The Contribution of Neuroimaging to Diagnosis in Idiopathic Intracranial Hypertension/Idiyopatik Intrakraniyal Hipertansiyonda Noro-Goruntulemenin Taniya Katkisi.
Idiopathic intracranial hypertension (IIH) is a syndrome characterized by increased intracranial pressure (ICP) of unknown etiology with normal neurologic examination and normal cerebrospinal fluid (CSF) findings, except for symptoms and signs such as headache, papilledema, tinnitus, sixth nerve palsy, and loss of vision (1). The diagnostic criteria were first proposed by Dandy (2) in 1937. An atypical variant of the classic clinical presentation described is patients with IIH without papilledema. These cases were included in the classification of the International Headache Society (3) and were published in many case reports and case series (4,5,6,7,8,9,10). Although its exact prevalence is not known, IIH without papilledema is less frequent. Therefore, the absence of papilledema in a patient does not exclude the possibility of IIH in the presence of other IIH symptoms and signs. In addition to the above-defined criteria, neuroimaging findings were reviewed and it has been recently finalized (11).
Magnetic resonance imaging (MRI) and MR-venography (MRV) are important in the exclusion of other clinical causes that may increase ICP In addition, the presence of at least 3 neuroimaging findings consistent with the diagnosis of IIH (empty sella, flattened posterior globe/sclera, transverse cerebral venous sinus stenosis and distention of the perioptic subarachnoid space with or without tortuosity of the optic nerve) supports the diagnosis of IIH in patients without papilledema. However, it is thought that these neuroimaging findings are sometimes interpreted differently by physicians and therefore may not be sufficiently objective.
In this study, it was aimed to investigate the inter-rater agreement and the possible contribution of the neuroimaging findings of patients diagnosed as having definite IIH.
Materials and Methods
The sample was selected from patients who were already being followed up by the headache and general neurology outpatient clinics or were newly admitted during the study and were diagnosed as having definite IIH according to the revised Friedman criteria. A total of 41 consecutive patients with both cranial MRI and MRV were included in the study.
Evaluation of Neuroimages
Neuroimages were evaluated by two neurologists, who were blinded to the clinical presentation of the cases, in terms of (a) empty sella, (b) flattened posterior globe/sclera, (c) tortuosity of the optic nerve, (d) transverse sinus stenosis/hypoplasia, and (e) non-specific white matter lesions, using a standardized form. Small, cortico-subcortical, hyperintense white matter lesions on T2-weighted images were defined as 'non-specific white matter lesions' in our study. Given that one of the study objectives was to examine the familiarity of the neurologists with the relevant imaging findings regardless of the opinion of a radiologist in clinical practice, two neurologists experienced (Researcher 1: 32 years and Researcher 2: 13 years) in the field of neuro-imaging in a reference neurology center who were thought to be more familiar with these findings were included in the study. The standard form in this study consisted of 5 items and included structured questions with two options (present or absent) related to the aforementioned findings.
The SPSS v22.0 program was used for the statistical analysis of the data. The results were evaluated by using kappa (K) analysis in terms of interrater agreement.
Thirty-eight patients were female and 3 were male. The mean body mass index was 29.2[+ or -]5.48 and CSF opening pressure was 371[+ or -]149.4 mm[H.sub.2]O.
When MRI and MRV examinations were evaluated according to whether there was any additional finding supporting the diagnosis, there was fair agreement for MRI ([kappa] = 0.333, p = 0.021) and substantial agreement for MRV ([kappa] = 0.735, p<0.0001). Regarding subheadings, there was moderate agreement for empty sella (Figure 1), tortuosity of the optic nerve (Figure 1) and nonspecific white matter lesions ([kappa] = 0.417, p=0.001; [kappa] = 0.523, p=0.001; [kappa] = 0.443, p=0.002, respectively), fair agreement for flattened posterior globe/sclera and transverse venous sinus stenosis (Figure 2) ([kappa] = 0.291, p=0.06; [kappa]=0.389, p=0.006, respectively), and substantial agreement for transverse venous sinus hypoplasia ([kappa]=0.801, p<0.001) (Table 1).
