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CS9.1 Myoclonus
Clinical Symposia / Clinical Neurophysiology 117 (2006) S5–S17
jects and to localize focal nerve conduction anomalies in patients. Methods: Inside a magnetically shielded room, magnetic responses evoked by electrical peripheral nerve stimulation (tibial, median, ulnar nerve; 9 s 1; n = 9000 noise weighted averages) were measured using a planar 49-channel SQUID-detector over plexus or nerve roots of healthy subjects and patients with traumatic nerve root lesions. Impulse propagation paths were reconstructed using a dipole model in a halfspace volume conductor. Results: Over the brachial plexus, cervical and lumbosacral nerve roots of healthy subjects somatosensory evoked magnetic fields were recorded with amplitudes up to 100, 30 and 20 fT, respectively. Spatio-temporal field mappings showed dipolar patterns for the CAC depolarization phase. Dipolar source reconstruction allowed to localize CAC propagation paths along plexus and nerve root fibers. In patients with nerve root compression the conduction block or slowing could be 3D-localized. Conclusion: MNG allows a non-invasive detailed tracing of neural activity propagating in proximal, clinical important, areas; in particular MNG was able to reveal focal anomalies of impulse conduction in patients. However, before MNG will find the way in the clinic, it is mandatory that the sensitivity and specificity of MNG is scrutinized in a clinical oriented approach in patients with well-defined conduction pathologies. doi:10.1016/j.clinph.2006.07.030
CS9.1 Myoclonus P. Brown Institute of Neurology, Sobell Department, UK Myoclonus consists of sudden, brief jerks caused by involuntary abrupt increases or lapses in muscle activity. The classification of myoclonus has been fraught with difficulties, but that based on physiological characterization has gained most acceptance and does serve to guide pharmacological therapy. Here, I will review this classification, highlighting recent advances in our understanding of the pathophysiology of cortical, subcortical and spinal myoclonus. In particular, I will stress those aspects of the pathophysiology of myoclonus that may be informative about mechanisms of normal motor control. doi:10.1016/j.clinph.2006.07.031
CS9.2 Paroxysmal dystonias M. Edwards Institute of Neurology, UCL, Sobell Department, UK Background: Paroxysmal dystonias are a diverse group of conditions characterised by attacks of involuntary
S13
movement, often precipitated by particular stimuli (e.g. movement, alcohol). Aims: To discuss the range of presentations of paroxysmal dystonias, their classification, pathophysiology and treatment. Methods: Presentation of literature and videos. Results: Paroxysmal dystonias can be classified into four main types: paroxysmal kinesogenic dyskinesia (PKD), paroxysmal non-kinesogenic dyskinesia (PNKD), paroxysmal exercise induced dystonia (PED), and paroxysmal nocturnal dystonia (PND). Primary forms of these disorders occur, and tend to have autosomal dominant inheritance. In primary forms of these conditions, patients are normal between attacks. PKC is characterised by short lived attacks (seconds–minutes) of abnormal limb posturing precipitated by sudden movement. The attacks are usually very successfully treated with carbamazepine. A number of families have been linked to the pericentromeric region of chromosome 16. Electrophysiological studies have found reduced short intracortical inhibition, reduced transcallosal inhibition, and reduced first phase of reciprocal inhibition. The abnormalities in transcallosal inhibition normalise with treatment. PNKD is characterised by longer attacks of abnormal movement (hours), precipitated by coffee, alcohol and fatigue. Some families have been found to have mutations in the myofibrillogenesis regulator 1 gene – a gene which is involved in metabolising some breakdown products of coffee and alcohol. PED is characterised by abnormal postures of the limbs that occur following prolonged exercise. This can occur as a primary disorder, but is also seen in Parkinson’s disease. PND is characterised by abnormal limb movement during sleep, and is caused by a variety of unrelated conditions including REM sleep behaviour disorder, periodic limb movements of sleep, and autosomal dominant nocturnal frontal lobe epilepsy (as well as other types of nocturnal seizures). In common with other paroxysmal disorders (e.g. episodic ataxias), the underlying deficit in many of these conditions is thought to be a channelopathy. Conclusions: Paroxysmal dystonias can occur as primary or secondary phenomena, and may be related to disorders of channel function. Clinical characteristics, in particular duration of attacks and precipitants of attacks, help with classification of these diverse disorders. doi:10.1016/j.clinph.2006.07.032
CS9.3 Startle disorders M.A.J. de Koning-Tijssen Academic Medical Centre, Amsterdam, Netherlands Diagnosis of startle disorders depends on detailed clinical history, video registration, genetic screening and if necessary, electrophysiological testing. Startle disorders can be divided in three main groups of disorders with abnormal responses to startling stimuli. Hyperekplexia forms the first
