Idiopathic Intracranial Hypertension Tied to Thinning of Skull Base, Calvarial Thickness

Idiopathic intracranial hypertension (IIH) is associated with thinning of the skull base and calvarial thickness, according to a retrospective, case-control study published in the Journal of Neuro-Ophthalmology.

Researchers divided 126 participants into 2 groups: 63 with an IIH diagnosis and 63 with a headache diagnosis (controls). Both groups had 61 women (97%) and the mean age was 31.5±8.7 years. Each control was chosen to match each case by age, sex and race. Adult patients were included if they underwent computed tomographic (CT) scans of the head, maxillofacial, or orbits within 3 months of their diagnosis. Exclusion criteria consisted of prior history of skull base or frontal bone pathology due to surgery or skull trauma, central nervous system infections, or incomplete radiologic data. 

Investigators used coronal and axial imaging to measure the thickness of the skull base (height of the internal auditory canal in the coronal plane) and the calvarium (measurement just anterior to foramen rotundum in the coronal plane). They measured and used zygoma thickness as an internal imaging control because it is not affected by intracranial forces.

The research team found that more patients with IIH had obesity (n=60, 95%) than control patients (n=23, 37%, P<.001). They noted no difference (P >.05) in smoking status, hypertension, obstructive sleep apnea, and oral or intravenous steroid use between both groups.  

All patients with IIH underwent lumbar puncture (LP) with an average opening pressure (OP) of 40.5±15.6 cm H₂O, while only 13 (20%) controls underwent an LP with an average OP of 19.5±8.5 cm H₂O, according to the report. No statistical differences were found in mean visual acuity between IIH and controls (logMar 0.22±0.45 logMar vs 0.09±0.30 logMar, P =.093, respectively). When compared with controls, patients with IIH were more likely to experience headache (97% vs 74%, P =.001), pulsatile tinnitus (48% vs 7%, P <.001), horizontal binocular diplopia (24% vs 4%, P =.006), confrontational visual field deficit (23% vs 2%, P =.003), and papilledema (74% vs 0%, P <.001).  

The study also found that patients with IIH showed thinner skull base and calvarium width compared with the controls (mean skull base thickness 4.17±0.94 mm vs 5.05±1.12 mm, P <.001 and mean calvarial width 1.50±0.50 mm vs 1.71±0.61 mm, P =.024). The researchers noted that Zygoma thickness was similar among both groups (mean zygoma thickness 1.18±0.30 mm in the IIH group vs 1.26±0.35 mm in the control group, P =.105). There was no statistically difference in skull base, calvarial, or zygoma thickness between patients with and without obesity, according to the subgroup analysis controlling for obesity.

This is the first study to demonstrate that IIH is associated with thinning of the skull base and calvarial thickness, the investigators report. Contrary to previous research, they found no association between obesity and thinning of the skull base or calvarial thickness.  

“Our study found that IIH was independently associated with skull base and calvarial thinning after controlling for known factors such as age, race, gender, OSA, and history of spontaneous cerebrospinal fluid (CSF) leaks,” according to the study authors. “Overall, this study adds to the discussion of skull base thinning and its complex associations with obesity, OSA, spontaneous CSF leaks, and now IIH.”

Study limitations include the retrospective design, potential selection bias, and failure to identify other factors which may contribute to thinning of the skull base and calvarial thickness. 

Reference

Barke M, Castro HM, Adesina O, et al. Thinning of the skull base and calvarial thickness in patients with idiopathic intracranial hypertension. J Neuro-ophthalmol. Published online February 15, 2022. doi:10.1097/WNO.0000000000001504