Marti, S.

Schuknecht, B.

Straumann, D.

Tarnutzer, A.

RERO DOC Digital Library

J Neurol (2008) 255:769–771DOI 10.1007/s00415-008-0806-x LETTER TO THE EDITORSJON 2806yrs) with idiopathic late-onset  cerebellar degeneration, in whom brain MRI demonstrated profound atrophy of the flocculus, whereas atrophy of nodulus and uvula was only mild (Fig. 1). Considering the relatively focal nature of the cere-bellar degeneration, we asked whether semicircular canal (SCC)-related reflexes, which are medi-ated mainly by the flocculus, and OL-related reflexes, which are  mediated primarily by the nodulus, are differentially affected in this patient. Since he exhibited promi-nent DBN, we also explored whether VVOR gains were asym-metric, i.e. lower during downward than during upward head rotations. The patient gave informed  written consent. The protocol was approved by the local ethics com-mittee. Vestibular-evoked potentials (VEMPs) were registered from the sternocleidomastoid muscle on both sides [13]. The caloric re-sponse was assessed with electro-nystagmography (monoaural  irrigation on either side, water  temperatures 30 °C and 44 °C). Quantitative head impulse testing was performed as described in [14]. Static ocular counterroll in Sarah MartiAlexander A. TarnutzerBernhard SchuknechtDominik StraumannDissociation between  canal- and otolith- function in cerebellar  atrophyReceived: 24 May 2007Received in revised form: 16 October 2007Accepted: 30 October 2007Published online: 21 February 2008Sirs: Vestibulo-cerebellar degenera-tion affects the vestibulo-ocular  reflex (VOR). For instance, the  capacity to modify VOR gains (via the flocculus [1, 2]) or to suppress vestibular nystagmus by changing the head re gravity (via the nodulus [3, 4]) may be impaired. Cerebellar patients may even demonstrate  bilateral vestibular loss [5]. Whether downbeat nystagmus (DBN), an ocular motor sign  frequently found with vestibulo-cerebellar degeneration, results from asymmetric vertical VOR (VVOR) function, remains debated [6]. Alternatively, DBN may be caused by loss of vertical floccular Purkinje cells [7], asymmetries in vertical smooth pursuit pathways [8, 9], or dissociation of coordinate systems for vertical saccade gener-ation and gaze-holding [10]. DBN is also influenced by otolith (OL) signals [11, 12]. We report on a patient (m, 82 sustained whole-body roll posi-tions and gravity-dependent modu-lation of DBN along the pitch plain were tested on a three-axis motor-driven turntable [12]. Bilateral loss of SCC function was documented by absent caloric responses (not shown) and subtotal gain reductions of the VOR along the planes of all SCCs (Fig. 2A).  Intact OL function was demon-strated by reproducible VEMP (threshold at 95 dB on both sides), preserved static ocular counterroll (Fig. 2B), and prominent modula-tion of DBN in the pitch plane with maximal slow-phase eye velocity in the prone position (Fig. 2C). SCC- and OL-dependent reflexes are mediated by different parts of the vestibulo-cerebellum. The  flocculus is important for the  control of the angular VOR [1, 2], while the nodulus and uvula are mainly involved in the control of OL-related reflexes [3, 4]. In our  patient, the dissociated vestibular deficits with impaired SCC-depen-dent, but preserved OL-dependent reflexes, might therefore be best  explained by the pattern of the  vestibulo-cerebellar degeneration predominantly affecting the floccu-S. Marti, MD () · A. A. Tarnutzer · D. StraumannDept. of NeurologyZurich University HospitalFrauenklinikstrasse 268091 Zurich, SwitzerlandTel.: +41-1/255-3996Fax: +41-1/255-4380E-Mail: sarah.marti@usz.chB. SchuknechtDept. of NeuroradiologyUniversity Hospital Zurich, SwitzerlandFig. 