Retrosigmoid approach to acoustic neuroma/vestibular Schwannoma (above collage): Acoustic neuroma/vestibular Schwannoma is a tumour of the 8th "vestibulocochlear" cranial nerve (for hearing and balance). These tumours are regarded as "benign", but can often cause more neurological disability if larger than 2-3 cm in diameter. Acoustic neuroma/vestibular Schwannoma can present with progressive hearing loss, ringing in the ears (tinnitus), episodes of dizziness (vertigo) and, when larger in size, can cause facial numbness or altered facial sensation (dysaesthesia from 5th "trigeminal" cranial nerve impingement), impaired facial muscle function or facial muscle spasms (from 7th "facial" cranial nerve impingement), and difficulty with limb movement and gait (from brainstem or "pontine" compression). Top left image: Acoustic neuroma/vestibular Schwannoma and the rarer "cochlear Schwannoma" arise from the "Obersteiner-Redlich Zone (ORZ)" in the bony part of the hearing/auditory canal near the brainstem (image reproduced from VG Khurana and colleagues, Journal of Neurosurgery, Volume 99; pages 779-782, 2003). Top centre image: This young patient presented with progressive deafness and facial sensory impairment. The preoperative MRI axial T1+contrast image shows a 3.2 cm acoustic neuroma (in red dotted circle) with a small "tail" (light blue region) in the internal auditory canal from where the tumour arose and subsequently "mushroomed" out into the brainstem area (cerebellopontine angle). Note the compressed brainstem (pons region). Top right image: The tumour's well developed yellowish-cream-coloured outer capsule is on view via the operating microscope. Bottom left image: The tumour is somewhat vascular, and is being progressively internally debulked by Dr Khurana using a precision-tip ultrasonic aspirator (CUSA). Bottom next image: A micro-stimulator (fine-tip dark silver instrument in centre of this image) is used to stimulate (and therefore test the viability/preservation of) the 7th cranial nerve (the whitish band here) which is stuck to the remaining tumour capsule. This delicate nerve bundle is meticulously freed from the neighbouring tumour capsule. Bottom next image: This image demonstrates the 5th cranial nerve's larger sensory (thick white cream-coloured band) and smaller motor (thinnish whiter band) function bundles. This nerve has been meticulously freed from the top of the tumour. Like the 7th cranial nerve, the 5th cranial nerve is "stimulated" by the surgeon to check that it is still working well throughout this operation. Bottom right image: The postoperative MRI axial T1+contrast image shows the vast majority of the tumour has been removed (no more "golf ball" here). A small amount of blood products lies in the cerebellopontine angle. A thin tail has been intentionally left in the acoustic canal where the tumour was most stuck to the very thinned out facial nerve. This vital nerve is most "at-risk" at its entry into the canal, where the tumour thins the nerve and compresses it against the bony walls here. Prior to his operation, the young patient was understandably adament that he did not want any facial nerve dysfunction and it was agreed that if there was a small remnant in the canal, and if it did grow in the future, a single pulse of stereotactic radiation could then be safely applied directly to the small remnant. The patient's facial sensory symptoms completely resolved after the surgery, his facial nerve function was intact, and he was discharged from hospital on the fourth day post-operatively.

Demonstration of cranial nerves of the brainstem (above collage) during surgeries by Dr Khurana for tumours impinging upon the brainstem, the brain's "highest-price real estate". All of these patients have made excellent recoveries following surgery. Top row (A-D): Acoustic neuroma/vestibular Schwannoma. A: Preoperative MRI showing a very large (4 cm) acoustic neuroma/Vestibular Schwannoma (red circle). These tumours IF SMALL can be quite adequately treated by focused radiation (stereotactic radiosurgery or SRS), however, LARGE ONES such as in this patient are best removed surgically owing to the ability to relieve problematic brainstem compression. B-D: demonstration of cranial nerves 11 (spinal accessory), 10 (vagus), 9 (glossopharyngeal), 7 (facial) and 5 (trigeminal). The posterior inferior cerebellar artery (PICA; a cause of glossopharyngeal neuralgia) is seen in B. The brainstem now decompressed is seen in C. A nerve microstimulator used by Dr Khurana, as seen in D, confirms that in this particular patient, the 7th cranial nerve is (by the years of growth of the tumour) thinned out and plastered to the outer capsule of the tumour. This tumour was near-totally removed but this 7th nerve thinly plastered component was left in place in order to preserve facial neuromuscular function in this young patient. The small remnant can be watched and if there is any growth, a pulse of SRS can then be safely applied given that the bulk of the tumour is no longer there and the now-centimetres of DISTANCE between any future SRS pulse and the brainstem renders SRS "safer". Middle row (E-G): E: Preoperative MRI showing a petroclival meningioma (red circle). F: The tumour (Tu) is exposed by elevation and reflection of the tentorium (Tent) and the tumour's close relationship to the thin and delicate cranial nerve 4 (trochlear) is seen. G: Postoperative MRI image showing no residual tumour (green circle). Bottom row (H-K): Brainstem epidermoid tumour (H, red arrow heads). This congenital tumour of skin-origin structures is pearly-white and thinly encapsulated (I), and has a cheesy consistency (J, red circle). K: After removal of the epidermoid's "keratin" content, cranial nerves 4 (trochlear), 5 (trigeminal), 6 (abducens), 7 (facial) and 8 (vestibulocochlear) can be seen. Here, Dr Khurana has worked with very fine microinstruments via small natural "windows" between the cranial nerves to debulk the tumour without injury to these delicate structures.