Empty sella, tortuosity of the optic nerve, and transverse sinus stenosis were evaluated as 'present' by both raters with perfect agreement in six patients without papilledema, ([kappa]=1.00, p<0.0001).
Regarding possible individual variability in the evaluation of neuroimaging findings that are related to the increase in ICP and are defined to assist in the diagnosis of IIH without papilledema, MRI and MRV findings
of patients with IIH were evaluated by two blinded raters in this study and there was fair agreement for MRI and substantial agreement for MRV. Regarding subheadings, there was moderate agreement for empty sella, tortuosity of the optic nerve, and non-specific white matter lesions, fair agreement for flattened posterior globe/sclera and transverse venous sinus stenosis, and substantial agreement for transverse venous sinus hypoplasia.
IIH leads to an increase in CSF opening pressure without an intracranial mass or ventriculomegaly and its pathophysiology is not yet understood (12). Although the main role of neuro-imaging in IIH is to exclude other pathologies that cause increased CSF pressure, MRI findings that can be detected by modern neuroimaging methods such as empty sella, tortuosity of optic nerve, flattened posterior globe/sclera, contrast enhancement of vessels in the optic disc, meningocele formation, diffusion restriction at the optic nerve head, and transverse sinus stenosis were found to be related to diagnosis (13). Although the sensitivity and prevalence of these findings vary between 6% and 66% in the literature, it is debateable as to whether they are really helpful to physicians in diagnosing IIH in patients without the classic presentation, as in IIH cases without papilledema presenting with a chronic daily headache profile with migrainous features (6,9,14,15).
Although empty sella is the oldest and most commonly reported neuroimaging finding in patients with IHH, it is also common in the general population (16). Although the sensitivity of empty sella in IIH ranges from 65% to 80% and its specificity ranges from 70% to 100%, this finding is not specific to IIH and may be observed in various causes of chronic intracranial hypertension such as cerebral venous sinus thrombosis and intracranial mass lesions (15,17,18,19,20,21). In our study, there was a moderate agreement for empty sella ([kappa] = 0.417) among the raters, who were trained in the same clinic and are colleagues.
Ophthalmic neuroimaging findings in IIH reflect the mechanical deformations of the optic nerve sheath, lamina cribrosa, and posterior sclera due to increased CSF pressure transferred through the intraorbital optic nerve, and these findings are generally reported based on subjective radiologic interpretations in studies (18,22,23). The sensitivity of flattened posterior globe/sclera varies between 43% and 85%, whereas its specificity is 98% (15,17,18,23). Flattened posterior globe/sclera is not specific for IIH because it can also be seen in cases such as ocular hypotonia (24). Tortuosity of the optic nerve has a sensitivity of 43% and specificity of 90% in IIH based on only subjective impressions (15,18,23). Our study also supported this subjectivity and there were fair ([kappa] = 0.291) and moderate ([kappa] = 0.523) inter-rater agreement for flattened posterior globe/sclera and tortuosity of the optic nerve, respectively.
The main role of intracranial vascular imaging in patients with suspected IIH is cerebral venous sinus thrombosis (25) and, more rarely, the exclusion of dural fistulae. Advances in neuroimaging studies have enabled reliable visualization of transverse venous sinuses in patients with IIH, in whom focal stenosis was previously missed (26,27,28). Farb et al. (26) demonstrated the presence of bilateral transverse sinus stenosis with a sensitivity and specificity of 93% in patients with IIH using MRV In one study, according to the definition of transverse venous sinus stenosis, it was reported that 100% of the patients with IIH had bilateral stenosis on MRV (29). However, such bilateral transverse venous sinus stenosis is also common in patients with intracranial hypertension not associated with IIH (21,30) and it may also be seen in normal individuals (31). Although it is difficult to evaluate the sensitivity of bilateral transverse venous sinus stenosis due to inconsistent definitions in studies, the presence of artifact and the use of various venous imaging techniques, the pooled sensitivity of contrast-enhanced MRV is estimated to be 97% (26,29,32). Fair agreement ([kappa] = 0.389) between the raters in terms of transverse sinus stenosis in our study indicates that this finding can be interpreted differently between the evaluators and its value is not very reliable.
