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WS-26-3 Alteration of blink reflexes in patients with supratentorial and infratentorial lesions
Workshop 26. Brain stem reflexes WS-26. BRAIN STEM REFLEXES
I WS-26-1
] Localizing value of excitatory and inhibitory trigeminal reflexes
B.W. Ongerboer de Visser. Department of Clinical
Neurophysiology, Academic Medical Centre, Amsterdam Recordings of the two blink reflexes (BR1, BR2), jaw (masseter) reflex (JR) and masseter inhibitory reflex (MIR) provide information on E M G performance at three levels in the trigeminal system, extending from the caudal medullary area to the upper midbrain. BR1 is relayed through an oligosynaptic arc in the pons. Impulses for BR2 descend through the spinal trigeminal tract (STY) and are conducted from the caudal STY nucleus through polysynaptic medullary pathways, running both ipsi- and contralaterally to the stimulated side before making connections with the facial nuclei. These trigemino-facial connections pass through the lateral reticular formation, medially to STT. Afferent nerve impulses for JR are related to proprioceptive cells in the trigeminal midbrain nucleus, which has collateral links with the masseter motoneurons in the pons. The M I R evoked by mental nerve stimulation and recorded bilaterally with the same electrode position used for JR, consists of early and late phases of electrical silent periods. (SPI, SP2) in masseter E M G activity. SP1 is mediated by one inhibitory interneuron in the midpons, that projects bilaterally to the masseter nuclei. Afferent for SP2 descend in Sq"F and connect with a polysynaptic chain at the pontomedullary junction. The last interneuron is inhibitory and gives rise to ipsi- and contralateral collaterals to the masseter motoneurons. This presentation will discuss patterns and combinations of reflex abnormalities related to symptoms, and CT-scan or MRI or neuropathological lesions that can be observed in intrinsic brainsten diseases. I
I
IWS-26-21 Brain stem reflexes Amos D. Korczyn. Sackler School of Medicine, Tel Aviv
University, Ramat Aviv 69978, Israel The pupillary cycle time can be of value in evaluating afferent optic nerve activity as well as autonomic efferent function, primarily in its parasympathetic but also in its sympathetic outflows. Although it is non-invasive and easy to perform, abnormalities are not specific. The vestibulo-ocular reflex (VOR) relies on efferent activity in the VIII cranial nerve and recording of ocular movements. This method can be very sensitive in detecting abnormalities of the brain-stem, e.g. in the pons, midbrain, as well as in the connecting medial longitudinal fascicle. Trigmenino-trigeminal reflexes, e.g. masseter inhibitory reflexes, and trigemino-facial reflexes, e.g. the blink reflex, are easily elicited electrophysiologically and accurately measured. They can reliably indicate the site of pontine lesions. The techniques used for performance of these reflexes will be demonstrated, together with indicative abnormal lesions.
IWS-26-31
Alteration of blink reflexes in patients with supratentorlal and infratentorial lesions
Hirotsune Kawamura, Takaomi Taira, Tatsuya Tanikawa, Hiroko Kawabatake, Hiroshi lseki, Tateki Nagao, Kintomo Takakura. Department of Neurosurgery, Neurological
Institute, Tokyo Women's Medical College, Tokyo, Japan Electrically elicited blink reflexes were investigated in 50 patients with unilateral hemispheric or diencephalic lesion and in 32 cerebello-pontine angle tumors and 20 brainstem lesions. In all
$51
of this series, the lesions were further localized by X-ray computed tomography and magnetic resonance imaging. The abnormality of the late blink reflexes presented 3 different patterns, afferent block or delay, efferent block and Type C abnormality reported by B.W. Ongerboer de Visser. For example, in case of the left lateral medullary dysfunction, t h e type C demonstrated normal late response on the intact side and an absence of the late response on the lesion side after stimulation of the rightsupraorbital nerve, and afferent block after stimulation of the left supra-orbital nerve ipsilateral to the lesion. In supratentorial and midbrain lesions, if the type C obtained, we could highly suggest the possibility of appearance of contralateral corticofugal excitatory effect either on the ascending pathway at the lateral bulbar reticular formation or the spinal trigeminal tract in the lower brainstem. However, the afferent block or delay came from loss of the contralateral corticofugal excitatory influence to only the spinal trigeminal tract. O n the other hand, in pontine, medullary lesions and C-P angle tumors, based on the different type of abnormality of the late blink reflex, we could suspect the location of brainstem dysfunction including or excluding ascending fibers to the facial nucleus at the lateral reticular formation of the lower brainstem. As for alteration of the late blink reflex, we will focus on clinical assessment of brainstem dysfunction in various CNS insults.
