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Show Journal of Nettro- Ophllmlmology 18( 4): 292- 293, 1998. © 1998 Lippincolt Williams & Wilkins, Philadelphia Epileptic Periodic Alternating Nystagmus Mark L. Moster, M. D., and Eric Schnayder, M. D. A patient developed periodic alternating nystagmus, periodic alternating gaze deviation, and periodic alternating head rota-lion as a manifestation of a seizure. This occurred as he awakened after hypoxic ischemic encephalopathy. Seizures should be added to the list of differential diagnoses of periodic alternating nystagmus. Key Words: Periodic alternating nystagmus- Epilepsy- Encephalopathy- Epileptic nystagmus. Periodic alternating nystagmus ( PAN) is a horizontal jerk nystagmus that reverses direction in a cyclic manner, with intervening periods of ocular rest ( 1). It is most frequently caused by acquired lesions of the vestibular nuclei, the vestibulocerebellum, and the craniocervical junction. Periodic alternating gaze deviation has been seen in acquired brainstem disorders ( 2,3). Alternating head deviation may accompany either entity. Nystagmus from focal epilepsy has been described ( 1,4) and usually consists of unilateral horizontal jerk nystagmus, most frequently beating contralateral to the lesion. We present a case of occipital lobe seizure that mimicked PAN. CASE REPORT A 68- year- old man was seen after coronary artery bypass graft and aortic valve replacement had been complicated by postoperative mediastinal hematoma, severe hypotension, and delayed awakening. Initial examination revealed him to be obtunded with intact brainstem reflexes. The following day he responded to painful stimuli and occasionally followed simple commands. He had normal lower extremity strength, but had severe upper extremity weakness and bilateral Babinski responses. Eye movements and pupils were normal. He was diagnosed with hypoxic ischemic encephalopathy and bilateral watershed infarcts between the anterior and middle Manuscript received June 8, 1998; accepted July 8, 1998. From the Department of Neurosensory Sciences ( M. L. M. E. S.), Albert Einstein Medical Center; and the Departments of Neurology and Ophthalmology Temple University School of Medicine ( M. L. M.), Philadelphia, Pennsylvania. Address correspondence and reprint requests to Mark L. Moster, M. D., Albert Einstein Medical Center, Dcpt. of Neurosensory Sciences, Klein Professional Building, Suite 300, 5501 Old York Road, Philadelphia, PA 19141, U. S. A. cerebral artery circulations, accounting for bilateral arm weakness. Later that day, a generalized seizure was treated with intravenous phenytoin. During the next day, he developed unusual eye movements. On examination, he was extubated, awake, followed simple commands and answered with appropriate simple sentences. Periodically he moved his eyes and head as follows: eyes deviated to the right with jerk nystagmus to the right for 1 minute. During this time, his head slowly moved to the right. Nystagmus then subsided, and his head returned to midline, followed by his eyes. After 10 seconds, he exhibited jerk nystagmus to the left, followed by slow deviation of his head 45° to the left. After 1 minute, gaze returned to midline with disappearance of nystagmus for 10 seconds. The described phenomenon was observed for approximately 10 cycles. He remained awake and able to follow simple commands. He could not cooperate in visual field testing but appeared to respond to stimuli in all four visual field quadrants. Upper extremity strength had improved to normal. Serum phenytoin level was therapeutic at 18.6 jig/ ml. Baclofen was initiated, with no effect on eye movements. The following day, he underwent an EEG and was noted to have two spells of right- beating nystagmus during the procedure, corresponding to a left occipital seizure with gradual generalization over both hemispheres. The patient was described as alert but confused during the these episodes. Oragepan was administered and periodic eye movements disappeared by the following day. Magnetic resonance imaging findings were normal and repeat EEG showed resolution of seizure activity. Mental status continued to improve, and he was discharged on the 12th hospital day. Neurologic examination 5 months later was unremarkable. Computed perimetry showed no hemianopia. DISCUSSION Epileptic nystagmus is a rare phenomenon, most often accompanied by horizontal jerk nystagmus with quick phases and gaze deviation away from the side of the seizure ( 1,4). Patients alert at the onset of nystagmus usually have a focal seizure emanating from the junctional region of the temporoparieto- occipital cortex. In contrast to unilateral jerk nystagmus, our patient 292 EPILEPTIC PERIODIC ALTERNATING NYSTAGMUS 293 had PAN, periodic alternating head rotation, and periodic alternating gaze deviation as manifestations of a focal onset seizure. Unfortunately, EEG recording was not obtained when the patient was seen clinically, and careful clinical examination was not performed during the EEG. Therefore, the exact mechanism of this epilepsy- induced phenomenon is unclear. However, based on the clinical observations and course, we concluded that a focal seizure in the left occipital lobe accounted for head and eye rotation and right- beating nystagmus. When the seizures spread to the right occipital lobe, the nystagmus calmed and then reversed direction. When the seizure generalized, nystagmus stopped altogether. Episodes of PAN occur in various clinical situations, including acquired lesions of the craniocervical junction, vestibulocerebellar pathways or brainstem, multiple sclerosis, cerebellar degeneration, Creutzfeldt- Jakob disease, infarction, trauma, encephalitis, neurosyphilis, visual loss, anticonvulsant toxicity and hepatic encephalopathy and as a variant of congenital nystagmus ( 1,5- 9). We now add focal seizure to this list of causes of PAN. Therefore, in the appropriate clinical setting, patients with unusual patterns of nystagmus should have an EEG as a part of their evaluations. REFERENCES 1. Leigh RJ, Averbuch- Hcllcr L. Nystagmus and related ocular motility disorders. In: Miller NR, Newman NJ, eds, Walsh anil Hoyl's clinical neuro- ophthalmologv- 5lh ed. Baltimore: Williams & Wilkins, 1998: 1461- 505. 2. Goldberg RT, Gonzalez C, Brcinin GM, el al. Periodic alternating gaze deviation witli dissociation of head movement. Arch Ophthalmol 1965; 73: 324- 30. 3. 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