Society proceedings 55P
extended Willison analysis and spectral analysis is best suited for the discrimination between neuropathic, myopathic and normal interfer- ence pattern EMG.
76. Diagnostic problems in voluntary nystagmus, a video- supported case report. - M.H. Strothjohann, F. Th6mke (Department of Neurology, University of Mainz, Langen- beckstr. 1, 55101 Mainz)
A 25 year old man reported sudden onset of diplopia, oscillopsia, unsteady gait and falls. Neurological examination revealed spontaneous horizontal pendular eye movements in the primary position which converted to jerk nystagmus on lateral gaze. Direct-current electro- oculography (EOG) showed pendular nystagmus in the primary posi- tion with variable intensity in alternation with nystagmus-free periods (up to 5 s). On lateral gaze, the nystagmus converted to a jerk nystag- mus of variable intensity. The nystagmus was superimposed on optoki- netic nystagmus and pursuit eye movements, and was completely sup- pressed by eye closure and convergence. Because of the reported sud- den onset of oscillopsia, diplopia, unsteady gait and falls, we initially interpreted our patient's nystagmus as an aquired pendular nystagmus due to a brainstem dysfunction of unknown etiology. The EOG-proven variable intensity of this nystagmus and the nystagmus-free periods, however, were not compatible with this assumption. After hearing that the patient had been admitted to various hospitals with the same com- plaints and the same neurological findings, we finally interpreted the condition as voluntary nystagmus superimposed on congenital nystag- mus with Munchhausen's syndrome.
77. Cortical inhibition phenomena after transcranial magnetic stimulation in therapy control of Parkinson's disease. - M. Tegenthoff a, P. Schwenkreis a, E. Fenger b, M. Vorgerd a, W. Greulich b, J.-P. Malin a (aDepartment of Neurology, Ruhr- University, Bochum; bDepartment of Neurology, University Witten-Herdecke, Witten-Herdecke)
Changes of the cortical excitation level in patients with diseases of the extrapyramidal system can be demonstrated by postexcitatory in- hibition (pl) after transcranial magnetic stimulation (TMS). Ten pa- tients with Parkinson's disease were examined in a follow-up study under definite changes of Amantadin 'medication: first investigation (TO); 4days medication pause; second investigation (TI); 7days Amantadin medication; final investigation (T2). Columbia University Rating Scale (CURS) was documented. Using TMS and a double stimulation paradigm (pl-D), threshold intensity and pl alter single stimulation (pI-S) were measured. Threshold intensity increased from TO (42.1 +8.5%) to TI (43.9_+7.4%), and then decreased to T2 (40.7 _+ 9.0%) (P < 0.05). pl-S showed a prolongation from TO to TI (+11.1 -+ 16.7 ms) (P < 0.05), and a shortening to T2 (-16.2 -+ 25.8 ms) (P < 0.(i5). From TO to T1 (0.7 _+ 45.7 ms) (P = 0.954), pl-D exhibited no changes, but decreased to T2 (-14.3 _+ 15.0ms) (P
56P Society proceedings
pat.) lingual responses. In 5 of 8 patients the responses of the orofacial muscles contralateral to the lesion were absent (4 pat.) or delayed (1 pat.). Enoral sensory function was normal in 7 of 8 patients; one patient showed hypesthesia of the right half of the tongue. Median nerve SSEPs were normal in all patients. HMPAO-SPECT imaging performed in 5 patients revealed cerebellar diaschisis in one, suggesting additional cerebro-ponto-cerebellar tract involvement. We conclude that impair- ment of the cortico-lingual and cortico-facial pathways is the most likely explanation of dysarthria in lacunar stroke syndromes.
81. Motor evoked potentials of the tongue, orofacial muscles in amyotrophic lateral sclerosis (ALS). - P.P. Urban, T. Vogt, H.C. Hopf (Neurologische Klinik und Poliklinik der Univer- sit,it Mainz, Mainz)
Detection of subclinical pyramidal tract involvement in ALS using magnetic evoked potentials (MEP) is limited by concurrent lower mo- tor neuron impairment. We evaluated tongue and orofacial MEP in ALS. In 20 ALS patients MEPs were recorded bilaterally from the tongue, buccinator, hypothenar (UL), and anterior tibial muscles (LL). Motor cortex, cervical and lumbar roots, and proximal cranial nerve segments were stimulated magnetoelectrically and the distal nerves electrically. The normal range was calculated from 50 and 43 subjects (limbs and cranial nerves), respectively. An upper motor neuron lesion was assumed when the cortical evoked response was absent or delayed (>mean + 2.5 SD) with the peripheral conduction time and M-response within normal limits. MEPs of the UL were abnormal in 6 patients (8 sides, 20.0%), of the LL in 8 patients (11 sides, 27.5%), the tongue in 11 patients (14 sides, 37.5%), and of orofacial muscles in 10 patients (17 sides, 42.5%). Regarding all limbs, an upper motor neuron lesion was demonstrated in 11 patients (14 sides, 35.0%). Additional MEPs of tongue and orofacial muscles raised the abnormal findings to 16 pa- tients each (tongue: 23 sides, 57.5%; orofacial: 29 sides, 72.5%). Py- ramidal tract signs in 10 patients were confirmed by MEP only includ- ing tongue and orofacial muscle abnormalities. MEPs of tongue and orofacial muscles show a higher sensitivity in detecting pyramidal tract impairment than limb muscle recordings. Combining all recording sites increases the diagnostic yield considerably.
