Negative Magnetic Resonance Imaging Results Research Articles

The role of 6-[18F]fluorodopamine positron emission tomography in the localization of adrenal pheochromocytoma associated with von Hippel–Lindau syndrome

[(123/131)I]metaiodobenzylguanidine (MIBG) scintigraphy is considered as the gold standard in the localization of pheochromocytoma. However, this method has less optimal sensitivity for the detection of pheochromocytoma associated with von Hippel-Lindau (VHL). Our preliminary results suggest that this is partially due to the low expression of cell membrane norepinephrine transporter system in VHL-related pheochromocytoma cells. Another probable cause may be the low affinity that [(123/131)I]MIBG has for these cells. Recently, 6-[(18)F]fluorodopamine ([(18)F]DA) positron emission tomography (PET) has been introduced as a novel functional imaging modality with high sensitivity for pheochromocytoma. Therefore, we investigated whether [(18)F]DA PET is more effective than [(123/131)I]MIBG scintigraphy in the diagnostic localization of VHL-related adrenal pheochromocytoma. In this study, we evaluated seven VHL patients in whom adrenal pheochromocytomas were confirmed by histopathology results. Adrenal pheochromocytomas were localized using computed tomography (CT), magnetic resonance imaging (MRI), [(123/131)I]MIBG scintigraphy and [(18)F]DA PET. [(18)F]DA PET localized pheochromocytoma in all the seven patients, as did in CT. In contrast, three out of the seven had negative results utilizing [(123/131)I]MIBG scintigraphy and one out of the six patients had negative MRI results. [(18)F]DA PET was found to show more promising results when compared with [(123/131)I]MIBG scintigraphy in the diagnostic localization of VHL-related adrenal pheochromocytoma, with a 100% rate of localization. Thus, [(18)F]DA PET in conjunction with CT/MRI should be considered as an effective method for the proper localization of VHL-related adrenal pheochromocytoma.

Fluorine-18-l-Dihydroxyphenylalanine (18F-DOPA) Positron Emission Tomography as a Tool to Localize an Insulinoma or β-Cell Hyperplasia in Adult Patients

Fluorine-18-L-dihydroxyphenylalanine (18F-DOPA) positron emission tomography (PET) is a promising method in localizing neuroendocrine tumors. Recently, it has been shown to differentiate focal forms of congenital hyperinsulinism of infancy. The current study was set up to determine the potential of 18F-DOPA PET in identifying the insulin-secreting tumors or beta-cell hyperplasia of the pancreas in adults. We prospectively studied 10 patients with confirmed hyperinsulinemic hypoglycemia and presumed insulin-secreting tumor using 18F-DOPA PET. Anatomical imaging was performed with computed tomography (CT) and magnetic resonance imaging (MRI). All patients were operated on, and histological verification was available in each case. Semiquantitative PET findings in the pancreas using standardized uptake values were compared to standardized uptake values of seven consecutive patients with nonpancreatic neuroendocrine tumors. By visual inspection of 18F-DOPA PET images, it was possible in nine of 10 patients to localize the pancreatic lesion, subsequently confirmed by histological analysis. 18F-DOPA uptake was enhanced in six of seven solid insulinomas and in the malignant insulinoma and its hepatic metastasis. Two patients with beta-cell hyperplasia showed increased focal uptake of 18F-DOPA in the affected areas. As compared to CT or MRI, 18F-DOPA PET was more sensitive in localizing diseased pancreatic tissue. 18F-DOPA PET was useful in most patients with insulinoma and negative CT, MRI, and ultrasound results. In agreement with previous findings in infants, preoperative 18F-DOPA imaging seems to be a method of choice for the detection of beta-cell hyperplasia in adults. It should be considered for the detection of insulinoma or beta-cell hyperplasia in patients with confirmed hyperinsulinemic hypoglycemias when other diagnostic work-up is negative.

