Disruptions in serotonergic regulation of cortical glutamate release in primate insular cortex in response to chronic ethanol and nursery rearing

Early-life stress has been shown to increase susceptibility to anxiety and substance abuse. Disrupted activity within the anterior insular cortex (AIC) has been shown to play a role in both of these disorders. Altered serotonergic processing is implicated in controlling the activity levels of the associated cognitive networks. We therefore investigated changes in both serotonin receptor expression and glutamatergic synaptic activity in the AIC of alcohol-drinking rhesus monkeys. We studied tissues from male rhesus monkeys raised under two conditions: Male rhesus monkeys (1) "mother reared" (MR) by adult females (n=9) or (2) "Nursery reared" (NR), that is, separated from their mothers and reared as a separate group under surrogate/peer-reared conditions (n=9). The NR condition represents a long-standing and well-validated nonhuman primate model of early life stress. All monkeys were trained to self-administer ethanol (4% w/v) or an isocaloric maltose-dextrin control solution. Subsets from each rearing condition were then given daily access to ethanol, water, or maltose-dextrin for 12 months. Tissues were collected at necropsy and were further analyzed. Using real time RT-PCR we found that ethanol-naive, NR monkeys had lower AIC levels of 5-HT(1A) and 5-HT(2A) receptor mRNA compared with ethanol-naive, MR animals. Although NR monkeys consumed more ethanol over the 12-month period compared with MR animals, both MR and NR animals expressed greater 5-HT(1A) and 5-HT(2A) receptor mRNA levels following chronic alcohol self-administration. The interaction between nursery-rearing conditions and alcohol consumption resulted in a significant enhancement of both 5-HT(1A) and 5-HT(2A) receptor mRNA levels such that lower expression levels observed in nursery-rearing conditions were not found in the alcohol self-administration group. Using voltage clamp recordings in the whole cell configuration we recorded excitatory postsynaptic currents in both ethanol-naive and chronic self-administration groups of NR and MR monkeys. Both groups that self-administered ethanol showed greater glutamatergic activity within the AIC. This AIC hyperactivity in MR alcohol-consuming monkeys was accompanied by an increased sensitivity to regulation by presynaptic 5-HT(1A) receptors that was not apparent in the ethanol-naive, MR group. Our data indicate that chronic alcohol consumption leads to greater AIC activity and may indicate a compensatory upregulation of presynaptic 5-HT(1A) receptors. Our results also indicate that AIC activity may be less effectively regulated by 5-HT in ethanol-naive NR animals than in NR monkeys in response to chronic ethanol self-administration. These data suggest possible mechanisms for increased alcohol seeking and possible addiction potential among young adults who had previously experienced early-life stress that include disruptions in both AIC activity and serotonin system dynamics.

The effects of chronic ethanol self-administration on hippocampal serotonin transporter density in monkeys

Evidence for an interaction between alcohol consumption and the serotonin system has been observed repeatedly in both humans and animal models yet the specific relationship between the two remains unclear. Research has focused primarily on the serotonin transporter (SERT) due in part to its role in regulating extracellular levels of serotonin. The hippocampal formation is heavily innervated by ascending serotonin fibers and is a major component of the neurocircuitry involved in mediating the reinforcing effects of alcohol. The current study investigated the effects of chronic ethanol self-administration on hippocampal SERT in a layer and field specific manner using a monkey model of human alcohol consumption. [(3)H]Citalopram was used to measure hippocampal SERT density in male cynomolgus macaques that voluntarily self-administered ethanol for 18 months. Hippocampal [(3)H]citalopram binding was less dense in ethanol drinkers than in controls, with the greatest effect observed in the molecular layer of the dentate gyrus. SERT density was not correlated with measures of ethanol consumption or blood ethanol concentrations, suggesting the possibility that a threshold level of consumption had been met. The lower hippocampal SERT density observed suggests that chronic ethanol consumption is associated with altered serotonergic modulation of hippocampal neurotransmission.

