대한임상신경생리학회지 8(1):1~5, 2006 ISSN 1229-6414 서울대학교의과대학분당서울대병원신경과학교실, 부산대학교의과대학신경과학교실의학연구소, 충남대학교의과대학신경과학교실 최광동 오선영 김지수 Head Thrust Test Kwang-Dong Choi, M.D.*, Sun-Young Oh, M.D., Ji Soo Kim, M.D. Department of Neurology, College of Medicine, Seoul National University, Seoul National University undang Hospital, Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine and Medical Research Institute*, Department of Neurology, Chungnam National University Hospital The head thrust maneuver is a simple bedside test of the higher frequency vestibulo-ocular reflex, which is based on Ewald's second law. It is performed by grasping the patient's head and applying a brief, small-amplitude, high-acceleration head turn, first to one side and then to the other. The patient fixates on the examiner's nose and the examiner watches for corrective rapid eye movements (saccades), which are a sign of decreased vestibular response. The "catch-up" saccades after a head thrust in one direction indicate a peripheral vestibular lesion on that side (in the labyrinth or the 8 th nerve including the root's entry zone in the brain stem). n individual pair of vertical semicircular canals can also be stimulated by turning the head to the right or left by 45 and then by rotating the head in the pitch plane relative to the body. Recent studies have suggested that assessment of individual semicircular canal function by head thrust test may provide useful information for anatomical and functional details of a variety of peripheral vestibulopathies and for predicting the prognosis of vestibular neuritis. In central vestibulopathy, the head thrust test may also be valuable sign to determine dysfunction of the central pathways from individual semicircular canals and its role for the development of diverse central nystagmus. Key Words: Head thrust test, Semicircular canal function, Vestibulopathy 서 론 전정안반사 (vestibulo-ocular reflex, VOR) 는머리회전시머리회전속도와동일하게반대방향으로안구를움직임으로서선명한시각 (vision) 을얻게하는반응으로, 전정신경의머리회전속도정보가전정신경핵 (vestibular nucleus) 을거쳐안구운동신경원 (ocular ddress for correspondence Ji Soo Kim, M.D., Ph.D. Department of Neurology, College of Medicine, Seoul National University Seoul National University undang Hospital 300 Gumi-dong, undang-gu, Seongnam-si, Gyeonggi-do, 463-707, Korea Tel: +82-31-787-7463 Fax: +82-31-719-6828 E-mail : jisookim@snu.ac.kr motor neuron) 으로전달되어발생한다. 1 전정안반사는잠복기가 16 ms 이내로다른안구운동들에비해상당히짧아, 머리회전에대해보다신속하게안구운동을유도한다. 전정안반사는머리회전에반응하는반고리관 (semicircular canal) 에의해유발되는각전정안반사 (angular VOR) 와머리의기울임, 상하또는전후운동과중력등이주어지는상태를감지하는이석기관 (otolithic organ) 에의하여유발되는선전정안반사 (translational VOR) 로분류할수있다. 전정안반사는저주파에서고주파영역전반에결쳐작동하며, 저주파영역에서의이득 (gain) 은 0.3~0.6으로낮은데반해, 고주파영역 (1~5 Hz) 에서는 1에가깝다. 낮은저주파영역에서의이득은원활추종운동 (smooth pursuit) 으로보상된다. 일상생활에서의전정안반사는대부분고주파영역 (1~5 Hz) 에서 Copyright 2006 by the Korean Society for Clinical Neurophysiology 1
