Residual and Recurrent Acoustic Neuroma in Hearing Preservation Procedures: Neuroradiologic and Surgical Findings

Abstract

Hearing preservation procedures in acoustic neuroma surgery entail a risk of recurrent tumor either from the preserved cochlear nerve (tumor cell remains or late degeneration) or from tumor remnants left in the lateral end of the internal auditory canal. There is disagreement about the frequency of such tumor remnants, and the diagnostic modalities are not precise. Magnetic resonance imaging with gadolinium-DTPA enhancement is effective in diagnosing a primary case, but may not be so clear for small residual or recurrent tumors. A review of the literature concerning residual/recurrent tumor after "total" removal in functional unilateral acoustic neuroma surgery provided several reports,1-9 but systematic studies were lacking.This study of a series of 104 acoustic neuroma cases operated on with a hearing preservation procedure assessed the rates of residual or recurrent tumor and the imaging data that were significant for its diagnosis. MATERIALS AND METHODSDuring the period 1975 to 1993, 104 consecutive patients presenting with acoustic neuroma were operated on with the same hearing preservation procedure: the suboccipital approach with meatotomy and direct exposure of the lateral end of the internal auditory canal (IAC). The procedure involved a bone resection of the posterior and part of the superior and inferior walls of the IAC and used as landmarks the vestibular aqueduct, the common crus, and the nonampullated crura of the posterior and the superior semicircular canals. In every case, the surgeon 105

Outcomes after gamma knife radiosurgery in solitary acoustic tumors and neurofibromatosis Type 2

“…Cerullo, et al, [2] noted a 10% recurrence rate by 10 years following resection. Mazzoni, et al, [19] reported their series of more than 100 patients in whom they attempted hearing preservation; the overall tumor recurrence rate was 8.1%. Post, et al, [24] found that four (7%) of 56 patients underwent an incomplete resection in their attempted hearing-preservation series and that three developed regrowth within 3 years.…”

Nodular enhancement within the internal auditory canal following retrosigmoid vestibular schwannoma resection: a unique radiological pattern

“…Clinical studies have confirmed that of the 3 commonly used surgical approaches, the retrosigmoid route has the highest risk that unintentional tumor will be left behind, especially in the lateral one-half to one-third of the IAC. 15,23 Furthermore, in contrast to small remnant disease left along the facial nerve in the midcistern, tumor at the fundus is well vascularized, and therefore, it may be more apt to demonstrate continued growth and clinically significant recurrence. 6 Several studies have examined postoperative MR imaging enhancement patterns following retrosigmoid VS resection, but all studies to date have not investigated the location of enhancement in relation to the extent of preoperative tumor.…”

“…While the retrosigmoid approach provides excellent medial exposure, the lateral one-third of the IAC cannot be routinely visualized if the inner ear is to be preserved, leaving the fundus particularly vulnerable to recurrence. 5,15,17,23 Several studies have found that, following GTR, the presence of nodular enhancement within the tumor bed predicts a high likelihood for future recurrence. 4,15,16,28 Over the past 10 years we have observed a number of patients in whom intense nodular enhancement was documented at the fundus of the IAC lateral to the preoperative radiological tumor margin following retrosigmoid GTR.…”

Acoustic neuromas

“…A report by Cerullo et al [17, Class III] noted a 10% recurrence rate by 10 years following resection. Mazzoni et al [18] reported their series of over 100 patients with attempted hearing preservation. The overall tumor recurrence rate was 8.1%.…”