Endoscopic Third Ventriculostomy for Hydrocephalus with Interhypothalamic Adhesion: A Case Report and Literature Review

Summary

Endoscopic third ventriculostomy (ETV) treats obstructive hydrocephalus by creating a new cerebrospinal fluid pathway. Interhypothalamic adhesion (IHA), a rare congenital anomaly, can complicate surgery by obscuring reference points. While it is crucial to avoid damaging the IHA, ETV can be performed with careful planning and imaging guidance.

Abstract

Endoscopic third ventriculostomy (ETV) is a well-established treatment for obstructive hydrocephalus; however, anatomical variations, such as the interhypothalamic adhesion (IHA), may obscure critical third ventricular landmarks and complicate intraoperative orientation. IHA is a rare congenital band of neural tissue connecting the medial hypothalamic walls and may pose a technical challenge during ventricular endoscopy. A case of obstructive hydrocephalus in which IHA was encountered during ETV is presented, and a structured surgical approach to safely perform ventriculostomy without disrupting the adhesion is described. Preoperative magnetic resonance imaging was used to assess ventricular anatomy and to plan the trajectory. Intraoperative ultrasound guidance facilitated accurate ventricular access. After identification of the infundibular recess and mammillary bodies, the third ventricular floor was perforated anterior to the mammillary bodies using a blunt instrument. A balloon catheter was employed to dilate the fenestration while minimizing traction on the IHA. Adequate cerebrospinal fluid flow was confirmed endoscopically. Postoperative imaging demonstrated stoma patency, and the patient showed clinical improvement during follow-up. This case illustrates that the presence of IHA does not preclude successful ETV when critical landmarks are clearly visualized, and a methodical intraoperative strategy is followed. Preservation of the adhesion may enhance procedural safety, and ventriculoperitoneal shunting should remain a secondary option when anatomical constraints prevent safe fenestration.

Introduction

Hydrocephalus is a life-threatening condition characterized by abnormal ventricular enlargement due to abnormal cerebrospinal fluid (CSF) dynamics. It is one of the most common neurosurgical conditions in pediatric patients and usually presents as progressive head enlargement in infants or increased intracranial pressure in older children¹. The etiology of hydrocephalus is multifactorial, encompassing both congenital forms associated with genetic abnormalities and acquired conditions that disrupt cerebrospinal fluid dynamics. These may include mechanisms involving impaired ventricular outflow, dysfunction of the subarachnoid space, altered cerebral pulsations, decreased cerebral compliance, and, more recently, proposed regulation of water transport^2,3,4,5.

Congenital hydrocephalus is associated with genetic abnormalities affecting brain development, while acquired cases result from disturbances in ventricular drainage, subarachnoid space function, or cerebral venous compliance^4,6,7. Early diagnosis and surgical intervention, including ventriculo-peritoneal shunting (VPS) or endoscopic procedures, remain critical to reduce morbidity and mortality⁸. While VPS provides effective and immediate CSF diversion, it is associated with long-term shunt dependency and potential complications such as infection, obstruction, and repeated revision surgeries. In contrast, endoscopic third ventriculostomy (ETV) offers a shunt-independent alternative by restoring physiological CSF circulation in selected patients with obstructive hydrocephalus. However, the success of ETV largely depends on favorable ventricular anatomy and clear identification of critical third ventricular landmarks.

Interhypothalamic adhesion (IHA), a recently identified variation, is defined by a parenchymal band connecting the medial margins of the hypothalamus across the third ventricle (Figure 1)^9,10. It is associated with anomalies such as grey matter heterotopia, cleft palate, optic atrophy, cerebellar hypoplasia, hippocampal under-rotation, and white matter lesions¹⁰. IHAs may result from defective programmed cell death, impaired migration, or accessory hypothalamic tissue during embryological development of the lamina terminalis¹¹. Importantly, the presence of IHA may pose a technical challenge to ETV by obstructing the third ventricular floor or altering critical anatomical landmarks. In such cases, distortion of the infundibular recess, mammillary bodies, or tuber cinereum may increase the risk of inaccurate fenestration or injury to adjacent neural and vascular structures¹². Furthermore, thickened third ventricular floor, narrow prepontine cistern, or unclear basilar artery visualization may compromise procedural safety and limit the feasibility of ETV. Therefore, a thorough preoperative imaging assessment is imperative to determine the feasibility and safety of ETV on an individual basis. Careful evaluation of ventricular size, floor thickness, prepontine cistern patency, and spatial relationship between the adhesion and the intended fenestration site is essential in patient selection^13,14. The aim of this study is to review the literature on a pediatric case of IHA and hydrocephalus that was treated with ETV.

