What’s new in Neuroimaging – March 2021

1 year ago

 

Recommendations for Neuroradiology Training during Radiology Residency by the American Society of Neuroradiology Section Chiefs Leadership Group

Wintermark, J. Anderson, V. Gupta, T.A. Kennedy, L.A. Loevner, R.F. Riascos, C. Robson, G. Saigal and C. Glastonbury

American Journal of Neuroradiology February 2021

https://doi.org/10.3174/ajnr.A6968

Recommendations: 

It is strongly recommended that radiology trainees have at least 16–24 weeks of training in neuroradiology under the direction of a neuroradiologist. Additionally, it is recommended that at least 8–12 of those weeks occur during the last 3 years of their training before they start practicing independently.

Continued interpretation and education in brain, spine, head & neck, and neurovascular imaging should occur throughout the residency. Although specific numbers of cases are not an indication of competency, a guideline for consideration is that a radiology trainee interpret at least 300 neuroimaging CT scans, 150 Neuroimaging MRI scans, and 50 neurovascular imaging studies (neuro CTAs and neuro MRAs) under the guidance and direction of a neuroradiologist during the last 3 years of their training, before he or she starts practicing independently.

It is strongly recommended that competency in Neuroimaging be tested. Resources for evaluation could include competency tests established in the home institution, performance on RadExam (https://www.acr.org/Lifelong-Learning-and-CME/Learning-Activities/RadExam), or similar testing formats.

Conclusion:

From a patient safety perspective, radiology trainees graduating on or after June 2021 and joining practice who have not met the recommendations listed above should seriously consider not interpreting even routine neuroradiology studies.

For the independent practice and interpretation of ad-vanced neuroradiology (including pediatric neuroradiology, head and neck radiology, and advanced neuroimaging), a formal, ACGME-approved neuroradiology fellowship is strongly recommended. A neuroradiology fellowship will ensure exposure, experience, and competency for both routine and advanced neuroradiology.

 

Spinal Compliance Curves: Preliminary Experience with a New Tool for Evaluating Suspected CSF Venous Fistulas on CT Myelography in Patients with Spontaneous Intracranial Hypotension

M.T. Caton, B. Laguna, K.A. Soderlund, W.P. Dillon and V.N. Shah

American Journal of Neuroradiology February 2021

https://doi.org/10.3174/ajnr.A7018

Clinical question:

This study describes a method to estimate craniospinal space compliance using saline infusion during CT myelography and explores the use of craniospinal space compliance and pressure-volume curves in patients with suspected cerebrospinal-venous fistula.

What was done:

Patients with suspected cerebrospinal-venous fistula underwent dynamic CT myelography. During the procedure, 1- to 5-mL boluses of saline were infused, and incremental changes in CSF pressure were recorded. These data were used to plot craniospinal space compliance curves.

Findings and results:

Thirty-four CT myelograms in 22 patients were analyzed. Eight of 22 (36.4%) patients had confirmed cerebrospinal-venous fistulas. Bolus infusion was well-tolerated with no complications and transient headache in 2/34 (5.8%). Patients with confirmed cerebrospinal-venous fistulas had higher compliance at opening pressure and overall compliance (2.6 versus 1.8 mL/cm H20, P < .01). There was no difference in the pressure volume index (77.5 versus 54.3 mL, P = .13) between groups.

Conclusion:

A method of deriving craniospinal space compliance curves using saline intrathecal infusion is described. Preliminary analysis of craniospinal space compliance curves provides qualitative and quantitative information about pressure-volume dynamics and may serve as a diagnostic tool in patients with known or suspected cerebrospinal-venous fistulas.

 

Prediction of Clinical Outcome in Patients with Large-Vessel Acute Ischemic Stroke: Performance of Machine Learning versus SPAN-100

Jiang, G. Zhu, Y. Xie, J.J. Heit, H. Chen, Y. Li, V. Ding, A. Eskandari, P. Michel, G. Zaharchuk and M. Wintermark

American Journal of Neuroradiology February 2021, 42 (2) 240-246

https://doi.org/10.3174/ajnr.A6918

What was done:

A retrospective multicenter cohort of 1431 patients with acute ischemic stroke was subdivided into recanalized and nonrecanalized patients. Extreme Gradient Boosting machine learning models were built to predict the mRS score at 90 days using clinical, imaging, combined, and best-performing features.

