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Show LETTERS TO THE EDITOR Editor's note: The Journal of Neuro- Ophthalrnology welcomes letters as written or e- mail correspondence. Send e- mail to: jdtrobe@ umich. edu. Downbeat Nystagmus and Dolichoectasia of the Vertebrobasilar Artery To the Editor: In 1989, we reviewed the case records and neuroim-aging studies of 41 patients with downbeat nystagmus evaluated by the Neuro- ophthalmology Service at the University of Iowa Hospitals and Clinics. We identified two of 41 ( 5%) patients with downbeat nystagmus of previously undetermined cause who had compression of the caudal brainstem by dolichoectasia of the vertebrobasilar arterial system ( 1). Based on that report, compression of the caudal brainstem by dolichoectasia of the vertebrobasilar artery has now been included in lists identifying the causes of downbeat nystagmus ( 2- 4). Since our report, others ( 5,6), including most recently Lee ( 7) in the September 2001 issue ofthe Journal ofNeuro- Ophthalmology, have identified additional patients with a similar association. Based on our further experience with additional patients with downbeat nystagmus due to other structural disorders and patients with anatomic compression ofthe caudal brainstem by dolichoectasia of the vertebrobasilar artery, we now question the validity ofthe association in all cases for the following reasons: 1. There are patients with anatomic compression and distortion of the caudal brainstem, more severe in degree than the cases referenced in this letter, by other structural disorders that have no downbeat nystagmus ( Fig. 1). 2. Similarly, there are patients with anatomic compression and distortion ofthe caudal brainstem, at least to the degree identified in the referenced cases in this letter, by a dolichoectatic vertebrobasilar artery who have no downbeat nystagmus ( Fig. 2). The anatomic relationship identified in the case reported by Lee ( 7), and the fact that nystagmus resolved after neurovascular decompression in the case reported by Himi et al. ( 6), are compelling points in favor of a cause- and-effect relationship between downbeat nystagmus and dolichoectatic arterial compression of the brainstem. Still, we now believe that other variables must exist in addition to anatomic compression to account for the development of downbeat nystagmus. For example, it may be that the specific point of compressive injury, more than compression in general, is important in producing downbeat nystagmus. FIG. 1. Midsagittal T1 magnetic resonance image of a 55- year- old woman with osteogenesis imperfecta. Note the herniation of the cerebellar tonsils through the foramen magnum ( short white arrow) and the anterior displacement of the medulla ( long white arrow). She has upbeat nystagmus in upgaze, rightbeat nystagmus in rightgaze, and rebound nystagmus, but, in 7 years of follow- up, has never developed downbeat nystagmus. Perhaps ischemic injury to a specific location is more important than compression in general. Intermittent neuro-logically isolated downbeat nystagmus has occurred in a patient with intermittent obstruction of the dominant FIG. 2. Parasagittal T1 magnetic resonance image of a 62- year- old man with bifrontal and bioccipital headaches for one year. His neurologic examination, including ocular motility, has been normal in 5 years of follow- up. Note the marked anatomic compression and distortion of the caudal brainstem by dolichoectasia of the vertebrobasilar artery ( white arrowheads), backward displacement of the caudal brainstem ( short white arrow), and kink at the cervicocranial junction ( long white arrow). / J> 0, DOL. 10.1097/ 01. WNQ. QQO Copyright © Lippincott Willi 0018244 ams t .8; 44.44,7 2. B4 . JJVeuro WilKins. Unauthorized reproduction o hthalmol, Vol. 22, No. 2, 2002 ns article is prohibited. LETTERS TO THE EDITOR JNeuro- Ophthalmol, Vol. 22, No. 2, 2002 vertebral artery ( 8). A combination of compressive and ischemic injury to a specific location may be required. Daniel M. Jacobson, MD Departments of Neurology and Ophthalmology Marshfield Clinic Marshfield, Wisconsin James J. Corbett, MD Departments of Neurology and Ophthalmology The University of Mississippi Medical Center Jackson, Mississippi Reply: I thank Drs. Jacobson and Dr. Corbett for their interest in my case report and for raising an interesting question about the pathogenesis and causality in these cases. The authors cite two lines of reasoning for questioning the relationship between dolichoectasia and downbeat nystagmus: 1. Compression and distortion of the caudal brainstem, that is often severe, might have no downbeat nystagmus and 2. Dolichoectatic vertebrobasilar artery cases with compression might not have downbeat nystagmus I think that the authors are probably correct that there are probably more factors than just compression alone that may be necessary to manifest symptoms. I would argue, however, that the same two points cited above would apply to all the presumed structural causes of downbeat nystagmus. That is to say, not all Chiari malformation ( even severe ones anatomically) produce nystagmus and many are found incidentally. The same could probably be said for hemifacial spasm and dolichoectasia, but we have more data after decompression in these patients to support a causal relationship. Andrew G. Lee, MD Department of Ophthalmology and Visual Sciences University of Iowa Hospitals and Clinics Iowa City, Iowa REFERENCES 1. Jacobson DM, Corbett JJ. Downbeat nystagmus associated with dolichoectasia of the vertebrobasilar artery. Arch Neurol 1989; 46: 1005- 8. 2. Leigh RJ, Zee DS. The diagnosis of disorders of eye movements. In Leigh RJ, Zee DS, eds. The Neurology of Eye Movements, edn 3. New York: Oxford University Press, 1999: 415- 6. 3. Leigh RJ, Averbuch- Heller L. Nystagmus and related ocular motility disorders. In Miller NR, Newman NJ, eds. Walsh and Hoyt's Clinical Neuro- ophthalmology, vol 1, edn 5. Baltimore: Williams andWilkins, 1998: 1472. 4. Dell'Osso LF, Daroff RB. Nystagmus and saccadic intrusions and oscillations. In Glaser JS, ed. Neuro- ophthalmology, edn 3. Philadelphia: Lippincott Williams and Wilkins, 1999: 386. 5. Krespi Y, Verstichel P, Masson C, Cambier J. Nystagmus battant vers le bas et dolichoectasie arterielle vertebrobasilaire. Rev Neurol ( Paris) 1995; 151: 196- 7. 6. Himi T, Kataura A, Tokuda S, et al. Downbeat nystagmus with compression of the medulla oblongata by the dolichoectatic vertebral arteries. Am JOtol 1995; 16: 377- 81. 7. Lee AG. Downbeat nystagmus associated with caudal brainstem compression by the vertebral artery. J Neuro- Ophthalmol 2001 ; 21: 219- 20. 8. Rosengart A, Hedges TR, Teal PA, et al. Intermittent downbeat nystagmus due to vertebral artery compression. Neurology 1993; 43: 216- 8. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohi |
