Magnetic Resonance Imaging Signal Alterations Research Articles

Gadolinium Presence in the Brain After Administration of the Liver-Specific Gadolinium-Based Contrast Agent Gadoxetate: A Systematic Comparison to Multipurpose Agents in Rats.

Clinical studies have reported different results regarding the signal intensity (SI) increase in the dentate nucleus on unenhanced T1-weighted magnetic resonance imaging (MRI) after repeated administrations of gadolinium-based contrast agents (GBCAs). The aim of this study was to evaluate MRI SI changes and gadolinium (Gd) brain concentrations in an animal model after repeated administration of liver-specific linear gadoxetate in comparison to multipurpose linear and macrocyclic GBCAs. Recently, it was demonstrated that small amounts of GBCAs are able to cross the blood-cerebrospinal fluid (CSF) barrier. Therefore, a secondary aim was to test if the administration of these GBCAs directly into the CSF results in a similar MRI pattern and brain Gd concentration than after systemic intravenous injection. Forty-eight Han-Wistar rats were equally divided into the following 4 groups: gadoxetate (liver-specific linear), gadodiamide (multipurpose linear), gadobutrol (multipurpose macrocyclic), and control (saline, artificial CSF). For systemic application, 6 animals per group received 8 intravenous injections on 4 consecutive days per week over 2 weeks using a dose of 0.15 mmol/kg for gadoxetate and 0.6 mmol/kg for multipurpose GBCAs per injection, which corresponds to the recommended clinical dose in humans. For CSF application, 6 animals per group received one intracisternal administration of 0.31 μmol Gd (gadoxetate) and 1.25 μmol Gd (multipurpose GBCAs) or an equal volume of artificial CSF. Brain MRI was performed after a period of 5 weeks to evaluate the SI in deep cerebellar nuclei (DCN) and brain stem. Subsequently, animals were euthanized and their brains were dissected for Gd quantification by inductively coupled plasma-mass spectrometry. Visually evident increased SIs in the DCN were observed in blinded image review only after administration of gadodiamide. The respective SI ratios between DCN and brain stem were significantly higher compared with the control groups (P = 0.009 and P = 0.002 for intravenous and intracisternal application, respectively), whereas no difference was found for gadoxetate and gadobutrol (P ≥ 0.9). Inductively coupled plasma-mass spectrometry revealed the lowest Gd content in the brain tissue after administration for gadoxetate. The mean Gd concentrations in the cerebellum were 0.08 nmol/g (gadoxetate), 2.66 nmol/g (gadodiamide), and 0.26 nmol/g (gadobutrol) after intravenous administration, and 0.28 nmol/g (gadoxetate), 3.23 nmol/g (gadodiamide), and 0.69 nmol/g (gadobutrol) after intracisternal application. This rat study demonstrates distinct differences in the presence of gadolinium in the brain between the liver-specific linear gadoxetate and the multipurpose linear GBCA gadodiamide. No MRI signal alterations were observed after 8 dose-adapted intravenous or a single intracisternal administrations of gadoxetate and multipurpose macrocyclic gadobutrol. The Gd concentrations in the brain 5 weeks after intravenous administration of gadoxetate were an order of magnitude lower compared with gadodiamide and slightly lower than for gadobutrol. Likely reasons for these differences are the 4-fold lower dose, the dual excretion pathway, and the higher complex stability of gadoxetate compared with multipurpose linear GBCAs. The similar findings for both routes of GBCA administration underlines the assumption that the very small amount of GBCAs that cross the blood-CSF barrier is further transported into the brain tissue.

High short-term return to sports rate despite an ongoing healing process after acute meniscus repair in young athletes.

Acute meniscus repair in young athletes is always a challenge due to the long rehabilitation process and time to return to sport (RTS). The purpose was to investigate signal alterations in short-term follow-up after acute meniscus repair on specific magnetic resonance imaging (MRI) scan sequences. It was hypothesized that (1) MRI signal changes over the first postoperative healing phase and represent a continuous healing process and (2) meniscus healing properties correlates with clinical outcomes and RTS. Young athletes with traumatic meniscus lesion and arthroscopic meniscus repair within 6weeks and available preoperative MRI were enrolled. Clinical examination, outcome scores (IKDC, KOOS, Lysholm Score, Tegner activity score) and RTS were surveyed preoperatively and 6 and 12weeks and 6months after surgery. Radiological follow-up examinations were performed 2, 4, 6, 12weeks and 6months after operation using a 3T-MRI. Evaluation was based on ISAKOS meniscus classification system, meniscus healing were classified according to Henning's criteria. At final follow-up (FU) 30 patients (28month, 2week) with a total of 35 meniscus tears (19 medial, 16 lateral) were included. Clinical scores improved significantly after surgery: IKDC Score (preOP: 39.4 ± 18.5, final FU: 78.8 ± 15.3) KOOS (preOP: 45.7 ± 22.1, final FU: 82.7 ± 12.5) and Lysholm Score (preOP: 42.8 ± 23.7, final FU: 84.4 ± 13.8) (p < 0.01). Tegner activity score showed a steadily increase to 4 (range 3-9) at 6months but did not reached the pre-injury level of 6 (range 3-9). RTS rate was 100% whereof 44.8% reached their pre-injury level. MRI examination revealed a continuous healing process and menisci were classified as 55.9% healed, 35.3% partially healed and 8.8% non-healed at final FU. This study showed that MRI signal alterations of the meniscus steadily occur within the first 6 months postoperatively. MRI reveals an ongoing healing process at final FU that have to be carefully considered when RTS is discussed with high demanding patients. However, young athletes provide good clinical results and RTS rate even though MRI alterations are still present. Therapeutic study, prospective case series, Level IV.

