Small vestibular schwannoma with hearing deficit – upfront radiosurgery

SKULL BASE REGION Cerebellopontine angle/internal auditory canal
PERTINENT LABORATORY FINDINGS Pretreatment audiogram: Class A hearing with bilateral sensorineural hearing loss, more pronounced in tumor ear; word recognition score at 100% in right ear and 90% in left ear

Case description

The patient presented at 71 years of age with sudden right-sided hearing loss and tinnitus. Magnetic resonance imaging (MRI) with gadolinium contrast was obtained, which revealed a small enhancing intracanalicular mass consistent with vestibular schwannoma (VS). The tumor, retrospectively, had been present on another MRI obtained the previous year as part of a research study ( Figure 8.40.1 ). An audiogram revealed a drop-off in right-sided hearing above 1000 Hz, with maintained word recognition at 100% ( Figure 8.40.2 ). Due to the small size of the tumor and good hearing status, he underwent stereotactic radiosurgery (SRS) for the tumor ( Figure 8.40.3 ). Serial imaging following initial SRS revealed interval growth of the tumor at 5 years ( Figure 8.40.4 ). Hearing decreased ( Figure 8.40.5 ) but was improved with hearing aids, and he developed imbalance. He underwent repeat Gamma Knife radiosurgery (GKRS) ( Figure 8.40.6 ).

Radiosurgery Machine Gamma Knife – Perfexion
Radiosurgery Dose (Gy)

  • Initial: 12.5 at the 50% isodose line

  • 3 isocenters to cover a volume of 0.292 cm 3

  • Repeat: 13.5 at the 50% isodose line

  • 5 isocenters to cover a volume of 0.819 cm 3

Number of Fractions

  • Initial: 1

  • Repeat: 1

Figure 8.40.1.

A. Pretreatment brain MRI with gadolinium contrast demonstrates a right-sided 9.7-mm homogeneously contrast-enhancing mass in the internal auditory canal most consistent with vestibular schwannoma. B. MRI without contrast obtained 1 year prior to presentation revealing an incidental mass.

Figure 8.40.2.

Pretreatment audiogram of the right (tumor) ear shows bilateral mild-to-severe sensorineural hearing loss between 2k–8k Hz, more pronounced in the mid-range in the right ear, with a maximum 10-dB gap. Word recognition was paradoxically lower in the left (nontumor) ear at 90%.

Figure 8.40.3.

Segmental MRI images performed with the stereotactic headframe in place on the day of treatment demonstrate the initial radiosurgical plan, including the 12.5-Gy treatment volumes (yellow) and 5-Gy (green) treatment volumes, as well as the adjacent cochlea (purple).

Figure 8.40.4.

A. MRI at 1 year following treatment reveals loss of central enhancement. B. MRI at 3 years following treatment revealed slight tumor growth. C. Tumor growth continued at 5 years.

Apr 6, 2024 | Posted by in GENERAL RADIOLOGY | Comments Off on Small vestibular schwannoma with hearing deficit – upfront radiosurgery

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