l WS-26-41 Paired stimuli and the blink reflex. Evidence for postpulse effects Josep Vails-Sol& Unitat d'EMG, Servei de Neurologia, Hospital
Clinic, Barcelona, Spain Paired stimulation is routinely used to assess brainstem neuronal excitability. The inhibition of the response to the second stimulus of the pair is a well known phenomenon. Other effects, less commonly investigated, have also an important physiological meaning. Using two different paradigms in 14 normal volunteers, we have documented that repeated presentations of a pair of stimuli induce facilitation of the response to the first stimulus of the pair. First, we recorded the response of the orbicularis oculi to forearm taps applied alone or paired with an expected supraorbital nerve electrical stimulus. Responses to taps alone were inconsistent and of very low amplitude. Responses to taps preceding the supraorbital nerve electrical stimulus were more consistent and significantly larger. Second, we gave auditory stimuli that could be followed at a variable time interval by a supraorbital nerve electrical stimulus. Series of 5 trials containing only the auditory stimulus were alternated with series of 5 trials containing both stimuli. Responses to the auditory stimulus showed habituation along the trial series regardless of whether or not there was an impending electrical stimulus. However, habituation was always less pronounced in the trial series containing both stimuli than in those containing only the auditory stimulus. In both studies we also observed inhibition of the response to the supraorbital nerve electrical stimulation, which was complete at intervals of 50 to 200 ms. The retrograde facilitatory effects described above can be described as postpulse facilitation and are attributed to sensitization of either the facial alphamotoneurons or other neurons at a premotoneuronal level.
t WS-26-5 ] Jaw reflexes in craniofacial pain syndromes G. Cruccu. Department of Neurological Sciences, University of Rome "La Sapienza", Rome, Italy Physiological and electrical stimulations in the trigeminal territory evoke excitatory or inhibitory reflexes in the jaw-closing muscles.
I WS-26-1
] Localizing value of excitatory and inhibitory trigeminal reflexes
B.W. Ongerboer de Visser. Department of Clinical
Neurophysiology, Academic Medical Centre, Amsterdam Recordings of the two blink reflexes (BR1, BR2), jaw (masseter) reflex (JR) and masseter inhibitory reflex (MIR) provide information on E M G performance at three levels in the trigeminal system, extending from the caudal medullary area to the upper midbrain. BR1 is relayed through an oligosynaptic arc in the pons. Impulses for BR2 descend through the spinal trigeminal tract (STY) and are conducted from the caudal STY nucleus through polysynaptic medullary pathways, running both ipsi- and contralaterally to the stimulated side before making connections with the facial nuclei. These trigemino-facial connections pass through the lateral reticular formation, medially to STT. Afferent nerve impulses for JR are related to proprioceptive cells in the trigeminal midbrain nucleus, which has collateral links with the masseter motoneurons in the pons. The M I R evoked by mental nerve stimulation and recorded bilaterally with the same electrode position used for JR, consists of early and late phases of electrical silent periods. (SPI, SP2) in masseter E M G activity. SP1 is mediated by one inhibitory interneuron in the midpons, that projects bilaterally to the masseter nuclei. Afferent for SP2 descend in Sq"F and connect with a polysynaptic chain at the pontomedullary junction. The last interneuron is inhibitory and gives rise to ipsi- and contralateral collaterals to the masseter motoneurons. This presentation will discuss patterns and combinations of reflex abnormalities related to symptoms, and CT-scan or MRI or neuropathological lesions that can be observed in intrinsic brainsten diseases. I
I
IWS-26-21 Brain stem reflexes Amos D. Korczyn. Sackler School of Medicine, Tel Aviv
University, Ramat Aviv 69978, Israel The pupillary cycle time can be of value in evaluating afferent optic nerve activity as well as autonomic efferent function, primarily in its parasympathetic but also in its sympathetic outflows. Although it is non-invasive and easy to perform, abnormalities are not specific. The vestibulo-ocular reflex (VOR) relies on efferent activity in the VIII cranial nerve and recording of ocular movements. This method can be very sensitive in detecting abnormalities of the brain-stem, e.g. in the pons, midbrain, as well as in the connecting medial longitudinal fascicle. Trigmenino-trigeminal reflexes, e.g. masseter inhibitory reflexes, and trigemino-facial reflexes, e.g. the blink reflex, are easily elicited electrophysiologically and accurately measured. They can reliably indicate the site of pontine lesions. The techniques used for performance of these reflexes will be demonstrated, together with indicative abnormal lesions.
