MRI changes during water loading in patients with polydipsia and intermittent hyponatremia.

OBJECTIVE: Patients with polydipsia and intermittent hyponatremia have greater ventricle-brain ratios (VBRs) than matched patients without polydipsia and intermittent hyponatremia and normal subjects. Unlike previous studies, this study controlled for the impact of water loading when examining the volume of intracranial structures. METHOD: Under controlled conditions, eight male schizophrenic patients with polydipsia and intermittent hyponatremia were first assigned to either normal fluid intake or oral water loading and then the alternative condition the following day. Magnetic resonance imaging (MRI) volumetric measurements were made with the use of a standardized protocol. RESULTS: During water loading, total VBR and lateral ventricle volume significantly decreased by 13.1% and 12.6%, respectively. A strong association between change in serum sodium concentration and change in VBR was noted across conditions. CONCLUSIONS: These findings indicate that 1) water loading does not account for the diminished brain volume observed in patients with polydipsia and intermittent hyponatremia in previous studies, and 2) hyponatremia can significantly alter brain morphology on MRI.

Posterior fossa hemorrhage after supratentorial surgery.

PURPOSE: To evaluate the imaging findings, possible pathogenesis, and frequency of hemorrhage near the tentorial surface of the cerebellum after supratentorial surgery. METHODS: Over a 5-year period, 13 patients with posterior fossa hemorrhage after supratentorial surgery were identified with postoperative CT studies, which were obtained in all patients after craniotomy. Four of the 13 patients also had postoperative MR examinations. Preoperative and postoperative radiologic studies and medical records were reviewed. RESULTS: All hemorrhages were located along the superior aspect of the cerebellum transversely oriented along the cerebellar fossa and fissures. None of the patients had coagulopathy or radiologic evidence of posterior fossa tumor or vascular malformation. None of the hemorrhages had an appearance typical of hypertensive hemorrhage. Ten patients (77%) had lumbar drains placed before surgery and all had epidural drains placed at the conclusion of surgery. One patient had surgery for a meningioma, and 12 had surgery for aneurysms. The frequency of hemorrhage after aneurysmal surgery was 3.5%. No neurologic deficits developed referable to the cerebellum. CONCLUSIONS: Hemorrhage should be viewed as a potentially benign sequela of surgery rather than as an indication of hypertension, aneurysm, or previously unrecognized vascular malformation or neoplasm.

Cerebral hemiatrophy: classification on the basis of MR imaging findings of mesial temporal sclerosis and childhood febrile seizures.

PURPOSE: To classify cerebral hemiatrophy on the basis of childhood febrile seizures and magnetic resonance (MR) imaging findings of mesial temporal sclerosis. MATERIALS AND METHODS: Medical records and brain MR images obtained in 23 patients aged 1-64 years with cerebral hemiatrophy were retrospectively reviewed. Age, neurologic deficit, and history of childhood febrile seizures were recorded and correlated with MR findings of mesial temporal sclerosis, focal cortical or white matter signal intensity abnormalities, ipsilateral thalamic or contralateral cerebellar atrophy, and compensatory calvarial changes. RESULTS: Eleven patients had MR mesial temporal sclerosis findings. Of these, nine had a history of childhood febrile seizures. Of the other 12 patients, only one had a history of childhood febrile seizures. All patients without mesial temporal sclerosis had focal parenchymal lesions in the distribution of the middle cerebral artery. CONCLUSION: Two patterns of central nervous system involvement in cerebral hemiatrophy are suggested: (a) MR mesial temporal sclerosis findings and a history of childhood febrile seizures and (b) no MR mesial temporal sclerosis findings and rarely a history of childhood febrile seizures. This correlates with previous descriptions of cerebral hemiatrophy (a) with multifocal neuronal loss after seizures and (b) with a more focal cerebral hemisphere abnormality usually due to vascular insult.

Reversible empty sella in idiopathic intracranial hypertension: an indicator of successful therapy?