The native T-type calcium current in relay neurons of the primate thalamus

The generation of thalamic bursts depends upon calcium currents that flow through transiently open (T)-type calcium channels. In this study, we characterized the native T-type calcium current underlying thalamic burst responses in the macaque monkey. Current clamp recordings from lateral geniculate nucleus (LGN) slices showed characteristic burst responses when relay cells were depolarized from relatively hyperpolarized membrane potentials. These bursts could also be elicited by stimulation of excitatory synaptic inputs to LGN cells. Under voltage clamp conditions, the inactivation kinetics of native currents recorded from primate LGN neurons showed consistency with T-type currents recorded in other mammals and in expression systems. Real-time reverse transcriptase PCR performed on RNA isolated from the LGN (including tissues isolated from magnocellular and parvocellular laminae) detected voltage-dependent calcium channel (Ca(v)) 3.1, Ca(v) 3.2, and Ca(v) 3.3 channel transcripts. Ca(v) 3.1 occurred at relatively higher expression than other isoforms, consistent with in situ hybridization studies in rats, indicating that the molecular basis for burst firing in thalamocortical systems is an important conserved property of primate physiology. Since thalamic bursts have been observed during visual processing as well as in a number of CNS disorders, studies of the expression and modulation of these currents at multiple levels are critical for understanding their role in vision and for the discovery of new treatments for disruptions of thalamic rhythms.

MR Imaging of BK virus encephalitis

BK virus infection is most often associated with urologic disease in patients who have undergone renal or bone marrow transplantation. We report a rare case of biopsy-confirmed BK virus encephalitis in an immunocompromised patient with hemorrhagic cystitis, in whom dramatic imaging findings were present despite relatively mild clinical symptoms. MR imaging demonstrated widespread increased signal intensity on T2- and fluid-attenuated inversion recovery-weighted images, with restricted diffusion, in the cerebellum, cerebral white matter, and deep gray matter structures. The simultaneous presence of urologic abnormalities and neurologic deficits in certain immunocompromised patients should prompt consideration of BK virus encephalitis.

Ethanol Modulation of Excitatory and Inhibitory Synaptic Transmission in Rat and Monkey Dentate Granule Neurons

BACKGROUND

The physiological mechanisms underlying the behavioral and cognitive effects of ethanol are not fully understood. However, there is now compelling evidence that ethanol acts, at least in part, by modulating the function of a small group of proteins that mediate excitatory and inhibitory synaptic transmission. For example, intoxicating concentrations of ethanol have been shown to enhance GABAergic synaptic inhibition and depress glutamatergic excitatory neurotransmission in a number of brain regions. Because all of these electrophysiological studies have been performed in rodent brain slice or neuronal culture preparations, direct evidence that ethanol exerts similar effects on synaptic transmission in the primate central nervous system is lacking.

METHODS

We have therefore developed methods to perform patch-clamp electrophysiological recordings from neurons in acutely prepared monkey (Macaca fascicularis) hippocampal slices. We have used these methods to compare the acute effects of ethanol on excitatory and inhibitory synaptic transmission in rat and monkey dentate granule neurons.

RESULTS

Under our recording conditions, ethanol significantly potentiated gamma-aminobutyric acid type A inhibitory postsynaptic currents in both rat and monkey neurons. In addition, ethanol significantly inhibited NMDA, but not AMPA, excitatory postsynaptic currents in dentate granule neurons from both species. Notably, no significant differences were observed in any of the pharmacological properties of inhibitory or excitatory synaptic responses recorded from rat and monkey neurons.

CONCLUSIONS

These data suggest that the differences in the behavioral effects of ethanol that have been observed between rats and higher-order mammals, such as monkeys and humans, may not reflect differences in the sensitivity of some of the major synaptic sites of ethanol action. Moreover, our results provide empirical evidence for the use of rodent brain slice preparations in elucidating synaptic mechanisms of ethanol action in the primate central nervous system.

Fellowship and practice trends in neuroradiology training programs in the United States

BACKGROUND AND PURPOSE

Neuroradiology has become an increasingly diverse and subspecialized discipline. We evaluated the current status and trends affecting fellowship programs and the practice of clinical neuroradiology at academic medical centers, with emphasis on invasive procedures.

METHODS

All 85 program directors at Accreditation Council for Graduate Medical Education-approved fellowships in neuroradiology were sent a detailed questionnaire pertaining to various demographic aspects of their program and the performance of certain radiologic examinations of the brain and spine.

RESULTS

Sixty-seven programs (79%) responded. As many as 50% of programs are 1 year in length. Twenty-five percent of 2-year fellows leave their program after 1 year of training. During the past 5 years, 36% of programs have decreased in size and 73% reported a decline in the number of applicants. The majority (55%) of programs have had applicants renege on their commitment to begin a fellowship. Twenty percent of 2-year programs do not offer training in endovascular interventional procedures. Neurosurgeons perform endovascular interventional procedures at 18% of centers. There is an 18-fold variation in the volume of neuroangiographic procedures performed each year and a 150-fold variation in the volume of myelographic procedures performed. In 29% of programs, neuroradiologists are nonparticipants in nonvascular interventional spinal procedures; in 40%, they share these procedures with musculoskeletal radiologists/nonradiologists.

