Evaluation of optic nerve with ultrasound elastography in patients with idiopathic intracranial hypertension: a case-control study

Abstract

Aim of study. Idiopathic intracranial hypertension (IIH) is a neurological condition characterised by increased intracranial pressure without a known cause, usually seen in young obese women. Optic nerve ultrasound elastography is a new imaging technique that evaluates the elastic properties of the optic nerve. In this method, deformations caused by mechanical forces applied on the optic nerve are measured using ultrasound waves and the elastic properties of the optic nerve are analysed. This study aimed to evaluate optic nerve (ON) and retrobulbar adipose tissue (RAT) elasticity, optic nerve sheath diameter (ONSD), and optic disc height (ODH) in patients with IIH. Clinical rationale for study. Demonstration of structural changes in the optic nerve in IIH patients. Material and methods. In this prospective study, bilateral ON and optic disc measurements were performed in 30 consecutive patients with IIH and 30 age- and sex-matched healthy volunteers. ONSD, ODH, and SWE (shear wave elastography) of the ON, and SWE of the RAT, were measured. Results. Of 30 patients with IIH, 26 were female and four were male. The mean age of the patients diagnosed with IIH was 37.9 ± 9.9 years and the mean age of the control group was 38.9 ± 10.5 years (p = 0.594). Similarly, no significant difference was found between the two groups in terms of body mass index (BMI): the mean BMI of the patients was 30.8 ± 5.51 and the mean BMI of the control group was 29.6 ± 4.7 (p = 0.214). In the patients, mean ONSD (4.8 ± 1.4 mm), ODH (1.04 ± 1.06 mm), ON SWE [14.7 (4.57–100.7) kPa], and RAT SWE [4.05 (1.6–11. 3) kPa] significantly differed from those in the control group: ONSD (3.1 ± 0.4 mm), ODH (0.4 ± 0.09 mm), ON SWE [10.3 (4.8–42.9) kPa], and RAT SWE [3.58 (1.5–16.7) kPA] (p = 0.001, p = 0.001, p = 0.01, p = 0.033, respectively). The cut-off values for ONSD, ODH, ON SWE and RAT SWE to discriminate IIH patients from controls were 3.5 mm, 0.5 mm and 11.37 kPa and 3.63 kPA, respectively, areas under the curve (AUC) were 0.888, 0.892, 0.67 and 0.613, respectively, and accuracy values were 80%, 81%, 61% and 60%, respectively. Conclusions. ON SWE, RAT SWE, ONSD and ODH measurements may be helpful in the diagnosis of IIH in addition to current imaging methods. Clinical implications. We observed structural changes in the optic nerve and surrounding fatty tissue in IIH, and these factors should be taken into account in future diagnosis and treatment.