82. The median nerve N30 is generated in area IV of the motor cortex. - T.D. Waberski a, H. Buchner a, N. Hollenborg a, J. Sil- ny b, M. Fuchs c, M. Wagner c (aKlinik fiir Neurologie, RWTH, Aachen; bHelmholtz Institut fiir Biomedizinische Technik, Aachen; Cphillips Forschungslaboratorien, Hamburg)
The frontal SEP component N30 was suspected to be generated in the SMA by the majority of investigators. Patients with Parkinson's or Huntington's disease show a reduced amplitude of the N30, as do nor- mal subjects performing active movements of the stimulated hand. A system was developed with which stimulation of the median nerve was triggered by movements of the fingers l-Ill. In 8 normal subjects the right median nerve was stimulated by movement of the right and, inde- pendently, of the left hand. In 3 additional subjects, a 3D-MR with electrode markers was recorded after the 64-channel SEP measure- ments. Previous experiments showed that the SEPs triggered by move- ment of the left hand were almost identical to the SEPs in rest. The SEPs by movement of the stimulated hand showed a minor reduction of the N20 and P22 amplitude and a clearly reduced amplitude of the frontal N30 and parietal P30, while the brainstem P40 remained un- changed. Mapping of the difference SEPs (movement of the left hand minus movement of the right hand) showed a bipolar field pattern with a maximum around 30 ms poststimulus. Dipole source analysis located as tangentially oriented source of the N30 within the central region hut slightly more frontal to the source of the N20. In 3 subjects, source reconstruction was performed within a realistically shaped head model relative to the individual anatomy and replicated the results. These data suggest a source of the N30 localizing within area IV of the motor
cortex with reduced activity during active movement of the stimulated hand.
83. Self-assessment and cognitive performance tests during EEG recording with a database-controlled interactive assessment tool (DIAT). - B. Weber, T. Dierks, K. Maurer (Department of Psychiatry I, University-Hospital Frankfurt, Frankfurt)
New developments in neurophysiological recordings have potential with respect to computer-based data processing. The testing and evaluation of more complex psychophysiological phenomena has be- come feasible, e.g. various psychological tests during electroencepha- lographic (EEG) recording. In order to develop new psycho- physiological tests, we need better tools for realising, for instance, differentiated self assessment or cognitive performance tests with sev- eral possible solutions. In a current examination we use a database- controlled interactive assessment tool (DIAT) for the verification of experimentally induced or varied emotional and cognitive states. Self- assessment is performed several times during the experimental EEG session in order to avoid possible intervening factors, such as retro- spectively distorted recall. Cognitive performance tests using a multiple choice pattern, for instance recognition tasks, can be facilitated by DIAT, too. The program is self-explainatory, interactive, and it can be operated perfectly by a 'mouse'. It was well accepted by the subjects. Nearly artifact-free EEG-recording during self-assessment or cognitive performance is possible because the experimental subjects only have to watch the monitor continuously and to move one hand slightly. A trig- ger signal is sent to the serial or parallel port for synchronisation of psychological and physiological data recordings.
84. Influence of neuroleptic medication and course of disease on dimensional complexity of brain electrical activity in schizo- phrenic patients. - B. Weber a, T. Dierks a, J. Eckert a, W.K. Strik b, K. Maurer b (aDepartment of Psychiatry I, University- Hospital Frankfurt, Frankfurt; bDepartment of Psychiatry, University-Hospital Wurzburg, Wurzburg)
In recent years the hypothesis of non-linear dynamics in physio- logical time series has been examined and differences in dimensional complexity of brain electrical activity (EEG) between schizophrenic patients and healthy controls have been found. In the present study dimensional complexity was assessed by computing the 'correlation dimension' (D2) of EEG-signals from 20 scalp electrodes during 10 2 s. under resting conditions in 22 mainly medicated subchronic and chronic schizophrenic patients and 22 medication-free age- and sex- matched healthy controls. The correlation dimension generally in- creased with age in both groups and was generally lower in schizo- phrenic patients compared with the healthy controls. Furthermore, subchronic schizophrenic patients showed generally lower D2-values compared with chronic patients. We found some evidence that neu- roleptic medication had an effect on D2-values. Our results are dis- cussed, taking into account findings of other studies with drug-free acute schizophrenics who showed a generally increased dimensional complexity of EEG in specific brain regions. Stage of schizophrenia as well as neuroleptic medication seem to be relevant variables for a biphasic course of D2-values with increase in acute, decrease in sub- chronic and finally partial re-increase in chronic schizophrenia. Further studies with standardised recording and analysis parameters should clarify the complex relations between age, course of disease, medica- tion, psychopathological symptoms, actual brain functions and D2.
85. Conduction block: diagnostic criteria in focal mononeuro- pathies. - F. Weber (Dept. of Neurology, Military Hospital, UIm)
Conduction block and abnormal temporal dispersion are important electrophysiologicul parameters for demyelination. A more than 50%