CONCLUSION

Interest in fellowship programs in neuroradiology is declining. An applicant's commitment to either begin a fellowship or complete 2 years of training cannot be regarded with assurance, and there is a lack of uniformity in many areas of the training experience, particularly in invasive diagnostic and therapeutic procedures.

Role of enhanced MRI in the follow-up of patients with medically refractory trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife: initial experience

PURPOSE

The purpose of this work was to evaluate the early posttreatment MR findings, and their clinical utility, in patients with trigeminal neuralgia undergoing stereotactic radiosurgery using the gamma knife.

METHOD

Twenty-six patients with medically refractory trigeminal neuralgia underwent stereotactic radiosurgery. A single dose of 70-90 Gy was administered to the proximal root entry zone (n = 21) or the retrogasserian portion (n = 5) of the trigeminal nerve. Posttreatment enhanced MRI and clinical assessment were performed at 3-6 months.

RESULTS

Five patients did not have radiologic follow-up. There were no changes identified in the treated trigeminal nerve or adjacent brainstem in 19 of 21 patients. Two patients with multiple sclerosis developed abnormal signal and enhancement in the brainstem and/or trigeminal nerve; neither had clinical complications. Onset of therapeutic effect ranged from 3 weeks to 3 months; 19 patients had a beneficial response.

CONCLUSION

Results of enhanced MRI 3-6 months after stereotactic radiosurgical treatment of trigeminal neuralgia do not correlate with the clinical response. Because beneficial clinical responses or treatment failures are apparent by 3 months, routine posttreatment MRI in these patients is not warranted.

Progression of changes in dopamine transporter binding site density as a result of cocaine self-administration in rhesus monkeys

The present study examined the time course of alterations in levels of dopamine transporter (DAT) binding sites that accompany cocaine self-administration using quantitative in vitro receptor autoradiography with [(3)H]WIN 35,428. The density of dopamine transporter binding sites in the striatum of rhesus monkeys with 5 d, 3.3 months, or 1.5 years of cocaine self-administration experience was compared with DAT levels in cocaine-naive control monkeys. Animals in the long-term (1.5 years) exposure group self-administered cocaine at 0.03 mg/kg per injection, whereas the initial (5 d) and chronic (3.3 months) treatment groups were each divided into lower dose (0.03 mg/kg per injection) and higher dose (0.3 mg/kg per injection) groups. Initial cocaine exposure led to moderate decreases in [(3)H]WIN 35,428 binding sites, with significant changes in the dorsolateral caudate (-25%) and central putamen (-19%) at the lower dose. Longer exposure, in contrast, resulted in elevated levels of striatal binding sites. The increases were most pronounced in the ventral striatum at the level of the nucleus accumbens shell. At the lower dose of the chronic phase, for example, significant increases of 21-42% were measured at the caudal level of the ventral caudate, ventral putamen, olfactory tubercle, and accumbens core and shell. Systematic variation of cocaine dose and drug exposure time demonstrated the importance of these factors in determining the intensity of increased DAT levels. With self-administration of higher doses especially, increases were more intense and included dorsal portions of the striatum so that every region at the caudal level exhibited a significant increase in DAT binding sites (20-54%). The similarity of these findings to previous studies in human cocaine addicts strongly suggest that the increased density of dopamine transporters observed in studies of human drug abusers are the result of the neurobiological effects of cocaine, ruling out confounds such as polydrug abuse, preexisting differences in DAT levels, or comorbid psychiatric conditions.

Chronic cocaine-mediated changes in non-human primate nucleus accumbens gene expression

Chronic cocaine use elicits changes in the pattern of gene expression within reinforcement-related, dopaminergic regions. cDNA hybridization arrays were used to illuminate cocaine-regulated genes in the nucleus accumbens (NAcc) of non-human primates (Macaca fascicularis; cynomolgus macaque), treated daily with escalating doses of cocaine over one year. Changes seen in mRNA levels by hybridization array analysis were confirmed at the level of protein (via specific immunoblots). Significantly up-regulated genes included: protein kinase A alpha catalytic subunit (PKA(calpha)); cell adhesion tyrosine kinase beta (PYK2); mitogen activated protein kinase kinase 1 (MEK1); and beta-catenin. While some of these changes exist in previously described cocaine-responsive models, others are novel to any model of cocaine use. All of these adaptive responses coexist within a signaling scheme that could account for known inductions of genes(e.g. fos and jun proteins, and cyclic AMP response element binding protein) previously shown to be relevant to cocaine's behavioral actions. The complete data set from this experiment has been posted to the newly created Drug and Alcohol Abuse Array Data Consortium (http://www.arraydata.org) for mining by the general research community.

