Foundation-funded study published on differentiation between Chiari malformation type 1 and SIH
We are pleased to report that a Foundation-funded research study has just been published in the Journal of Neurosurgery titled “Differentiation of Chiari malformation type 1 and spontaneous intracranial hypotension using objective measurements of midbrain sagging.” This retrospective investigation from Duke University Medical Center aimed to determine whether spontaneous intracranial hypotension (SIH) can be distinguished from Chiari 1 malformation (CM1) on brain MRI.
The paper’s authors (Jessica L. Houk MD, Timothy J. Amrhein MD, Linda Gray MD, Michael D. Malinzak MD, PhD, and Peter G. Kranz MD) were able to observe highly significant differences between patients with spontaneous intracranial hypotension and patients with Chiari 1 malformation. In particular, they found that measures of midbrain sagging can help discriminate between the two conditions and may help to prevent misdiagnosis and unnecessary surgery. See more details in the abstract below.
Differentiation of Chiari malformation type 1 and spontaneous intracranial hypotension using objective measurements of midbrain sagging
Principal Investigator: Peter G. Kranz, MD
Institution: Duke University Medical Center
Project: Differentiation of Chiari malformation type 1 and spontaneous intracranial hypotension using objective measurements of midbrain sagging
Date of Award: November 2018
Publication Date: Published online October 29, 2021; DOI: 10.3171/2021.6.JNS211010.
AUTHORS: Jessica L. Houk MD, Timothy J. Amrhein MD, Linda Gray MD, Michael D. Malinzak MD, PhD, and Peter G. Kranz MD
CITATION: J Neurosurg. 2021 Oct 29:1-8. doi: 10.3171/2021.6.JNS211010. Epub ahead of print. PMID: 34715671.
OBJECTIVE: Chiari malformation type 1 (CM-1) and spontaneous intracranial hypotension (SIH) are causes of headache in which cerebellar tonsillar ectopia (TE) may be present. An accurate method for differentiating these conditions on imaging is needed to avoid diagnostic confusion. Here, the authors sought to determine whether objective measurements of midbrain morphology could distinguish CM-1 from SIH on brain MRI.
METHODS USED: This is a retrospective case-control series comparing neuroimaging in consecutive adult subjects with CM-1 and SIH. Measurements obtained from brain MRI included previously reported measures of brain sagging: TE, slope of the third ventricular floor (3VF), pontomesencephalic angle (PMA), mamillopontine distance, lateral ventricular angle, internal cerebral vein–vein of Galen angle, and displacement of iter (DOI). Clivus length (CL), an indicator of posterior fossa size, was also measured. Measurements for the CM-1 group were compared to those for the entire SIH population (SIHall) as well as a subgroup of SIH patients with > 5 mm of TE (SIHTE subgroup).
RESULTS OF THE STUDY: Highly significant differences were observed between SIHall and CM-1 groups in the following measures: TE (mean ± standard deviation, 3.1 ± 5.7 vs 9.3 ± 3.5 mm), 3VF (−16.8° ± 11.2° vs −2.1° ± 4.6°), PMA (44.8° ± 13.1° vs 62.7° ± 9.8°), DOI (0.2 ± 4.1 vs 3.8 ± 1.6 mm), and CL (38.3 ± 4.5 vs 44.0 ± 3.3 mm; all p < 0.0001). Eight (16%) of 50 SIH subjects had TE > 5 mm; in this subgroup (SIHTE), a cutoff value of < −15° for 3VF and < 45° for PMA perfectly discriminated SIH from CM-1 (sensitivity and specificity = 1.0). DOI showed perfect specificity (1.0) in detecting SIH among both groups. No subjects with SIH had isolated TE without other concurrent findings of midbrain sagging.
STUDY CONCLUSIONS: Measures of midbrain sagging, including cutoff values for 3VF and PMA, discriminate CM-1 from SIH and may help to prevent misdiagnosis and unnecessary surgery.
ABBREVIATIONS: 3VF = slope of the third ventricular floor; CL = clivus length; CM-1 = Chiari malformation type 1; CVF = CSF-venous fistula; DOI = displacement of iter; LVA = lateral ventricular angle; MPD = mamillopontine distance; PMA = pontomesencephalic angle; SIH = spontaneous intracranial hypotension; TE = tonsillar ectopia; VHA = venous hinge angle.
PMID: 34715671
DOI: 10.3171/2021.6.JNS211010