Noninvasive EM image guidance in shunt surgery reduces poor shunt placement, resulting in a significant decrease in the early shunt revision rate.

We sought to characterize vestibular schwannoma (VS) pseudoprogression after radiosurgery to assess its incidence, causative factors, and association with radiation-induced adverse effects. We performed a retrospective study of VS treated with Gamma Knife radiosurgery during 2005-2009. Seventy-five patients had at least 24 months of clinical and radiographic follow-up (median, 29 months) and were included. Tumor response was calculated volumetrically using Gamma plan software on consecutive MRIs. All treatment plans were reviewed for dosimetry characteristics. Forty-nine VS (65%) were stable or regressed after treatment. Seventeen (23%) underwent pseudoprogression, with onset of enlargement at 6 months. Seven (9%) remained larger than initial treatment volume at last follow-up. Nine (12%) had persistent growth. Three patients underwent subsequent microsurgery. One patient required intervention at 3 months for cystic enlargement; otherwise, all patients with progressive enlargement had stable VS until at least 24 months. Twenty-six patients (34.7%) developed nonauditory adverse radiation effects after treatment, including cranial neuropathy, ataxia, and hydrocephalus. There was no statistical association between onset of clinical deterioration and tumor response. Volume changes in the first 24 months after radiosurgery rarely herald treatment failure. Any volume change after 24 months is indicative of treatment failure. Pseudoprogression does not appear to be independently linked to radiation-induced morbidity, and there are no patient-related or radiosurgical parameters that predict tumor response.

The success rate of ETVs in adults is comparable, if not better, than in children. In addition to the well-defined role of ETV in the treatment of hydrocephalus caused by tumors and aqueduct stenosis, ETV may also have a role in the management of CM-I, LOVA, persistent shunt infection, and IVH resistant to other CSF diversion procedures.

Endoscopic third ventriculostomy is a safe and durable means of controlling hydrocephalus in tumor cases. Its success rate is high--comparable to that reported in aqueduct stenosis cases. Although ETB is probably not as accurate for diagnosis as biopsy with frame-based stereotactic guidance, it is associated with a lower mortality rate and, in the correct clinical setting, may be justifiably attempted as an initial biopsy procedure at the same time as ETV via a single-trajectory approach.

Neuronavigation enables safe, accurate surgery, and may ultimately reduce complications and improve outcome. Electromagnetic technology allows frameless, pinless, image-guided surgery, and can be used in all procedures for which neuronavigation is appropriate. This technology was found to be particularly advantageous compared with other technologies in cases in which freedom of head movement was helpful. Electromagnetic neuronavigation was therefore well suited to CSF diversion procedures, awake craniotomies, and cases in which rigid head fixation was undesirable, such as in neonates. This technology extends the application of neuronavigation to routine shunt placement and ventricular catheter placement in patients with traumatic brain injury.