Conference details: 1-3 June, 2014, Washington, US
Report by: Dr Imran Noorani, Wessex Neurological Centre, Department of Neurosurgery, University Hospital Southampton

The 2014 biennial meeting of the American Society of Stereotactic and Functional Neurosurgery (ASSFN) was hosted by the Renaissance Downtown Hotel, Washington D.C on June 1 – 3. The city provided a delightful background to the conference, with a number of cultural and scenic sites that make it world-renowned, including the White House which was within walking distance of the conference. This conference is arguably the most prestigious functional neurosurgery meeting worldwide, and it surpassed my expectations.

The first day started with discussion of the history of functional neurosurgery and of the society itself, describing how functional neurosurgery has moved from almost purely epilepsy surgery to the modern day that increasingly comprises deep brain stimulation for a number of neurological disorders, spinal cord and vagal nerve stimulation, as well as advances in epilepsy surgery. Dr Slavin, President of ASSFN described how the society has grown over the decades, corresponding to the expansion of the field itself. The afternoon session focused on evolving technologies in pain treatment. Here, I gave a talk on our results of percutaneous surgery for trigeminal neuralgia in multiple sclerosis patients in University Hospital Southampton, demonstrating that it is as effective as in patients with idiopathic trigeminal neuralgia. The talk was well-received and provided me with constructive comments for future work. Following this, there was a presentation on spinal cordotomy, outlining that this is a treatment for patients with terminal and otherwise unresponsive pain, typically in cancer patients. It involves myelographic or CT-guidance, but it was highlighted that an endoscopic approach can now be undertaken to make a radiofrequency lesion of the spinothalamic tract in the spinal cord for contralateral pain relief. Another talk was on how the dorsal root ganglion can be used as a target for neuromodulation for pain. This differs from spinal cord stimulation for pain which aims to stimulate the dorsal columns to reduce pain transmission. It was stated that the dorsal root ganglia can be localised between the medial and lateral foramina of the vertebral pedicles under fluoroscopic guidance, and there has been success with this treatment for pain.

Continuing the same theme, an intriguing presentation introduced how the nucleus accumbens can be a deep brain stimulation target for pain in highly specialised cases, such as intractable central post-stroke pain. Preliminary data demonstrated that stimulating this nucleus improves the affective component of pain in that it reduced anticipation of pain, and therefore maybe particularly useful in cases of allodynia.

Andres Lozano, Professor of Neurosurgery at McGill University, was the invited honoured guest speaker in functional neurosurgery. On the second day of the meeting, he gave an exciting lecture on the new and innovative neurosurgery for memory, which he has been pioneering over the last five years or so. He explained how he stumbled upon using the fornix as a DBS target for memory when he was stimulating this region as an intended treatment for obesity but found that it caused the patient to recall distant memories in vivid detail! There is now a large multicentre randomised controlled trial testing the effectiveness of fornix DBS as a treatment for mild dementia, with promising initial data1. Given the exhilarating nature of the subject and the rapidity with which this field is rapidly progressing, Professor Lozano’s lecture was met with a standing ovation. The rest of the afternoon focused on epilepsy, including presentations on anterior thalamic DBS and DBS on multiple targets in Papez’ circuit.

The third and final day of the conference kicked-off with a large series of talks of emerging DBS for neuropsychiatric disorders, in particular depression and obsessive-compulsive disorder. Professor Mayberg, the initial pioneer of using DBS for depression, suggested why it is difficult to prove the success of this treatment: depression is a very heterogeneous condition with many different symptoms that vary between patients, so dividing the patients into meaningful subgroups may be necessary for DBS to benefit specific types of patients; also, it may be that different patient subgroups respond to stimulation in different areas, such as area 25 and the ventral tegmental area. The comparison was made with Parkinson’s disease, for which the success of treatment is much easier to assess: DBS often has an immediate impact on tremor; whereas no such easy measure of treatment success is yet available for depression, establishing the need for novel biomarkers2, 3.

Dr Elias later gave an exquisite account of focused ultrasound as a novel treatment for essential treatment. Focused ultrasound can create a small lesion in the thalamus, and reduce tremor frequency by over 50%. The major advantage of this approach is that it is ‘incisionless’, in that no burr-hole needs to be made, and therefore this is thought to bring forward many essential tremor patients for treatment who would otherwise not have wanted treatment because of reservations about the more invasive DBS. However, DBS is modifiable (the settings can be adjusted to optimise treatment) and is currently performed faster than focused ultrasound. The clinical benefit of focused ultrasound for essential tremor has been recently demonstrated in high-profile trials, including one by Dr Elias’ group4, 5.

The conference was well-organised, with many of the stars of functional neurosurgery being invited as guest speakers, and I believe I speak for many of the participants in expressing my enjoyment of the meeting. The next meeting in 2016 will be in Chicago and is eagerly awaited.

References:

1: Laxton AW, Tang-Wai DF, McAndrews MP, Zumsteg D, Wennberg R, Keren R, Wherrett J, Naglie G, Hamani C, Smith GS, Lozano AM. A phase I trial of deep brain stimulation of memory circuits in Alzheimer’s disease. Ann Neurol. 2010. Oct;68(4):521-34.

2: Lozano AM, Giacobbe P, Hamani C, Rizvi SJ, Kennedy SH, Kolivakis TT, Debonnel G, Sadikot AF, Lam RW, Howard AK, Ilcewicz-Klimek M, Honey CR, Mayberg HS. A multicenter pilot study of subcallosal cingulate area deep brain stimulation for treatment-resistant depression. J Neurosurg. 2012 Feb;116(2):315-22.

3: Mayberg HS, Lozano AM, Voon V, McNeely HE, Seminowicz D, Hamani C, Schwalb JM, Kennedy SH. Deep brain stimulation for treatment-resistant depression. Neuron. 2005 Mar 3;45(5):651-60.

4: Lipsman N, Schwartz ML, Huang Y, Lee L, Sankar T, Chapman M, Hynynen K, Lozano AM. MR-guided focused ultrasound thalamotomy for essential tremor: proof-of-concept study. Lancet Neurol. 2013 May;12(5):462-8

5: Elias WJ, Huss D, Voss T, Loomba J, Khaled M, Zadicario E, Frysinger RC Sperling SA, Wylie S, Monteith SJ, Druzgal J, Shah BB, Harrison M, Wintermark M. A pilot study of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2013 Aug 15;369(7):640-8.

ACNR 2014: V14;I3
Published online 29/7/14