PMC10481850_01
Preoperative axial T1-weighted enhanced magnetic resonance imaging showing a well-margined, heterogeneous enhancing mass at the left cerebellopontine angle (48 x 33 x 34 mm), compatible with a vestibular schwannoma (a). Preoperative coronal fast imaging employing steady-state acquisition (FIESTA) showed that the brainstem was compressed by the tumor and deviated contralaterally (b). Preoperative axial FIESTA revealed a tight cerebellopontine cistern on the right side, and the trigeminal nerve was deviated and compressed toward the petrous bone. There were no obvious vessels responsible for the compression of the right trigeminal nerve, such as the superior cerebellar artery (c).
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F1
Magnetic resonance imaging (MRI) showed a heterogeneously enhanced mass measuring 4.8 x 3.3 cm in the left cerebellopontine angle (CPA) and a tight cerebellopontine cistern of the right CPA [Figure 1].
Blink reflex with a lesion elicited with right supraorbital nerve stimulation. Reflex responses were recorded on the left (upper) and right (lower) eyelids. Stimulation of the right supraorbital nerve elicited an ipsilateral R1 response (lower) with a delayed latency of 14.2 ms, an ipsilateral R2 response with a normal latency of 30.3 ms, and contralateral R2 response (upper) with a normal latency of 28.8 ms.
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F2
Preoperative evaluation of the BR showed a delayed R1 latency after stimulation of the right supraorbital nerve, despite a normal R2 latency and normal R1 and R2 latencies after right and left supraorbital nerve stimulation, respectively, suggesting neuropathy in the afferent pathway between the right REZ and the principal nucleus of the trigeminal nerve in the pons [Figure 2].
Postoperative T1-weighted enhanced magnetic resonance (MR) imaging showed a small residual tumor and enlargement of the cerebellopontine cistern (a). Postoperative coronal fast imaging employing steady-state acquisition (FIESTA) MR images showed that the brainstem deviation was improved (b). Postoperative axial FIESTA MR images showed normalization of the right cerebellopontine cistern, normalization of the brainstem, and trigeminal nerve position compared to before tumor resection (c).
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F3
Postoperative MRI demonstrated a significant reduction in brainstem compression and widening of the right cerebellopontine cistern [Figure 3].
Blink reflex elicited with a lesion on the right supraorbital nerve. Reflex responses were recorded on the lower left (upper) and right (lower) eyelids. Stimulation of the right supraorbital nerve elicited an ipsilateral R1 response (lower) with a normal latency of 11.9 ms, an ipsilateral R2 response with a normal latency of 31.1 ms, and contralateral R2 response (upper) with a normal latency of 28.1 ms.
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F4
The BR test performed on the 50th postoperative day showed normalization of the ipsilateral R1 latency, followed by right stimulation and enlargement of the amplitude of the R1 wave, indicating improvements in right trigeminal nerve function [Figure 4].