Stereotactic radiosurgical pallidotomy and thalamotomy with the gamma knife: MR imaging findings with clinical correlation--preliminary experience

PURPOSE

To evaluate the temporal evolution and appearance of a radiosurgical lesion at magnetic resonance (MR) imaging and the clinical response in patients undergoing stereotactic radiosurgical pallidotomy or thalamotomy with the gamma knife.

MATERIALS AND METHODS

Seventeen patients with medically refractory movement disorders underwent stereotactic radiosurgical pallidotomy (n = 2) or thalamotomy (n = 15). A single dose of 120-140 Gy was administered to a target in the globus pallidus interna or ventralis intermedius thalamic nucleus. Postprocedure gadolinium-enhanced MR imaging and clinical assessment were performed at 1 month and 3 months.

RESULTS

At 3 months, the radiosurgical lesion most commonly (n = 11) appeared as a ring-enhancing focus 5 mm or less in diameter surrounded by vasogenic edema that extended less than 7 mm in radius beyond the target. Five patients had ring-enhancing lesions 7 mm or more in diameter; four of these developed symptomatic perilesional edema at 3 (n = 2) or 8 (n = 2) months after the procedure. Onset of therapeutic effect began approximately 4 weeks after treatment. In the 15 patients with tremor, there was a mean decline of 2.1 on the Tremor Rating Scale.

CONCLUSION

Findings in this pilot study suggest that radiosurgical thalamotomy is a promising treatment for medically refractory tremor. Three-month follow-up MR studies show a ring-enhancing lesion surrounded by a variable amount of vasogenic edema. Visualization of the radiosurgical lesion and the clinical response are delayed compared to that with radio-frequency procedures.

The relationship between the functional abilities of patients with cervical spinal cord injury and the severity of damage revealed by MR imaging

BACKGROUND AND PURPOSE

The appearance of the damaged spinal cord after injury correlates with initial neurologic deficit, as determined by the American Spinal Injury Association grade and manual muscle test score, as well as with recovery, as assessed by manual muscle test scores. The purpose of this study was to determine whether the presence of spinal cord hemorrhage and the size and location of spinal cord edema on MR images is predictive of functional recovery in survivors of cervical spinal cord injury (SCI).

METHODS

The degree of damage to the cervical spinal cord was measured on the MR images of 49 patients who underwent imaging within 72 hours of sustaining SCI. The effects of hemorrhage and length/location of edema on changes in the value of the motor scale of the functional independence measure (FIM) were assessed on admission to and discharge from rehabilitation.

RESULTS

Patients without spinal cord hemorrhage had significant improvement in self-care and mobility scores compared with patients with hemorrhage. There was no significant effect of spinal cord hemorrhage on changes in locomotion and sphincter control scores. The rostral limit of edema positively correlated with admission and discharge self-care scores and with admission mobility and locomotion scores. Edema length had a negative correlation with all FIM scales at admission and discharge.

CONCLUSION

The imaging characteristics of cervical SCI (hemorrhage and edema) are related to levels of physical recovery as determined by the FIM scale. Imaging factors that correlate with poor functional recovery are hemorrhage, long segments of edema, and high cervical locations.

Effect of cocaine self-administration on dopamine D2 receptors in rhesus monkeys

The present study used autoradiography to examine the effects of chronic self-administration of cocaine on the density of dopamine D2 receptors in nonhuman primates. Three rhesus monkeys intravenously self-administered an average of 1.35 mg/kg cocaine per day for 18-22 months until they were euthanized immediately after a self-administration session. Binding site density of the D2 ligand [3H]raclopride (2 nM) was assessed in these monkeys as well as three untreated controls, using quantitative in vitro receptor autoradiography. As compared to untreated controls, D2 binding site density was significantly lower in the animals that self-administered cocaine in all regions of the striatum rostral to the anterior commissure. These regions include the anterior and central regions of the caudate nucleus, putamen, olfactory tubercle, and both the shell and core of the nucleus accumbens. Within the substantia nigra and ventral tegmental area, by contrast, no differences were found in the density of D2 binding sites. These findings suggest a pervasive effect of cocaine on the regulation of D2 receptors in the striatum. The lack of change within the ventral midbrain, however, suggests a differential regulation of D2 receptors in the striatum and ventral midbrain. This study confirms and extends our knowledge of the neurobiological changes in the mesolimbic dopamine system that result from chronic exposure to cocaine.

