Gadolinium-DTPA enhanced magnetic resonance imaging in acoustic neuroma diagnosis and management.

Gadolinium-DTPA (Gd-DTPA) is a paramagnetic contrast agent that increases the intensity of acoustic neuromas (AN) on T1-weighted magnetic resonance imaging (MRI) scans. Over a 9-month period we have reviewed Gd-DTPA-enhanced MRI scans on 32 consecutive cases (35 tumors) involving the internal auditory canal (IAC) and cerebellopontine angle (CPA). The majority of patients (84%) were imaged on latest generation 1.5 Tesla scanners. Every tumor studied showed marked enhancement after Gd-DTPA administration. This improved contrast permitted identification of three small tumors that were not evident on unenhanced scans. Gd-DTPA appears to be particularly useful in the evaluation of recurrent or residual AN. In three patients with known residual tumor after planned subtotal excisions, the remaining tumor could only be differentiated from surrounding scar, cerebral spinal fluid (CSF), and brain parenchyma after contrast enhancement. In one of these, a small rim of tumor capsule left on the facial nerve was evident only on Gd-DTPA-enhanced T1 images. Gd-DTPA also provides a more reliable estimate of the depth of tumor penetration in the IAC. This information is useful in selecting candidates suitable for a hearing conservation approach.