Specific brain imaging signs may help clinicians improve triage in patients with spontaneous intracranial hypotension (SIH), new research suggests.
Although a disabling orthostatic headache and other symptoms generally point to a diagnosis of SIH, management of the disorder can be less certain. Now a new scoring system based on six objective MRI signs may aid the management of the condition.
In a study of 136 participants, a low score identified those with a low likelihood of having a cerebral spinal fluid (CSF) leak with 93% sensitivity and 93% specificity. At the same time, a high score correctly identified those with a high chance of a CSF leak with 79% sensitivity and 98% specificity.
"The proposed score is easy to use and may help headache specialists to assess objectively whether SIH patients should further be investigated," principal investigator Tomas Dobrocky, MD, deputy senior physician at the University Institute of Diagnostic and Interventional Neuroradiology, Inselspital, University of Bern, Switzerland, told Medscape Medical News.
The findings were published online February 18 in JAMA Neurology.
No Validated System
Despite well-established diagnostic signs of SIH, and prior studies evaluating MRI findings in this patient population, to date there is no validated classification system based on the most relevant imaging features, the researchers note.
For example, subdural fluid collection, enhancement of the pachymeninges, engorgement of venous structures, pituitary hyperemia, and sagging of the brain are among the individual, classic MRI signs of SIH.
For the study, the investigators reviewed all the reported brain MRI signs, identified the three most relevant qualitative and the three most relevant quantitative findings, weighed their importance, and then validated the 9-point scoring system in a "real-life" cohort of patients.
Their approach stratifies patients into low (a score of 2 or less), intermediate (3 or 4), or high probability (a score of 5 or more) of having an underlying CSF leak.
Classifying patients this way could identify those "who may benefit from more invasive myelographic examinations and subsequent targeted therapy," the researchers write.
Use of intrathecal contrast media, for example, could reveal a spinal CSF leak that warrants treatment with an epidural blood patch or microsurgical exploration, Dobrocky said.
The investigators assessed 56 patients (71% women; mean age, 45 years) who presented with SIH and a dural CSF leak confirmed on CT myelography between February 2013 and October 2017. This "derivation cohort" was used to identify the most relevant signs. Clinical symptom duration in the participants ranged from a few days to several years.
The study also included 60 patients acting as the healthy control group who were matched for age and sex. This group did not experience headaches and had unremarkable MRI brain imaging.
An independent neuroradiologist and two neuroradiology fellows, each blinded to individual patient details, evaluated brain MRI scans.
The researchers also took the extra step of validating their scoring system in a separate cohort of 20 consecutive patients. This "validation cohort" presented between November 2017 and August 2018 with suspected SIH, and included 11 people with myelographically established CSF leak on CT exam and nine without a CSF leak.
High Sensitivity, Specificity
Three of the criteria included in the scoring system were major signs: pachymeningeal enhancement, engorgement of venous sinus, and effacement of the suprasellar cistern of 4.0 mm or less. These features each received three points.
In addition, three minor signs were identified: subdural fluid collection, effacement of the prepontine cistern of 5.0 mm or less, and mamillopontine distance of 6.5 mm or less. Each of these features received one point.
Presence of these six signs varied significantly between the derivation cohort and control group participants (P < .001).
A total 60 participants scored a 2 or less, suggesting a low probability of a CSF leak. This outcome included 56 people with a true negative result and 4 with a false negative.
In contrast, 45 other participants scored a 5 or more. In all but one of these patients, the scoring system correctly identified a CSF leak.
"The good discriminatory ability of the proposed score was confirmed in a real-life setting," the researchers write.
For example, the scoring system correctly classified seven people in this cohort as having a low likelihood for a CSF leak. This correlated with 100% sensitivity and 78% specificity.
At the same time, nine of 10 participants who scored 5 or greater did in fact have a CSF leak, for an 82% sensitivity and 89% specificity.
When asked, Dobrocky said he was surprised by some of the findings.
"According to our results, some traditionally reported signs on brain MRI in SIH patients are actually quite rare — tonsillar descent, for example. Some quantitative signs previously reported had a very low inter-rater agreement and were not considered in the final score," he said.
The motive to create a clinical scoring system was, in part, personal, Dobrocky said.
"Our hospital is a referral center for headache, including patients with suspicion for intracranial hypotension," he said. "Consequently we are often faced with the question [of] whether further investigations should be performed."
Although a dynamic myelographic technique is necessary to localize a CSF leak precisely, such interventions are invasive, time-consuming, costly, and demanding for patients and caregivers, the researchers note.
Triaging based on MRI findings instead could make sense "because brain MRI is the first imaging of choice in the workup of patients with clinical suspicion for SIH, to rule out an underlying intracranial pathology."
Promptly consider an epidural patch when a patient scores a 5 or greater, the investigators suggest. In contrast, when a patient scores a 2 or less, they recommend noninvasive spine imaging to rule out presence of epidural CSF.
They add that they do not advocate invasive diagnostic imaging requiring intrathecal injection of contrast and ionizing radiation for patients with a lower probability of a CSF leak.
The investigators have plans to expand the current research.
"Our future goal is the verification of the score in a larger multicenter cohort," Dobrocky said.
Commenting on the findings to Medscape Medical News, Kaustubh Limaye, MD, clinical assistant professor of neurology at the University of Iowa in Iowa City, called SIH a "clinical and radiologic diagnostic dilemma."
"Paucity of hallmark symptoms and signs in this condition often delay the diagnosis and pose a management challenge," Limaye said.
The investigators proposed a radiologic diagnostic score of six imaging signs with good inter-rater reliability and discriminative power chosen from among commonly described seven qualitative and nine quantitative radiologic signs, he added.
"This scoring was tested on a prospective cohort of patients and was found to have a high diagnostic accuracy," said Limaye, who was unaffiliated with the current research. However, he was principal investigator for a previous review article evaluating SIH from diagnosis to management.
"This scoring may help physicians to better triage patients before they are scheduled for more invasive tests," he said.
Limitations of the study include its retrospective nature, single-center design, and small sample size, Limaye added.
Dobrocky and Limaye have reported no relevant financial disclosures.
JAMA Neurol. Published online February 18, 2019. Abstract
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Cite this: Damian McNamara. New Scoring System May Aid Intracranial Hypotension Management - Medscape - Feb 25, 2019.