Patricia Byrne

Application of electromagnetic technology to neuronavigation: a revolution in image-guided neurosurgery

OBJECT The authors investigated the practicality of electromagnetic neuronavigation in routine clinical use, and determined the applications for which it is at the advantage compared with other systems. METHODS A magnetic field is generated encompassing the surgical volume. Devices containing miniaturized coils can be located within the field. The authors report on their experience in 150 cases performed with this technology. RESULTS Electromagnetic neuronavigation was performed in 44 endoscopies, 42 ventriculoperitoneal shunt insertions for slit ventricles, 21 routine shunt insertions, 6 complex shunt insertions, 14 external ventricular drain placements for traumatic brain injury, 5 awake craniotomies, 5 Ommaya reservoir placements, and for 13 other indications. Satisfactory positioning of ventricular catheters was achieved in all cases. No particular changes to the operating theater set-up were required, and no significant interference from ferromagnetic instruments was experienced. Neurophysiological monitoring was not affected, nor did it affect electromagnetic guidance. CONCLUSIONS 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.

Effect of electromagnetic-navigated shunt placement on failure rates: a prospective multicenter study.

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.

Use of the NeuroMate Stereotactic Robot in a Frameless Mode for Movement Disorder Surgery

Background/Aims: To evaluate the use of the NeuroMate stereotactic robot with a novel ultrasound registration system for movement disorder surgery (MDS). Methods: Using the robot in a frameless mode, 51 patients underwent MDS. Surgical planning was carried out using MRI data obtained more than 24 h before surgery. Results: 37 out of 50 targets in the subthalamic nucleus were satisfactorily identified with a single microelectrode trajectory and the final electrode positions were at a mean distance of 1.7 mm from the calculated target. There was a significant improvement in motor scores of the Unified Parkinson’s Disease Rating Scale III (off medication) at 6 (43%) and 18 months (51.7%) compared to pre-operative scores (p < 0.05). Conclusions: The frameless robot using only MRI data can be used for MDS. The temporal separation of imaging from the surgical procedure provides additional time for detailed image analysis and planning.

Bilateral deep brain stimulation for cervical dystonia: long-term outcome in a series of 10 patients.

BACKGROUND:Bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) was shown to be effective in cervical dystonia refractory to medical treatment in several small short-term and 1 long-term follow-up series. Optimal stimulation parameters and their repercussions on the cost/benefit ratio still need to be established. OBJECTIVE:To report our long-term outcome with bilateral GPi deep brain stimulation in cervical dystonia. METHODS:The Toronto Western Spasmodic Torticollis Rating Scale was evaluated in 10 consecutive patients preoperatively and at last follow-up. The relationship of improvement in postural severity and pain was analyzed and stimulation parameters noted and compared with those in a similar series in the literature. RESULTS:The mean (standard deviation) follow-up was 37.6 (16.9) months. Improvement in the total Toronto Western Spasmodic Torticollis Rating Scale score as evaluated at latest follow-up was 68.1% (95% confidence interval: 51.5-84.6). In 4 patients, there was dissociation between posture severity and pain improvement. Prevalently bipolar stimulation settings and high pulse widths and amplitudes led to excellent results at the expense of battery life. CONCLUSION:Improvement in all 3 subscale scores of the Toronto Western Spasmodic Torticollis Rating Scale with bilateral GPi deep brain stimulation seems to be the rule. Refinement of stimulation parameters might have a significant impact on the cost/benefit ratio of the treatment. The dissociation of improvement in posture severity and pain provides tangible evidence of the complex nature of cervical dystonia and offers interesting insight into the complex functional organization of the GPi.

Variability in position of the subthalamic nucleus targeted by magnetic resonance imaging and microelectrode recordings as compared to atlas co-ordinates.

Background: Traditional methods for localisation of target nuclei for deep brain stimulation (DBS) have used brain atlas co-ordinates for initial targeting. It is now possible to visualise the subthalamic nucleus (STN) on magnetic resonance imaging (MRI) and determine the individual variability of its position. Methods: The present study was performed in patients undergoing STN DBS for Parkinson’s disease. The STN was directly targeted from axially obtained MRI and verified with microelectrode recordings. Postoperatively, the most effective contact was identified for each patient, and its position was calculated. Results: Fifty electrodes were inserted in 25 patients. The target position varied considerably in relation to the mid-commissural point. The mean effective contact position lies just dorsal to the location of the STN in a standard brain atlas. Conclusion: The STN varies in position, and can be accurately targeted from MRI alone.

Deep brain stimulation of the subthalamic nucleus: effectiveness in advanced Parkinson’s disease patients previously reliant on apomorphine

Objectives: To assess the efficacy of bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) in patients with advanced Parkinson’s disease previously reliant on apomorphine as their main antiparkinsonian medication. Methods: Seven patients with motor fluctuations despite optimal medical treatment given as predominantly apomorphine infusion (n=6), or intermittent apomorphine injections (n=1) underwent bilateral STN DBS using frameless stereotactic surgery. Standard assessments of parkinsonism and motor fluctuations, using Unified Parkinson’s Disease Rating Scale (UPDRS) were performed before and six months after surgery. Assessments were performed both on and off medication, and postoperative with the stimulators switched on and off. Results: Bilateral STN DBS improved motor scores (UPDRS III) by 61% when off medication (p<0.05). Clinical fluctuations (UPDRS IV items 36–39) were reduced by 46.2% (p<0.05). Total daily apomorphine dose was reduced by 68.9% (p<0.05) and apomorphine infusion via a pump was no longer required in four patients. There were no operative complications. Two patients required treatment for hallucinations postoperatively but there was no significant change in mini-mental state examination. Conclusions: In patients with advanced Parkinson’s disease, previously reliant on apomorphine, bilateral STN DBS is an effective treatment to reduce motor fluctuations and enable a reduction in apomorphine use.

Relationship of most effective DBS electrode location for Parkinsonism to neurophysiological, MR and atlas localisation of subthalamic nucleus

(CIDP) is an acquired disorder of the peripheral nervous system with a likely autoimmune pathogenesis. Despite numerous studies no consensus has been achieved regarding the identity of the autoantigens and the presence of antibodies to them. We used the Western Immunoblot technique to seek antibodies to myelin protein antigens in sera collected from 32 CIDP, 37 Guillain–Barre Syndrome (GBS) and 64 control subjects. Eight CIDP and 12 GBS patients showed immunoreactivity to peripheral nerve antigens. This was significantly higher than normal controls (CIDP p = 0.04 and GBS p = 0.0065). Of these, six CIDP and seven GBS sera had immunoreactive bands at 28 kDa, the position of myelin protein zero (P0). Although no clinical or neurophysiological characteristics were significantly related to the presence or absence of antibodies in CIDP or GBS patients, CIDP patients with immunoreactive bands tended to show better responses to IVIG and plasma exchange and also tended to be female. Antibodies against a 28 kDa antigen are present in a significant number of patients, 20% in this study, with inflammatory neuropathy. In CIDP this may imply a pathological role for antibodies to P0.