Carbon Monoxide Poisoning: Neuro-Ophthalmologic Findings in Three Patients
Gill Roper-Hall, DBOT, CO; Sangeeta Khanna, MD; Jafar Kafaie, MD
Saint Louis University
St. Louis, MO
Introduction: Carbon monoxide is a colorless, odorless, tasteless and non-irritating gas which enters the bloodstream through the lungs causing hypoxia. CO exposure may result in a variety of neurologic sequelae. The eye movement system may be particularly vulnerable.
Methods: Three teachers were referred for neuro-ophthalmological and orthoptic evaluation for persistent ocular problems 2.5 years after CO exposure when a heater at school malfunctioned. Evaluation included HVF, OCT, color vision, dilated fundus exam, and full motility work up. Neurologic examinations, including MRI, were performed prior to referral.
Results: Visual acuity, fundus, visual fields, color vision, OCT (optic nerve/macular ganglion cell), ductions, versions, pursuit and saccades were normal. All three patients had asthenopia, intermittent diplopia, blurred vision, headache, convergence dysfunction and decreased accommodation. All had been prescribed base in prisms for reading elsewhere.|Persistent neurologic findings included headache, dizziness, mild balance and memory problems, depression and anxiety in three patients, with photophobia, hyperacusis and motion-intolerance in two. All three patients had documented MRI abnormalities.
Discussion: CO poisoning causes acute damage to the brain and other tissues and may cause vergence, accommodation and vestibulo-ocular dysfunction. Vestibular therapy may be helpful. Convergence exercises are of limited value but may be supplemented with base in prisms and appropriate magnification.
Conclusion: The findings were remarkably similar to patients with post-concussion syndrome. Delayed neurologic sequelae (DNS) has been reported. Patients should be followed long-term for their ocular problems or as symptoms demand.
References: Raub JA, Benignus VA. CO and the nervous system. Neuroscience Biobehavioral Reviews.2002;26:925.