Abstracts / Journal of Clinical Neuroscience 15 (2008) 337–369 365

463: Neuronal firing patterns of higher order thalamocortical

neurons during Inter-ictal absence seizure transition: Poten-

tial implications for loss of consciousness

Terence J. O’Brien a, Didier Pinault b; a Unversity of

Melbourne, Australia; b Universite Louis Pasteur (Faculte

de Medecine), France

Purpose: Thalamocortical (TC) neurons play a criticalrole in absence related generalized spike-and-wave dis-charges (SWD) being recruited into a highly synchronisedrhythmic firing pattern which blocks the normal functionof first order (FO) thalamic nuclei to transmit primary sen-sory information. However, this alone is unlikely to explainthe loss of consciousness experienced by patients. Littleinformation exists about the involvement of higher-order(HO) TC neurons, which relay corticocortical signals andplay an important role in the integration of sensorimotorinformation, attention and cognition.

Method: Single-cell recordings of TC neurons weremade in vivo, under neurolept anaesthesia, along withEEG recording of the related sensorimotor cortex, in adultmale Generalised Absence Epilepsy Rats from Strasbourg(GAERS) (n = 13). Firing patterns in the posterior (Po;n = 39) thalamic group were compared with the ventroba-sal (VB; n = 20) thalamus (i.e. the principle somatosensoryHO and FO nuclei respectively).

Results: Interictally the median percentage of burst firing/cell was higher in Po cells (15% vs. 5%, p = 0.07), with ahigher median maximal number of action potentials perburst (5 vs. 4, p = 0.02). With the ictal transition both neuro-nal types switched early (240 ± 12 vs. 210 ± 8 msecs prior toseizure onset, p = 0.85) to a rhythmic firing pattern that washighly synchronised with the EEG SWDs and had a high fir-ing probability (0.76 ± 0.04 vs. 0.68 ± 0.06, p = 0.31). Thefiring of the Po cells in relation to each SWD was earlier(�19 ± 2 vs. �12 ± 3 msecs, p = 0.01) and showed moreburst firing (median/cell 50% vs. 30%, p < 0.001).

Conclusions: Somatosensory HO TC neurons areinvolved in the absence-related firing pattern as early andas extensively as their FO counterparts, with more promi-nent burst firing. These features would be expected to resultin a disruption of the function of HO TC neurons to relayand integrate corticocortical information, and thereforemay play a mechanistic role in the loss of consciousness.

doi:10.1016/j.jocn.2007.07.073

601: Respiratory decompensation: An unrecognized potential

complication of Botulinum toxin in at risk patients

Andrew Hughes, Rajinder K. Dhamija, Doug Brown;

Austin Health, Australia

Background: Botulinum toxin is widely used for the treat-ment of dystonia and spasticity. Although relatively safe,

transient local weakness and rarely generalized weaknessrelated to systemic spread can be seen. Pulmonary decom-pensation following botulinum toxin has not previouslybeen described. We report a patient developing type 2 respi-ratory failure following treatment with Botulinum toxin.

Case report: A 45-year-old man with long standing com-plete T5 paraplegia was treated with increasing doses of bot-ulinum toxin for severe lower limb adductor spasticity. Hehad no previous history of any other neuromuscular disease.Initial tratment with 1500 mouse units (mu) of Botulinumtoxin (Dysport), divided equally into each adductor group,resulted in no improvement. Four months later the dose wasincreased to 2500 mu with improvement but a still subopti-mal response. After a further 4 months he received a thirdseries of adductor injections totaling 3000 mu. Eight dayslater he developed gradually increasing upper limb weak-ness, dyspnoea associated with early morning headacheand anxiety, mild dysphagia and some difficulty with cough.His neurological examination revealed new mild diffuseupper limb weakness (4/5). There was no objective facialor bulbar muscle weakness. Pulmonary evaluation showedmarkedly reduced FEV1 (1.4L) and Vital Capacity (1.5L)consistent with a severe restrictive ventilatory defect. Maxi-mal inspiratory and expiratory pressures were severelyreduced. Arterial gases showed pCO2 52 mmHg, pO2 118mmHg, pH 7.39, and bicarb 31 mmol/l with Base Excess+5 mmol/ l, consistent with compensated Type 2 respiratoryfailure. Upper limb NCS and routine EMG were normal.Single fiber EMG showed abnormal jitter and blocking.Repetitive stimulation was normal. The patient was man-aged conservatively and made a full recovery over 4 weeks.

