A minimally invasive supraorbital keyhole approach through superciliary arch for giant olfactory Groove angiopericytoma: case report

We sought to demonstrate a giant hemangiopericytoma within the olfactory groove resected by a minimally invasive supraorbital keyhole approach through superciliary arch, which is commonly used to remove relatively small meningioma, pituitary adenoma and craniopharyngioma. A 50-year-old female presented with a 1-year history of progressive headaches, anosmia, hyposmia, and visual deterioration. Anosmia and visual impairment were found by physical examination. The magnetic resonance imaging (MRI) scan demonstrated a large irregularly shaped intra-dural mass at bottom of right frontal lobe. A minimally invasive supraorbital keyhole approach through superciliary arch is performed for resecting this giant tumor. Surgical complications and degree of resection were recorded to evaluate the efficacy of this surgical method. Histological examination confirmed a diagnosis of hemangiopericytoma originating from the olfactory groove. Gross total resection of the intracranial hemangiopericytoma was possible with minimal brain retraction. Simpson grade I was achieved, and there were no presentation of new neurologic deficits, postoperative hematomas, and cerebrospinal fluid leakage in patient. We suggested that it is worthwhile a try to remove giant olfactory groove hemangiopericytoma by the minimally invasive supraorbital keyhole approach through superciliary arch, allowing for minimal damage of normal brain parenchyma, and improving prognosis.


Introduction
Hemangiopericytoma of the central nervous system, also known as vascular pericytes tumor, which is a rare mesenchymal tumor which derive from malignant transformation of pericytes.
The magnetic resonance imaging (MRI) scan demonstrated an irregularly shaped 6.1× 5.2 × 5.2cm intra-dural mass at bottom of right frontal lobe, which was enhanced by gadolinium contrast with the cork-screw type of intra-tumoral vessels, highly suspicious of hemangiopericytoma or meningiomas arising from the olfactory groove Figure 1 A-C. The skull was free of mass invasion. A large intra-dural mass at bottom of right frontal lobe was heterogeneously enhanced T1-weighted axial, coronal, and sagittal contrast MRI, with the cork-screw type of intra-tumoral vessels (A, B and C).

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To remove mass and reduce brain damage, we decided using a minimally invasive supraorbital keyhole approach through superciliary arch Figure 2A. After general anesthesia, the patient is placed supine on the operating table with their head fixed in a three-pin Mayfield head holder. The head of patient is elevated until exceeding the level of the thorax, and retroflexed 15-30°.
The skin is incised laterally from the supraorbital incisura within the eyebrow in a lateral-to-medial direction Figure 2A. Following the skin incision, the subcutaneous dissection is continued in the frontal direction to achieve optimal exposure of the frontolateral supraorbital area. The frontalis muscle is then cut with a monopolar knife parallel to the orbital rim in a medial-to-lateral direction. A single hole is made using a highspeed drill at the level of the frontal skull base. A minimal craniotomy is carried on using a high-speed craniotome, which cut the surface within a size of approximately 25×20mm. The dura is opened in a simple "C" shape and retracted

Discussion
Intracranial hemangiopericytomas are very rare vascularized mesenchymal tumors with an incidence of less than 1% [1], and they represented 2.5% of all meningeal tumors [20].
Hemangiopericytomas are highly vascular tumors, which derived from pericytes around capillaries and postcapillary venules. Up to now, only one case of Hemangiopericytoma derived from olfactory groove was previously reported [2]. We added another case of giant hemangiopericytoma originating from olfactory groove, which was removed by a minimally invasive supraorbital keyhole approach through superciliary arch.
Though there was no specificity in brain CT and MRI for most tumors originated from the anterior skull base [21][22][23], the origination of huge tumors could be presented by MRI [24]. The

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of intracranial hemangiopericytoma will take a more bleeding risk than resection of meningioma. The previous brain MRI studies demonstrated that the cork-screw type of intra-tumoral vessels suggested intracranial hemangiopericytoma [21,24], whilst the spoke-wheel type of intra-tumoral vessels seemed more like meningioma25. Presenting the cork-screw type of intra-tumoral vessels in MRI Figure 1  The previous studies also reported that surgeons tried to grossly resect giant olfactory groove meningiomas by unilateral tailored fronto-orbital approach and invasive interhemispheric approach [7,8]. Up to now, only one case of intracranial hemangiopericytoma arising from the olfactory groove was gross totally resected by Bicoronal frontal craniotomy [2]. However, these approaches usually require more operative time, and need a large bony defects and long skin incisions, which might be relevant with poor prognoses.
We first tried to remove giant olfactory Groove angiopericytoma through the minimally invasive supraorbital keyhole approach through superciliary arch. Postoperative complications of this minimally invasive craniotomy usually include leakage of CSF, supraorbital hypesthesia, palsy of the frontal branch of the facial nerve, wound healing disturbance or wound infection, blindness and hemiplegia [33]. Except for supraorbital hypesthesia, other postoperative complications did not occur in our patient with this minimally invasive supraorbital keyhole approach through superciliary arch.
We believe that this minimally invasive supraorbital keyhole approach through superciliary arch is a good choice for hemangiopericytoma in the olfactory groove due to the good outcome on the postoperative recovery. This approach has some advantages: a minimal skin incision, minimal bony exposure, minimal soft-tissue trauma, and less damage to olfactory nerve. Gross total resection is perfectly possible with minimal brain retraction. Concentration, familiar with anatomical structure and reliable hemostasis technology are needed to resect tumor in order to avoid injuring intracranial neurovascular structures using this minimally invasive supraorbital keyhole craniotomy through superciliary arch.

Conclusion
Intracranial hemangiopericytomas are rare tumor which are highly vascular tumors. The surgical removal can carry significant risk. In this case, the minimally invasive supraorbital keyhole approach through superciliary arch provides an effective and safe route for giant hemangiopericytoma in the olfactory groove with little or no need for brain retraction. Base on familiar with anatomical structure and reliable hemostasis technology, total resection of the tumor with abundant blood supply in the anterior skull base, can be achieved with minimal invasive supraorbital keyhole approach through superciliary arch.