Friday 3 February 2012

Recurrent Acoustic Schwannoma

Post operative follow up MRI Brain
Operated for imaging wise Acoustic Schwannoma.
Operative notes mentions Right retromastoid Craniotomy with tumor excision -  Lateral Sub Occipital Approach. 
Histopathology report mentions Acoustic Schwannoma.
The follow up MRI shows: 
Gliosis involving right cerebellar hemisphere.
A nodular lesion in right side IAC in the region of 7th -8th CN complex isointense on T2w images of thin axial sections of 3D FIESTA sequence with uniform enhancement on post contrast T1 suggestive of recurrent / residual Schwannoma.

The issue of recurrence of Acoustic Schwannoma is poorly studied by the surgical literature and is probably underestimated.
Chances of recurrence are relatively high with Retro mastoid approach due to restriction of exposure to the far end of the tumor risking an incomplete resection.
Greater residual tumor thickness on MR imaging after the initial surgery is one of most important factors related to postoperative tumor regrowth and such patients require frequent follow up imaging.

Because acoustic tumors grow slowly, new research supports partial or near-total removal, whereby small remnants of tumor capsule are left attached to critical nerves. Tumor recurrence is essentially the same with total and near-total removal, but facial nerve damage is significantly reduced with near-total. If the tumor remnant grows, radiation may be used.
Outcomes of surgery depend on the size and adherence of the tumor, total and near total excision  and off course the skill of the surgical team.
Partial-removal techniques have higher rates of hearing and facial function preservation; however, the long-term results of these techniques are still being investigated.
In Post operative follow up MR Imaging for Acoustic Schwannoma, axial sections of 3D FIESTA and Post contrast T1 are the two most important sequences. 

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