Evaluation of intervertebral disc herniation and hypermobile intersegmental instability in symptomatic adult patients undergoing recumbent and upright MRI of the cervical or lumbosacral spines.

PURPOSE: The purpose of the study was to determine the difference in findings between recumbent and upright-sitting MRI of the cervical and lumbosacral spine in patients with related sign and symptoms. MATERIALS AND METHODS: A total of 89 patients were studied (lumbosacral spine: 45 patients; cervical: 44 patients). T1-weighted (TR: 350, TE: 20) fast spin echo and T2-weighted (TR: 2500, TE: 160) fast spin echo images were acquired in the sagittal and axial planes in both the recumbent and sitting-neutral positions. The images were acquired on the Upright MRI unit (Fonar Corporation, Melville, NY). Differences were sought between the recumbent and upright-sitting positions at all levels imaged, in both planes. RESULTS: The total number of cases of pathology was 68, including instances of posterior disc herniation and anterior and posterior spondylolisthesis. Focal posterior disc herniations were noted in 55 patients (cervical: 31, lumbosacral: 24) [62% of patients]. Six of these herniations (cervical: 4, lumbosacral: 2) [11%] were seen only on the upright-sitting study. Focal posterior disc herniations were seen to comparatively enlarge in size in 35 patients on the upright-seated examination (cervical: 21, lumbosacral: 14) [72%], and reduce in size in 9 patients (cervical: 5, lumbosacral: 4) [18%]. Degenerative anterior (n: 11) and posterior (n: 2) spondylolisthesis was seen in 13 patients (cervical: 0, lumbosacral: 13) [15% of patient total]. Anterior spondylolisthesis was only seen on the upright-seated examination in 4 patients (cervical: 0, lumbosacral: 4) [31%]. Anterior spondylolisthesis was comparatively greater in degree on the upright-seated study in 7 patients (cervical: 0, lumbosacral: 7) [54%]. Posterior spondylolisthesis was comparatively greater in degree on the recumbent examination in 2 patients (cervical: 0, lumbosacral: 2) [15%]. The overall combined recumbent miss rate in cases of pathology was 15% (10/68). The overall combined recumbent underestimation rate in cases of pathology was 62% (42/68). The overall combined upright-seated underestimation in cases of pathology was 16% (11/69). CONCLUSIONS: Overall, upright-seated MRI was found to be superior to recumbent MRI of the spine in 52 patents (recumbent missed pathology [n: 10]+recumbent underestimated pathology [n: 42]=52/89 total patients: 58%) in cases of posterior disc herniation and anterior spondylolisthesis. This seems to validate the importance of weight-bearing imaging in the spine that might be expected to unmask positional enlarging disc herniations and worsening spondylolisthesis. Overall, recumbent MRI was found to be superior to upright-seated MRI in 11 cases (11/89: 12%). The latter finding was possibly due to the fact that upright seated position is actually partial flexion that might be expected to reduce some cases of hypermobile posterior spondylolisthesis.

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.

Acute and subacute physiological and histological studies of the central nervous system after intrathecal gadolinium injection in the anesthetized rat.

RATIONALE AND OBJECTIVES: To determine the acute physiological and subacute neurohistological effects of gadopentetate dimeglumine (GdD) administered intrathecally. METHODS: Twenty-four rats were separated into two study groups. In the first group, the acute effects of intrathecal GdD on cortical electroencephalographic activity, renal sympathetic nerve activity, arterial blood pressure, and heart rate were determined. In the second group, histological evaluation of the neural tissues was performed 10 days after treatment. In both the physiological and histological studies, a single GdD dose of 2.5 micromol/g brain (10 microL) was administered intrathecally. Control animals were injected intrathecally with the same volume of a sucrose solution that had the same osmolality as GdD. RESULTS: In the physiological study, GdD and sucrose injections elicited no significant change in any of the parameters recorded. In the histologic study, examination revealed two cases of pre-existing chronic spinal cord gliosis; one of these rats also exhibited signs of pre-existing chronic choroid plexus inflammation. No acute or subacute alterations observed could be specifically linked to the intrathecal administration of GdD. CONCLUSIONS: Intrathecally administered GdD was accompanied by no significant change in any of the physiologic or histologic parameters examined. Based on the relatively short time interval between GdD treatment and histologic examination, the neural tissue abnormalities (gliosis/inflammation) observed in two animals were judged to be incidental and likely due to prior chronic pre-existing processes such as viral infection. Although additional studies are required to verify the safety and effectiveness of intrathecal GdD in humans, data from the present study in animals provide evidence that when intrathecal GdD is used in doses sufficient to improve MRI of the cerebrospinal fluid compartment, it is likely to be accompanied by a low incidence of acute changes in neural function or structure.