Angiotensin-(1-7) immunoreactivity in the hypothalamus of the (mRen-2d)27 transgenic rat

The distribution of angiotensin-(1-7) immunoreactive neurons was compared to those of vasopressin-(VP) and oxytocin-(OT) immunoreactive (IR) neurons in the hypothalamus of adult (mRen-2d)27 transgenic hypertensive and Sprague-Dawley rats. In both strains, angiotensin (Ang)-(1-7)-IR cells were found in the supraoptic nucleus (SON), and in the anterior (ap-), medial (mp-), and lateral (lp-) parvocellular, and posterior magnocellular (pm-) subdivisions of the paraventricular (PVN) nucleus. Three-dimensional reconstructions showed that cells immunoreactive to Ang-(1-7) and VP were specifically co-distributed in the SON and in the pmPVN. Double-labeling neurons for both peptides revealed that both Ang-(1-7) and VP were colocalized in a subpopulation of neurons in the pmPVN and SON. In combination with previous studies, our results suggest that Ang-(1-7) and VP are colocalized, co-released and may have a combined action at a common target. In addition, the introduction of the mouse submandibular renin (mRen-2d) transgene into Sprague-Dawley rats does not appear to have altered the fundamental organization of hypothalamic peptide systems involved in fluid homeostasis.

Effect of cocaine self-administration on striatal dopamine D1 receptors in rhesus monkeys

An array of evidence indicates that long-term exposure to cocaine alters several components of the brain dopamine system. Because the release of dopamine in the nucleus accumbens (NAc) has been implicated in mediating the reinforcing effects of cocaine, changes in dopamine function can have profound effects on drug-seeking and drug-taking behavior. The present study examined the effects of the chronic self-administration of cocaine on the D1 family of dopamine receptors in the rhesus monkey. The brains of three rhesus monkeys that had intravenously self-administered an average of 1.35 mg/kg cocaine per day for 18-22 months were compared to the brains of three cocaine-naive controls. The in vitro quantitative autoradiographic technique was used to quantify binding densities of the D1 ligand [3H]SCH-23390 on cryostat-cut sections of fresh frozen tissue. In animals that self-administered cocaine, the density of D1 binding was significantly lower in the regions of the striatum at the level where the nucleus accumbens is most fully developed. The shell of the NAc showed the largest difference with significantly lower D1 binding also detected in adjacent regions of the caudate nucleus and the putamen. No differences were found in the rostral pole of the NAc or the dorsal striatum at that level. These findings suggest that chronic self-administration of cocaine can modulate the density of dopamine D1 receptors in specific portions of the primate striatum. Such changes might underlie some of the behavioral consequences, like drug dependence and craving, of long-term cocaine use.

Enhanced MR imaging of hypertrophic pachymeningitis

OBJECTIVE

This report illustrates the contrast enhancement characteristics on MR imaging of three patients with hypertrophic pachymeningitis and provides an explanation for the observed imaging findings.

CONCLUSION

A differential pattern of enhancement, consisting of intense enhancement of the peripheral margin of the abnormal pachymeninges, was present in all cases. In two patients, much of the remaining abnormal pachymeninges did not enhance at all. On the basis of the microscopic pathology of hypertrophic pachymeningitis, the physiology of normal meningeal enhancement on MR imaging, and the described MR appearance of other pachymeningeal lesions, this differential pattern of enhancement should strongly suggest the diagnosis of hypertrophic pachymeningitis.

Forecasting motor recovery after cervical spinal cord injury: value of MR imaging

PURPOSE

To determine whether magnetic resonance (MR) imaging quantification of cervical spinal cord damage improves the prediction of motor recovery after spinal cord injury.

MATERIALS AND METHODS

The extent of cervical spinal cord injury was measured on MR images obtained in 104 patients (aged 17-70 years) within 72 hours of spinal cord injury. The effects of hemorrhage and edema length on motor outcome were examined for at least 12 months.

RESULTS

Patients with spinal cord hemorrhage had significantly lower upper and lower extremity motor scores at the time of injury and at 12 months than did patients without hemorrhage (P < .001). There was little recovery of lower extremity function even in patients without hemorrhage. Upper extremity motor function improved significantly in all patients (P < .001); patients without hemorrhage showed the largest improvements. The motor recovery rates for patients without hemorrhage were 0.74 (upper extremities; range, 0-1) and 0.55 (lower extremities; range, 0-1); those for patients with hemorrhage were 0.31 (range, 0-1) and 0.091 (range, 0-1). Stepwise multiple regression analyses indicated that MR information on hemorrhage and the length of edema increases the ability to predict clinical outcome by 16%-33% over that with initial clinical scores alone.