Findings and results:

In 3 groups of patients, the baseline NIHSS was the most significant predictor of outcome among all the parameters, with relative weights of 0.36∼0.69; ischemic core volume on CTP ranked as the most important imaging biomarker with relative weights of 0.29∼0.47. The model with the best-performing features had a better performance than the other machine learning models. The area under the curve of the model with the best-performing features was higher than SPAN-100 model and reached statistical significance for the total (P < .05) and the nonrecanalized patients (P < .001).

Conclusion:

Machine learning–based feature selection can identify parameters with higher performance in outcome prediction. Machine learning models with the best-performing features, especially advanced CTP data, had superior performance of the recovery outcome prediction for patients with stroke at admission in comparison with SPAN-100.

SPAN: Stroke Prognostication Using Age and National Institutes of Health Stroke Scale

 

Spinal dural leaks in patients with infratentorial superficial siderosis of the central nervous system—Refinement of a diagnostic algorithm

Lucie Friedauer, Beata Rezny‐Kasprzak, Helmuth Steinmetz, Richard du Mesnil de Rochemont, Christian Foerch

https://doi.org/10.1111/ene.14611

Clinical question

This study builds on the work of Wilson et al where patients with superficial siderosis were classified into four different sub-types:

(i) Isolated siderosis involving the supratentorial brain;

(ii) Symmetric infratentorial siderosis without a causative intracranial bleeding event in history (iSS type 1 – idiopathic);

(iii) Symmetric infratentorial siderosis with a causative intracranial bleeding event in history (iSS type 2 – this includes both an identified and unidentified cause of hemorrhage);

(iv) Limited (non-symmetric) infratentorial siderosis

The aim of this study was to determine the frequency of spinal dural CSF leaks amongst patients with symmetric iSS pattern on magnetic resonance imaging (MRI) scans. This included both iSS type 1 patients and also iSS type 2 patients with unidentified cause of hemorrhage.

Methods

This was a single center study conducted with a retrospective and a prospective part. The retrospective part was patient identification; all patients with superficial siderosis were identified from the imaging database between 2007 and 2018.

In the second part, all patients with symmetric iSS (infratentorial superficial siderosis) without a causative intracranial bleeding event in history (iSS type 1) were evaluated for the presence of spinal epidural fluid collections with MR imaging of the spinal cord for a potential dural leak.

Patients with iSS type 2 (i.e., with a causative intracranial bleeding event in history) were also screened for dural CSF leaks if the etiology of the bleeding event could not be determined (intracerebral/subarachnoid hemorrhage of unknown etiology).

Relative frequencies for siderosis groups for both the dataset from Wilson et al and our dataset were calculated and compared by chi-squared test statistics for significant differences

Findings and results:

There were 97,733 MRI brains in the study period from which 93 patients with superficial siderosis were recruited. Of the 93 included cases of siderosis, 42 had isolated supratentorial siderosis, 4 had iSS type 1 (i.e., iSS without history of a causative intracranial bleeding event), 26 had iSS type 2 (i.e., iSS with history of a causative intracranial bleeding event), and another 21 patients had limited infratentorial siderosis.

These corresponds to relative frequencies of 0.4 per 1,000 brain MRI scans for symmetric iSS (i.e., iSS types 1 and 2) (95% CI 0.256–0.541) and of 0.05 per 1,000 scans for iSS type 1 (95% CI 0.014–0.129).

The predominant causes in iSS type 2 patients were aneurysmatic subarachnoid hemorrhage and brain tumors.

In the next step, the 4 patients with iSS type 1 were prospectively evaluated for the presence of spinal dural CSF leaks which was positive in all cases (100%).

All patients classified as iSS type 2 who had an unknown etiology of the bleeding event despite routine diagnostic workup (n = 4) were reclassified as iSS type 1. 1 was lost to follow up and in 1 other patient a spinal dural CSF leak was identified. Thus, in five of seven (71%) patients with modified iSS type 1 a spinal dural CSF leak could be identified.

