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Meharpal Sangra, Simon Clark, Caroline Hayhurst and Conor Mallucci

Object

Image-guided neuroendoscopy is being increasingly used in an attempt to reduce the morbidity associated with surgery and to make navigation easier. It has a particularly useful application in the pediatric population for the treatment of conditions such as complex hydrocephalus and arachnoid cysts. However, its use has been limited by the requirement for rigid head fixation, which may be difficult in infants because of the immaturity of the skull. In addition there can be line-of-sight issues, which can be a problem with optical-based systems. Electromagnetic navigation has eliminated the requirement for head immobilization, and its successful use in the infant population has been reported. The authors present their series to date, define its role, and discuss its advantages over other forms of image-guided navigation.

Methods

The authors used the electromagnetic StealthStation and software (Medtronic) for neuronavigation. A dynamic reference frame was attached to the head using an adhesive dressing. The patient was positioned without rigid fixation and was registered using a specially designed stylet. Navigation was through a stylet, which could be placed within the endoscope. Direct advantages were no rigid head fixation, the ability to maneuver the endoscope without the requirement for a bulky optical attachment, and no loss of navigation caused by user obstruction of reflective fiducial markers. The authors performed a total of 28 procedures in 23 patients. There were 9 arachnoid cyst marsupializations, 4 multiple fenestrations for multiloculated hydrocephalus, 4 aqueductal stenting procedures for encysted fourth ventricles, 5 endoscopic third ventriculostomies, 3 septum pellucidotomies, 2 tumor biopsies, and 1 tumor cyst decompression.

Results

Electromagnetic navigation was successful in all cases. Two complications were reported: a subdural collection, requiring bur hole drainage after a successful fenestration of the arachnoid cyst and failed treatment of complex hydrocephalus requiring subsequent placement of a ventriculoperitoneal shunt.

Conclusions

The electromagnetic technology provides reliable image-guided endoscopy. It has several advantages over alternative forms of stereotaxy, and the ability to use it without the need for rigid head fixation makes it eminently suitable for the pediatric population. Its use and application in the treatment of a variety of different conditions has been demonstrated successfully.

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Michael D. Jenkinson, Caroline Hayhurst, Mohammed Al-Jumaily, Jothy Kandasamy, Simon Clark and Conor L. Mallucci

Object

Endoscopic third ventriculostomy (ETV) is the treatment of choice for hydrocephalus, but the outcome is dependent on the cause of this disorder, and the procedure remains principally the preserve of pediatric neurosurgeons. The role of ETV in adult patients with hydrocephalus was therefore investigated.

Methods

One hundred ninety adult patients underwent ETV for hydrocephalus. Cases were defined as primary ETV (newly diagnosed, without a previously placed shunt) and secondary ETV (performed for shunt malfunctions due to infection or mechanical blockage). Causes of hydrocephalus included tumor, long-standing overt ventriculomegaly (LOVA), Chiari malformation Types I and II (CM-I and -II), aqueduct stenosis, spina bifida, and intraventricular hemorrhage (IVH). Successful ETV was defined as resolution of symptoms with shunt independence. Operative complications and ETV failure rate were investigated according to the causes of hydrocephalus and between the primary and secondary ETV groups.

Results

In the primary group, ETV was successful in 107 (83%) of 129 patients, including those with tumors (52 of 66), LOVA (21 of 24), CM-I (11 of 11 cases), CM-II (8 of 9), aqueduct stenosis (8 of 9), and IVH (2 of 2). In the secondary group, ETV was successful in 41 (67%) of 61 patients and was equally successful in cases of mechanical shunt malfunction (35 of 52 patients) and infected shunt malfunction (6 of 9 patients). The median time to ETV failure was 1.7 months in the primary group and 0.5 months in the secondary group. The majority of ETV failures occurred within the first 3 months, and thereafter, the Kaplan-Meier survival curves plateaued. There were no procedure-related deaths, and complications were seen in only 5.8% of cases.

Conclusions

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.

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Simon Clark, Meharpal Sangra, Caroline Hayhurst, Jothi Kandasamy, Michael Jenkinson, Maggie Lee and Conor Mallucci

Object

The aim of this study was to prospectively evaluate the use of noninvasive electromagnetic neuronavigation in children, in particular its use in complex hydrocephalus and slit ventricle syndrome.

Methods

Prospective data was collected from all pediatric patients undergoing insertion of ventriculoperitoneal shunts using electromagnetic frameless neuronavigation from January 2006 to November 2007.

Results

Twenty-three patients fulfilled the study criteria. All ventricles were cannulated on the first pass. There were no immediate or early postprocedural complications. All but 1 patient had resolution of symptoms (mainly chronic headache) on follow-up (median 7 months, range 1–17 months). The proximal revision rate was 9% (2 of 23 patients). One patient required distal catheter revision. Infection occurred in 1 patient.

Conclusions

Electromagnetic neuronavigation using a frameless and pinless system is especially suited for pediatric patients. The authors hypothesize that successful placement of ventricular catheters will reduce morbidity and improve shunt longevity.

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Caroline Hayhurst, Tjemme Beems, Michael D. Jenkinson, Patricia Byrne, Simon Clark, Jothy Kandasamy, John Goodden, Rishi D.S. Nandoe Tewarie and Conor L. Mallucci

Object

As many as 40% of shunts fail in the first year, mainly due to proximal obstruction. The role of catheter position on failure rates has not been clearly demonstrated. The authors conducted a prospective cohort study of navigated shunt placement compared with standard blind shunt placement at 3 European centers to assess the effect on shunt failure rates.

Methods

All adult and pediatric patients undergoing de novo ventriculoperitoneal shunt placement were included (patients with slit ventricles were excluded). The first cohort underwent standard shunt placement using anatomical landmarks. All centers subsequently adopted electromagnetic (EM) navigation for routine shunt placements, forming the second cohort. Catheter position was graded on postoperative CT in both groups using a 3-point scale developed for this study: (1) optimal position free-floating in CSF; (2) touching choroid or ventricular wall; or (3) intraparenchymal. Episodes and type of shunt revision were recorded. Early shunt failure was defined as that occurring within 30 days of surgery. Patients with shunts were followed-up for 12 months in the standard group, for a median of 6 months in the EM-navigated group, or until shunt failure.

Results

A total of 75 patients were included in the study, 41 with standard shunts and 34 with EM-navigated shunts. Seventy-four percent of navigated shunts were Grade 1 compared with 37% of the standard shunts (p = 0.001, chi-square test). There were no Grade 3 placements in the navigated group, but 8 in the standard group, and 75% of these failed. Early shunt failure occurred in 9 patients in the standard group and in 2 in the navigated group, reducing the early revision rate from 22 to 5.9% (p = 0.048, Fisher exact test). Early shunt failures were due to proximal obstruction in 78% of standard shunts (7 of 9) and in 50% of EM-navigated shunts (1 of 2).

Conclusions

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