CONCLUSION

An initial MR imaging evaluation of the spinal cord after spinal cord injury provides supplemental prognostic information on the recovery of motor function in the upper and lower extremities.

Performance of neuroradiologic examinations by nonradiologists

PURPOSE

To determine the level of participation by nonradiologists in performing neuroradiologic examinations.

MATERIALS AND METHODS

Medicare part B claims data from fiscal year 1992 were analyzed for CPT (current procedural terminology) codes related to computed tomography (CT) and magnetic resonance (MR) imaging of the brain, head and neck, and spine, as well as myelography, angiography, and diskography. Data were tabulated by place of service (hospital-based vs freestanding imaging centers) and by medical specialty.

RESULTS

Among 363,224 Medicare claims for CT and MR imaging of the brain, head and neck, and spine, 91% of the examinations were performed in hospitals and 9% in offices or freestanding centers; 98% of studies were interpreted by a radiologist. The largest share of radiology billing by nonradiologists was from office-based or freestanding imaging centers (9%), versus 2% at hospital-based facilities.

CONCLUSION

Radiologists perform the vast majority of neuroradiologic examinations. Most neuroradiologic examinations performed by nonradiologists are from neurologists at freestanding/office-based imaging centers.

Cocaine alters cerebral metabolism within the ventral striatum and limbic cortex of monkeys

The functional consequences of acute cocaine administration in nonhuman primates were assessed using the quantitative 2-[14C]deoxyglucose method. Local rates of cerebral metabolism were determined after an intravenous infusion of 1.0 mg/kg cocaine or vehicle in six awake cynomolgus monkeys (Macaca fascicularis) trained to sit calmly in a primate chair. Cocaine administration decreased glucose utilization in a discrete set of structures that included both cortical and subcortical portions of the limbic system. Glucose metabolism in the core and shell of the nucleus accumbens was decreased markedly, and smaller decrements were observed in the caudate and anterior putamen. In addition, cocaine administration produced significant decreases in limbic cortex. Metabolism was decreased in orbitofrontal cortex (areas 11, 12o, 13, 13a, 13b), portions of the gyrus rectus including area 25, entorhinal cortex, and parts of the hippocampal formation. The cortical regions in which functional activity was altered provide dense projections to the nucleus accumbens, and the decreased activity in these projections may be responsible in part of the large alterations in functional activity within the ventral striatum. Decreased metabolism also was evident in the anterior nuclear group of the thalamus, raphe nuclei, and locus ceruleus. The acute cerebral metabolic effects of cocaine in the conscious macaque, therefore, were contained primarily within a set of interconnected limbic regions, including ventral prefrontal cortex, medial temporal regions, the ventral striatal complex, and anterior thalamus. The decreased rates of glucose metabolism reported here resemble decrements found using positron emission tomography in humans. In the rat, by contrast, metabolic activity increased and changes were focused in subcortical regions. The present results represent an important expansion of the neural circuitry on which cocaine acts in the monkey as compared with the rat, and this in turn implies that cocaine affects a broader spectra of behaviors in primates than in rodents.

MR of malignant optic glioma of adulthood

A case of malignant optic glioma of adulthood is imaged in its early and late stages with high-resolution MR. The images show the mass to arise from the right optic nerve before invasion of the optic chiasm.

MR imaging in the diagnosis of intramedullary spinal cord diseases that involve specific neural pathways or vascular territories

Prior to the advent of MR imaging, the internal architecture of the spinal cord could not be directly imaged. The solution of many technical problems (e.g., respiratory motion, cardiac and CSF pulsation, inadequate spatial resolution) has provided the opportunity for an increasingly refined analysis of intramedullary lesions. This article begins with a brief review of the results of high-resolution MR imaging studies of the cadaveric spinal cord. The article then focuses on MR imaging in the diagnosis of intramedullary diseases that involve specific neural pathways or vascular territories. Lesions are categorized as degenerative, inflammatory, traumatic, or ischemic. These diseases generally have distinctive clinical findings that reflect dysfunction of particular ascending sensory tracts or descending motor tracts. The corresponding abnormalities on MR images reflect the pathologic changes that occur in the affected neural pathways. Knowledge of the appearance of these diseases on MR images allows the formation of a narrow differential diagnosis and, in many cases, the confident exclusion of neoplasm as the cause of myelopathy.

MR imaging: quality assessment method and ratings at 33 centers

PURPOSE

To outline a quality assessment method with peer review for magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Thirty-three providers in the Philadelphia area were rated on a random sample of 132 brain, 124 cervical spine, and 113 lower extremity MR imaging examinations performed during 1990. Blinded peer review was performed by panels of three subspecialty-trained academic radiologists. Technical performance, completeness, and report appropriateness of each MR imaging examination were evaluated. Aggregated scores were calculated to rate provider performance for each of the three parameters of quality.