Conclusions: Localized lower limb weakness from Botu-linum toxin in paraplegic patients may not always be offunctional concern and may encourage the use of largerdoses to treat severe spasticity. Our case demonstrates thatgeneralised mild weakness in patients with reduced respira-tory reserve can result in respiratory compromise.

doi:10.1016/j.jocn.2007.07.074

602: Progressive supranuclear palsy presenting as classic

levodopa-responsive Parkinson’s disease of 20 years duration

Andrew Hughes, Rajinder K. Dhamija, Marion Hoffman,

Renate Kalnins; Austin Health, Australia

Background: Despite established clinical diagnostic cri-teria for Progressive Supranuclear Palsy (PSP) cases resem-bling Parkinson’s disease (PD) are well recognised.Atypical features for PD are however almost always pres-ent late in the clinical course. We report a case of patholog-ically proven PSP with a typical and prolonged clinicalcourse for PD.

Case report: In 1985 a 65-year-old man was diagnosedwith PD after presenting with rest tremor involving the left

366 Abstracts / Journal of Clinical Neuroscience 15 (2008) 337–369

hand and foot, bradykinesia of finger movements, cog-wheeling and reduced arm swing. Levodopa led to signifi-cant improvement and he remained clinically stable(modified Webster’s score between 11 and 13; equates tomild disability) for the next 10 years. In 1997 he developedincreasing levodopa-related motor fluctuations and dyski-nesias, postural instability and gate freezing. He declinedgradually but continued to respond well to levodopa (mod-ified Webster’s score ‘‘OFF” 19, ‘‘ON” 13 at levodopa chal-lenge in 1998). In 2002 he developed hallucinations and milddelusions characteristic of levodopa-related neuropsychiat-ric toxicity. Despite occasional falls he remained indepen-dently mobile until 2005 when he died from pneumonia.At no time did he develop significant cognitive impairment,supra nuclear gaze palsy, bulbar dysfunction or axial rigid-ity. Histological examination revealed marked neuronal lossin substantia nigra and locus caeruleus. No Lewy bodieswere found in brain stem nuclei, basal forebrain or cerebralcortex. Immunohistochemical staining showed extensiveneuronal tau positive cytoplasmic neurofibrillary tanglesin substantia nigra, globus pallidus, caudate nucleus, puta-men, and medulla oblongata in a typical distribution forPSP. Alpha-synuclein staining was minimal.

Conclusions: Clinicopathological series have highlightedclinical features useful in distinguishing PSP from PD. Thisexceptional case is reported to highlight that rarely PSP canmimic the ‘‘full hand” of clinical features thought typicalfor PD.

doi:10.1016/j.jocn.2007.07.075

605: Teaching nurses how to diagnose and manage epilepsy in

a developing country: The east timor epilepsy project

Ernie Somerville; South Eastern Sydney and Illawarra Area

Health Service

Aim: To describe the use of flowcharts to guide diagno-sis and management of epilepsy by general health workersin a developing country.

Description: The East Timor Epilepsy Project (ETEP)has 2 main arms: (1) Training general health workers todiagnose and treat epilepsy and (2) Education of commu-

nity leaders that epilepsy is a treatable condition. Bothactivities are carried out at around the same time in thesame districts. Flowcharts are a powerful tool for allow-ing diagnosis and management of medical conditions byhealth workers with limited training in the specific condi-tion. The ETEP aims to train general nurses how to useflowcharts in epilepsy. A standardised questionnaire isfirst administered to the patient and family. 6 of theseresponses are used in flowchart to make or exclude adiagnosis of generalised tonic-clonic seizures by their fam-ily or community. The starting point is any patient who isthought by their community to possibly have epilepsy(there is no requirement for loss of consciousness, shak-ing or falls). The main differential diagnosis is syncopeand the flowchart attempts to make a positive diagnosis.If epileptic seizures are diagnosed, there is then a promptto detect acute symptomatic seizures due to intracranialinfection, such as cerebral malaria, meningitis andencephalitis. If present, urgent referral to a hospitaloccurs. A further prompt ensures that patients are nottreated after their first seizure. Four questions are thenused to detect juvenile myoclonic epilepsy and generalisedtonic-clonic (GTC) seizures on awakening. If either syn-drome is present, the patient receives valproate; otherwise,carbamazepine is used. Nurses then use a treatment flow-chart. This begins with a number of prompts, includingcounselling on safety, first aid, compliance, side effectsand for females, contraception and folic acid. Initial dosesare low and are titrated according to response. When sei-zures continue, there are prompts to review the diagnosis,check for precipitating factors and non-compliance beforeincreasing the dose. Referral to a doctor is advised if thediagnosis is uncertain, seizures continue at the maximumdose or there has been a 2-year seizure-free period.

Conclusions: The use of the flowcharts in training andreview sessions with East Timorese patients and nurses sug-gests a high sensitivity and specificity in the diagnosis ofGTC seizures. Longer term follow-up will be required toconfirm the value of the treatment flowcharts. The projectincludes an evaluation component, which will providesome quantitative data.

doi:10.1016/j.jocn.2007.07.076