IWS-26-31
Alteration of blink reflexes in patients with supratentorlal and infratentorial lesions
Hirotsune Kawamura, Takaomi Taira, Tatsuya Tanikawa, Hiroko Kawabatake, Hiroshi lseki, Tateki Nagao, Kintomo Takakura. Department of Neurosurgery, Neurological
Institute, Tokyo Women's Medical College, Tokyo, Japan Electrically elicited blink reflexes were investigated in 50 patients with unilateral hemispheric or diencephalic lesion and in 32 cerebello-pontine angle tumors and 20 brainstem lesions. In all
$51
of this series, the lesions were further localized by X-ray computed tomography and magnetic resonance imaging. The abnormality of the late blink reflexes presented 3 different patterns, afferent block or delay, efferent block and Type C abnormality reported by B.W. Ongerboer de Visser. For example, in case of the left lateral medullary dysfunction, t h e type C demonstrated normal late response on the intact side and an absence of the late response on the lesion side after stimulation of the rightsupraorbital nerve, and afferent block after stimulation of the left supra-orbital nerve ipsilateral to the lesion. In supratentorial and midbrain lesions, if the type C obtained, we could highly suggest the possibility of appearance of contralateral corticofugal excitatory effect either on the ascending pathway at the lateral bulbar reticular formation or the spinal trigeminal tract in the lower brainstem. However, the afferent block or delay came from loss of the contralateral corticofugal excitatory influence to only the spinal trigeminal tract. O n the other hand, in pontine, medullary lesions and C-P angle tumors, based on the different type of abnormality of the late blink reflex, we could suspect the location of brainstem dysfunction including or excluding ascending fibers to the facial nucleus at the lateral reticular formation of the lower brainstem. As for alteration of the late blink reflex, we will focus on clinical assessment of brainstem dysfunction in various CNS insults.
l WS-26-41 Paired stimuli and the blink reflex. Evidence for postpulse effects Josep Vails-Sol& Unitat d'EMG, Servei de Neurologia, Hospital
Clinic, Barcelona, Spain Paired stimulation is routinely used to assess brainstem neuronal excitability. The inhibition of the response to the second stimulus of the pair is a well known phenomenon. Other effects, less commonly investigated, have also an important physiological meaning. Using two different paradigms in 14 normal volunteers, we have documented that repeated presentations of a pair of stimuli induce facilitation of the response to the first stimulus of the pair. First, we recorded the response of the orbicularis oculi to forearm taps applied alone or paired with an expected supraorbital nerve electrical stimulus. Responses to taps alone were inconsistent and of very low amplitude. Responses to taps preceding the supraorbital nerve electrical stimulus were more consistent and significantly larger. Second, we gave auditory stimuli that could be followed at a variable time interval by a supraorbital nerve electrical stimulus. Series of 5 trials containing only the auditory stimulus were alternated with series of 5 trials containing both stimuli. Responses to the auditory stimulus showed habituation along the trial series regardless of whether or not there was an impending electrical stimulus. However, habituation was always less pronounced in the trial series containing both stimuli than in those containing only the auditory stimulus. In both studies we also observed inhibition of the response to the supraorbital nerve electrical stimulation, which was complete at intervals of 50 to 200 ms. The retrograde facilitatory effects described above can be described as postpulse facilitation and are attributed to sensitization of either the facial alphamotoneurons or other neurons at a premotoneuronal level.
t WS-26-5 ] Jaw reflexes in craniofacial pain syndromes G. Cruccu. Department of Neurological Sciences, University of Rome "La Sapienza", Rome, Italy Physiological and electrical stimulations in the trigeminal territory evoke excitatory or inhibitory reflexes in the jaw-closing muscles.