Idiopathic intracranial hypertension is commonly associated with an empty sella, caused by herniation of subarachnoid cerebrospinal fluid through an absent or patulous diaphragma sellae. We describe the findings in two patients who presented with headache, papilledema, and visual disturbances. Diagnosis of idiopathic intracranial hypertension was made on the basis of clinical symptoms and laboratory data. Initial imaging studies in each patient showed an empty sella. After treatment, one with acetazolamide and the other with lumboperitoneal shunting, the appearance of the sellar contents became normal.

Sinus tympani: anatomic considerations, computed tomography, and a discussion of the retrofacial approach for removal of disease.

Surgical access to the sinus tympani remains a challenge for otologic surgeons. Usually, the retrotympanum is approached through the middle ear in an anterior to posterior direction during chronic ear surgery. Whether this is via a posterior tympanotomy or after canal wall down tympanomastoidectomy, visualization of the most posterior recess of the sinus tympani is often inadequate. The purpose of this investigation is two fold: (1) to describe the highly variable anatomy of the posterior tympanic cavity and (2) to review the retrofacial approach to the sinus tympani. Histologic sections, cadaver dissections, and diagrammatic illustrations are combined with computed tomographic (CT) imaging to provide a three-dimensional understanding of the sinus tympani and adjacent labyrinthine structures. Viewed from the mastoid, the anatomic structures that define the boundaries of the retrofacial approach include the facial nerve and stapedius muscle laterally, the lateral semicircular canal superiorly, the posterior semicircular canal posteromedially, the vestibule anteromedially, and the jugular bulb inferiorly. When the sinus tympani is well developed, saucerization within these boundaries gives wide access into the sinus and round window niche. The authors suggest that preoperative imaging can select patients who are candidates for a retrofacial approach to expose and remove disease in the sinus tympani. Contraindications to this approach include axial CT image measurements showing a contracted space between the posterior semicircular canal and the medial aspect of the facial nerve, lack of posterior expansion of the sinus tympani, and in cases where these measurements are marginal, the presence of a high jugular bulb or anteriorly positioned sigmoid sinus.

The value of CT in determining potential instability of simple wedge-compression fractures of the lumbar spine.

PURPOSE: To determine whether plain films alone are sufficient in the evaluation of stability of simple wedge-compression fractures of the lumbar spine. METHODS: Plain films and CT scans of 53 consecutive patients seen during a 2-year period with lumbar spine fractures were retrospectively reviewed. Six readers blinded to the CT diagnosis independently read each patient's plain films. Plain-film findings were scored on a five-point graded response scale using criteria proposed by Gehweiler and Daffner. In addition, a fracture was considered to be possibly unstable if there was involvement of more than one vertebral level or greater than 50% loss of anterior vertebral body height. CT findings represented the standard for comparison. CT scans were independently evaluated by three additional readers. Two-column involvement, middle-column involvement alone but with retropulsion, multiple-level involvement, or greater than 50% loss of vertebral height indicated potential instability. RESULTS: For 14 stable and 39 potentially unstable lumbar spine fractures, the pooled (mean) plain-film negative predictive value for detection of potentially unstable fractures was 0.62 (95% confidence interval, 0.53 to 0.70), with a sensitivity of 0.83 (95%, confidence interval; 0.78 to 0.87), and specificity of 0.80 (95% confidence interval, 0.70 to 0.87). CONCLUSION: Plain films are not adequate for determining stability of lumbar spine fractures.

CSF-suppressed T2-weighted three-dimensional MP-RAGE MR imaging.

Fluid-attenuated inversion recovery (FLAIR) is a pulse sequence used for acquiring T2-weighted images of the brain and spine in which the normally high signal intensity of CSF is greatly attenuated. The CSF-suppressed T2-weighted contrast of this technique may be more sensitive to a variety of disorders than that of conventional T2-weighted imaging. The primary disadvantage associated with conventional spin-echo implementations of FLAIR is the relatively limited anatomic coverage that can be achieved in a reasonable imaging time. We developed and optimized a three-dimensional magnetization-prepared rapid gradient-echo (3D MP-RAGE) pulse sequence that combines CSF-suppressed T2-weighted contrast similar to existing FLAIR techniques with anatomic coverage characteristic of 3D imaging. A preliminary evaluation of the new sequence was performed by imaging healthy volunteers and patients with multiple sclerosis.

