A patient is suspected to have vestibular Shwanomma. The investigation of choice for its diagnosis is:
B i.e. Gadolinium enhanced MRI Contrast enhancement using paramagnetic agent gadolinium DTPA in MRI leads to better visualization of acoustic neuroma (shwanomma). So Gadolinium enhanced MRIQ became definitive investigation for acoustic neuroma (vestibular shwanomma). Neuromas / Neurinomas / Neurolemmomas arise from Schwann cells which invest the cranial nerves; therefore they are more correctly called Schwannomas. They can arise from any cranial or spinal root except the optic and olfactory nerves, which are myelinated by oligodendroglia rather than Schwann cells. Schwannomas most frequently arise in eighth (VIII) cranial nerve and are known as vestibular or acoustic Schwannoma /Neuronia. 8th nerve tumor are the most common tumors affecting the petrous pyramid - as 80% arise within the internal auditory meatus (IAM), usually from vestibular nerve. Fifth (V) cranial nerve is the second most common site. Tumors arising from Vth (5), VIIth (7), XIth (11) or XII (12) cranial nerves may affect temporal bone. These are all very rare except in cases of neurofibromatosis (NF) type 2. Thin section T2 MRI is the standard investigation to demonstrate or exclude the presence of an acoustic neuroma. Vestibular Schwannomas are iso to hypo intense globular mass centered over IAC on T2 images and the enlargement of internal auditory canal is distinguishing feature that differentiates them from other cerebello pontine angle masses. However, gadolinium enhancement on T1 weighted images is usually used to confirm diagnosisQ. Gadolinium enhancement is also required in NF2, for follow UPS after paial or total removal of acoustic neuroma. Now, latest MRI scanners using either gradient-echo or spin- echo 3DFT constructive interference in steady state (CISS) can produce thin section T2 images. Meningiomas are 2nd most common tumors arising in cerebello pontine angle. Unlike Schwannomas, meningiomas usually calcify & tend to have broad attachment to the petrous ridge, which may show characteristic hyperostosis. Meningiomas show intense contrast enhancement with gadolinium MRI (GdMR).
Contrast enhanced CT scan
Gadolinum enhanced MRI
SPECT
PET scan