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.

Magnetic resonance imaging in patients with central nervous system pathology: a comparison of OptiMARK (Gd-DTPA-BMEA) and Magnevist (Gd-DTPA).

RATIONALE AND OBJECTIVES: The objective of the two pivotal phase 3 studies was to evaluate the safety and efficacy of OptiMARK (Gd-DTPA-bis(methoxyethylamide) [Gd-DTPA-BMEA]) compared with Magnevist (Gd-DTPA) in magnetic resonance imaging of the central nervous system. METHODS: Two multicenter, randomized, double-blind, parallel group studies were conducted in 395 patients with known or suspected central nervous system pathology. Subjects were randomized to receive a single 0.1 mmol/kg intravenous injection of either Gd-DTPA-BMEA or Gd-DTPA. The safety of Gd-DTPA-BMEA and Gd-DTPA was monitored for up to 72 hours after study drug administration. Precontrast and postcontrast administration magnetic resonance scans were acquired using identical imaging planes and techniques. RESULTS: No deaths or unexpected adverse events were reported in either group. A comparison of adverse events by intensity and relation demonstrated no statistically significant differences between the two groups. Gd-DTPA-BMEA and Gd-DTPA were equivalent with respect to confidence in diagnosis, conspicuity, and border delineation. CONCLUSIONS: Gd-DTPA-BMEA and Gd-DTPA demonstrated comparable efficacy profiles, and the safety profiles were considered similar.

Analysis of cross-sectional area measurements of the corpus callosum adjusted for brain size in male and female subjects from childhood to adulthood.

Interest in anatomic evaluation of the corpus callosum is based upon the expectation that its function will be influenced by its structure. Using MR images, the size of the corpus callosum was determined by measuring its area in the midsagittal plane. A callosal index was calculated for each subject by dividing the callosal size by cerebral size, also measured from the MR image. This callosal index was designed to allow comparison of callosal size between different groups, despite differences in brain size that existed between the groups. The validity of this index was supported by the statistically significant, positive correlation between measured callosal area and cerebral size. Using MR images and the callosal index, adult males were shown to have a larger corpus callosum and larger cerebrum, compared to adult females. However, the callosal index was identical for male and female subjects. This demonstrated there relative size of the callosum was the same for males and females. Childhood development of the corpus callosum was documented through the first two decades of life by a progressive increase in the callosal index. In adults, cerebral atrophy caused a decline in callosal size, but no decline due to simple advancing age was found in normal adult subjects. This use of cerebral size to calculate a callosal index appeared to be useful in comparing callosal size between subjects and may be useful in future study of other disease states of the corpus callosum.

Clinical manifestations of hydrocephalus caused by impingement of the corpus callosum on the falx: an MR study in 40 patients.

The clinical features of patients with hydrocephalus include generalized reductions in coordinated motor and cognitive functions. Although some group similarities have been noted, the outward manifestations of this dysfunction vary in degree and character, with some subjects revealing no overt signs of the underlying hydrocephalus. A retrospective review of subjects with MR criteria of hydrocephalus was undertaken to reevaluate the specific imaging correlates of the signs and symptoms associated with this pathologic process. Forty adults with hydrocephalus on MR evaluation were carefully scrutinized in an effort to elucidate specific clinicoradiologic patterns of abnormality. Spin-echo MR techniques were used with T1 and/or T2 weighting in three orthogonal planes. MR criteria of hydrocephalus encompassed dilated lateral ventricles to include the temporal horns, a pronounced upward elevation of the corpus callosum, and an outward expansion of the cerebral hemispheres at the expense of the subarachnoid space overlying the convexities. The significant related morphologic change on MR that has not been previously described in hydrocephalus was a localized dorsal flattening and thinning of the posterior body of the corpus callosum. Importantly, all but three of the 24 patients with this phenomenon manifested varying combinations of imbalance, gait disturbance, incontinence, short-term memory deficits, and global dementia. In the presence of hydrocephalus, but in the absence of this specific callosal configuration, only one of the remaining 16 subjects revealed symptoms that might suggest the presence of hydrocephalus (i.e., profound dementia). The structure responsible for this focal callosal flattening and thinning in hydrocephalus is the rigid free surface of the falx cerebri as it impinges on the caudal extent of the upwardly expanding corpus callosum and supracallosal hippocampal formation. This mechanical insult hypothetically causes variable axonal dysfunction, ranging from decreased to increased neurophysiologic activity. In summary, it is postulated that callosal impingement represents a dynamic partial hemispheric disconnection and accounts, in part, for the complex clinical state associated with hydrocephalus.

