Ultrasound-guided initial diagnosis and follow-up of pediatric idiopathic intracranial hypertension

Abstract

Background: Idiopathic intracranial hypertension in children often presents with non-specific symptoms found in conditions such as hydrocephalus. For definite diagnosis, invasive intracranial pressure measurement is usually required. Ultrasound (US) of the optic nerve sheath diameter provides a non-invasive method to assess intracranial pressure. Transtemporal US allows imaging of the third ventricle and thus assessment for hydrocephalus.

Objective: To investigate whether the combination of US optic nerve sheath and third ventricle diameter can be used as a screening tool in pediatric idiopathic intracranial hypertension to indicate elevated intracranial pressure and exclude hydrocephalus as an underlying pathology. Further, to analyze whether both parameters can be used to monitor treatment outcome.

Materials and methods: We prospectively included 36 children with idiopathic intracranial hypertension and 32 controls. Using a 12-Mhz linear transducer and a 1-4-Mhz phased-array transducer, respectively, optic nerve sheath and third ventricle diameters were determined initially and during the course of treatment.

Results: In patients, the mean optic nerve sheath diameter was significantly larger (6.45±0.65 mm, controls: 4.96±0.32 mm) and the mean third ventricle diameter (1.69±0.65 mm, controls: 2.99±1.31 mm) was significantly smaller compared to the control group, P<0.001. Optimal cut-off values were 5.55 mm for the optic nerve sheath and 1.83 mm for the third ventricle diameter.

Conclusions: The combined use of US optic nerve sheath and third ventricle diameter is an ideal non-invasive screening tool in pediatric idiopathic intracranial hypertension to indicate elevated intracranial pressure while ruling out hydrocephalus. Treatment can effectively be monitored by repeated US, which also reliably indicates relapse.

Keywords: Idiopathic intracranial hypertension; Non-invasive diagnosis; Optic nerve sheath diameter; Pediatric; Pseudotumor cerebri; Third ventricle diameter; Ultrasound.

Fig. 1

B-scan ultrasound (US) of the optic nerve sheath and third ventricle diameters in a 13-year-old girl from the control group. a For transorbital US examination, a 12-Mhz linear transducer is placed axially on the closed eyelid. The examiner’s hand can be placed lightly on the side of the patient’s head to improve stability. b For transtemporal US examination, a 1–4-MHz phased-array transducer is placed axially and pre-auricularly between the lateral canthus and the upper border of the ear. The probe orientation marker on the side of the probe should be oriented forward so that the frontal intracranial structures appear on the left side of the monitor. c Transorbital US of the optic nerve sheath diameter (4.71 mm) with exact region of optic nerve sheath diameter measurement (arrows). The optic nerve (ON) appears hypoechogenic. d Transtemporal US of the third ventricle diameter (3.1 mm), showing hyperechogenic walls of the third ventricle (thin arrows), bilateral, hypoechogenic-appearing thalami (asterisks), hyperechogenic-appearing pineal gland (thick arrow), ipsilateral brain parenchyma (arrowhead), and contralateral skull bone (broken arrow). e 1.5× magnification of a section of (d) showing the region of the third ventricle. Area of exact third ventricle diameter measurement (solid line) and the midline of the brain (broken line)

Fig. 2

B-scan ultrasound (US) of the optic nerve sheath and third ventricle diameters in an 11-year-old girl with idiopathic intracranial hypertension. a Transorbital US shows an enlarged optic nerve sheath diameter (6.48 mm). The optic nerve (ON, thick line and arrow) appears hypoechogenic and is surrounded by the partially hyperechogenic optic nerve sheath. The wall of the optic nerve sheath appears hyperechogenic. The sheath contains the hypochogenic-appearing optic subarachnoid space, that is filled with cerebrospinal fluid and subdivided by multiple trabeculae [28], with hyperechogenic appearance (asterisks). The outer border of the optic nerve sheath (thin arrows) is the exact region of optic nerve sheath diameter measurement. Area of optic nerve sheath diameter measurement, 3 mm posterior to the retina (black arrows), retina (broken line). The vitreous body appears hypoechogenic. b Transtemporal US shows narrow third ventricle diameter (0.9 mm). Bilateral thalami (asterisks) and hyperechogenic walls of the third ventricle (arrows)

Fig. 3

Baseline US optic nerve sheath and third ventricle diameters in idiopathic intracranial hypertension and control group. Box-plot diagram of US optic nerve sheath and third ventricle diameter in mm, ***P<0.001., ONSD optic nerve sheath diameter, TVD third ventricle diameter, US ultrasound

Fig. 4

Receiver operating characteristic (ROC) analysis of ultrasound (US) optic nerve sheath diameter, US third ventricle diameter and combined use of US optic nerve sheath and third ventricle diameters to detect idiopathic intracranial hypertension in children. a Area under the ROC (AUROC) curve for US optic nerve sheath diameter cut-off value (≥5.55 mm). b AUROC curve for US third ventricle diameter cut-off value (≤1.83 mm). c Combined use of US optic nerve sheath and third ventricle diameter cut-off values, n=68. IIH idiopathic intracranial hypertension, NPV negative predictive value, ONSD optic nerve sheath diameter, OR odds ratio, PPV positive predictive value, TVD third ventricle diameter

Fig. 5

Follow-up ultrasound (US) optic nerve sheath and third ventricle diameter in children with idiopathic intracranial hypertension. Box-plot diagrams of (a) US optic nerve sheath diameters prior to, after treatment, and during long-term follow-up with significant decrease of optic nerve sheath diameter in 27 patients after initial treatment and in five children after relapse therapy (b) US third ventricle diameter prior to, after treatment, and during long-term follow-up with significant increase of third ventricle diameter in 16 patients from pre to follow-up 1 and significant increase in five children after relapse therapy. Follow-up time details are given in b. *P<0.05, **P<0.01, ***P<0.001. FU follow-up, m month, ONSD optic nerve sheath diameter, Post^a after initial treatment, Post^b after treatment for recurrence, Pre before initial treatment, Rec. recurrence, SD standard deviation, TVD third ventricle diameter