Magnetic Resonance Imaging Signal Alterations in Paraspinal Muscles in Dogs with Acute Thoracolumbar Intervertebral Disk Extrusion.

Muscle signal alteration detected on MRI is seen in diverse pathologic conditions. We observed signal alterations within the paraspinal muscles in dogs with acute thoracolumbar intervertebral disk extrusion. The aim of this retrospective study was to describe MRI features of paraspinal muscle signal alteration in dogs with acute thoracolumbar intervertebral disk extrusion and to investigate an association of the signal alterations with neurological grade, type and location of intervertebral disk extrusion, degree of spinal cord compression, and presence of epidural hemorrhage. Medical records of dogs undergoing MRI because of thoracolumbar intervertebral disk extrusion between August 2014 and June 2016 were reviewed. MRI was evaluated for SI changes within the paravertebral musculature, their location, extension, affected muscles, contrast enhancement, and signal void in T2* sequences. Intervertebral disk herniation was categorized as acute non-compressive nucleus pulposus extrusion (ANNPE) or compressive intervertebral disk disease. In five patients, muscle biopsies of areas with signal intensity changes were taken during surgery. In total, 103 dogs were enrolled in the study. Paraspinal muscle signal alterations were visible in 37 dogs (36%) affecting the epaxial musculature (n = 17), hypaxial musculature (n = 12), or both (n = 8). All signal alterations were hyperintense on T2-weighted images and iso- or hypointense in T1-weighted images. Signal void in T2* was not observed in any dog. Postcontrast sequences were available in 30 of the 37 dogs and showed enhancement in 45%. There was neither an association with degree of compression nor epidural hemorrhage. Intervertebral disk extrusion caudal to L1 and a higher neurological grade was associated with the presence of muscle changes. Histopathology revealed mild to moderate acute muscle fiber degeneration with edema and necrosis in three of five samples. The MRI, as well as the muscle samples, show rather unspecific changes. The underlying pathomechanism might be related to ischemia or muscle spasm, but also denervation edema may explain the signal alteration.

Diarrhea-associated hemolytic uremic syndrome with severe neurological manifestations treated with IgG depletion through immunoadsorption

Diarrhea-associated hemolytic uremic syndrome (HUS) is characterized by acute kidney injury with microangiopathic hemolytic anemia and thrombocytopenia with a diarrhea prodrome, typically caused by Shiga-like toxin-producing Escherichia coli. Supportive management is generally recommended. A 58-year-old female with diarrhea-associated HUS developed delayed-onset severe neurological manifestations including coma, status epilepticus, and subcortical magnetic resonance imaging signal alterations. Rescue treatment with immunoglobulin (Ig)G depletion through immunoadsorption was followed by significant improvement in neurological and renal function. The patient recovered with only minimal sequelae. Delayed-onset neurological abnormalities may occur in diarrhea-associated HUS. Novel specific treatment options include IgG depletion through immunoadsorption. Severe clinical and imaging findings do not preclude a good outcome.

Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease

Several molecular subtypes of sporadic Creutzfeldt–Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt–Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt–Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt–Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease. Patients with sporadic Creutzfeldt–Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt–Jakob disease’ but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt–Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt–Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt–Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease to include findings from magnetic resonance imaging scans.