RESULTS

Two or three panelists assessed technical performance as inadequate in 15 cases, completeness as incomplete in 58 cases, and the interpretative report as inappropriate and affecting treatment in 72 cases. Eleven providers received an unsatisfactory rating on one or more parameters of quality. The association between unsatisfactory ratings and the use of low-field-strength (< or = 0.6-T) imagers was statistically significant (P < .008).

CONCLUSION

Substantial deficiencies were identified in the performance of examinations and interpretation of MR images in the Philadelphia area in 1990. These findings indicate the need for a program to monitor quality of MR imaging.

Multiple sclerosis in the spinal cord: MR appearance and correlation with clinical parameters

PURPOSE

To determine the characteristic magnetic resonance (MR) imaging features of multiple sclerosis (MS) that affect the spinal cord.

MATERIALS AND METHODS

Sixty-eight patients underwent MR imaging of the cervical and/or thoracic spine. Plaques were analyzed for lesion length, cross-sectional area and location, signal intensity, and morphology. The clinical parameters of MS type, duration of disease, sex, and age were also correlated with these MR imaging findings.

RESULTS

One hundred twenty-four demyelinating plaques were found in these 68 patients; 38 had more than one plaque. The majority of plaques were two body segments in length or less and peripherally located, and occupied less than 50% of the cross-sectional area of the cord. Plaques associated with cord atrophy were more likely to occur with the relapsing-progressive form of MS. Cord swelling was found only in the relapsing-remitting form of MS.

CONCLUSION

Spinal cord MS plaques are characteristically peripherally located, are less than two vertebral segments in length, and occupy less than half the cross-sectional area of the cord.

Manuscript peer review at the AJR: facts, figures, and quality assessment

Concern by the government, funding institutions, and the public for quality assurance in all aspects of medical endeavors mandates critical examination of various professional activities. Although peer review is generally regarded as the best system for selecting and improving scientific papers for publication, the efficacy of this process has never been proved. Moreover, the administrative functions of the editorial staff are often poorly understood. The purpose of this article is to make peer review a the AJR less esoteric and more understandable by quantifying some of its activities. This information is then assessed as it relates to the quality of this important step in scientific publication.

MR imaging in a case of postvaccination myelitis

We describe a case of acute transverse myelitis after the administration of the recombinant form of hepatitis B vaccine. Abnormal enhancement of MR imaging accompanied residual neurologic deficit.

Vascular neoplasms and malformations, ischemia, and hemorrhage affecting the spinal cord: MR imaging findings

This essay illustrates the imaging spectrum of vascular neoplasms and malformations, ischemia, and hemorrhage affecting the spinal cord. Most of these abnormalities occur far more frequently in the brain. The goal of this essay is to provide a sound anatomic and radiologic basis for the evaluation of these diseases. Knowledge of the unique cross-sectional anatomy, blood supply, and venous drainage of the spinal cord is essential in understanding the radiographic appearance of certain vascular lesions. The superior spatial resolution of fast spin-echo pulse sequences and improvements in MR angiography have expanded the role of MR imaging in the diagnosis of spinal cord diseases. These techniques are emphasized in this essay, and potential diagnostic pitfalls are highlighted. The diseases illustrated are grouped in the categories of enlarged vessels, ischemia, and hemorrhage.

Metallic artifacts on MR images of the postoperative spine: reduction with fast spin-echo techniques

PURPOSE

To determine whether the relative insensitivity of T2-weighted fast spin-echo (FSE) techniques to magnetic susceptibility can be exploited to reduce metallic artifacts on images of the postoperative spine and, thus, improve the interpretation of the postoperative study.

MATERIALS AND METHODS

Three neuroradiologists retrospectively evaluated sagittal T2-weighted conventional spin-echo and FSE images obtained in 15 patients with metallic artifacts from various sources including drill particles from anterior cervical diskectomy, posterior fixation wires, fixation rods or plates, and an inferior vena cava filter. The amount of artifact present and whether these artifacts affected image interpretation were evaluated.

RESULTS

Among the 45 paired evaluations, the artifact was judged to be less apparent with FSE sequences in 39. In eight of 45 evaluations (18%), the interpretation of the area of interest was possible only on the FSE images.

CONCLUSION

FSE imaging, especially when performed with shorter echo spacing, increases the amount of T2-weighted information in the presence of metallic artifact because it decreases magnetic susceptibility effects.

