Analysis and characterization of interhypothalamic adhesions in adults: No longer only a pediatric finding

Abstract

Background and purpose: Inter-hypothalamic adhesions (IHAs) are parenchymal tissue bridges traversing the third ventricle, previously reported only in the pediatric population. We aim to understand the prevalence of IHA in the adult population, assess their size and location, and ultimately investigate whether IHA volumes correlate with age.

Materials and methods: Patients who underwent routine high-resolution 3D T2WI MRI studies of the temporal bone/internal auditory canal at an otolaryngology clinic between 2008 and 2014 were consecutively selected. The presence of IHAs was confirmed when a parenchymal structure could be traced across the third ventricle, connecting bilateral hypothalamus, and was visible in at least two planes. They were classified based on their location within the third ventricle, considering their connection with hypothalamic nuclei. Patient clinical information were collected from electronic charts. The prevalence and volumes of IHAs were calculated. Associations between age and IHA volume, as well as between IHA type, age, volume, and gender, were analyzed.

Results: 779 patients, with a mean age of 54.7 years were included. Among them, 44 IHAs were identified within 41 patients, resulting in a prevalence of 5.26% in our cohort. Type 1 IHA was the most frequently encountered type, comprising 70.5% of all cases. No significant correlation was observed between IHA volumes and age. Additionally, no associations were found between IHA type and age, volume, or gender.

Conclusion: IHAs are not exclusive to the pediatric population; they are also present in adults, with a prevalence of 5.26% in patients undergoing temporal bone/internal auditory canal MRI.

Keywords: Inter-hypothalamic adhesion; hypothalamic adhesion; magnetic resonance imaging; prevalence; volumetric assessment.

Figure 1.

Patient selection flowchart FOV: Field of View, n: Number.

Figure 2.

Visual evaluation of IHAs was conducted using high-resolution 3D T2WI MRI scans primarily acquired for imaging of the temporal bone/internal auditory canal but extending into the third ventricle. All patients underwent evaluation in three different planes: (A) coronal, (B) sagittal, and (C) axial. A positive result was considered if adhesions were visually identifiable in at least two different planes. White arrows show lamina terminals, yellow arrowheads show a type 1b IHA. IHA: Inter-hypothalamic Adhesion.

Figure 3.

Anatomical Categorization of IHAs. An imaginary oblique line between the SR and IR divides the third ventricle into anterior and posterior compartments. Type 1 IHAs are located in the anterior segment and are further subdivided based on their distance from the lamina terminalis (a: adjacent, b: ≤1 mm, c: >1 mm). Type 2 IHAs are located superior to the IR and might extend into both compartments. Type 3 IHAs are located in the posterior compartment (a: not contacting the floor, b: adjacent to the floor). IHA: Inter-hypothalamic Adhesion, AC: anterior commissure, LT: lamina terminalis, OC: optic chiasm, TC: tuber cinereum, MB: mammillary body, SR: supraoptic recess, IR: infundibular recess.

Figure 4.

Examples for each defined subtype.

Figure 5.

Population chart showing number of positive cases in each age. IHA: Inter-hypothalamic Adhesion.

Figure 6.

Volumetric assessment of each identified inter-hypothalamic adhesion is distributed by age. There was no correlation between age and IHA volume. IHA: Inter-hypothalamic adhesion.