jects and to localize focal nerve conduction anomalies in patients. Methods: Inside a magnetically shielded room, magnetic responses evoked by electrical peripheral nerve stimulation (tibial, median, ulnar nerve; 9 s 1; n = 9000 noise weighted averages) were measured using a planar 49-channel SQUID-detector over plexus or nerve roots of healthy subjects and patients with traumatic nerve root lesions. Impulse propagation paths were reconstructed using a dipole model in a halfspace volume conductor. Results: Over the brachial plexus, cervical and lumbosacral nerve roots of healthy subjects somatosensory evoked magnetic fields were recorded with amplitudes up to 100, 30 and 20 fT, respectively. Spatio-temporal field mappings showed dipolar patterns for the CAC depolarization phase. Dipolar source reconstruction allowed to localize CAC propagation paths along plexus and nerve root fibers. In patients with nerve root compression the conduction block or slowing could be 3D-localized. Conclusion: MNG allows a non-invasive detailed tracing of neural activity propagating in proximal, clinical important, areas; in particular MNG was able to reveal focal anomalies of impulse conduction in patients. However, before MNG will find the way in the clinic, it is mandatory that the sensitivity and specificity of MNG is scrutinized in a clinical oriented approach in patients with well-defined conduction pathologies. doi:10.1016/j.clinph.2006.07.030
CS9.1 Myoclonus P. Brown Institute of Neurology, Sobell Department, UK Myoclonus consists of sudden, brief jerks caused by involuntary abrupt increases or lapses in muscle activity. The classification of myoclonus has been fraught with difficulties, but that based on physiological characterization has gained most acceptance and does serve to guide pharmacological therapy. Here, I will review this classification, highlighting recent advances in our understanding of the pathophysiology of cortical, subcortical and spinal myoclonus. In particular, I will stress those aspects of the pathophysiology of myoclonus that may be informative about mechanisms of normal motor control. doi:10.1016/j.clinph.2006.07.031
CS9.2 Paroxysmal dystonias M. Edwards Institute of Neurology, UCL, Sobell Department, UK Background: Paroxysmal dystonias are a diverse group of conditions characterised by attacks of involuntary
S13
movement, often precipitated by particular stimuli (e.g. movement, alcohol). Aims: To discuss the range of presentations of paroxysmal dystonias, their classification, pathophysiology and treatment. Methods: Presentation of literature and videos. Results: Paroxysmal dystonias can be classified into four main types: paroxysmal kinesogenic dyskinesia (PKD), paroxysmal non-kinesogenic dyskinesia (PNKD), paroxysmal exercise induced dystonia (PED), and paroxysmal nocturnal dystonia (PND). Primary forms of these disorders occur, and tend to have autosomal dominant inheritance. In primary forms of these conditions, patients are normal between attacks. PKC is characterised by short lived attacks (seconds–minutes) of abnormal limb posturing precipitated by sudden movement. The attacks are usually very successfully treated with carbamazepine. A number of families have been linked to the pericentromeric region of chromosome 16. Electrophysiological studies have found reduced short intracortical inhibition, reduced transcallosal inhibition, and reduced first phase of reciprocal inhibition. The abnormalities in transcallosal inhibition normalise with treatment. PNKD is characterised by longer attacks of abnormal movement (hours), precipitated by coffee, alcohol and fatigue. Some families have been found to have mutations in the myofibrillogenesis regulator 1 gene – a gene which is involved in metabolising some breakdown products of coffee and alcohol. PED is characterised by abnormal postures of the limbs that occur following prolonged exercise. This can occur as a primary disorder, but is also seen in Parkinson’s disease. PND is characterised by abnormal limb movement during sleep, and is caused by a variety of unrelated conditions including REM sleep behaviour disorder, periodic limb movements of sleep, and autosomal dominant nocturnal frontal lobe epilepsy (as well as other types of nocturnal seizures). In common with other paroxysmal disorders (e.g. episodic ataxias), the underlying deficit in many of these conditions is thought to be a channelopathy. Conclusions: Paroxysmal dystonias can occur as primary or secondary phenomena, and may be related to disorders of channel function. Clinical characteristics, in particular duration of attacks and precipitants of attacks, help with classification of these diverse disorders. doi:10.1016/j.clinph.2006.07.032
CS9.3 Startle disorders M.A.J. de Koning-Tijssen Academic Medical Centre, Amsterdam, Netherlands Diagnosis of startle disorders depends on detailed clinical history, video registration, genetic screening and if necessary, electrophysiological testing. Startle disorders can be divided in three main groups of disorders with abnormal responses to startling stimuli. Hyperekplexia forms the first