(v2 = 37.0, p < 0.0001). Syringomyelia was more oftenassociated with an isolated Chiari I malformation in Pacificpeople (84.4%) as compared to 42.9% of Maori and 38.2%of Caucasian/others (v2 = 62.3, p < 0.0001).

Conclusion: The prevalence of syringomyelia is higher innorthern New Zealand than in studies performed prior tothe advent of MRI. The prevalence is particularly high inMaori and Pacific people. The cause of the ethnic differ-ences in the prevalence of syringomyelia identified in thisstudy is unexplained and warrants further investigation.

doi:10.1016/j.jocn.2007.02.042

612: Long-term assessment of oxcarbazepine in a naturalistic

setting: a retrospective study

Udaya Seneviratne, Wendyl D’Souza, Mark Cook; St.

Vincent’s Hospital

Objectives: To assess the long-term outcome ofoxcarbazepine (OXC) in a naturalistic setting, either as amonotherapy or add-on therapy, by determining the reten-tion rate and efficacy of the treatment.

Methods: This is a retrospective study. Patients werescreened from the epilepsy patients’ medical records trea-ted at St. Vincent’s Hospital Melbourne from 1 January2002 to 30 June 2005. All epilepsy patients treated withOXC were included in this study. The follow up startedat the introduction of OXC and ended at closing date(30 June 2005) or at discontinuation of treatment. Demo-graphic variables, epilepsy syndrome, date of commence-ment of OXC, reasons for commencement, date ofceasing OXC and reasons, pattern of OXC therapy(monotherapy or add-on therapy), current antiepilepticdrugs (AED) with dosages, and qualitative seizure out-come (seizure free, improved, no change, worse) at 1 yearwere retrieved from case records. Summary statisticsincluded mean, standard deviation, minimum, maximumand median for continuous variables, and number andpercentages for categorical variables. Retention rates ofOXC at 1 and 3 years were estimated for each cohortgroup using Kaplan–Meier estimates and corresponding95% confidence intervals.

Results: A total of 98 patients were studied. The major-ity (66.3%) were diagnosed with temporal lobe epilepsy.14.3% received OXC as monotherapy while 85.7% wereon add-on therapy. Reasons for commencing OXCincluded poor seizure control with other AEDs (86.7%),intolerability of other AEDs (11.2%) and allergy to otherAEDs (1%). The mean daily dose of OXC used in the totalpopulation was 947.28 ± 492.21 mg. At 1 year percentageof patients either seizure free or with reduced seizure fre-quency in the monotherapy and add-on therapy groupswere 100% and 72.7% respectively. Only 6 patients discon-tinued OXC therapy. Using the Kaplan–Meier survivalanalysis, the retention rates of OXC at 1 and 3 years were

estimated to be 0.853 (0.749–0.956) and 0.737 (0.570–0.904)respectively.

Conclusions: OXC is well tolerated by patients both asmonotherapy and add-on therapy. The long–term outcomeof treatment shows high retention rates.

doi:10.1016/j.jocn.2007.02.043

613: Self-paced and reactive saccades in Parkinson’s DiseaseMervyn D. Ferdinands, Owen White, N. Georgiou-

Karistianis, Lyn Millist, Caroline Winograd-Gurvich;

Royal Melbourne Hospital

Eye movements are an effective means of evaluatingmotor impairments in patients with Parkinson’s disease(PD). In our previous study, we have noted that self-pacedsaccades to constantly illuminated targets tend to over-shoot in normals, and to a lesser extent in Parkinsonianpatients. (Winograd-Gurvich C et al. Self-paced and repro-grammed saccades in Parkinson’s disease (submitted forpublication). In addition, while PD patients were able toreprogram the amplitude of a saccade, performance wasmore variable (in terms of latency and accuracy) whenreprogramming for saccade direction. Saccades reactingto visual stimuli that appear and then extinguish, ie reactivesaccades, whether predictable or not, tend to undershootwith corrective saccades to acquire targets accurately. Thiswould seem to be separating a purely fronto-collicularpathway, in the case of self-paced saccades, from a pari-eto-fronto-collicular pathway.

This study aims to extend our investigation of inhibitorymechanisms and their effects on saccade performance. Weare looking at saccadic function in Parkinsonian patientsto self-paced and reactive saccades to fixed targets, bothin the presence of and in the absence of visual distractorsplaced in the same horizontal plane and in off verticalplanes.