MR of enhancing nerve roots in the unoperated lumbosacral spine.

PURPOSE: To evaluate prospectively the unoperated lumbosacral spine by gadolinium-enhanced MR for evidence of clinically correlative abnormal enhancement of nerve roots. METHODS: Two hundred patients were prospectively studied with intravenous gadolinium- (0.1 mmol/kg) enhanced MR. Evidence was sought of intrathecal enhancement of lumbosacral nerve root(s), and the correlation of this enhancement with the clinical syndrome was evaluated. RESULTS: Ten patients demonstrated abnormally enhancing lumbosacral nerve root(s) (5%). Of these, seven (70%) were associated with focally protruding disk pathology. The three (30%) remaining patients had isolated enhancement of multiple nerve roots in the absence of significant associated anatomic pathology. Overall, the correlation of radicular enhancement with the presenting clinical syndrome was excellent. CONCLUSION: A breakdown in the blood-nerve barrier as observed on gadolinium-enhanced MR serves as a marker for nerve root pathology in the unoperated lumbosacral spine, which may have clinical relevance in certain clinical situations.

The cisternal ventricle.

Hydrocephalus communicating with the basilar subarachnoid cisterns may manifest itself as enlargement of these spaces. Confirmation of this finding is based on resolution of dilatation after ventricular shunting. A series of eight patients points out the CT characteristics, the differential diagnosis, and the importance of the cisternal ventricle in the transmission of CSF.

Focal tuberculous cerebritis.

Five cases of focal tuberculous cerebritis, seen over a period of 10 years, revealed unique clinicoradiologic patterns that differentiate these lesions from other forms of cerebral tuberculosis. Histologically, the process consists of microgranulomata, a lymphocytic infiltrate, Langhans' giant cells, epithelioid cells, and variable evidence of rare tubercle bacilli. The relatively poor clinical outcome in this series indicates the importance of timely recognition of this disease so that proper treatment can be instituted as early as possible in an effort to arrest the underlying inflammatory reaction with a resulting minimum neurologic insult. Intense focal gyral enhancement on CT and a corresponding palisading gyral blush on angiography are invariably observed radiologically.

The vidian artery in childhood tonsillar hypertrophy.

Cerebral arteriography performed in two children for cerebral pathology incidentally revealed prominent arterial supply to pharyngeal tonsillar tissue arising directly from the internal carotid arteries bilaterally. Embryologic considerations seem to indicate developmental origins of this vessel from early emanations of the first fetal aortic arch. Clinical implications revolve around the possible relation of the vidian artery to serious hemorrhage during or after otherwise uncomplicated tonsillectomy.

The optic syrinx: cavernous degeneration of the optic nerve demonstrated by iopamidol optic neurography.

Cavernous degeneration of the optic nerve has been described predominantly in association with long-standing glaucoma, although less frequently it has been reported in other, disparate disease processes. The only descriptions to date have been in pathologic specimens in vitro. This is the first report to describe syrinx formation of the optic nerves in vivo in two patients with nonglaucomatous conditions affecting the optic nerves.

The optic neurogram: evaluation of CSF "block" caused by compressive lesions at the optic canal.

