PMC8248077_01
(a) Preoperative T2-weighted image (b) preoperative tractography.
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F1
Magnetic resonance imaging revealed a heterogenous hyperintense mass (maximum diameter of 16 mm) with a hypointense rim located at the lower half of the ventral pons [Figure 1a]. Because of the ventral location of the patient's CM, as preoperative tractography showed posterior displacement of the corticospinal tract (CST) [Figure 1b], we selected the ATPA to realize a more anterolateral trajectory.
(a) Schema demonstrating the scalp incision and craniotomy range. (b) The middle base was flattened. (c) The dura mater was elevated up to the point where the GSPN submerges inside the V3. (d) Extradural anterior-medial petrosectomy was carried out in the range up to the GSPN on the lateral border, ICA on the deep anterior border, geniculate ganglion, basal turn of the cochlea and AE on the posterior border, and V3 on the medial border. The extent further expanded inferior-posteriorly by opening the anterior superior wall of the IAC and removing the tip of the petrous bone up to the height of the IPS. (e) The REZs of the trigeminal nerve, swollen pons, BA, AICA, and CN VI were confirmed. (f) The brainstem was incised at the point of the Peritrigeminal zone with yellow discoloration between the AICA loop and CN VI, and the hemangioma was completely removed. GSPN: Greater superficial petrosal nerve, V3: Mandibular division of the trigeminal nerve, AE: Arcuate eminence, IAC: Internal auditory canal, BA: Basilar artery, AICA: Anterior inferior cerebellar artery, CN VI: Abducens.
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F2
A question mark scalp incision started at the midpoint of the zygomatic arch (anterior to the tragus), extended by one fingerbreadth posteriorly, and then turned anteriorly to the superior frontal area [Figure 2a]. Right temporal craniotomy was performed and the middle base was flattened using a 5-mm diamond drill [Figure 2b]. The dura mater was elevated interdurally, leaving the GSPN on the middle base, up to the point where the GSPN submerges inside the foramen ovale, and the tip of the petrosal bone and the latter half of the trigeminal impression were exposed [Figure 2c]. Opening the anterior superior wall of the internal auditory canal (IAC) and removing the tip of the petrous bone up to the height of the inferior petrosal sinus (IPS) further broadened the extent of the petrosectomy inferior-posteriorly to expose the posterior fossa dura as wide as possible [Figure 2d]. The root entry zone (REZ) of the trigeminal nerve, swollen pons, basilar artery (BA), anterior inferior cerebellar artery (AICA), and abducens nerve arising from the bulbopontine groove were confirmed [Figure 2e]. The brainstem was incised at the point of the PTZ with yellow discoloration between the AICA loop and abducens nerve, and the CM was drawn toward the center and completely removed [Figure 2f].
(a) Postoperative T2-weighted image showing that the hemangioma was completely removed (b) postoperative bone window computed tomography showing the extent of petrosectomy.
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F3
The lesion was completely removed postoperatively [Figure 3a] and the symptoms mitigated rapidly.