최광동 오선영 김지수 이루어지며, 일상적인보행 (locomotion) 시에도 0.5~5 Hz 고개흔들림이발생한다. 2 하지만, 임상에서흔히사용되고있는전정안반사의검사들은저주파영역에만국한되어있어 ( 온도안진검사 : 0.003 Hz, 회전의자검사 : 0.01~0.64 Hz), 일상생활에서의전정안반사를반영하는데무리가있으며, 가쪽반고리관 (horizontal semicircular canal) 의기능평가에만국한되어있다는한계점이있다. 이에반해 (head thrust test) 는 2 Hz 이상고주파영역에서의전정안반사를평가할수있고, 임상에서누구나손쉽게시행할수있으며, 무엇보다도수직반고리관들의기능평가가가능하다는점에서임상적중요성이크다. 본장에서는의원리, 검사법과실제말초및중추성전정신경병증에서의임상적적용에대해설명하고자한다. 검사원리 의원리는빠른속도로반고리관을자극할때흥분성자극이억제성자극보다강하다는 Ewald 제 2 법칙에근거를둔다. 1 수평전정안반사의경우, 머리가수직축을중심으로우측으로회전하면 (yawing) 우측가쪽반고리관의내림프는팽대부방향으로움직여흥분성신호가발생하고, 반대로좌측가쪽반고리관에서는반팽대부방향으로내림프가움직여억제성신호가발생한다. 우측가쪽반고리관의흥분성신호는우측전정신경핵의제 I 형신경세포와좌측의제 II 형신경세포를흥분시키므로좌측제 I 형신경세포는좌측가쪽반고리관의억제성신호와억제성신경세포인인접한제 II 형신경세포의흥분에의하여더욱억제되고, 또한흥분된우측의제 I 형신경세포는교차로 (commissural fiber) 를통한억제성신호에의하여탈억제된제 II 형신경세포의영향으로더욱흥분되어일차구심성신경을통한신호보다더욱강화된원심성신호가유발된다. 1,3 가쪽반고리관에서기원한일차구심신경섬유는안쪽및가쪽전정신경핵 (medial and lateral vestibular nucleus) 으로전달되며, 흥분성 신호는반대편외전신경핵 (abducens nucleus) 을통해왼쪽외직근 (lateral rectus muscle) 을수축시키고, 동시에외전신경의중간신경세포는안쪽세로다발 (medial longitudinal lemniscus, MLF) 을통해반대편동안신경핵 (oculomotor nucleus) 에흥분성신호를전달하여우측내직근 (medial rectus muscle) 을수축시킴으로써결과적으로양쪽안구는좌측으로회전한다. 1 원숭이와사람의전정신경은휴지기에도약 90 spikes/s 로흥분을하고있으며, 4,5 전정계회전속도에대한민감도는약 0.5 spikes/ /s 로 180 /s 의회전속도에서억제성자극은거의 0 으로떨어진다. 따라서, 일측말초성전정신경병증의경우병변쪽으로 180 /s 미만의저주파머리회전에서는정상인반대편내이의억제성신호에의해전정안반사가유지되지만, 180 /s 이상의고주파회전에서는억제성신호가 0 이하로떨어질수없기때문에적절한전정안반사가발생하지못하므로가양성으로나타난다. 수직반고리관들에서의도같은원리로설명될수있다. 검사방법 1. 수평반고리관검사 양손으로환자의머리를잡고검사자의코를쳐다보도록한뒤, 고개를좌측또는우측으로약 10~20 정도회전시킨상태에서빠른속도 ( 회전속도 200~400 /s, 가속도 2000~4000 /s 2 ) 로정면으로고개를회전시키면서, 환자의눈을관찰한다 (Fig. 1). 6 고개회전시회전방향과반대로향하는한번이상의교정성단속운동 (corrective saccade) 이관찰되면양성으로판단한다. 과거에환자가직접고개를회전하는능동적 (active) 가시행되기도하였으나, 검사의예민도가떨어져서실제임상에서는수동적 (passive) 검사만을시행한다. 7 2. 수직반고리관검사 앞반고리관 (anterior semicircular canal) 은수직평 Figure 1. Head thrust test of horizontal semicircular canals. () With subject's face turned a little to the right and her eyes fixed on a distant target, subject waits for her head to be moved rapidly to left by examiner. () fter leftward head movement, gaze is still fixed on target so that no refixation saccades are required. 2 J Korean Society for Clinical Neurophysiology / Volume 8 / June, 2006
면에서 41 전외방으로, 뒤반고리관 (posterior semicircular canal) 은 56 후외방으로위치하며, 앞반고리관과뒤반고리관은서로 90 도의각도를유지하고있다. 가쪽반고리관과마찬가지로수직반고리관도서로쌍을이루고 있는데우측의앞반고리관과좌측의뒤반고리관, 우측의뒤반고리관과좌측의앞반고리관이쌍을이루고있어, 한쪽이자극되면쌍을이루는반대쪽의반고리관은억제가이루어지는기능적인짝 (functional pair) 을형성하고있다 (Fig. 2). 고개를좌측으로약 45 회전시키면우측앞반고리관과좌측뒤반고리관이정면을향하게되고, 이자세에서아래쪽으로빠르게고개를회전시키면우측앞반고리관이흥분하게되어안구는상방으로움직인다 (Fig. 3). 8 반대로상방으로의빠른머리회전시에는좌측뒤반고리관의흥분으로안구가하방으로움직인다. 마찬가지로고개를우측으로약 45 회전시킨상태에서는좌측앞반고리관과우측후반고리관의기능을평가할수있다. 3. 검사실검사 Figure 2. Functional pairs of semicircular canals. 기존의전기또는비디오안구운동기록기로는머리의움직임을측정할수없고, 비디오안구운동기록기의경우고글에움직임을측정할수있는장치를부착한다하더라도, 두부충동시고글의미끌어짐이발생할수있고, 수직방향으로머리회전시고글때문에환자의시야가가려져목표물을놓치는경향이있으며, 낮은 sampling 속도 (60 Hz) 등의문제로인해현재두부충동을이용한안구 C D E F Figure 3. Head thrust test of vertical semicircular canals. () Right anterior/left posterior semicircular canals plane (RLP) with head rotated to the left and head thrust test of right anterior () and left posterior canals (C). (D) Left anterior/right posterior semicircular canals plane (LRP) with head rotated to the right and head thrust test of left anterior (E) and right posterior canals (F). J Korean Society for Clinical Neurophysiology / Volume 8 / June, 2006 3