1  High resolution MR with a Ciss sequence covering the cerebellum (slice thickness 0.85 mm) shows marked atrophy of the flocculus (black arrow) bilaterally, while the nodulus (white arrow) is relatively spared769_771_Marti_JON_2806.indd   769 14.05.2008   14:11:40 Uhr770−5 0 5 −5 0 5 −5 0 5 −5 0 5 −5 0 5 3 4 vertical eye position [deg] supine up down 45 deg supine45 deg proneprone upright 1 2 time [sec] 4.9 deg/s 3.5 deg/s 2.2 deg/s 1.9 deg/s 2.4 deg/s −15 −10 −5 0 5 10 15 −15 −10 −5 0 5 10 15 left anterior / right posterior right anterior / left posterior −15 −10 −5 0 5 10 15 −15 −10 −5 0 5 10 15 −15 −10 −5 0 5 10 15 −15 −10 −5 0 5 10 15 horizontal  head−in−space [°]eye−in−space [°] Gr = 0.12 Gl = 0.21 Gr = 0.13 Gr = 0.10 Gl = 0.25 Gl = 0.14 Gl = 0.72 Gr = 0.87 Gr = 0.92 Gr = 0.90 Gl = 0.59 Gl = 0.77 left ear down upright right ear down  chair position [deg]  tors eye pos [deg] −3 −2 −1 0 1 2 3 75 45 30 20 10 0 10 20 30 45 75 a b c Fig. 2  Data are presented in coordinates used by clinicians, i.e. eye rotations to the right, up, and clockwise from the subject’s point of view are positive. A Search-coil recordings of eye and head movements in space during head impulses in the directions of all six semicircular canals (SCC). Left panel: horizontal impulses to the right (positive) and to the left. Middle panel: vertical-torsional impulses in the plane of the right posterior (positive) and left anterior SCC. Right panel: vertical-torsional impulses in the plane of right anterior (positive) and left posterior SCC. Black traces: recordings in the patient; the vestibulo-ocular reflex (VOR) is markedly reduced in all directions. Grey traces: recordings in a healthy subject for comparison. Gr, Gl: VOR gains. B Static ocular counterroll testing on three-axis motor driven turntable (Acutronic, Jona, Switzerland): Modulation of torsional eye position in response to static whole-body roll tilt (75, 45, 30, 20, and 10° left- and right-ear-down) positions, while the subject was looking straight ahead at a laser dot. Black traces: recordings of the patient; the modulation of static ocular counterroll as a function of head roll was similar in right- and left-ear down positions. Grey traces: recordings in an age-matched healthy subject (f, 74 yrs old) for comparison. C Modulation of downbeat nystagmus slow-phase velocity as a function of whole-body position in the pitch plane. Representative sections of vertical eye position traces (duration 5 s) are shown for each of the five turntable positions. The patient directs his gaze towards a flashing laser dot straight ahead. The median vertical slow-phase eye velocity for each section is indicated. Upward ocular drift was maximal in prone and minimal in the supine position769_771_Marti_JON_2806.indd   770 14.05.2008   14:11:41 Uhr  771lus, but relatively sparing the nodu-lus. Whether a primary degenera-tive process of both cerebellar and brainstem structures led to the subtotal loss of VOR function, re-mains unclear [5]. Alternatively, since the cerebellar network is par-ticularly prone to retro- and trans-neuronal degeneration [15], the  severe reduction of VOR gains in our patient with long-standing and marked floccular atrophy is proba-bly caused by a mechanism of sec-ondary retrograde degeneration of floccular brainstem target neurons involved in angular VOR gain con-trol. Clearly, this hypothesis needs further confirmation by histopath-ological studies. A peripheral ori-gin of the vestibular deficits cannot be ruled out, but seems unlikely, because – to our best knowledge – no peripheral vestibular