The gray-scale ink-jet printer: value in making hard copies of digital images.

Referring physicians often are supplied with copies of images to illustrate a report of the findings of a radiologic study or so that the radiologist can retain the original images. The increasing costs of production, film, and recovery of chemicals have enhanced the requirement for a clean, low-cost dry printing process. An ink-jet gray-scale paper printer (Unitone, Scitex Medical Systems, Bedford, MA) can print high-quality (300 dots per inch [dpi]) images with an effective 10-bit gray scale range by using the Hertz continuous ink-jet method [1-3], which does not require the use of a darkroom or hazardous chemicals. Several types of media (matte paper, glossy paper, transparency film) with a printing area of 26.9 x 43.7 cm (10.6 x 17.4 inches) may be used. The consumables are approximately 50-70% less expensive than the cost of silver halide film, providing a cost advantage over film for referral and archival copies. The results of an initial evaluation of the ink-jet printer at our institution are reported here.

Magnetic resonance imaging of neuronal grafts in the primate.

This preliminary study demonstrates the vital role that magnetic resonance imaging plays in the study of neuronal grafts in a nonhuman primate model of Huntington's disease. MRI scans were used to accurately locate and stereotactically lesion the anterior putamen of an adult rhesus monkey, thereby mimicking the anatomical and biochemical changes in Huntington's disease. Follow-up scans were utilized to confirm correct placement of the lesion and to stereotactically implant primate fetal neuronal tissue precisely into the lesion. Additionally, MRI appeared capable of imaging the fetal striatal grafts in rhesus monkeys. While the precise cellular composition of growing grafts was not identifiable on MRI scans, differentiation between normal, lesioned, and engrafted tissue was possible. Correlation of the magnetic resonance images of the grafted regions with actual graft tissue in perfused sections of the brain was shown. The use of magnetic resonance imaging, as indicated in these neuronal implantation studies, allows for a wide variety of future research possibilities where noninvasive and precise localization of the graft is mandated.

Pleomorphic xanthoastrocytoma, a distinctive astroglial tumor: neuroradiologic and pathologic features.

PURPOSE: To analyze and discuss CT and MR features of pleomorphic xanthoastrocytoma (PXA) and present salient histopathologic features of this distinctive astroglial tumor. METHOD: CT, MR, and histopathologic studies on seven patients with the histologic diagnosis of PXA were reviewed retrospectively. RESULTS: All patients were in their first 3 decades of life when first diagnosed and demonstrated peripherally situated supratentorial tumors of varying size involving the superficial cortex and leptomeninges. Five of six cases examined with CT showed areas of mixed attenuation with four demonstrating well-demarcated enhancement. MR demonstrated low or mixed signal intensity on T1-weighted and high or mixed signal intensity on T2-weighted sequences. All five who received gadopentetate dimeglumine showed well-defined enhancement. Three showed cyst formation. Typical histologic features included marked cellular pleomorphism with giant cells, bizarre nuclei, variable cytoplasmic lipidization and positive immunoreactivity for glial fibrillary acidic protein. Necrosis and endothelial-pericytic cell proliferation were absent. CONCLUSION: PXA has a highly suggestive neuroradiologic and distinctive histopathologic appearance.

Treatment of cerebral vasospasm with intra-arterial papaverine.

Cerebral vasospasm continues to be the leading treatable cause of morbidity and mortality following aneurysmal subarachnoid hemorrhage. In this preliminary anecdotal series of 12 patients who were candidates for balloon angioplasty, vasospasm was treated instead with intra-arterial papaverine. Eight patients had marked angiographic reversal of the arterial narrowing following papaverine infusion, four of whom showed dramatic reversal of profound neurological deficits. Two patients deteriorated clinically 5 days after the initially successful papaverine infusions. In both, repeat angiography demonstrated severe recurrent vasospasm, which was partially reversed with a second intra-arterial papaverine treatment. Two patients developed focal neurological deficits during papaverine infusion, which resolved spontaneously over several hours after cessation of the intra-arterial infusion. Arterial narrowing in the posterior circulation and middle cerebral artery distribution appeared to be more responsive to papaverine infusion than was spasm in the anterior cerebral arteries. The infusion of 300 mg of papaverine over 1 hour seemed to be an adequate and safe dose to effect these angiographic and clinical improvements.

