Sagittal MRI often overestimates the degree of cerebellar tonsillar ectopia: a potential for misdiagnosis of the Chiari I malformation

Tubbs, R. Shane; Huang, Yan; Demerdash, Amin; Chern, Joshua J.; Fries, Fabian N.; Oskouian, Rod J.; Oakes, W. Jerry

doi:10.1007/s00381-016-3113-3

Cited by 14 publications

(5 citation statements)

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“…16 Furthermore, sagittal MRI has been shown to overestimate the degree of tonsillar herniation, leading to a risk of misdiagnosis and unnecessary consults and referrals. 63 Other imaging modalities, such as cardiac-gated phasecontrast MRI or cine MRI, can be useful for evaluating CIM patients, assessing CSF flow and tonsillar dynamics at the foramen magnum. Phase-contrast MRI differs from normal MRI, in that it studies dynamic processes, such as blood and CSF flow, as opposed to the static anatomical properties revealed by standard MRI modalities.…”

Section: Imaging and Diagnostic Studies In Cimmentioning

confidence: 99%

The Chiari I malformation

McClugage¹,

Oakes²

2019

Journal of Neurosurgery: Pediatrics

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As with many pathologies, the course of our understanding of the Chiari I malformation (CIM) has developed extensively over time. The early descriptions of the Chiari malformations by Hans Chiari in 1891 opened the door for future classification and research on this topic. However, even over a long timeframe, our understanding of the pathophysiology and, more importantly, treatment, remained in its infancy. As recently as the 1970s, CIM was not discussed in popular neurology textbooks. Syringomyelia is listed as a degenerative disorder with no satisfactory treatment. Radiation therapy was considered an option in treatment, and surgery was thought to play no role. During the last 40 years, equivalent to the duration of a neurosurgical career, our understanding of the pathophysiology and natural history of CIM, coupled with modern MRI, has improved the treatment paradigm for this patient population. More importantly, it has given us evidence confirming that CIM is a disorder responsive to surgical intervention, giving patients once thought to be destined for lifelong disability a comparatively normal life after treatment. The purpose of this article is to offer a review of CIM and its important associated entities. The authors will discuss the evolution in understanding of the Chiari malformation and, importantly, distinguish between symptomatic CIM and asymptomatic tonsillar ectopia, based on imaging and presenting symptomatology. They will discuss techniques for surgical intervention, expected outcomes, and complications after surgery. Proper patient selection for surgery based on appropriate symptomatology is tantamount to achieving good surgical outcomes in this population, separating those who can be helped by surgery from those who are unlikely to improve. While our knowledge of the Chiari malformations continues to improve through the efforts of clinical and basic science researchers, surgeons, and patients, our current understanding of these entities represents a monumental improvement in patient care over a relatively short time period.

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Section: Imaging and Diagnostic Studies In Cimmentioning

confidence: 99%

The Chiari I malformation

McClugage¹,

Oakes²

2019

Journal of Neurosurgery: Pediatrics

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“…On coronal images, 19 patients have one of the tonsils that were 3 mm below although each was 3 mm on the sagittal images. They concluded that CM1 had an asymmetrical tonsillar ectopia and the sagittal images overestimate the ectopic cerebellar tonsils in patients with CM1 [17]. In our study, tonsillar ectopia was calculated based on midsagittal MRI in 25 patients.…”

Section: Discussionmentioning

confidence: 79%

Surgical Outcomes of Adult Chiari Malformation Type 1: Experience at a Tertiary Institute