False Negative Magnetic Resonance Imaging Results: A Report of 2 Cases

Objectives The purpose of this study is to present 2 clinical case studies in which large herniated disks were not detected on magnetic resonance imaging (MRI), leading to false negative results, and discuss some issues regarding potential shortcomings of MRI. Clinical Features Cases of cervical and lumbar herniated nucleus pulposus (HNP) are presented. Each patient had severe pain and neurological deficit. The patients had positive physical examination findings suggestive of HNP despite the negative MRI scans. Both subsequently underwent myelography and computed tomography to arrive at the final and definitive diagnosis of HNP. Intervention and Outcome Both patients failed a course of conservative care that included manual and mechanical traction, manual mobilization, myofascial release techniques, epidural steroid injections, oral steroid and narcotic medications, and rehabilitative exercises. Both patients eventually required surgical decompression. Conclusion False negative MRI results in these cases of large HNPs emphasize the importance of case history and physical examination findings as the basis for ordering diagnostic tests. The conclusion of this article is simple; no single diagnostic test should be considered as 100% accurate, as false negative studies may occur that may mislead the patient and clinician.

Acute Wrist Trauma: Value of a Short Dedicated Extremity MR Imaging Examination in Prediction of Need for Treatment

To assess predictive value of a short magnetic resonance (MR) imaging examination in addition to or instead of radiography in patients with acute wrist trauma to identify patients who require additional treatment versus those who do not and can be discharged without further follow-up. Informed consent was obtained from all participating patients; the institutional review board approved the randomized controlled trial and use of data to create prediction models. Of 90 patients (37 female, 53 male; mean age, 40.0 years), 87 with acute wrist trauma were randomized to undergo radiography (n = 43) or radiography and a short MR imaging examination with low-field-strength dedicated extremity MR system (n = 44). Age, sex, trauma mechanism, presence of tenderness of the anatomic snuffbox, radiographic results, MR imaging results, and treatment data were collected. Univariable and multivariable logistic regression analysis was used to create four models for prediction of treatment need. Thirty-six patients had one or more fractures; one patient had a marked soft-tissue lesion. In univariable analysis, age (odds ratio, 1.02; 95% confidence interval: 1.00, 1.05), anatomic snuffbox tenderness (odds ratio, 2.31; 95% confidence interval: 0.90, 5.96), radiographic results (odds ratio, 31.2; 95% confidence interval: 8.90, 109), and positive MR imaging results versus MR imaging not performed (odds ratio, 1.86; 95% confidence interval: 0.57, 6.06) were significantly predictive of treatment need. In multivariable analysis, radiographic results (odds ratio, 24.7; 95% confidence interval: 6.59, 93.1) and positive MR imaging results (odds ratio, 6.28; 95% confidence interval: 1.27, 31.0) were significantly predictive of treatment need. Negative MR imaging results were not significantly predictive (odds ratio, 0.87; 95% confidence interval: 0.20, 3.82). A short MR imaging examination with a low-field-strength MR imaging system following radiography in initial evaluation of patients with acute wrist trauma has additional value in prediction of treatment need; it does not have value in identification of patients who can be discharged without further follow-up.

Familial pediatric rapidly progressive extrapyramidal syndrome: is it Hallervorden-Spatz disease?

