What’s new in Neuroimaging – November 2020

2 years ago

Imaging Features of Acute Encephalopathy in Patients with COVID-19: A Case Series

Kihira, B.N. Delman, P. Belani, L. Stein, A. Aggarwal, B. Rigney, J. Schefflein, A.H. Doshi and P.S. Pawha

American Journal of Neuroradiology October 2020, 41 (10) 1804-1808;

DOI: https://doi.org/10.3174/ajnr.A6715

This is a case series illustrating varying imaging presentations of acute encephalopathy in 5 patients with COVID-19. The MRI features included leukoencephalopathy reflected by white matter signal abnormality, diffusion restriction that involves the gray matter and white matter, microhemorrhages, and leptomeningitis. These imaging appearances ranged between features of autoimmune encephalitis, post-hypoxic leukoencephalopathy, hemorrhagic leukoencephalopathy, and post-viral autoimmune demyelination. Significant respiratory distress is seen in up to 25% of patients with COVID-19 and thus hypoxic leukoencephalopathy contributes to imaging findings of COVID-19 making it difficult to separate primary pathology from secondary complications of hypoxia. At this moment, encephalopathy is thought to be multifactorial.

 

Clinical and Neuroimaging Correlation in Patients with COVID-19

B.C. Yoon, K. Buch, M. Lang, B.P. Applewhite, M.D. Li, W.A. Mehan, T.M. Leslie-Mazwi and S.P. Rincon

American Journal of Neuroradiology October 2020, 41 (10) 1791-1796;

DOI: https://doi.org/10.3174/ajnr.A6717

This was a retrospective study performed at an academic hospital in the United States. It examined the frequency of acute intracranial abnormalities as seen on CT and/or MR brain imaging in patients with COVID-19 and investigated possible association between these findings and clinical parameters such as length of hospital stay, requirement for intubations, death, obesity, and development of acute kidney injury. 641 patients were seen in the institution over the study period, and of these, 150 underwent CT and/or MR brain imaging. Of these 150, 26 (17%) had abnormal neuro-imaging; hemorrhage in 11, infarction in 13, and leukoencephalopathy in 7. There was significant association between abnormal neuro-imaging and intensive care unit admission (P= .039), intubation (P= .004), and acute kidney injury (P= .030). This suggested that in patients with worsening systemic disease, brain imaging should be considered.

 

Tentorial Venous Anatomy: Variation in the Healthy Population

J.S. Rosenblum, J.M. Tunacao, V. Chandrashekhar, A. Jha, M. Neto, C. Weiss, J. Smirniotopoulos, B.R. Rosenblum and J.D. Heiss

American Journal of Neuroradiology October 2020, 41 (10) 1825-1832;

DOI: https://doi.org/10.3174/ajnr.A6775

This study evaluated the normal variation of tentorial venous anatomy in the healthy population by retrospectively reviewing head CTA/CTV in a total of 238 patients with examinations done for routine care or research purposes. The transtentorial network comprises 2 main tentorial sinuses and 3 main veins. The sinuses are the medial and lateral tentorial sinuses which may be distinct or connected (when connected, it is termed the ringed configuration). The veins are the medial, intermediate, and lateral tentorial veins. This study also evaluated relationships between these variations in tentorial venous anatomy with the extent of skull base development as measured by cranial morphometrics. They found 3 configurations: group 1A and group 1B which had ringed configuration (n = 50/238) and group 2 which did not have a ringed configuration (n = 188/238). Group 1A (n = 38/50) had a medialized ringed configuration, and group 1B had a lateralized ringed configuration (n = 12/50). The ringed configuration of group 1 was related to the presence of split confluence of sinuses, which correlated with a decreased internal auditory canal–petroclival fissure angle. Configuration 1A was related to the degree of petrous apex pneumatization. Understanding of this anatomy is helpful in preoperative evaluation of complex surgical procedures that involved tentorial incisions. An understanding of this is also useful in explaining mechanisms of complications/variations in complications in cases of compromised tentorial venous system and transverse sinus thrombosis.

 

MR Imaging Features of Middle Cranial Fossa Encephaloceles and Their Associations with Epilepsy. 

D.R. Pettersson, K.S. Hagen, N.C. Sathe, B.D. Clark, D.C. Spencer

Published October 8, 2020, as 10.3174/ajnr.A6798

Clinical question:

Can we use MRI imaging characteristics of the middle cranial fossa encephaloceles to predict the probability of epilepsy?

What was done:

The MR imaging features of middle cranial fossa encephaloceles in seizure and nonseizure groups were characterized with the hope to detect features predictive of epilepsy.