Superior sagittal sinus thrombosis in the presence of idiopathic bilateral internal jugular vein stenosis

Cerebral venous outflow obstruction and anomalies in cerebral venous circulation predispose to dural sinus thrombosis. This case report illustrates the magnetic resonance and angiographic findings in a patient who had superior sagittal sinus thrombosis secondary to idiopathic bilateral internal jugular vein stenosis, a previously unrecognized entity. The findings suggest that bilateral stenosis of the internal jugular veins at their junction with the innominate veins causes obstruction to cerebral venous outflow leading to dural sinus thrombosis.

A modality-specific somatosensory area within the insula of the rhesus monkey

Response properties of neurons in the monkey's granular insula (Ig) were examined with somatic, auditory, visual, and gustatory stimuli. Results indicate that a major portion of Ig is a somatic processing area exclusively, with units that have large and often bilateral receptive fields, consistent with the view that this area serves as a higher-order, modality-specific link in the somatosensory-limbic pathway.

Magnetic resonance imaging related to neurologic outcome in cervical spinal cord injury

The purpose of this study was to examine the relationship between the initial intramedullary hemorrhage, as seen by magnetic resonance imaging (MRI), and the neurologic deficit and eventual neurologic outcome of acute cervical spinal cord injured subjects. MRI and motor assessments were performed on 24 subjects with motor complete (Frankel A & B) and incomplete (Frankel C & D) injuries. Recovery was determined by evaluating an initial and a final motor power following spinal cord injury (SCI), as defined by the manual muscle test (grade 1-5) and motor index score (MIS). Results showed that all 15 subjects having hemorrhage had motor complete injuries (Frankel A & B). Sixteen percent of the muscles in the upper extremities and 3% of the muscles in the lower extremities in these 15 subjects improved to a grade of > or = 3/5 at the final evaluation post-SCI. In comparison, of the nine subjects not having hemorrhage, eight had motor incomplete injuries (Frankel C & D) and had 73% and 74% of muscles improving in the upper and lower extremities, respectively. In addition, a change in MIS from initial to final evaluations showed a significant difference between subjects with hemorrhage and subjects without hemorrhage (upper extremities: p = .002 and lower extremities: p = .0001). In conclusion, the initial MR image and neurologic assessment correlated with motor power recovery.

Abnormalities of the posterior inferior cerebellar artery: MR imaging findings

The purpose of this essay is to review the normal MR appearance of the posterior inferior cerebellar artery (PICA) and to illustrate the MR findings of representative PICA abnormalities. Because of beam-hardening artifacts, the lower posterior fossa is difficult to evaluate with CT. MR imaging is not hampered by these artifacts. Moreover, the superb sensitivity of MR and its multiplanar imaging capability permit excellent diagnostic accuracy in this region. The PICA is well suited for evaluation on routine MR images, particularly because of the inherent contrast (signal void) of large arteries due to rapid flow. MR imaging has greatly improved our ability to noninvasively diagnose abnormalities of cerebral blood vessels and their resultant manifestations. Some of the diseases that affect the PICA include neoplasms, aneurysms, arteriovenous malformations, and occlusions. The MR images in this essay illustrate the normal appearance of the PICA, as well as these pathologic features. T1-weighted (e.g., 600/15 [TR/TE]), proton density-weighted (e.g., 2000/20), and T2-weighted (e.g., 2400/80) MR images were obtained in axial, sagittal, and coronal planes. The PICA can be evaluated with MR angiography also, although the relatively small size and tortuosity of the artery may preclude adequate visualization.

Lesions causing a mass in the medial canthus of the orbit: CT and MR features

Few detailed radiologic articles treat the medial canthus as a "compartment" of the orbit. Nasal stuffiness and epiphora (excessive tearing) are frequent clinical manifestations of diseases involving the medial canthus of the orbit. Although some lesions can be adequately evaluated by clinical examination, imaging may show unsuspected deep extensions of the abnormality. CT has traditionally been the imaging method of choice because of the inherent contrast between structures in this region and its superb depiction of bone detail (Fig. 1). MR imaging can be useful in detecting subtle marrow invasion caused by lesions extending beyond the confines of the medial canthus (e.g., frontal bone, maxilla). In this pictorial essay, we illustrate the CT and MR appearances of diseases that can manifest as a medial canthal mass and provide practical differential diagnoses. Lesions can be inflammatory, neoplastic, or developmental in origin. Moreover, these lesions can result from abnormalities in the adjacent nasolacrimal apparatus, orbit, paranasal sinuses, and nasal cavity, or they can reflect an underlying systemic illness.