최광동 오선영 김지수 운동의측정은자기추적코일장치 (scleral magnetic search coil system) 를이용하고있다. 환자를자기장이흐르는정육면체모양의자기추적틀내에위치시키고, 두개의코일중하나는환자의한쪽눈에부착하여안구운동을측정하고, 다른하나는이마에부착하여고개움직임을측정한다. 검사도중환자는안구로부터약 90 cm 떨어진목표물을지속적으로주시하도록한뒤빠른속도 ( 회전속도 200~400 /s, 가속도 2000~4000 /s 2 ) 로고개를각방향으로회전시켜전정안반사의이득을구한다. 전정안반사의이득은안구운동의속도에대한고개움직임속도로구할수있다 (Fig. 4). 8 임상적적용 1. 말초성신경병증 1988 년에 Halmagyi 와 Curthoys 등이전정신경절제술 (vestibular neurectomy) 을받은환자들을대상으로처음시행한이후는현재까지반고리관의기능을평가하는임상검사로널리시행되고있다. 6 전정신경절단술을받은환자에서의민감도는 100% 까지보고되고있고, 6,9 자기추적코일장치로이러한환자들을추적관찰한연구들에의하면의이상은수년후에도지속된다고알려져있다. 이에반해, 비수술적인일측성전정신경병증에서의민감도는 35~71%, 특이도는 84~95 % 로비교적낮게보고되고있으며, 10-13 전정신경염후자기추적코일장치로추적관찰한 연구들에의하면전정신경절단술을받은환자와는달리첫수주이내부터저하되었던병변측의이득이회복되기시작한다고한다. 14 이는손상되었던말초전정기관의회복에의하거나남아있던전정신경에의한중추성보상기전에기인하는것으로알려져있다. 일반적으로는온도안진검사에서비대칭성이 50% 이상인경우양성으로나타나며, 15 최근의한보고에의하면전정신경염의급성기에가양성인환자들의경우온도안진검사의회복율이낮아급성기의양성유무가전정신경염의예후에도중요하다고한다. 16 1998년이후부터는수직반고리관에대한가시행되어내이의모든전정기관에대한개별적인기능평가가가능하게되었고, 8 이를통해말초성전정신경병증의해부학적침범정도와병리학적특성 ( 신경병증또는혈관병증 ) 등을간접적으로알수있게되었다. 보고된논문들에의하면, 전정신경염환자들의일부에서는병변측모든반고리관들의기능이저하되어, 전정신경염이아래전정신경 (inferior vestibular nerve) 도같이침범할수있음을주장하기도하였고, 17 난치성메니에르병 (Meniere's disease) 으로전정신경절단술을받은후에도반복적인어지럼증을호소하는환자들의경우기능이남아있는뒤반고리관에서어지럼증이발생하는것이밝혀지기도하였다. 18 2. 중추성신경병증 중추성전정신경병증에서는를이용한연 C Figure 4. Head thrust test with magnetic search coil technique. () The eye coil is placed on the suject's left eye and the head coil is mounted on the subject's forehead. Head and gaze velocities in semicircular canal paresis (ICP) values for lateral, anterior, and posterior semicircular canals. Gaze is stable in normal subject () in response to head impulse, and therefore, the ICP values are low. Gaze is unstable in a patient unilateral superior vestibular neuritis (C) during head impulse toward the affected lateral and anterior semicircular canals. 4 J Korean Society for Clinical Neurophysiology / Volume 8 / June, 2006
구가많지않아향후활발한연구가필요할것으로생각된다. 몇몇보고들에의하면, 하향안진 (downbeat nystagmus) 을가진환자에서수평 (yaw), 수직 (pitch), 회선 (roll) 가정상인점으로미루어, 수직전정안반사의불균형이하향안진의직접적인원인이아닐수있음을주장하기도하였고, 19 우측핵간안근마비 (internuclear ophthalmoplegia, INO) 환자에서시행한에서좌측의뒤반고리관의기능은심하게저하되어있는데반해좌측의앞반고리관의기능은비교적유지되어있어, 앞반고리관의중추성경로가안쪽세로다발이아닌, 다른경로를경유할것이라고주장하기도하였다. 20 결 론 는임상적으로말초성전정신경병증을진단하는데있어아주손쉽고, 우수한검사이다. 모든반고리관들에대한기능적평가를통해말초성전정신경병증의해부학적침범정도를평가할수있고, 이를통해병변의특성을유추하거나, 전정신경염의경과관찰시회복정도및예후를예측하는데도유용하다. 또한, 중추성전정신경병증의경우각반고리관에서기원하는전정안반사로의기능을개별적으로평가할수있어다양한유형의안진발생에이들전정안반사로의기능적이상이어떤역할을하는지에대한연구에있어서도효과적인분석틀을제공할수있으며, 이들반사로의해부학적경로를규명하는데도유용할것으로판단된다. REFERENCES 01. Leigh RJ, Zee DS. The neurology of eye movements. New York: Oxford University Press, 1999. 02. Grossman GE, Leigh RJ, bel L, Lanska DJ, Thurston SE. Frequency and velocity of rotational head perturbations during locomotion. Exp rain Res 1988;70:470-476. 