The clinical features of two children of a family with rapidly progressive extrapyramidal-pyramidal-dementia complex have been described. Inheritance seems most likely to be autosomal recessive. Magnetic resonance imaging results of brain were negative. Even so, the authors argued in favor of a diagnosis of Hallervorden-Spatz disease because the cases fulfilled the clinical criteria for diagnosis of this disease. Apart from the negative magnetic resonance findings, the other unusual feature was the early development of levodopa-induced dyskinesia. Few conditions need to be considered in the differential diagnosis of a childhood-onset rapidly progressive extrapyramidal syndrome. Such conditions include Wilson’s disease, Hallervorden-Spatz disease (HSD), juvenile form of Huntington’s disease, juvenile neuronal ceroid lipofuscinosis, early-onset Machado-Joseph disease neuroacanthocytosis, storage disorders, and variant form of dopa-response dystonias (DRD). Rarer conditions are Leigh’s disease, Lafora body disease, and dentato-rubro-pallido-luysian atrophy. HSD is a rare disorder characterized by progressive extrapyramidal dysfunction and dementia. Onset is most commonly in late childhood or early adolescence. The disease can be familial or sporadic. When familial, it is inherited recessively and has been linked to chromosome 20 [1]. Recently, a mutation in the pantothenate kinase ( PANK2) gene on band 20pl3 has been described in patients with typical HSD [2]. HSD produces typical magnetic resonance imaging (MRI) changes in brain, [3,4] aiding in antemortem diagnosis. The typical finding is of bilaterally symmetrical hyperintense signal changes in the external segment of globus pallidus, with surrounding hypointensity on T 2-weighted image. These imaging features are fairly diagnostic and have been termed the “eye-of-the tiger sign” [5]. The hyperintensity represents pathologic changes, including gliosis, demyelination, neuronal loss, and axonal swelling, and the surrounding hypointensity is caused by loss of signal secondary to iron deposition [5]. Described herein are the clinical aspects of a family with autosomal recessive inheritance with rapidly progressive extrapyramidal-pyramidal-dementia complex but with negative brain MRI results. The diagnosis should be considered a variant form of HSD.

Role of clonazepam in the treatment of idiopathic downbeat nystagmus.

Downbeat nystagmus is defined as spontaneous nystagmus present with fixation in the primary position or lateral gaze. Those who have downbeat nystagmus but negative magnetic resonance imaging results are termed as idiopathic. Patients with idiopathic downbeat nystagmus, although unconcerned with their etiology, have visual symptoms such as oscillopsia, diplopia, or blurred vision. The purpose of this study is to evaluate the efficacy of clonazepam in treating idiopathic downbeat nystagmus. Patients with downbeat nystagmus were rechecked by electronystagmography (ENG); then 0.5 mg clonazepam was administered orally. One hour later, follow-up ENG was performed again to evaluate the evolution of the downbeat nystagmus. If the test was effective, then 1.0 mg clonazepam twice daily was administered to the patients. Seven cases had downbeat nystagmus, including idiopathic in five, cerebellar degeneration in one, and cerebellopontine angle tumor in one. The efficacy rate for the clonazepam test was 100% in five cases of idiopathic downbeat nystagmus, whereas it was ineffective in the case of cerebellar degeneration. After long-term therapy with clonazepam, all patients with idiopathic downbeat nystagmus experienced elimination of oscillopsia, relief of diplopia, and improvement of visual acuity. Although temporary relief of downbeat nystagmus was observed 1 hour after the clonazepam test, downbeat nystagmus was not eliminated permanently. We recommend long-term therapy by clonazepam with a dosage of 1.0 mg twice daily in cases of idiopathic downbeat nystagmus. Reducing the downbeat nystagmus as well as eliminating the oscillopsia can be anticipated.

The cost-effectiveness of magnetic resonance imaging for patients with equivocal neurological symptoms.

To determine the incremental cost-effectiveness of magnetic resonance imaging (MRI) and computed tomography (CT) in young adults presenting with equivocal neurological signs and symptoms. A decision analysis of long-term survival using accuracy data from a diagnostic technology assessment of MRI and CT in patients with suspected multiple sclerosis, information from the medical literature, and clinical assumptions. In the baseline analysis, at 30% likelihood of an underlying neurologic disease, MRI use has an incremental cost of $101,670 for each additional quality-adjusted life-year saved compared with $20,290 for CT use. As the probability of disease increases, further MRI use becomes a cost-effective alternative costing $30,000 for each quality-adjusted life-year saved. If a negative MRI result provides reassurance, the incremental costs of immediate MRI use decreases and falls below $25,000 for each quality-adjusted life-year saved no matter the likelihood of disease. For most individuals with neurological symptoms or signs, CT imaging is cost-effective while MR imaging is not. The cost-effectiveness of MRI use, however, improves as the likelihood of an underlying neurological disease increases. For selected patients who highly value diagnostic information, MRI is a reasonable and cost-effective use of medical resources when even the likelihood of disease is quite low (5%).