Papaker¹,

Abdallah²,

Çınar³

2021

Cureus

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BackgroundChiari type I malformation (CM1) is a herniation of the caudal cerebellum and/or medulla oblongata into the upper spinal canal, occurring in pediatric and adult populations. We aimed to analyze the surgical outcomes of adult patients with CM1 consecutively treated with a posterior fossa decompression and duraplasty (PFDD) in a tertiary institution. Patients and methodsWe retrospectively reviewed the medical charts of 45 adult patients with CM1 who underwent PFDD at the Neurosurgery Department of our institution between January 2012 and December 2017. Radiological evaluation was based on pre-and postoperative syrinx/cord ratio, syrinx length, and regression of the ectopic cerebellar tonsils on coronal and sagittal magnetic resonance imaging (MRI) images, and clinical assessment of the patients was performed with the Chicago Chiari Outcome Scale (CCOS). ResultsOf the 45 patients included in the study, 25 (four men, 21 women) were diagnosed with symptomatic CM1 with an age average of 36.6±11.4 (18-66) years. Headache was the most common symptom (72.0%), while pinprick losses were prevalent in 13 (52.0%) patients. The mean postoperative CCOS score was 14.7±2.0 (8-16). Symptoms improved in 20 patients (80.0%) at the last follow-up. The mean regression in ectopic tonsils on midsagittal and coronal images were 9.1±1.8 (range: 0-16.5) mm and 8.3±1.2 (0-12.0) mm, respectively (p<0.05). The syrinxes had regressed completely or significantly in 7 (87.5%) of eight patients with syrinx. ConclusionOur findings showed that PFDD is sufficient to relieve most of the major symptoms and resolve the syrinx cavity without additional surgical interventions. The CCOS keeps its measurability of assessment of the clinical outcomes. A reliable radiological evaluation should be performed on midsagittal and coronal MRI images.

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“…In 2016, Tubbs et al. 23 measured ETH on coronal images in 50 pediatric patients using the inferior margin of the foramen magnum as a reference line. They observed that measurements of both individual tonsils were generally smaller than midsagittal tonsillar measurements and concluded that midsagittal measurements overestimate ETH and can thus falsely diagnose some patients with tonsillar ectopia (ETH <5 mm) as CMI.…”

Section: Discussionmentioning

confidence: 99%

Diagnostic utility of parasagittal measurements of tonsillar herniation in Chiari I malformation

et al. 2021

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Background and purpose Although the cerebellar tonsils are parasagittal structures, the extent of tonsillar herniation (ETH) in Chiari I malformation (CMI) is currently measured in the midsagittal plane. We measured the ETH of each cerebellar tonsil in the parasagittal plane and assessed their diagnostic utility by comparing them to the midsagittal ETH measurements in predicting cough-associated headache (CAH), an indicator of clinically significant disease in CMI. Methods Eighty-five CMI patients with 3D-MPRAGE images were included. Neurosurgeons determined the presence of CAH. Sagittal images were used to measure ETH in the midsagittal (MS_ETH) and parasagittal planes (by locating tonsillar tips on each side on reformatted coronal images). Given the parasagittal ETH (PS_ETH) asymmetry in the majority of cases, they were considered Smaller_PS_ETH or Larger_PS_ETH. The accuracy of ETH measurements was assessed by the receiver operating characteristic (ROC) curve. Results Of 85 patients, 46 reported CAH. ROC analysis showed an area under the curve (AUC) of 0.78 for Smaller_PS_ETH significantly better than 0.65 for MS-ETH in predicting CAH ( p = 0.001). An AUC of 0.68 for Larger_PS_ETH was not significantly different from MS_ETH. The sensitivity and specificity of predicting CAH were 87% and 28% for MS_ETH >6 mm versus 90% and 46% for Smaller_PS_ETH >6 mm, and 52% and 67% for MS_ETH >9 mm versus 48% and 87% for Smaller_PS_ETH >9 mm. At ETH >15 mm, no differences were seen between the measurements. Conclusions Diagnostic utility of ETH measurements in detecting clinically significant CMI can be improved by parasagittal measurements of the cerebellar tonsillar herniation.

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Sagittal MRI often overestimates the degree of cerebellar tonsillar ectopia: a potential for misdiagnosis of the Chiari I malformation

Abstract: Sagittal MRI overestimates the degree of tonsillar ectopia in patients with Chiari I malformation. Misdiagnosis may occur if sagittal imaging alone is used. The cerebellar tonsils are paramedian structures, and this should be kept in mind when interpreting midline sagittal MRI.

Cited by 14 publications

References 10 publications

The Chiari I malformation

The Chiari I malformation

Surgical Outcomes of Adult Chiari Malformation Type 1: Experience at a Tertiary Institute

Diagnostic utility of parasagittal measurements of tonsillar herniation in Chiari I malformation

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