-brain barrier.

Intrathecal Gadolinium-Enhanced MR Myelography/Cisternography

The high level of safety and tolerance of IV administrated gadolinium has been proved through extensive clinical use (Goldstein et al. 1990; Niendorf et al. 1991a, 1991b). However, only a limited number of laboratory studies have been performed focusing on the possible usage and neurotoxic or inflammatory reactions of paramagnetic contrast agents injected into the subarachnoid space (Dichiro et al. 1985; Allard et al. 1987; Ray et al. 1996; Skalpe and Tang 1997; Ray et al. 1998; Skalpe 1998; Jinkins et al. 1999). Only one study on two human patients with meningeal carcinomatosis who underwent intraventricular gadolinium injection has been published (Siebner et al. 1997). The present chapter details the results of a controlled pilot medical experiment (Zeng et al. 1999). It should be noted that the intrathecal gadolinium is not presently an approved route of administration of gadolinium worldwide.