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Editor,—Reverse ocular bobbing is an abnormal spontaneous eye movement in which the eyes move rapidly and conjugately upwards (fast phase), followed by a slow drift (slow phase) back to the primary position (that is, the reverse of ocular bobbing—fast conjugate downwards deviation, with a slow return up to the midline). This eye movement disorder may be seen in patients with viral encephalitis, metabolic encephalopathy, and in those with pontine lesions.1 Converse ocular bobbing (also referred to as reverse ocular dipping or slow upward ocular bobbing), consists of a slow phase upwards, followed by a fast phase back to the primary position, and has also been reported in patients with viral or metabolic encephalopathy, and in those with pontine infarction.1 Opsoclonus, also referred to as “saccadomania” or “dancing eyes”, is characterised by intermittent bursts of large amplitude high velocity multidirectional back to back saccades, and has also been reported in patients with viral encephalitis and metabolic encephalopathy, as well as in those with occult neuroblastoma and drug toxicity.2 When these back to back saccades occur purely horizontally, they are known as “ocular flutter” and can be a stage of resolving opsoclonus. We report a case of converse ocular bobbing, reverse ocular bobbing, with synkinetic blinking, opsoclonus, and ocular flutter occurring in a patient with Epstein–Barr viral encephalitis.
A 2½ year old female with a delayed diagnosis of mucopolysaccharidosis type 1 (MPS I) underwent a bone marrow transplant (BMT). Preoperative assessment revealed hearing loss of 60–65 dB, marked ventricular dilatation, but no evidence of raised intracranial pressure. Her visual acuity was recorded as being 6/24 using Cardiff acuity cards, but it was felt that the vision may be better than this as the child was uncooperative during vision testing. She had moderate corneal clouding, and her retina and optic discs appeared normal. BMT preparative chemotherapy consisted of fludarabine/melphalan/antilymphocyte globulin, and the patient received an HLA matched unrelated donor bone marrow infusion, with additional graft versus host disease prophylaxis consisting of cyclosporin and methyl prednisolone. Fourteen days post-BMT, the neutrophil count had recovered (the BMT preparative chemotherapy induces a febrile neutropenia in these children, which typically recovers at 2–3 weeks post BMT), but the patient remained febrile on broad spectrum antibiotics and antifungal agents. Twenty nine days post-BMT, she became irritable, her pyrexia persisted, and her upper limbs became hypertonic. Her conscious level then deteriorated and computed tomograph (CT) scan revealed acute hydrocephalus with very large ventricles and an emergency external ventricular drain was inserted. Epstein–Barr virus (EBV) was detected in the cerebrospinal fluid by polymerase chain reaction (PCR), EEG showed generalised slowing with occasional sharp waves, and magnetic resonance imaging with gadolinium revealed extensive abnormal signals in the cerebral white matter. A diagnosis of EBV encephalitis was made. The patient was commenced on phenytoin in case there was underlying seizure activity. On examination of her eyes at that time, she was not fixing or following and had developed abnormal eye movements, which consisted of converse ocular bobbing in the initial phase (that is, slow phase up/fast phase down, see above). Each upward slow phase was accompanied by a blink. On observation 2 days later she had developed reverse ocular bobbing (that is, fast phase up/slow phase down) as oppose to converse bobbing. The upward fast phase was accompanied by a blink which she seemed to be attempting to overcome with her frontalis muscle which was overacting in synchronicity with the blinks. A repeat CT scan demonstrated resolving hydrocephalus and persistent cerebral oedema. Repeat lumbar puncture revealed decreasing EBV titres (as measured using quantitative PCR), which eventually became negative. There was a subsequent improvement in her condition, and her parents had noticed much less eye movement activity. However, on examination she was still demonstrating intermittent episodes of reverse ocular bobbing with synkinetic blinking, and now intermittent bursts of both opsoclonus and ocular flutter.
Ocular bobbing, dipping (also referred to as inverse bobbing—slow downward movement, followed by a fast upward movement to the primary position), and reverse bobbing have been reported on different occasions in the same patient,3 as have opsoclonus and ocular bobbing.4 Synchronism of inverse ocular bobbing (slow phase down/fast up) and blinking has been reported in a 7 year old female with severe cerebral trauma; the rapid phase of the eye movement was synchronous with phasic contraction of the orbicularis oculi.5
The above case of reverse and converse ocular bobbing with synchronous blinking, together with the later development of opsoclonus and ocular flutter in a child with viral encephalitis is the first such combination of eye movement disorders to be reported in one individual. The abnormal eye movements in this child may be a result of her encephalitis, mucopolysaccharidosis, or the treatment she received. It is difficult to determine which phenomenon or combination is responsible. When such abnormal eye movements occur either together or in isolation, viral encephalitis should be considered.
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