The accuracy of magnetic resonance imaging in patients with suspected multiple sclerosis. The Rochester-Toronto Magnetic Resonance Imaging Study Group

To design and implement a methodologically rigorous study to examine the accuracy of magnetic resonance imaging (MRI) in a patient population clinically suspected of having multiple sclerosis (MS). Three hundred three patients, who were referred to two university medical centers because of the suspicion of MS, underwent MRI of the head and double-dose, contrast-enhanced computed tomography (CT) of the head. The images were read by two observers individually and without knowledge of the clinical course or final diagnosis. Patients were followed up for at least 6 months and reevaluated clinically with subsequent neurological examination. Final diagnosis (MS or not MS) was made by a panel of neurologists on the basis of the clinical findings at presentation, those that developed during follow-up, and other diagnostic tests. The results of the imaging procedures were excluded to avoid incorporation bias. Diagnostic accuracy was assessed using receiver-operating characteristic analysis and likelihood ratios. Magnetic resonance imaging of the head was considerably more accurate than CT in diagnosing MS. The area under the receiver-operating characteristic curve for MS was 0.82 (compared with 0.52 for CT) indicating that MRI was a good but not definitively accurate test for MS. A "definite MS" reading on an MRI of the head was specific for MS (likelihood ratio, 24.9) and essentially established the diagnosis, especially in patients clinically designated as "probable MS" before testing. However, MRI of the head was negative for MS in 25% and equivocal in 40% of the patients considered to have MS by the diagnostic review committee (sensitivity, 58%). Magnetic resonance imaging of the head provided assistance in the diagnosis of MS when lesions were visualized. Its ability far exceeded imaging with double-contrast CT. The sensitivity and, therefore, the predictive value of a negative MRI result for MS were, however, not sufficiently high for a normal MRI to be used to conclusively exclude the diagnosis of MS.

The Accuracy of Magnetic Resonance Imaging in Patients With Suspected Multiple Sclerosis

<h3>Objective.</h3> —To design and implement a methodologically rigorous study to examine the accuracy of magnetic resonance imaging (MRI) in a patient population clinically suspected of having multiple sclerosis (MS). <h3>Design and Setting.</h3> —Three hundred three patients, who were referred to two university medical centers because of the suspicion of MS, underwent MRI of the head and double-dose, contrast-enhanced computed tomography (CT) of the head. The images were read by two observers individually and without knowledge of the clinical course or final diagnosis. Patients were followed up for at least 6 months and reevaluated clinically with subsequent neurological examination. Final diagnosis (MS or not MS) was made by a panel of neurologists on the basis of the clinical findings at presentation, those that developed during follow-up, and other diagnostic tests. The results of the imaging procedures were excluded to avoid incorporation bias. Diagnostic accuracy was assessed using receiver-operating characteristic analysis and likelihood ratios. <h3>Results.</h3> —Magnetic resonance imaging of the head was considerably more accurate than CT in diagnosing MS. The area under the receiver-operating characteristic curve for MS was 0.82 (compared with 0.52 for CT) indicating that MRI was a good but not definitively accurate test for MS. A "definite MS" reading on an MRI of the head was specific for MS (likelihood ratio, 24.9) and essentially established the diagnosis, especially in patients clinically designated as "probable MS" before testing. However, MRI of the head was negative for MS in 25% and equivocal in 40% of the patients considered to have MS by the diagnostic review committee (sensitivity, 58%). <h3>Conclusions.</h3> —Magnetic resonance imaging of the head provided assistance in the diagnosis of MS when lesions were visualized. Its ability far exceeded imaging with double-contrast CT. The sensitivity and, therefore, the predictive value of a negative MRI result for MS were, however, not sufficiently high for a normal MRI to be used to conclusively exclude the diagnosis of MS. (<i>JAMA</i>. 1993;269:3146-3151)