Pineal Region Angiolipoma Resection by Supracerebellar Infratentorial Endoscopic Approach: A Case Study

Introduction

The pineal region is located deep in the center of the brain, making it a neurosurgeon’s “forbidden zone”. The pineal region tumors are usually divided into 5 broad categories: germ cell tumors, pineal parenchymal tumors, papillary tumors, benign pineal region tumors, and glial tumors. These pineal region tumors are relatively infrequent, comprising about 1.2% of all central nervous system (CNS) tumors [1]. However, the deep location of the pineal region, surrounded by complicated and vital neurovascular structures, remains a challenging target for neurosurgeons. Wide surgical exposure is crucial and often used to approach this area, causing considerable operative morbidity and mortality [2]. The endoscopic supracerebellar infratentorial (SCIT) approach provides a less invasive access to the pineal region by taking advantage of the natural skull base corridors [3,4]. Angiolipomas (ALs), first identified as a specific disease in the 1960s, are benign mesenchymal-derived tumors. However, intracranial ALs are extremely rare, and as opposed to intraspinal ALs, they are generally subdural and often occur in the sellar and parasellar areas [5]. This report describes a 23-year-old man presenting with ataxia and bilateral upper-limb tremor due to a pineal region AL resected endoscopically by SCIT approach.

Case Report

A 23-year-old man was transferred to our hospital with chief concerns of ataxia and low-frequency resting tremor of both upper limbs for 1 month. General physical and blood biochemical examinations were normal, and his personal history was unremarkable. Additionally, he denied experiencing any seizure-like symptoms or other symptoms or signs of raised intracranial pressure, such as nausea, vomiting, and visual disturbances. Cranial computed tomography (CT) scans demonstrated an irregular-shaped supracerebellar infratentorial hypodense mass, and dynamic brain magnetic resonance imaging (MRI) showed an obviously enhancing pineal region lesion (20×26×29 mm) with mass effect on the quadrigeminal bodies of the midbrain (Figure 1A–1D). It had uniformly high signal on T1-weighted (T1W) and T2-weighted (T2W) imaging, inhibited on recovery of short tau inversion, but not inhibited on diffusion-weighted imaging (DWI), corresponding to an adipose tissue signal. Additionally, MRI scans also revealed some flow void signals of blood vessels within the mass. These features suggested that the lesion might be a lipoma with vascular components.

After completing the preoperative preparation, the patient underwent tumor removal via a purely endoscopic SCIT approach. The surgical procedures were performed using the same micro-surgical techniques, but with endoscopic illumination from far to near, which made it possible to obtain a panoramic scene along the midline trajectory and clear details of the surgical field. The intraoperative findings revealed an encapsulated, yellowish, solid, fatty tumor mass extending from the upper vermis of the cerebellum to the pineal region, with rich blood supplies (Figure 2A, 2B). The venous complex in the pineal region was well-visualized and protected (Figure 2C). Some calcification existed between the cerebellum vermis and the tumor. The tumor was first debulked and then gradually totally removed piece-by-piece using ultrasonic aspiration. During the surgical procedure, dramatic bleeding occurred, but was quickly controlled due to the technical advantage of full endoscopic close observation (Figure 2D).

With the aid of an intraoperative neurophysiological monitor and neuronavigation, the surgical procedure went smoothly, but was followed by delayed postoperative recovery from anesthesia and limb weakness. However, during the clinical follow-up of 3 months, the patient gradually recovered completely without any neurological dysfunction. The results from histopathology indicated that the tumor was composed of mature adipose tissue with vessels of varying diameters (Figure 3A), and this morphological feature corresponded to the diagnosis of intracranial angiolipoma for this patient. Postoperative MRI further verified total tumor resection without signs of recurrence or brain stem and cerebellar infarction (Figure 3B–3D).

Discussion

This present case study provides intraoperative and histological evidence of AL in the pineal region and demonstrates successful surgery for intracranial ALs removal in the pineal region, highlighting purely endoscopic surgery as a viable treatment option for this condition.

ALs are uncommon in the central nervous system (CNS), and intracranial ALs are even rarer. Thus far, most reported intracranial ALs were found in the sellar and parasellar areas [6–13]. These reported sellar and parasellar ALs were all closely related to cavernous sinus, which easily lead to severe bleeding during surgery. Therefore, only partial resection could be achieved for these ALs. ALs in other regions, such as frontal [14], intraventricular [15] or thalamic areas, have also been reported [16]. These 3 previously reported ALs had small arterial supply, which allowed total tumor resection. According to our literature search, the present case is the third report of intracranial posterior fossa Als, but it is the first one in the pineal region. The other 2 cases of ALs were in the intracranial posterior fossa, including one in the cerebellopontine angle（CPA（region [14], which was found in biopsy, and the other was in the infratentorial left cistern, which was removed by microscopic surgery [17].

At present, the etiology of intracranial ALs remains unclear. Histologically, ALs are divided into 2 different types including capsulated non-infiltrating and non-capsulated infiltrating ALs [5]. This classification is a part of a broad spectrum of lesions (including hemangiomas, lipomas and angiomyolipomas) caused by abnormal development of the primitive pluripotential mesenchymal cells from which smooth muscle, vascular endothelium, and adipose tissue develop [5]. In the present case, the histological evidence from the appearance of proliferating vascular endothelium cells in AL might indicate its histological homology with intracranial hemangioma.

Our case in the pineal region presented significant operative challenges because of its proximity to the brainstem and adhesion to the upper vermis of the cerebellum. Additionally, the complicated vessel component of the lesion increased the risk of intraoperative bleeding and interfered with the total tumor resection. The limited viewing angle of the operative field can make it difficult to perform complete resection through microscopy surgery [17]. The purely endoscopic SCIT approach in our case provided less invasive access to the pineal region by taking advantage of the natural skull base corridors, as documented previously by some other neurosurgeons [2–4,18]. Usually, pineal region tumors are situated in the posterior and inferior walls of the third ventricle, and the venous complexes – internal cerebral veins, vein of Galen, Rosenthal vein, and precentral cerebellum vein - are all involved in this region [1]. Taking advantage of full endoscopic close observation, the important veins in the pineal region were well protected during total resection of AL in our case. Additionally, the dramatic bleeding was quickly controlled.

Total surgical resection is the first choice for treatment of most intracranial tumors. However, some previous reports [5,14–16] suggested that intracranial ALs rarely can be total resected and free of neurological dysfunction, especially in case of non-capsulated infiltrating subtype of ALs, due to potential catastrophic intraoperative hemorrhage. In our case, the fully endoscopic SCIT approach resulted in complete tumor removal and postoperative improvement of neurological symptoms, highlighting purely endoscopic surgery as a viable surgical option for intracranial ALs in the pineal region.

Conclusions

The present case provides intraoperative and histological evidence of ALs in the pineal region. Our case demonstrates successful endoscopic surgery for ALs removal by the SCIT approach, suggesting endoscopic surgery as a potential alternative option for this condition. This experience encourages considering purely endoscopic surgery for ALs in the pineal region as a viable primary surgical treatment.