PMC8720428_01
Preoperative images on heavily T2-weighted magnetic resonance (MR) image (a) and source image of MR angiography (b) showing neurovascular compression at the root exit zone (REZ) of the left facial nerve by the anterior inferior cerebellar artery. Intraoperative photographs showing (c) the REZ of the affected nerve (Asterisk) was readily relieved by the offending artery (Black arrow) with minimum manipulation. Postoperative day 3, (d) head computed tomography image showing a subdural hematoma in the left cerebellopontine angle (CPA). Outstanding high-density lesion at the REZ is surgical prosthesis (Black arrow). T2-weighted MR images (e, f) showing a subdural hematoma in the left CPA and a cerebellar hemorrhage with perifocal edema that could indicate venous infarction.
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F1
Magnetic resonance (MR) imaging revealed the presence of neurovascular compression at the root exit zone (REZ) of the left facial nerve by the left anterior inferior cerebellar artery [Figure 1a and b]. After a retro-mastoid keyhole craniotomy, the affected nerve was decompressed with mobilization and dislocation of the offending artery by setting a piece of Teflon proximal to the REZ [Figure 1c]. CT scan revealed a subdural hematoma in the left cerebellopontine angle (CPA) with hydrocephalus [Figure 1d]. MR images also indicated an intracerebellar hemorrhage with perifocal edema [Figure 1e and f].
Investigations for the causality of delayed intracranial hemorrhage revealed (a, b) interruption of the ipsilateral internal jugular vein (IJV) at the level of the C1 (White arrow) on angiography. (c) The venous outflow was congested but not occluded, which revealed on further delayed phase. (d) Preoperative MR angiogram showed no stenosis at this portion of the IJV (Arrow head). (e) The three-dimensional computed tomography (3D-CT) venogram showing an elongated styloid process (ESP) that was 48 mm in length (Black arrow) and compressed the IJV at the level of the third segment of the vertebral artery (White arrow). (f) The former axial images of the 3D-CT venogram also showed that the IJV (White arrow) was pinched between the ESP (Black arrow) and the rectus capitis lateralis. It is notable that the transverse process of C1 vertebra did not contribute to the pinching directly in this case.
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F2
Angiography did not reveal any underlying vascular malformation; however, we noticed that the left IJV was obstructed at the level of C1 by some structure [Figure 2a-c], ipsilateral IJV stenosis was not evident on preoperative MR images [Figure 2d]. The three-dimensional CT (3D-CT) venogram reconstructed images revealed that this offending structure was an ESP that was 48 mm in length as measured [Figure 2e]. The former axial images of the 3DCT venogram also indicated that the IJV passed transversely across between the ESP and the rectus capitis lateralis muscle and was pinched between them [Figure 2f].
Magnetic resonance (MR) venography showing alteration of the signal flow on the bilateral transverse-sigmoid sinus. (a) MR venography with posterior-extension of the neck position showing high-signal flow on the left transverse-sigmoid sinus. (b) MR venography with antero-flexion of the neck position showing significant reduction of the signal flow on the affected side (a and b; White arrow).
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F3
MR venography performed before discharge also revealed reduction of signal flow on ipsilateral transverse-sigmoid sinus by cervical antero-flexion compared with posterior-extension [Figure 3a and b].