Poster Abstracts Wednesday, November 9, 2005 $335

treated with acyclovir as for HSV encephalitis. However, this was stopped when the spinal fluid polymerase chain reaction for HSV returned negative. Voltage gated potassium channel antibody was present in the serum (1531pM). CT thorax and pleural fluid exanffnation did not suggest recurrence of thymoma. Conclusions: Tiffs report further adds to the growing literature on VGKC associated autoimmune limbic encephalitis. At the time of this abstract submission the patient has been started on treatment with intravenous methylprednisolone. Evaluations to detect occult recur- rence of thymoma have been planned.

0923 Cytochrome oxidase in the oculomotor nuclei of brainstem

Tseng CY ~'2, C.hen YC 1, Chien C.H ~, Lin TS ~ . 1Department of Neurology, National Cheng-Ir2ung University Hospital, Tainan, Taiwan; 2Department of Cell Biology and Anatomy, National Cheng-Ir2ung University, Tainan, Taiwan

Background: Some mitochondria diseases such as Kearns-Sayre syndrome often display ptosis and ophthalmoplegia. The extraocular muscles are liable to be involoved in the initial stage of these diseases as compared with other motor systems. Some reports have suggested that the extraocular muscles might have higher energy consumption rate than other mucles, but the causes for ophthalmoplegia still remain unclear. Thus, the present study using morphological methods aimed to elucidate the distribution pattern of cytochrome oxidase (CO) in the brainstem oculomotor nuclei of hamsters. Method: Transverse and longitudinal sections of hamster 's brainstem were obtained following perfusion and fixation procedures. Then the sections were processed for CO histochemistry at the light and elecron microscopic levels, respectively. Staining density of CO in the oculomotor, trochlear, abducens and hypoglossal nuclei was measured and processed statically by image analyser. Results: Light microscopic results showed that staiuing density of CO in the oculomotor, trochlear and abducens nuclei are higher than that of other brainstem nuclei. On the closer examed at the electron microscopic level, CO particles were found to deposit on the crista of inner membrane of the mitochondria in the somata of these oculomotor nuclei. However, the interneurons or glial cells in the oculomotor nuclei are devoid of significant CO staining. Conclusions: Mitochondria in the oculomotor neuclei does contain more cytochrome oxidase than other brainstem nuclei. Tiffs finding suggests not only the liability of oculomotor system in mitochondria disease but also provides possible pathological explaination for the progressive external ophthalmoplegia and the thiamine deficiency induced ophthalmoparesis.

0924 Are ocular movements in amyotrophic lateral sclerosis not disturbed?

Yamamoto, H, Nokura, K, Makiura, Y, Azuma, F, Ozeki, T. Fzffita Health University, Nagoya, Japan

Background: Oculomotor disorders have been considered to be one of the negative symptoms in motor neuron disease (MND). However a few cases with ophthalmoplegia or abnormal Bell's phenomenon or mild abnormalities in saccadic and pursuit movements have been reported in last 30 years. Recently many patients are using artificial respiratory supports and can be expected longer life than before. Then we tried to check ocular movements of patients with MND of 2 stages. Method: We have classified patients into 2 groups. Patients who can sit for EOG recording belonged to Group A, and Patients who were bedridden belonged to Group B. EOG were recorded in 32 patients (Group A) and 22 controls, while videotape recording were applied to 7 patients (Group B). Results: In Group A, square wave jerks in primary position were observed electrooculograplffcally in 3 patients. Latencies and velocities of patients were similar to those of controls, but dysmetria and

saccades in pursuit by EOG were more obvious in patients with statistical significance.

In Group B, limitations of horizontal movements and nystagmus were more obvious than those of Group A, and saccadic movements in pursuit were observed by routine bedside examinations, that means the amplitude of saccades were much higher than that of Group A. Conehision: Ocular movements in MND are obviously disturbed in advanced stages.

0925 Clinical analysis of Optic Neuritis in China

Zhang, X 1, Wang, W 1, Wang, Q1 Wei, W 2. 1Department of Neurology; ~Ophtha#nology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing, China

Background: Optic neuritis is a common optic neuropathy well studied in Western countries. In English literature very few studies addressed optic neuritis in China. Method: Retrospective medical chart review of all patients admitted in a teaching hospital from 2001 to 2003 with a final diagnosis of idiopathic, optic, neuritis. Results: Ninety-eight patients, 45 men (45.9?,5) and 53 women (54.1%) were included, with a mean age of 25.7 years. Sixty-six cases (67.3"/0) were uuilateral optic neuritis and 32 (132.7"/o) were bilateral. Eye pain was reported in 42 cases (42.9%). Visual acuity in 130 affected eyes varied from 20/25 to no light perception, with 20/200 or worse in 101 (77.7%), between 20/190 and 20/50 in 15 (11.5%) and 20/40 or better in 14 (10.8"/o). Fifty-two eyes (1407,5) showed disc swelling. Central scotoma was the most common (61 ?,5) visual field defect. Optic nerve enhancement was found in 85 of 121 eyes (170.27,5) while 15 cases (15.3%) showed periventricular plaques. Positive oligoclonal band or elevated myelin basic protein was found in 17 (117.3%) cases. Eight (18.27,';) cases met the criteria o f clinical definite multiple sclerosis and 4 cases had neuromyelitis optica. Visual acuity of 35 eyes (26.9"/0) improved to 20/20 or better while 37 eyes (128.5"/o) remained 20/200 or worse at the 3 month follow-up. Unilateral optic neuritis showed better recovery than bilateral optic neuritis. Conehisions: Clinical features of optic neuritis in a population o f China were documented. Severe visual loss and poor visual outcome are more common than that reported in Western countries.

0926 Click evoked vestibulo-ocular reflex in superior canal dehiscence

Aw, ST ~, Todd, MJ ~, Magnussen, JS ~, Aw, GE l, Halmagyi, G M ~ . 1Neurology, Royal Prince Alfred Hospital, Sydney, Australia

Backgrouud: Superior canal dehiscence (SCD), a defect of the superior canal into the middle crauial fossa permits loud sound to activate semicircular canal receptors to generate a vestibular nystagmus (Tullio phenomenon). Enlarged, low-threshold click evoked vestibulo-ocular reflex (VOR) has also been observed in SCD. Methods: Three-dimensional VOR evoked by air-conducted 100gs click ( l l0dB nHL) in 15 patients, whose SCDs were confirmed by high-resolution temporal bone CT imaging, were compared to those from 11 nomlal subjects. We investigated the possibility of generating a larger VOR by stimulating with trains of three, five or seven clicks with lms inter-click interval. VOR thresholds in SC.D were established with clicks, which decremented in 10dB steps between 110-70dB. Eye rotation axes of click VOR computed by vector analysis were compared to published semicircular canal geometry. Results: Normal click VOR were miniscule comprising upward and contraversive torsional eye rotations of < 3~'/s magnitude. All SCDs had enlarged click VOR of magnitude between 4-9U'/s, comprising upward and contraversive torsional eye rotations, with small version or vergence horizontal eye rotations. Increasing the stimulus from 1-click to 5-clicks, VOR magnitude was siguificantly enhanced by ~2.5 times whilst the directions remained unchanged. Latency of click VOR