CASE PRESENTATION:
A 2.5-year-old girl with a history of omphalocele repair was admitted to the Pediatric Emergency Unit with complaints of difficulty maintaining balance while sitting. Neurologic examination findings were as follows: spontaneous respiration, spontaneous eye opening, and isochoric pupils. Light reflexes were positive. Spontaneous movement of all extremities was equal and adequate. The patient was able to articulate individual words. Her head circumference measured 50.5 cm, exceeding the 90th percentile, and the fontanelle was distended.

DIAGNOSIS:
Following an emergency evaluation, the patient underwent non-contrast cranial computed tomography (CT), which revealed findings consistent with triventricular hydrocephalus and a band-like formation in the hypothalamic and thalamic region (Figure 2). The Evans index was calculated as the ratio of the maximum frontal horn width to the maximum internal diameter of the skull on axial imaging and was 0.48, confirming significant ventricular enlargement. Subsequent magnetic resonance imaging (MRI) was performed to exclude an underlying mass lesion and to better characterize the intraventricular anatomy. MRI confirmed marked triventricular hydrocephalus and revealed a band-like parenchymal structure extending between the medial hypothalamic walls, consistent with IHA, in addition to an interthalamic adhesion (Figure 3). The callosal angle measured 44°, supporting pathologic ventriculomegaly. The third ventricle was enlarged, and mid-sagittal imaging demonstrated a preserved prepontine cistern without evidence of a posterior fossa mass lesion. Findings were consistent with aqueductal stenosis, confirming an obstructive pattern of hydrocephalus. Given the clinical signs of increased intracranial pressure and radiologic confirmation of obstructive hydrocephalus secondary to aqueductal stenosis, the emergency situation was explained to the patient’s legal guardians, and urgent surgical intervention was planned.

Protocol

This study describes a single patient case and does not constitute human subject research according to institutional policies. Formal Institutional Review Board approval was therefore not required. Written informed consent for the surgical procedure and publication of clinical and radiological data was obtained from the patient’s legal guardians. All procedures were conducted in accordance with institutional guidelines and the principles of the Declaration of Helsinki.

1. Preoperative preparation

1. The patient was transferred to the operating room for emergency surgical intervention.
2. Positioned in the supine position under general anesthesia.
3. A soft head support was utilized to achieve approximately 10 degrees of neck flexion.
4. The coronal suture was identified through palpation.
5. The site was marked at a point 2.5 cm anterior to the coronal suture and approximately 2.5 cm lateral to the midline on the right frontal.
6. Following standard aseptic and antiseptic protocols, the surgical field was prepared.