How was it done:

A prospective study of 77 patients with MCF encephaloceles during an 18 month period at a single institution. All available brain MR imaging for each patient was reviewed by the certified neuroradiologist. Thirty-five of 77 (45%) had a history of seizure,  twenty of 77 (26%) had temporal lobe epilepsy, and forty-two or 77 (55%) had no history of seizures. The patient’s middle cranial fossa encephalocele features on MR imaging were characterized by depth, area, number, location, presence of adjacent encephalomalacia, and degree of associated parenchymal morphologic distortion. Then MR imaging features were compared between the seizure and nonseizure groups.

Findings and results:

There were no statistically significant differences in the conventional MR imaging features of MCFEs between those patients with a history of seizure and those without a history of seizures. MCFEs that are large or numerous, MCFEs associated with encephalomalacia, and MCFEs associated with severe morphologic distortion of adjacent brain parenchyma can be seen with similar frequency between patients with and without a history of seizures. A comparison of just those patients with temporal lobe epilepsy (20 pts) with those with no history of seizure (42 pts) also found no significant difference in MR imaging features. Additionally, 66% of patients with MCFE had multiple MCFEs, and MCFEs were seen bilaterally in 51% of cases.

Conclusion:

Middle cranial fossa encephaloceles are an increasingly recognized cause of epilepsy; however, they are also often encountered on neuroimaging in patients with no history of seizure. Anatomic MR imaging features of middle cranial fossa encephaloceles such as size, number, adjacent encephalomalacia, and the degree of adjacent parenchymal morphologic distortion may not be useful in predicting the likelihood of epileptogenicity.

Implications:

While possibly associated with a seizure disorder, the presence of a MCF encephalocele needs to be correlated with the clinical presentation as patients with this imaging finding need not have a seizure disorder. The radiologists who encounter an MCFE during routine clinical practice may be advisable to search for additional and contralateral encephaloceles. But the conventional MR imaging features of MCFE cannot reliably differentiate symptomatic (seizure-related) from asymptomatic MCFEs.

Senior Editor Commentary by Dr.Ortiz:

An interesting paper in that MCF encephaloceles are thought to be uncommon.  Perhaps the inclusion criteria are broader for a finding to be considered an MCF encephalocele in this study?

Senior Editor Commentary by Dr.Ibrahim:

I agree with Dr. Ortiz regarding the uncommon incidence of MCFE. This work is very important as it highlights the incidental nature of some of these MCFE and the need for clinical correlation for their significance.

 

Variability of T2-Relaxation Times of Healthy Lumbar Intervertebral Discs is More Homogeneous within an Individual Than across Healthy Individuals

Sharma, R.E. Walk, S.Y. Tang, R.Eldaya, P.J. Owen, D.L. Belavy

Published October 8, 2020, as 10.3174/ajnr.A6791

Clinical question:

Can we use T2 relaxometry results of the same individual’s healthy disk to assess intervertebral disc degeneration, or should the normative values be based on a pool of extraneous control groups?

What was done:

Prospectively acquired T2-relaxometry data from 606 intervertebral discs in 101 volunteers without back pain (47 men, 54 women between 25–35 years old) were evaluated, and intrasubject and intersubject variation in T2 times of intervertebral discs were graded by two neuroradiologists on the Pfirrmann scale.

How was it done:

Intrasubject variation of intervertebral discs was assessed relative to other healthy intervertebral discs of the same patient (Pfirrmann grade, ≤2). Multiple intersubject variability measures were calculated using healthy extraneous references ranging from a single randomly selected intervertebral disc to all healthy extraneous intervertebral discs, without and with segmental stratification. These variability measures were compared for healthy and degenerated (Pfirrmann grade ≥ 3) intervertebral discs.

Findings and results:

The mean T2 values of healthy (493/606, 81.3%) and degenerated intervertebral discs were 121.1 and 91.5, respectively (P<0.001). The mean intrasubject variability for healthy intervertebral discs was 9.8 ± 10.7 ms, lower than all intersubject variability measures (P<0.001), and provided the most pronounced separation for healthy and degenerated intervertebral discs. Among intersubject variability measures, using all segment-matched healthy discs as references provided the lowest variability (P<0.001).

Conclusion:

Normative measures based on the T2 times of healthy intervertebral discs from the same individual are likely to provide the most discriminating means of identifying degenerated intervertebral discs based on T2 relaxometry.

Implications:

Many previous studies have suggested that T2-relaxometry can provide a reliable, objective, and continuous quantitative measure of the health of lumbar IVDs. Despite these advantages, this technique has failed to replace traditional subjective assessment of the signal intensity of IVDs on T2-weighted images for the categorization of a given IVD as healthy or degenerated. The analysis of the same data demonstrated that while the level of stratification might be important when cohorts of IVDs are being compared, T2 times of healthy IVDs at other levels in the same individual are likely to provide a better measure of the health of a given IVD than T2 times of a healthy IVD of other healthy individuals.