As mentioned in a previous study in our clinic (33), nonspecific white matter lesions, which are sometimes confused with demyelinating diseases by physicians in patients with IIH, were evaluated in our study although they are not included in the Friedman diagnostic criteria, and moderate agreement was found ([kappa]=0.443).
Although the two evaluators were experienced in their fields, the fair-to-moderate agreement for neuro-imaging findings defined in IIH in our study was interpreted in relation to the recent recognition of these imaging findings in the diagnosis of IIH, as well as the fact that these evaluations remained highly subjective in line with the literature.
When evaluating a patient with IIH, it was thought that it would be appropriate to exclude mass lesions and examine the neuro-radiologic images carefully in terms of new criteria, and to consider the clinical findings. The findings becoming measurable with the help of new studies will provide more standardized results when interpreting them.
Ethics Committee Approval: Retrospective study.
Informed Consent: Retrospective study.
Peer-review: Internally peer-reviewed.
Concept: B.S., E.S., E.E., N.Y., O.C., B.B., Design: B.S., E.S., E.E., N.Y., O.C., B.B., Data Collection or Processing: B.S., E.S., Y.S., E.E., N.Y., O.C., B.B., Analysis or Interpretation: B.S., E.S., E.E., N.Y., O.C., B.B., Literature Search: B.S., E.S., Y.S., E.E., N.Y., O.C., B.B., Writing: B.S., E.S., Y.S., E.E., N.Y., O.C., B.B.
Conflict of Interest: No conflict of interest was declared by the authors.
Financial Disclosure: The authors declared that this study received no financial support.
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[iD] Bedia Samanci (1), [iD] Erdi Sahin (1), [iD] Yavuz Samanci (2), [iD] Esme Ekizoglu (1), [iD] Nilufer Yegilot (1), [iD] Oguzhan Coban (1), [iD] Betul Baykan (1)
(1) Istanbul University Istanbul Faculty of Medicine, Department of Neurology, Istanbul, Turkey
(2) Tekirdag State Hospital, Clinic of Neurosurgery, Tekirdag, Turkey
Address for Correspondence/Yazisma Adresi: Bedia Samanci MD, Istanbul University Istanbul Faculty of Medicine, Department of Neurology, Istanbul, Turkey
Phone: +90 507 204 14 64 E-mail: firstname.lastname@example.org ORCID ID: orcid.org/0000-0003-0667-2329
Received/Gelis Tarihi: 10.03.2018 Accepted/Kabul Tarihi: 25.10.2018
Presented in: This study has been presented as a contradictive poster at 53rd National Neurology Congress.
Table 1. Comparison of neuroimaging findings of two researchers and interrater reliability Researcher Researcher Inter-rater reliability 1 (n) 2 (n) Empty sella 18 7 [kappa]=0.417, p=0.001 (**) Flattened 10 8 [kappa]=0.291, p=0.06 (*) posterior globe/sclera Tortuosity of the 13 16 [kappa]=0.523, p=0.001 (**) optic nerve Transverse sinus 23 14 [kappa]=0.389, p=0.006 (*) stenosis Transverse sinus 19 15 [kappa]=0.801, p<0.001 (***) hypoplasia Non-specific white 10 5 [kappa]=0.443, p=0.002 (**) matter lesions (*) Fair agreement, (**) Moderate agreement, (***) Substantial agreement
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|Title Annotation:||Original Article / Ozgun Arastirma|
|Author:||Samanci, Bedia; Sahin, Erdi; Samanci, Yavuz; Ekizoglu, Esme; Yegilot, Nilufer; Coban, Oguzhan; Bayka|
|Publication:||Turkish Journal of Neurology|
|Date:||Jun 1, 2019|
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