Preliminary results of this study will be presented.

doi:10.1016/j.jocn.2007.02.044

614: The pharyngeal-cervical-brachial form of Guillain-

Barre syndrome in childhood

Monique M. Ryan, Kavitha Mogale, Jayne H. Antony;

Children’s Hospital at Westmead

There are a number of variant forms of the Guillain-Barre syndrome which are characterized by their localisedor regional involvement of the peripheral and autonomicnerves. As there is no single clinical or serologic markerfor Guillain-Barre syndrome, diagnosis of this conditionis based upon consistent clinical, laboratory and neuro-physiologic findings, with exclusion of other conditionsmimicking this disorder. Recognition of atypical cases

Abstracts / Journal of Clinical Neuroscience 14 (2007) 1009–1040 1021

enables anticipatory monitoring for disease complicationsand identifies therapeutic options for affected children. Aregional variant with predominant facial, neck and armweakness without sensory loss has been reported in adultsbut only very rarely described in childhood. We report clin-ical and neurophysiologic findings in two children with thepharyngeal-cervical-brachial form of Guillain-Barre syn-drome. These are the youngest cases of this uncommon dis-order reported to date.

doi:10.1016/j.jocn.2007.02.045

615: A study on stem cell function in the ischemia-damaged

area after stroke

Aria Omrani; NanoMedical Studies Group, Iran

Studies in neonatal mice show that if neural stem cells(NSCs) are seeded on synthetic extracellular matrix andimplanted into an ischemia-damaged area, then newparenchyma composed of neurons and glia is formedand becomes vascularized. Findings by Eriksson et alindicated neurogenesis from precursors in the subventric-ular zone (SVZ) in vivo in humans, and precursors capa-ble of forming neurons in human subcortical whitematter. For efficient repair after stroke it may be neces-sary to provide NSCs with a platform so that they canreform appropriate brain structure and connections.However, NSCs are concentrated along the subventricu-lar zone, and their migration to the zone of infarctionis limited by a long migratory pathway. Bone marrowcells, being distributed throughout all tissues by thebloodstream, have easy access to the zone of infarction.Brain injury, specifically cerebral ischemia, enhancesbone marrow plasticity and provides an environmentthat supports the differentiation of bone marrow-derivedcells into endothelial cells and neurons. Neovasculariza-tion of the peripheral and coronary vasculature can beenhanced by the exogenous delivery of bone marrow-derived endothelial progenitor cells (EPCs). Some animalstudies indicate intrastriatal and intravenous delivery ofmarrow stromal cells results in a small percentage ofthese cells expressing neuronal markers in ischemic brain.Considering the differentiation of bone marrow-derivedprogenitor cells into endothelial cells and NeuN-express-ing cells , the utility of bone marrow–derived cells offersa novel potential treatment for stroke. The type of func-tional recovery after stroke depends on the site ofimplantation. Some studies report no recovery of senso-rimotor function in rats with intraventricular grafts,whereas animals with intraparenchymal grafts either ipsi-lateral or contralateral to the lesion have shown reducedsensorimotor asymmetry.

doi:10.1016/j.jocn.2007.02.046

616: Axonal excitability properties in hemifacial spasm

Arun V. Krishnan a, Michael Hayes b, Matthew C.

Kiernan a; a Prince of Wales Medical Research Institute

and Prince of Wales Hospital; b Concord Hospital

Introduction: Hemifacial spasm (HFS) is characterisedby involuntary, irregular contractions of muscles inner-vated by the facial nerve. Whether the facial nerve has arelative predisposition for ectopic activity has not beenclarified, nor has the process through which these abnor-mal responses are generated. Nerve excitability techniques,which provide information about membrane potential andaxonal ion channel function, may provide further insightsinto the pathophysiology of HFS.

Method: The excitability properties of the facial nervewere initially measured in a group of control subjectslooking for biophysical differences that may predisposethe facial nerve to ectopic activity. In a second seriesof studies, patients with HFS were investigated. In total,compound muscle action potentials were recorded fromnasalis in 12 controls and 9 HFS patients followingstimulation of the facial nerve anterior to the earlobe.Stimulus-response behaviour using two stimulus dura-tions, threshold electrotonus to 100-ms polarizing cur-rents, a current threshold relationship and the recoveryof excitability following supramaximal stimulation wererecorded on both affected and unaffected sides in HFSpatients.

Results: When compared to normative data from theupper (median nerve) and lower limbs (tibial nerve), therewas ‘fanning-in’ of threshold electrotonus, reduced supe-rexcitability and increased subexcitability in facial nervestudies (P < 0.05), consistent with relative axonal depolar-isation. In subsequent studies in HFS patients, there wereno significant differences in distal facial nerve excitabilityproperties from the affected side in HFS patients whencompared either to the unaffected side or to normativefacial nerve data.

Conclusion: A relative depolarisation of the facial nervein control studies may suggest a propensity for this nerve todevelop ectopic impulse activity. Peripheral facial nervestudies in HFS patients suggest that ectopic impulse gener-ation arises from a more proximal or central location suchas the facial nerve nucleus.

doi:10.1016/j.jocn.2007.02.047

617: Efficacy of conservative treatment, fludrocortisone, and

domperidone for symptomatic orthostatic hypotension in

Parkinson’s diseaseKerrie L. Schoffer, John D. O’Sullivan, Karen O’Maley,

Robert Henderson; Royal Brisbane and Women’s Hospital

Purpose: Orthostatic hypotension (OH) is the most fre-quently reported autonomic feature of Idiopathic Parkin-

1022 Abstracts / Journal of Clinical Neuroscience 14 (2007) 1009–1040