Pfirrman grading system for reference:

Grade I: disc is homogeneous with bright hyperintense white signal intensity and normal disc height.

Grade ll: disc is inhomogeneous, but keeping the hyperintense white signal, normal disc height.

Grade lll: disc is inhomogeneous with an intermittent gray signal intensity, the distinction between nucleus and annulus is unclear, disc height is normal or slightly decreased.

Grade IV: disc is inhomogeneous with a hypointense dark gray signal intensity, there is no more distinction between the nucleus and annulus, disc height is slightly or moderately decreased.

Grade V: disc is inhomogeneous with a hypointense black signal intensity, there is no more difference between the nucleus and annulus, the disc space is collapsed.

Senior Editor Commentary by Dr.Ortiz:

Alternatively, T2 -relaxometry data may have a role in the sequential longitudinal of a given individual on follow-up MR examinations including those in which there have been surgical and percutaneous interventions.

Senior Editor Commentary by Dr.Ibrahim:

This work is important as it creates a normalized value for the MR appearance of the intervertebral discs, this can be used in the future for textural analysis of the intervertebral discs, though this work is not intended to create such results by the authors.

 

Detailed Arterial Anatomy and Its Anastomoses of the Sphenoid Ridge and Olfactory Groove Meningiomas with Special Reference to the Recurrent Branches from the Ophthalmic Artery 

M.Hiramatsu, K. Sugui, T. Hishikawa, J. Haruma, Y.Takahashi, S. Murai, K. Nishi, Y. Yamaoka, Y. Shimazu, K. Fujii, M. Kameda, K. Kurozumi, I. Date

Published October 1, 2020, as 10.3174/ajnr.A6790

Clinical question:

Can we predict the high likelihood of the feeding vessels of the sphenoid ridge and olfactory groove meningiomas?

What was done:

The MR imaging features of middle cranial fossa encephaloceles in seizure and nonseizure groups were characterized with the hope to detect features predictive of epilepsy.

How was it done:

This study included 20 patients admitted to the department of neurological Surgery at Okayama University between April 2015 and March 2020. There were a total of 16 sphenoid ridge meningiomas and 4 olfactory groove meningiomas identified and evaluated. Preoperative DSA was performed with the patient under local anesthesia. After obtaining 2D-DSA of the ECA and ICA, which are ipsilateral to the tumor, 3D-DSA with a 5-second protocol was performed on the branching feeders of the vessels.  Collateral anatomy was also analyzed by  3D rotational angiography and slab MIP images of these lesions.

Findings and results:

19 (95%)lesions had feeders from the ophthalmic artery, 15 (75%) lesions had feeders from the internal carotid artery, and 15 (75%) lesions had feeders from the external carotid artery. Feeders from the ophthalmic artery, recurrent meningeal arteries were involved in 18 lesions (90%) and 75% had anastomoses between each feeder.

Conclusion:

Detailed arterial anatomy of the sphenoid ridge and olfactory groove meningiomas is complicated due to the fine angioarchitecture and anastomoses between each feeder. This is the first report to demonstrate the detailed arterial anatomy and frequency of recurrent branches from the ophthalmic artery and their anastomoses using detailed imaging techniques.

Implications:

Most of the meningiomas in the sphenoid ridge and olfactory groove had feeders from the ophthalmic and internal carotid arteries. Preoperative embolization for meningioma is often performed in practice. Although its usefulness is widely accepted, the embolization of target vessels other than the ECA has been reported as a risk for procedural complications. If there is an anastomosis between each feeder, proximal occlusion of the feeder, which can be easily catheterized, can result in increased blood flow to the tumor from the residual feeder. One should consider embolizing the common trunk of both feeders or the proximal parts of both feeders. A detailed understanding of arterial microanatomy is also useful in surgery. If we identify all of the feeders using preoperative angiography, we can search for feeders on the basis of the anatomic landmarks of the bone and devascularize them in a safe and efficient manner.

Senior Editor Commentary by Dr. Ortiz:

The treatment of sphenoid ridge meningiomas is challenging, regardless of the specific therapy (surgery, embolization, stereotactic radiosurgery), due to the intimate proximity of this notoriously infiltrative lesion to critical orbital and supra/para-sellar structures. Endovascular embolization like any other invasive procedure must balance risk and benefit. An awareness of the intricate balanced arterial supply in this region is helpful towards understanding that risk. Being aware of altering that balance and understanding that partial embolization only may be feasible is important in order to maintain a low risk profile for this procedure.

Interested readers are also referred to the following article:

Guilherme Barros, Abdullah H Feroze, Rajeev Sen et al. Predictors of preoperative endovascular embolization of meningiomas: subanalysis of anatomic location and arterial supply. JNIS 2020.  This is a nice complementary article.

References
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