Downbeat Nystagmus

Downbeat NystagmusComaThe patient is a 72 year old man who was found down and admitted as an emergency in coma. Neurological examination: Patient in coma failed to respond to painful stimuli. Downbeat nystagmus Lid nystagmus Pupils 2 mm OU responsive to light Corneal reflexes absent Oculocephalic reflex absent No response to cold water calorics CT brain: Large pontine hemorrhage.This 72 year old comatose patient was filmed in the ICU. He had no response to painful stimuli. His eyes show: • Rapid downbeating nystagmus • Lid nystagmus • Pupils 2 mm OU responsive to light • Corneal reflexes absent • Absent oculocephalic reflexes • No response to cold water calorics He died a few days later. No autopsy was performed. Downbeat Nystagmus There are three forms of nystagmus caused by lesions affecting the central vestibular pathways: 1. Downbeat nystagmus 2. Upbeat nystagmus 3. Torsional nystagmus Downbeat nystagmus is caused by a central vestibular imbalance due to lesions of the vestibulocerebellum, especially the flocculus and paraflocculus and brainstem pathways. The Purkinje cells of the flocculus preferentially discharge for downward movements and it has been suggested that there is an underlying upward eye velocity bias in the central vestibular or pursuit system or in the peripheral vestibular system which is normally inhibited by the cerebellum. With lesions of the vestibulocerebellum, cerebellar inhibition is disrupted and the upward bias uncovered, resulting in spontaneous downbeat nystagmus. Downbeat nystagmus in cerebellar cases may be modified by a number of factors, including orbital position, head position and movement, head shaking and caloric stimulation. Downbeat versus Bobbing I initially thought that this case was one of ocular bobbing. But, if you compare this case with the video clip of ocular bobbing in the DVD attached to Leigh JR, Zee DS. The Neurology of Eye Movements, 4th Edition, you will see that the eye movements of ocular bobbing are considerably slower than the patient here. Ocular bobbing is a unique vertical eye movement disorder consisting of intermittent, usually conjugate, downward movement of the eyes followed, after a brief tonic interval, by a slower return to primary position. Attention was first directed to ocular bobbing by Fisher in 1959, and its clinical prevalence first defined by Susac, Hoyt, Daroff et al in 1970. They stressed the diversity of diseases associated with it and the differing clinical settings in which it may be encountered. Fisher suggested that ocular bobbing may reflect the residual eye movements of patients who have severe limitation of horizontal and vertical eye movements. Observation by Dr. David Zee (DZ) DZ thought, after viewing the video clip in my case, that the downbeat nystagmus could either be explained by asymmetrical involvement of the vestibular nuclei or the projections of the paramedian tracts to the flocculus. Hypoxia of the cerebellum would be another possibility. This case is a unique example of downbeat nystagmus in a patient with bilateral horizontal gaze palsy where the major hemorrhage affected the pons. The rostral-caudal extent of the hemorrhage was unknown. Table 10-1 Etiology of Downbeat Nystagmus, Pg482 (7) Box 10-2 Clinical Features of Downbeat Nystagmus Pg 484 (7). This case should be reviewed alongside ID4-1 a young woman with locked-in syndrome and ocular dipping.No neuroimaging studies are available in this patient.Pontine Hemorrhage1. Ash PR, Keltner JL. Neuro-ophthalmic signs in pontine lesions. Medicine 1979;58:304-319. http://www.ncbi.nlm.nih.gov/pubmed/312988 2. Baloh RW, Yee RD. Spontaneous vertical nystagmus. Rev Neurol (Paris) 1989;145:527-532. http://www.ncbi.nlm.nih.gov/pubmed/2682931 3. Cogan DG. Downbeat nystagmus. Arch Ophthalmol 1968;80:757-768. http://www.ncbi.nlm.nih.gov/pubmed/5303364 4. Fisher CM. Clinical syndromes of cerebral hemorrhage. In: Fields, WS ed. Symposium of Pathogenesis and Treatment of Cerebrovascular Disease. Springfield: Charles C. Thomas, 1961;318-342. 5. Fisher CM. Ocular bobbing. Arch Neurol 1964, 11:543-546. http://www.ncbi.nlm.nih.gov/pubmed/14200662 6. Halmagyi GM, Rudge P, Gresty MA, Sanders MD. Downbeating nystagmus: a review of 62 cases. Arch Neurol 1983;40:777-784. http://www.ncbi.nlm.nih.gov/pubmed/6639406 7. Leigh RJ, Zee DS. Diagnosis of Nystagmus and Saccadic Intrusion. Chp10 475-558. In: The Neurology of Eye Movements. 4th Ed. Oxford University Press, New York 2006. 8. Rosenberg ML. Spontaneous vertical eye movements in coma. Ann Neurol 1986;20:635-637. http://www.ncbi.nlm.nih.gov/pubmed/3789678 9. Susac JO, Hoyt WF, Daroff RB, Lawrence W. Clinical spectrum of ocular bobbing. J Neurol Neurosurg Psychiatry 1970, 33:771-775. http://www.ncbi.nlm.nih.gov/pubmed/5531897 10. Zee DS, Friendlich AR, Robinson DA. The mechanism of downbeat nystagmus. Arch Neurol 1974;30:227-237. http://www.ncbi.nlm.nih.gov/pubmed/4591431curriculum_fellow; VBneurodispontinehemorrhage; MTcomatosepatien