Physiologic abnormalities in the paranasal sinuses during experimental rhinovirus colds.

Six (18%) of 34 healthy, asymptomatic young adults had mucosal thickening or fluid in the paranasal sinuses on screening magnetic resonance imaging (MRI) examination. When 19 of these subjects were challenged with rhinovirus, 18 became infected. Twelve of the 18 infected subjects had technically satisfactory serial MRI examinations, and four (33%) of these developed MRI abnormalities of the ethmoid or antral sinuses that were temporally associated with the acute infection. The mean total nasal secretion weights were 22 gm/5 days in the four subjects whose MRI abnormalities were associated with the acute infection compared with 5.5 gm/5 days in the eight subjects who had normal MRI examinations during the acute infection (p = 0.06). Abnormalities of the paranasal sinuses, which were associated with increased volumes of nasal secretion, were detected by MRI examination during rhinovirus infection. These abnormalities may have a role in the pathogenesis of acute sinusitis associated with colds.

Chordoma of the petrous bone.

We have presented two cases of chordoma arising from an unusual location within the skull. Chordomas in the skull usually arise from within the body of the clivus, reputedly from notochordal remnants. The first case, which was diagnosed both with CT and MRI, had its origin from the petrous bone, with extension into the left cerebellopontine angle. Chordoma was not considered high on the list of differential diagnoses. A right pontine hemorrhage, which was evacuated surgically, was diagnosed in the second case both from its clinical appearance and from that on CT scan. Only when bone windowing technique was used with CT was a lytic lesion of the right petrous bone evident. Chordoma was only diagnosed on autopsy. In reviewing these two cases and the literature, it is evident that chordoma must be considered in the differential diagnosis of erosive lesions of the petrous bone.

Lumboperitoneal shunt combined with myelotomy for treatment of syringohydromyelia.

This study was undertaken to investigate whether a direct communication between the fourth ventricle and the syrinx exists in the majority of patients with syringohydromelia and whether intraspinal pressure plays a role in the pathogenesis of this disorder. A series of 13 patients with syringohydromyelia delineated by magnetic resonance (MR) imaging was reviewed, and the intracranial pressure (ICP) and lumbar spinal pressure (LSP) were recorded concomitantly in three patients. Lumboperitoneal shunting was performed in seven patients, six of whom also underwent myelotomy of the caudal spinal cord. Magnetic resonance imaging visualized a cerebrospinal fluid (CSF) channel connecting the fourth ventricle with the syrinx in only one of the 13 patients, and in the remaining 12 patients it revealed a long segment of the spinal cord free of syrinx below the fourth ventricle. This finding is in accordance with recent MR studies of syringohydromyelia. The concomitant recording of ICP and LSP in our patients who had myelomeningocele and Chiari II malformation showed findings contradicting the reports of Williams. Lumbar spinal pressure was equal to ICP under steady-state conditions, and was elevated by straining or crying more markedly than ICP. Craniospinal pressure dissociation with ICP greater than with LSP, as described by Williams, was not observed. Lumboperitoneal shunting concomitant with myelotomy and syringopleural shunting 1 month after myelotomy resulted in marked and sustained shrinkage of the syrinx and neurological improvement in four patients. It was concluded that the majority of patients with syringohydromyelia and Chiari malformation lack a direct communication connecting the fourth ventricle with the syrinx. The results suggest that CSF moves under pressure into the spinal cord, contributing to the formation and maintenance of the syrinx, and that LP shunting combined with myelotomy can effect shrinkage of the syrinx.

Neonatal dural venous sinus thrombosis associated with central venous catheterization: CT and MR studies.

We report a case of extensive thrombosis of dural venous sinuses associated with placement of a central venous catheter in the jugular vein. Cases such as this one, though uncommon, underscore a potentially devastating complication associated with central venous catheterization and emphasize caution in catheter placement particularly in neonates.