A 13-year-old girl, previously healthy with no visual complaints, fell off a playground roundabout onto a concrete surface. She lost consciousness for a few minutes and, on regaining consciousness, immediately became aware of blurred vision with oscillopsia. She was born at full term and her general development during childhood was unremarkable. She had no family medical history of note.
Visual acuity was 20/20 bilaterally. Her eye examination was normal except for intermittent ocular flutter (OF) and, at times, opsoclonus. There was no myoclonus, ataxia, or signs of cerebellar dysfunction. The patient recalled the event of her head trauma and did not suffer amnesia. A brain MRI and studies for paraneoplastic antibodies were normal. The episodes of oscillopsia continued intermittently, exacerbated by fatigue, without relieving factors and would resolve spontaneously within a few hours. This initially was diagnosed as voluntary nystagmus.
Eye movement recordings during an episode showed fixation instability with saccadic intrusions. Superimposed on these were conjugate, high-frequency, high-amplitude, back-to-back horizontal saccadic movements with no intersaccadic intervals (Figs. 1 and 2). The episode continued for approximately 45 minutes. A trial of gabapentin was prescribed but this was not tolerated. Over a period of 1 year, the symptoms gradually improved with less severe and frequent episodes.
OF and opsoclonus are eye movement abnormalities consisting of back-to-back saccades without an intersaccadic interval, differentiating them from nystagmus and other types of saccadic intrusions. Diagnosis can be made clinically and/or confirmed with eye recordings. An important differential to consider is voluntary nystagmus which, unlike OF, is usually not sustained for more than 30 seconds (1).
OF is associated with a wide range of disorders of the central nervous system including encephalitis, myoclonic encephalopathy of infants, toxic metabolic states, and demyelinating disease. Paraneoplastic antibodies also may cause OF with neuroblastoma most commonly implicated in children, whereas small cell lung cancer and breast cancer are most commonly involved in adults. Idiopathic OF also has been reported (1).
Although the pathophysiology of OF remains uncertain, theories have been proposed involving the brainstem and the cerebellum. In the brainstem model, saccadic oscillations are thought to arise from altered membrane properties of saccadic burst neurons that affect their interaction with omnipause neurons (OPN). In the cerebellar model, dysfunctional Purkinje cells are incapable of inhibiting neurons in the fastigial nucleus, thereby reinforcing OPN inhibition and allowing saccadic burst neurons to be free to oscillate (1).
In our case, OF occurred immediately after mild head trauma and no other cause was identified. Our patient may have suffered microscopic structural damage to saccadic burst neurons or Purkinje cells, precipitating flutter. This may have led to a change in the ion channel constitution of the neurons involved. This is supported by the work of Yuen et al (2) who found an increase in the number of sodium channels in damaged neurons within the first 24 hours after mild traumatic injury. In addition, some patients with OF respond to carbamazepine, a drug known to act on the sodium channel (3).
Turazzi et al (4) reported a 20-year-old man who, after head trauma, had opsoclonus and also was comatose with decerebrate rigidity. Dempsey et al (5), in a retrospective review of clinical signs associated with concussion, mentioned that one adult who sustained a concussion developed OF.
STATEMENT OF AUTHORSHIP
Category 1: a. Conception and design: A. Manta, S. Ugradar, and M. Theodorou; b. Acquisition of data: A. Manta, S. Ugradar, and M. Theodorou; c. Analysis and interpretation of data: A. Manta, S. Ugradar, and M. Theodorou. Category 2: a. Drafting the manuscript: A. Manta, S. Ugradar, and M. Theodorou; b. Revising it for intellectual content: A. Manta, S. Ugradar, and M. Theodorou. Category 3: a. Final approval of the completed manuscript: A. Manta, S. Ugradar, and M. Theodorou.
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