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Oculopalatal myoclonus is characterised by rhythmic pendular vertical eye movements associated with synchronous contraction of the soft palate.1 It produces intractable oscillopsia,2 and is normally the result of brainstem haemorrhage.2 However, it is does not usually become manifest until several months or even years later, with the longest recorded interval being 49 months.3 We present an unusual case of a patient who sustained a brainstem haemorrhage following trauma. Eight years later he was incidentally noted to have oculopalatal myoclonus, and surprisingly was asymptomatic.
Case report
A 61 year old man was admitted to the neurosurgery department following head trauma. A computed tomography (CT) scan showed subarachnoid bleeding. An magnetic resonance image (MRI) revealed left frontal and posterior parietal contusions and a small brainstem haemorrhage. Following the head injury he complained of double vision on downgaze. Examination revealed bilateral fourth cranial nerve palsies, which resolved spontaneously.
Nine months later the patient developed acute angle closure glaucoma in his right eye, which was unresponsive to medical therapy. He subsequently underwent a right trabeculectomy. Thereafter, his visual acuities were 6/18 in the right eye and 6/6 in the left eye, and he was reviewed annually at a glaucoma clinic.
While attending 8 years after his head injury, an audible click was heard emanating from the patient. He was unaware of this because of longstanding sensorineural deafness. However, on further questioning his wife stated that she had been aware of the clicking for several months. Examination of the soft palate revealed rhythmic contractions that were synchronised with the auditory clicking. There was a right unilateral vertical pendular nystagmus, although no nystagmus was noted in the left eye. A diagnosis of oculopalatal myoclonus secondary to the brainstem haemorrhage 8 years previously was made. An MRI scan (T2 weighted images with contrast) was performed and found to be normal. The patient was unaware of oscillopsia, presumably as a consequence of his reduced visual acuity secondary to the previous episode of angle closure glaucoma. As he was asymptomatic no treatment was indicated.
Comment
Oculopalatal myoclonus is a rare condition normally resulting in intractable oscillopsia, thought to be caused by a lesion in the myoclonic triangle, which consists of the red nucleus, the ipsilateral inferior olive, and the contralateral dentate nucleus.4 To our knowledge, this is the first reported case of asymptomatic oculopalatal myoclonus. It also illustrates that the latency period may be longer than that previously described.