Indentation and Transverse Diameter of the Meckel Cave: Imaging Markers to Diagnose Idiopathic Intracranial Hypertension

A. Kamali; K.C. Sullivan; F. Rahmani; A. Gandhi; A. Aein; O. Arevalo; P. Rabiei; S.J. Choi; X. Zhang; R.E. Gabr; R.F. Riascos

doi:10.3174/ajnr.A6682

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Fig 1.
Two coronal T2-weighted images of the Meckel cave in a healthy subject (A) versus a patient with IIH (B). The white arrows in A represent the curvature of the Meckel cave and no indentation in a healthy subject. The white arrow in B demonstrates an acute angle of indentation and a bilobed appearance of the Meckel cave in a patient with IIH. The 2-way arrows in B demonstrate the craniocaudal diameter (along the oblique axis of the right MC) and transverse diameter of the left MC (perpendicular to both walls in the widest segment of the MC on the coronal plane).
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Fig 2.
Coronal T2 view of a dilated MC in a patient with IIH. The black arrows represent the indentation of the Meckel cave. The white arrow shows the dilated cisternal space of the V3 segment of the left trigeminal nerve and points to the foramen ovale where the V3 nerve exits the intracranial space at the skull base. Dilation of this cisternal space may contribute to the indented appearance of the MC in patients with IIH.
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Fig 3.
The appearance of the Meckel cave in a healthy person (A) versus a patient with IIH (B) on the axial T2 planes. The 2-way arrows represent the wall-to-wall measurement of the Meckel cave in the AP (A) and transverse (B) diameters.
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Fig 4.
Figs 4–7. The AUC was used to evaluate the overall differentiability of a marker to identify those with IIH from healthy controls. The optimal cutoff point for the marker was obtained by evaluating the Youden index. On the basis of the optimal cutoff point, we reported estimates of sensitivity, specificity, positive predictive value, and negative predictive value, together with their 95% Wald confidence intervals. Maximum transverse values. A, coronal data. B, axial data.
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Fig 5.
Right transverse values. A, Coronal data. B, Axial data.
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Fig 6.
Left transverse values. A, Coronal data. B, Axial data.
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Fig 7.
Receiver operating characteristic curves for MC volumes: right MC (right), left MC (center), and maximum values (left).

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Table 1:

Incidence, sensitivity, and specificity of imaging findings in IIH and control groups

Imaging Signs	IIH	Controls	Sensitivity	Specificity
Optic nerve sheath dilation	63 (84%)	12 (16%)	84	84
Empty/partial empty sella	69 (92%)	20 (26%)	92	74
Posterior scleral flattening	41 (55%)	0	55	100
Papilledema	34 (45%)	0	45	100
Bilateral TSS	55 (73%)	6 (8%)	73	92
Enlarged MC	56 (75%)	11 (14%)	75	86

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Table 2:
Demographics for 2 groups
IIH (n = 75) Healthy Controls (n = 75) P Value
Age (mean ± SD) (yr) 33.84 ± 9.15 34.65 ± 9.37 .59
Male sex 6 (8%) 15 (20%) .034
LP opening pressure (median) (IQR) 29 (24–38) Not Available
Note:—IIH indicates idiopathic intracranial hypertension patients; LP, lumbar puncture; IQR, interquartile range.
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Table 3:
Meckel cave indentation^{^a}
Yes No Total
IIH 57 18 75
Healthy controls 21 54 75
↵a Seventy-six percent sensitivity, 72% specificity, positive predictive value of 73% and negative predictive value of 75% for the diagnosis of IIH.

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Table 4:

Descriptive statistics in IIH patients (n = 75) and controls (n = 75)^{^a}

Variable	Patients with IIH	Controls	P Value
Right MC height	11.51 ± 1.78	9.51 ± 1.46	<.001
Left MC height	11.93 ± 1.90	9.53 ± 1.43	<.001
Max MC height	12.50 ± 1.92	9.97 ± 1.51	<.001
Right MC AP	12.37 ± 2.43	9.68 ± 1.43	<.001
Left MC AP	12.92 ± 2.70	9.55 ± 1.47	<.001
Max MC AP	13.41 ± 2.48	10.13 ± 1.43	<.001
Right MC transverse	5.14 ± 1.21	3.94 ±0.73	<.001
Left MC transverse	4.94 ± 0.96	3.88 ± 0.75	<.001
Max MC transverse	5.49 ± 1.11	4.14 ± 0.72	<.001
Right volume	747.3 ± 293	368.7 ± 121	<.001
Left volume	775.4 ± 278	357.2 ± 115	<.001
Max volume	938.4 ± 333	424.0 ± 131	<.001

Note:—Max indicates maximum.
↵a Mean ± SD are shown. Summary statistics for anterior-posterior (AP) and transverse diameters of MC on axial T2, and craniocaudal diameter of MC on coronal T2 weighted sequences. Max is larger value between right and left. Volume is product of height, AP, and transverse diameters.

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Table 5:

AUC estimates for differentiating patients with IIH from controls

Variable	AUC	95% CI
Right MC height	0.816	(0.748–0.884)
Left MC height	0.852	(0.793–0.911)
Max MC height	0.850	(0.789–0.910)
Right MC AP	0.830	(0.768–0.893)
Left MC AP	0.861	(0.804–0.917)
Max MC AP	0.874	(0.821–0.927)
Right MC transverse	0.810	(0.740–0.879)
Left MC transverse	0.807	(0.737–0.877)
Max MC transverse	0.852	(0.791–0.913)
Right volume	0.907	(0.861–0.954)
Left volume	0.922	(0.881–0.964)
Max volume	0.936	(0.900–0.972)

Note:—Max indicates maximum.

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Table 6:
Estimated Spearman correlation coefficients (n = 75)^{^a}
Variable 1 Variable 2 Estimated Spearman Correlation Coefficient 95% CI P Value
Right MC volume CSF opening pressure −0.104 −0.323−0.127 .38
Left MC volume CSF opening pressure −0.050 −0.274−0.179 .67
↵a The Spearman correlation coefficient was only −0.10 for right MC volume and CSF pressure, and −0.05 for left MC volume and CSF opening pressure. Correlation coefficients are very close to zero. We may conclude that opening CSF pressure is not correlated with right or left MC volumes.