Conclusion

Persisting spinal dural CSF leaks can frequently be identified in patients with symmetric infratentorial superficial siderosis pattern. Diagnostic workup in these cases should include magnetic resonance imaging of the whole spine.

Implications

In cases of symmetric infratentorial superficial siderosis pattern without bleed / identifiable cause for bleeding, diagnostic workup should include magnetic resonance imaging of the whole spine.

Senior editor comments

This study highlights the importance of considering CSF leaks (and not only vascular malformations) as a cause for superficial siderosis. Notably, frequency estimates of siderosis were quite low in this study, however the numbers of studies having T2* vs SWI were not reported, and the prevalence is likely to be higher if SWI is routinely incorporated into neuroimaging protocols.

 

Brain MRI Findings in Severe COVID-19: A Retrospective Observational Study

Stéphane Kremer , François Lersy, Jérome de Sèze, Jean-Christophe Ferré, Adel Maamar, Béatrice Carsin-Nicol, Olivier Collange, … et al.

https://doi.org/10.1148/radiol.2020202222

Clinical question

This study aimed to describe neuroimaging findings seen in severe COVID-19 infections (excluding ischemic infarcts, venous thrombosis)

Methods

This was a retrospective multicenter study involving 16 hospitals.

Consecutive patients with COVID-19 infection and neurologic manifestations who underwent brain MRI were included from March 23, 2020, to April 27, 2020.

Inclusion criteria were (a) positive nasopharyngeal or lower respiratory tract reverse transcriptase polymerase chain reaction assays,(b) severe COVID-19 infection defined as a requirement for hospitalization and oxygen therapy, (c) neurologic manifestations, and(d) abnormal brain MRI findings. Exclusion criteria were patients with missing or noncontributory data regarding brain MRI or brain MRI showing ischemic infarcts, cerebral venous thrombosis, or chronic lesions unrelated to the current event.

Findings and results

From 190 consecutive patients seen in the study period, 30 men (81%) and 7 women (19%) were recruited. The most common neurologic manifestations were alteration of consciousness (27 of 37, 73%), abnormal wakefulness when sedation was stopped (15 of 37, 41%), confusion (12 of 37, 32%), and agitation (seven of 37, 19%).

The neuroimaging findings were;

  1. 16 (43%) patients with unilateral FLAIR and/or diffusion hyperintensities located in the mesial temporal lobe;
  2. 11 (30%) patients with non-confluent multifocal white matter hyperintense lesions on FLAIR/diffusion, with variable enhancement, associated with hemorrhagic lesions;
  3. 9 (24%) patients with extensive and isolated white matter microhemorrhages;
  4. 4 (11%) patients with extensive and confluent supratentorial white matter FLAIR hyperintensities;
  5. 2 (5%) patients with FLAIR and diffusion ovoid hyperintense lesion located in the central part of the splenium of the corpus callosum;
  6. 2 (5%) patients with non-confluent multifocal white matter hyperintense lesions on FLAIR/diffusion, with variable enhancement;
  7. 2 (5%) patients with acute necrotizing encephalopathy
  8. 2 (5%) patients with FLAIR or diffusion hyperintense lesions involving both middle cerebellar peduncles

28 (76%) patients had one pattern, 7 (19%) with two patterns, and 2 (5%) showed three patterns.

The comparison between patients with and those without intracerebral hemorrhagic lesions showed that the hemorrhagic complications were more frequently associated with severe illness as demonstrated by greater rates of ICU admission (20 of 20 [100%] vs 12 of 17 [71%], P = .01), ARDS (20 of 20[100%] vs 11 of 17 [65%], P = .005), and with pathologic wakefulness when sedative therapies were stopped (13 of 20 [65%] vs two of 17 [12%], P = .002).

Conclusion

Eight distinctive neuro-radiologic patterns were described. Some of these findings were noted to mimic findings seen with acute disseminated neuro-encephalitis (ADEM) and delayed post hypoxic leukoencephalopathy. The pathophysiology of these findings remains unclear.

Implications

This study broadens our understanding of the varied neuroradiology imaging findings seen in COVID-19. Additionally, it demonstrates correlation between hemorrhagic findings and more severe disease.

References
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