2. Operation

1. A 5 cm linear incision was made centered on the marked point.
2. Hemostasis was achieved using bipolar cautery.
3. Skin and subcutaneous tissues were dissected, and an automated skin retractor was placed.
4. The periosteum was removed with an Adson periosteal elevator.
5. A burr hole was created slightly lateral to Kocher’s point using a high-speed perforator. The lateral semicircular margin of the burr hole was removed using a high-speed drill and Kerrison rongeur to accommodate the insertion of the endoscopic working channel under ultrasound guidance.
6. The thin layer of bone remaining on the dura was removed with a dissector.
7. Intraoperative ultrasound was used to visualize the lateral ventricles, the Foramen of Monro, and the third ventricle. A high-frequency linear probe (7–12 MHz) was utilized with a depth setting of approximately 4–6 cm.
8. Gain was adjusted to optimize ventricular wall visualization while minimizing artifact. Sterile saline was intermittently applied to the burr hole to improve acoustic coupling and image clarity.
9. The ultrasound puncture probe was connected to the endoscope working channel.
10. The dura was opened in a crossed shape using a #11 scalpel.
11. Bipolar cautery was applied to coagulate the underlying pia mater.
12. The endoscope working channel was inserted perpendicular to the brain parenchyma under real-time ultrasound guidance. Upon reaching the lateral ventricle, the flow of CSF from the working cannula was observed.
13. Trajectory was continuously adjusted to target the ipsilateral frontal horn while avoiding the caudate nucleus and cortical veins. Safe ventricular entry was confirmed by sudden loss of resistance and free CSF egress through the cannula.
14. The endoscope working channel was held in place, and the trocar and ultrasound probe were withdrawn.
15. The endoscope was then inserted through the working channel.
16. Within the lateral ventricle, the choroid plexus, the Foramen of Monro, the septal vein, and the thalamostriate vein were identified under direct endoscopic visualization. The band-like adhesions were observed at the level of the Foramen of Monro.
17. Safe passage through the Foramen of Monro was confirmed by visual identification of both the septal and thalamostriate veins forming the venous angle, ensuring that the endoscope advanced medial to the choroid plexus and without contact with venous structures. Without damaging them, the endoscope was passed through the Foramen of Monro and into the third ventricle (Figure 4).
18. The floor of the third ventricle, including the IHA, infundibular recess, and mammillary bodies, was identified.
19. A blunt perforation was performed using the tip of a monopolar coagulator in the most translucent region of the third ventricular floor (between the mammillary bodies and the infundibular recess) without damaging the IHA.
20. The correct fenestration site was confirmed by identifying the mammillary bodies posteriorly and the infundibular recess anteriorly, ensuring midline orientation and visualization of the basilar artery pulsation beneath the floor prior to perforation.
21. A 4F balloon catheter was inserted through the initial fenestration, and the balloon was repeatedly inflated and deflated to gradually widen the opening to approximately 5 mm in diameter. Balloon inflation was performed incrementally under direct visualization to avoid excessive traction on the surrounding ventricular floor and IHA.
22. Cerebrospinal fluid flow was observed upon deflation of the balloon. Adequate CSF circulation was confirmed by visualization of pulsatile flow through the stoma and free communication with the prepontine cistern, including clear visualization of basilar artery pulsations beneath the fenestration.
23. The endoscopic system and automatic skin retractor were then removed.
24. The final hemostasis was achieved using bipolar cautery.
25. Subcutaneous tissue was approximated with 3-0 absorbable polyglactin sutures, and skin closure was completed using surgical staplers. The procedure was completed after confirmation of hemostasis, adequate stoma patency, and absence of intraoperative complications.

Results

Postoperatively, the patient received analgesics (acetaminophen or ibuprofen) for pain control. A non-contrast cranial CT scan was obtained within 24 h to exclude hemorrhage (Figure 2). Neurological examinations were performed hourly during the first 24 h and every four hours thereafter until discharge. The patient was discharged on postoperative day two with instructions for wound care and outpatient follow-up. Because the patient was pediatric and required...

Discussion

Hydrocephalus remains a significant global health challenge. Walter Dandy, in 1913, classified hydrocephalus into two primary categories: communicating (non-obstructive) and non-communicating (obstructive). This classification forms the foundation of the understanding of this condition and has guided subsequent research into its pathophysiology and management¹⁵. Since Dandy’s pioneering work, advances in technology and surgical techniques have significantly improved outcomes for patients wit...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Adson periosteal elevator	Ruggles-Redmond	RO263	Semi-sharp, 5 mm, curved 6-3/8, length 164 mm
Automatic skin retractors	Integra	3,72,245	Heiss Automatic Skin Retractor Length - Overall (mm): 102 Length 1 - Tip/Jaw (mm): 8
Balloon catheter	Edwards Fogarty	120804FP	Length (cm): 80, Catheter size (F):4,  Inflated balloon diameter (mm):9
Bisture	Beybi	24,02,502	Beybi Bisture Tip. No:20 and No:11
High-speed drill	Medtronic Midas Rex MR8	MR8 Electric Plus EM850	Perforator tip used
Kerrison Rongeur	Aesculap	FK950B	Length (cm): 7 in, Jaw Size widht: 3.0 mm, Jaw opening: 10.0 mm
Operating sheath	Karl Storz LOTTA	28164 LSB	Graduated, rotating, outer diameter 6.8 mm, working length 13 cm
Trocar	Karl Storz LOTTA	28164 LLO	Use with Operating Sheaths for ventricular puncture
Ultrasound	BK	bk5000	Use via N11C5s Transducer (9063) for ventricular puncture
Ventriculoscope	Karl Storz LOTTA Ventriculoscope with HOPKINS	28164 LAB	Wide angle telescope 30°, angled eyepiece, outer diameter 6.1 mm, length 18 cm, working channel diameter 2.9 mm, irrigation/suction channel diameter 1.6 mm