Transient Magnetic Resonance Imaging Signal Alterations in the Brainstem after Microvascular Decompression for Trigeminal Neuralgia: Case Report

We present a case of transient signal alterations along the brainstem path of the trigeminal nerve after microvascular decompression in a patient with trigeminal neuralgia. Such signal changes have been previously reported to represent infarction, but in our patient, they seemed to represent reactive neural and nuclear changes attributable to operative manipulation. A 43-year-old woman presented with gradually increasing, medically refractory recurrent trigeminal neuralgia 16 months after initial successful microvascular decompression for trigeminal neuralgia. Repeat microvascular decompression resulted initially in complete pain relief; however, her pain suddenly returned on the 3rd postoperative day. Magnetic resonance imaging (MRI) of this recurrent pain revealed new signal alterations along the brainstem path of the trigeminal nerve. Other than marked reduction in her trigeminal neuralgia, the patient had no postoperative alterations of trigeminal sensory or motor function. The patient's residual postoperative trigeminal neuralgia was successfully treated with carbamazepine. Because of the absence of worrisome signs and symptoms corresponding to the MRI signal alterations, no additional therapy was elected. Follow-up MRI in 1 month revealed near-complete resolution of the postoperative signal alterations along the brainstem path of the trigeminal nerve. MRI signal alterations along the brainstem path of the trigeminal nerve after microvascular decompression may be only reactive and do not always represent infarction. Depending on the clinical picture, observation may be all that is necessary in such cases.

The role of magnetic resonance imaging in routine decision making for meniscal surgery.

This clinical study evaluated factors affecting the decision for meniscal surgery in a patient population seen routinely at a trauma clinic. The study hypothesis was that patients who sustain a traumatic injury to the knee or have a long history of clinical symptoms are likelier to be operated on. We investigated 149 patients clinically and by magnetic resonance imaging (MRI). Group A (n = 62) underwent arthroscopic surgery and group B (n = 87) were treated conservatively. Multiple logistic regression analysis was used to examine correlations with regard to age, gender, injury pattern, period between the injury and first clinical examination, and MRI results. We found no significant difference between the two groups with regard to gender (P = 0.1), injury pattern (P = 0.44), or period between injury and first clinical examination (P = 0.5). Patients in group A were significantly older than those in group B (P = 0.044), and, as expected, MRI signal alterations were significantly higher in group A than in group B (P = 0.001). In acutely injured patients MRI helps to establish an accurate diagnosis, and in cases of positive MRI findings in a symptomatic patient, the surgeon should not wait 4-6 weeks but should immediately recommend surgery.

The impact of vasoactive substances on intraosseous pressure and blood flow alterations in the femoral head: a study based on magnetic resonance imaging.

In beagle dogs, the alterations of intraosseous pressure and blood supply in the femoral head that result from the administration of vasoactive substances were examined, and the changes were documented by magnetic resonance imaging (MRI). Vasoactive substance were infused into the medial and lateral circumflex femoral arteries of 12 beagle dogs. All infusions were done under standardised conditions with simultaneous measurements of venous blood flow and intraosseous pressure distribution in the proximal femur. The drugs were infused in three cycles of 30 min each separated by 30 min recovery periods, followed by MRI examination at the end of each experiment. At an intraosseous pressure of 14.3 (+/- 4.2) mmHg in the femoral head epiphysis (I), 11.6 (+/- 2.7) mmHg in the greater trochanter (II) and 9.3 (+/- 3.2) mmHg in the femoral shaft (III), a baseline flow of 96.2 (+/- 18.8, n = 12) ml/min was measured in the femoral vein. After infusing bradykinin at a concentration of 10(-6) moles, which is commonly known to lead to cerebral and subcutaneous oedema formation by vessel dilatation, the intraosseous pressure increased to (I): 49.1 (+/- 6.2) mmHg, (II): 42.5 (+/- 5.8) mmHg and (III): 38.3 (+/- 7.1) mmHg in the three measured femoral areas (n = 3). After the bradykinin injection, femoral vein flow increased to a peak value of 238.4 (+/- 43.4) ml/min and then dropped to 62.3 (+/- 14.2) ml/min after discontinuation of the bradykinin infusion. In a second and third series of tests, hyperosmolar (20% NaCl) and hypo-osmolar (distilled water) solutions were applied, also resulting in increased but lower mean intraosseous pressure values (17.3 +/- 4.1 and 25.7 +/- 5.1 ml/min, respectively) in all regions. When administering bradykinin, MRI scans taken immediately after completion of the experiment showed substantial oedema in the femoral muscular system, but without any changes of osseous signals in T1- or short time inversion recovery (STIR)-weighted images, nor did any changes occur when solutions of 20% NaCl or distilled H2O were injected. The results of our experiments demonstrate that acute increases of intraosseous pressure do not cause MRI signal alterations. We therefore conclude that in addition to the described pressure increase, other intraosseous alterations must occur to lead to the detectable signal changes found among patients with diagnosed femoral head necrosis. Finally, the short time period between the rise in intraosseous pressure and performing a conventional MRI may be one reason for missing the development of an intraosseous oedema. On the other hand, conventional MRI might have additional disadvantages for detecting intraosseous fluid compared with a dynamic imaging modality.