disease would cause such selective and  severe impairment of SCC func-tion, while sparing the otolith path-ways. Finally, the persistence of DBN despite massively decreased vertical SCC function in our pa-tient speaks against the hypothesis that DBN in general results from a VVOR asymmetry [6], but rather supports the theory that some cases of DBN may be caused by loss of vertical gaze-velocity sensitive floccular Purkinje cells, which have predominantly downward on- directions [7]. ■ Acknowledgment  The Vestibulo-Oculo-motor Laboratory of the Neurology Depart-ment at Zurich University Hospital (D.S., A.T., S.M) is supported by the Swiss Na-tional Science Foundation (31-63465.00 /#3200BO-1054534), and Betty and David Koetser Foundation for Brain Research  (Zurich, Switzerland). S.M. is also supported by the Bonizzi-Theler Foundation, Zurich, Switzerland.References 1. Robinson DA (1976) Adaptive gain control of vestibuloocular reflex by the cerebellum. J Neurophysiol 39:954–969 2. Miles FA, Fuller JH, Braitman DJ, Dow BM (1980) Long-term adaptive changes in primate vestibuloocular  reflex. III. Electrophysiological obser-vations in flocculus of normal mon-keys. J Neurophysiol 43:1437–1476 3. Hain TC, Zee DS, Maria BL (1988) Tilt suppression of vestibulo-ocular reflex in patients with cerebellar lesions. Acta Otolaryngol 105:13–20 4. Angelaki DE, Hess BJ (1995) Inertial representation of angular motion in the vestibular system of rhesus mon-keys. II. Otolith-controlled transforma-tion that depends on an intact cerebel-lar nodulus. J Neurophysiol 73:1729–1751 5. Migliaccio AA, Halmagyi GM,  McGarvie LA, Cremer PD (2004)  Cerebellar ataxia with bilateral vestib-ulopathy: description of a syndrome and its characteristic clinical sign. Brain 127:280–293 6. Walker MF, Zee DS (2005) Asymmetry of the pitch vestibulo-ocular reflex in patients with cerebellar disease. Ann N Y Acad Sci 1039:349–358 7. Marti S, Straumann D, Glasauer S (2005) The origin of downbeat nystag-mus: an asymmetry in the distribution of on-directions of vertical gaze-veloc-ity Purkinje cells. Ann N Y Acad Sci 1039:548–553 8. Zee DS, Friendlich AR, Robinson DA (1974) The mechanism of downbeat nystagmus. Arch Neurol 30:227–237 9. Marti S, Bockisch CJ, Straumann D (2005) Prolonged asymmetric smooth-pursuit stimulation leads to downbeat nystagmus in healthy human subjects. Invest Ophthalmol Vis Sci 46:143–14910. Glasauer S, Hoshi M, Kempermann U, Eggert T, Buttner U (2003) Three- dimensional eye position and slow phase velocity in humans with down-beat nystagmus. J Neurophysiol 89:338–35411. Gresty M, Barratt H, Rudge P, Page N (1986) Analysis of downbeat nystag-mus. Otolithic vs semicircular canal influences. Arch Neurol 43:52–5512. Marti S, Palla A, Straumann D (2002) Gravity dependence of ocular drift in patients with cerebellar downbeat  nystagmus. Ann Neurol 52:712–72113. Colebatch JG, Halmagyi GM (2000) Vestibular evoked myogenic potentials in humans. Acta Otolaryngol 120:11214. Schmid-Priscoveanu A, Bohmer A, Obzina H, Straumann D (2001) Caloric and search-coil head-impulse testing in patients after vestibular neuritis. J Assoc Res Otolaryngol 2:72–7815. Smith MC (1975) Histological findings after hemicerebellectomy in man:  anterograde, retrograde and trans-neuronal degeneration. Brain Res 95:423–442769_771_Marti_JON_2806.indd   771 14.05.2008   14:11:41 Uhr

Dissociation between canal- and otolithfunction in cerebellar atrophy

http://doc.rero.ch/record/318740/files/415_2008_Article_806.pdf

Dissociation between canal- and otolithfunction in cerebellar atrophy

Abstract

Similar works

Full text

Available Versions

RERO DOC Digital Library