Patients with progressive blindness resulting from bony proliferative diseases such as osteopetrosis may benefit from optic canal decompression. A radiologic technique is described whereby the practicality of surgical optic canal widening is evaluated preoperatively using the intrathecal water-soluble contrast agent lopamidol. Conceptually, if a patient who is losing vision demonstrates a block on the optic neurogram, then likely there is still sufficient neural tissue within the optic canal and sheath to cause obstruction, and therefore decompression may be indicated. However, if preoperatively there is no block to lopamidol, then surgical intervention is not indicated, as the nerve has already undergone severe atrophy to the point of "autodecompression." Cases of differing etiologies, with and without blocks, illustrate the utility of the method and point out the importance of early surgical management to prevent irreversible damage to the optic nerve.

Posttraumatic ethmoidal pseudomeningoencephalocele.

Three cases are presented that illustrate the potential of craniofacial trauma to generate pseudomeningocele formation in the region of the ethmoidal air cells. In each case there was the further association of herniation of cerebral substance through the chronic diastatic fracture resulting in an acquired encephalocele. Contrast cisternography showed this important combination of anatomic findings and aided in planning the subsequent reparative surgery.

Optic hydrops: isolated nerve sheath dilation demonstrated by CT.

This report illustrates the potential of the optic subarachnoid space to dilate selectively with various disease processes involving the orbit, optic canal, sella, and parasellar regions. According to the concept of optic hydrops, isolated papilledema, in the absence of increased intracranial pressure, may be caused by focal disease of these regions.

Variability of corpus callosal area measurements from midsagittal MR images: effect of subject placement within the scanner.

Variation in corpus callosum area measured from midsagittal MR images was evaluated in 12 healthy subjects who were each imaged four to seven times. Statistically significant differences between measurements of the same subject were found on 47% of the images, with an average difference of 5.9% between images.

Paradoxical cerebral emboli associated with pulmonary arteriovenous shunts: report of three cases.

Paradoxical embolism to the cerebral circulation is rarely diagnosed in life; however, three such cases have recently been observed: two with multiple congenital pulmonary arteriovenous malformations and one with an acquired arteriovenous fistula. In each case the pulmonary lesion(s) were treated by percutaneous balloon embolizations. Paradoxical embolism should be included in the differential diagnosis of cerebral arterial embolism for which there is no obvious source, especially when there is also evidence of concurrent peripheral venous thrombosis and/or pulmonary embolism.

Amaurosis fugax caused by a dural arteriovenous fistula from the ophthalmic artery.

A 52-year-old man presented with transient monocular blindness that was both spontaneous and exacerbated by exertion. Dynamic orbital CT revealed a delay in the perfusion of the left optic nerve head suggestive of a steal phenomenon. Subsequent selective arteriography demonstrated an arteriovenous fistula between the falx artery originating from the ophthalmic artery and the superior sagittal venous sinus. In the proper clinical setting, a hemodynamic steal should be considered in the differential diagnosis of amaurosis fugax.

Hyperdense middle cerebral arteries identified on CT as a false sign of vascular occlusion.

PURPOSE: To evaluate the middle cerebral artery (MCA) on CT, including its relationship to cerebral infarction. METHODS: Thirteen patients with either a unilateral or bilateral hyperdense M1 segment of the MCA were evaluated. History of hypertension, diabetes, and hematocrit were obtained and compared with a control group of patients without a hyperdense MCA. RESULTS: None of the patients had a unilateral hyperdense MCA ipsilateral to a clinically identifiable stroke. Patients with a hyperdense MCA had a statistically higher hematocrit and also a higher prevalence of hypertension and diabetes mellitus than patients without a hyperdense MCA. The higher hematocrit may have increased the density of the blood, while both diabetes and hypertension are associated with calcification within blood vessel walls. CONCLUSION: A hyperdense MCA is not a reliable indicator of occlusion of this vessel or subsequent infarction.

MR imaging of "spray heads": toluene abuse via aerosol paint inhalation.

PURPOSE: Three male patients with a history of spray-paint inhalation are presented. METHODS: Spin-echo MR was used to evaluate the central nervous system changes secondary to toluene inhalation delivered via spray-paint fumes. RESULTS: The remarkable findings included the loss of cerebral and cerebellar gray-white matter discrimination, scattered multifocal deep white matter lesions, and gross generalized atrophy of the cerebrum, the cerebellum, and the corpus callosum. CONCLUSION: Although the observed changes are nonspecific, combined with a positive history the diagnosis of inhalation toluene abuse can be made on the basis of consistent MR findings.