Downbeat Nystagmus - Periodic Alternating Nystagmus

Downbeat Nystagmus; Periodic Alternating NystagmusPowerPoint Presentation: Downbeat Nystagmus and Periodic Alternating Nystagmus: http://library.med.utah.edu/NOVEL/Wray/PPT/Downbeat_Nystagmus_PAN.ppt Shirley H Wray, M.D., Ph.D.Blurred visionThis patient carries a diagnosis of multiple sclerosis.This is a unique patient with multiple sclerosis who has periodic downbeat nystagmus and periodic alternating nystagmus (PAN). The combination of downbeat nystagmus and PAN was first reported in a case of multiple sclerosis by Keane in 1974 (5). It is also reported to occur in the setting of severe hypomagnesemia possibly associated with thiamine deficiency (1). The eye movements show: 1. No nystagmus initially in primary gaze 2. A period of downbeat nystagmus in central gaze 3. A period of PAN 4. No nystagmus on upgaze. Part way through the period of downbeat nystagmus, the direction of the nystagmus changes to a spontaneous horizontal jerk nystagmus present in central gaze, which reverses direction approximately every two minutes - diagnostic of PAN. Periodic Alternating Nystagmus: Because the period of oscillation in one direction is long, about 4 minutes, the diagnosis of PAN may be missed unless the examiner observes the nystagmus for several minutes. As the nystagmus finishes one cycle of right beating nystagmus, a brief transition period occurs during which there may be brief beats of downbeat nystagmus before the next half cycle starts of left beating nystagmus. Although rare, acquired PAN is perhaps the best understood of all forms of nystagmus and was the first for which an effective treatment was identified with the drug baclofen. Convergence can be used to suppress PAN in some patients. Box 10-5 Clinical features of Acquired Periodic Alternating Nystagmus Pg 493(8). The pathogenesis of PAN is due to a lesion of the cerebellar nodulus and uvula. Acquired PAN has been reported in association with a number of conditions. Table 10-4 Etiology of Periodic Alternating Nystagmus Pg 459 (8).Neuroimages were not available in this patient.Lesions of the cerebellar nodulus and uvula.DemyelinationTable 10-4 Etiology of Periodic Alternating Nystagmus Pg459 (8)The GABA-ergic drug, baclofen (30 mg/day), abolishes acquired PAN in most patients, but only helps occasional patients with the congenital form of PAN. This patient was seen prior to the availability of baclofen to treat PAN.1. Du Pasquier R, Vingerhoets F, Safran AB, Landis T. Periodic downbeat nystagmus. Neurology 1998;51:1478-1480. http://www.ncbi.nlm.nih.gov/pubmed/9818889 2. Furman JM, Wall C III, Pang D. Vestibular function in periodic alternating nystagmus. Brain 1990;113:1425-1439. http://www.ncbi.nlm.nih.gov/pubmed/2245304 3. Garbutt S, Thakore N, Rucker JC, Han Y, Kumar AN, Leigh RJ. Effects of visual fixation and convergence in periodic alternating nystagmus due to MS. Neuroophthalmol 2004;28:221-229. 4. Halmagyi GM, Rudge P. Gresty MA, Leigh RJ, Zee DS. Treatment of periodic alternating nystagmus. Ann Neurol 1980; 8:609-611. http://www.ncbi.nlm.nih.gov/pubmed/7212648 5. Jay WM, Williams BB, DeChicchis A. Periodic alternating nystagmus clearing after cataract surgery. J Clin Neuro-ophthalmol 1985;5:149-152. http://www.ncbi.nlm.nih.gov/pubmed/2934414 6. Keane JR. Periodic alternating nystagmus with downward beating nystagmus. Arch Neurol 1974; 30:399-402. http://www.ncbi.nlm.nih.gov/pubmed/4821784 7. Leigh RJ, Robinson DA, Zee DS. A hypothetical explanation for periodic alternating nystagmus: Instability in the optokinetic-vestibular system. Ann N.Y. Acad Sci 1981;374:619-635. http://www.ncbi.nlm.nih.gov/pubmed/6978650 8. Leigh RJ, Zee DS. Diagnosis of Nystagmus and Saccadic Intrusion. Chp 10:475-558. In: The Neurology of Eye Movements, Fourth Edition. Oxford University Press, NY. 2006. 9 . Matsumoto S, Ohyagi Y, Inoue I, Oishi A, Goto H, Nakagawa T, Yamada T, Kira J-I. Periodic alternating nystagmus in a patient with MS. Neurology 2001;56:276-277. http://www.ncbi.nlm.nih.gov/pubmed/11160975MTperiodicalternatingnystagmu