03. Carleton SC, Carpenter M. fferent and efferent connections of the medial, inferior and lateral vestibular nuclei in the cat and monkey. rain Res 1983;278:29-51. 04. Goldberg JM, Fernandez C. Physiology of peripheral neurons innervating semicircular canals of the squirrel monkey. I. Resting discharge and response to constant angular acceleration. J Neurophysiol 1971;34:635-660. 05. Miles F, raitman DJ. Long-term adaptive changes in primate vestibuloocular reflex. II. Electrophysiological observations on semicircular canal primary afferents. J Neurophysiol 1980;43:1426-1436. 06. Halmagyi GM, Curthoys IS. clinical sign of canal paresis. rch Neurol 1988;45:737-739. 07. lack R, Halmagyi GM, Thurtell MJ, Todd MJ, Curthoys IS. The active head-impulse test in unilateral vestibulopathy. rch Neurol 2005;62:290-293. 08. Cremer PD, Halmagyi GM, w ST, et al. Semicircular canal plane head impulses detect absent function of individual semicircular canals. rain 1998;121:699-716. 09. Halmagyi GM, Curthoys IS, Cremer PD, et al. The human horizontal vestibulo-ocular reflex in responses to highacceleration stimulation before and after unilateral vestibular neurectomy. Exp rain Res 1990;81:479-490. 10. Harvey S, Wood DJ, Feroah TR. Relationship of the head impulse test and head-shake nystagmus in reference to caloric testing. m J Otol 1997;18:207-213. 11. Della Santina CC, Cremer PD, Carey JP, Minor L. Comparison of head thrust test with head autorotation test reveals that the vestibulo-ocular reflex is enhanced during voluntary head movements. rch Otolaryngol Head Neck Surg 2002;128:1044-1054. 12. Perez N, Rama-Lopez J. Head-impulse and caloric tests in patients with dizziness. Otol Neurotol 2003;24:913-917. 13. Schubert MC, Tusa RJ, Grine LE, Herdman SJ. Optimizing the sensitivity of the head thrust test for identifying vestibular hypofunction. Phys Ther 2004;84:151-158. 14. Palla, Straumann D. Recovery of the high-acceleration vestibulo-ocular reflex after vestibular neuritis. J ssoc Res Otolaryngol. 2004;5:427-435. 15. Hamid M. More than a 50% canal paresis is needed for the head impulse test to be positive. Otol Neurotol 2005;26: 318-319. 16. Nuti D, Mandala M, roman T, Zee DS. cute vestibular neuritis: Prognosis based upon bedside clinical tests (Thrusts and Heaves). nn N Y cad Sci 2005;1039:359-367. 17. w ST, Fetter M, Cremer PD, Karlberg M, Halmagyi GM. Individual semicircular canal function in superior and inferior vestibular neuritis. Neurology 2001;57:768-774. 18. Lehnen N, w ST, Todd MJ, Halmagyi GM. Head impulse test reveals residual semicircular canal function after vestibular neurectomy. Neurology 2004;62:2294-2296. 19. Glasauer S, von Lindeiner H, Siebold C, uttner U. Vertical vestibular responses to head impulses are symmetric in downbeat nystagmus. Neurology 2004;63:621-625. 20. Cremer PD, Migliaccio, Halmagyi GM, Curthoys IS. Vestibulo-ocular reflex pathways in internuclear ophthalmoplegia. nn Neurol 1999;45:529-533. J Korean Society for Clinical Neurophysiology / Volume 8 / June, 2006 5