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A 17-year-old girl reported a 2-week history of progressively worsening daily headaches most prominent on waking in the morning, and 1-week history of vomiting and diplopia. She had been previously well except for a ventriculoperitoneal shunt inserted at the age of 5 months for aqueduct stenosis. On examination, her body mass index was 24 kg/m2. She was afebrile. Her visual acuity was 6/6 on the right and 6/9 on the left, while her visual perimetry was normal. She had a left lateral rectus palsy and unilateral disc oedema in the left eye (figure 1). The remaining neurological and systemic examinations were normal. A CT scan of the head showed the shunt in situ and no evidence of hydrocephalus. However, cerebrospinal fluid (CSF) manometry found an opening pressure of 550 mm CSF. Her headache improved immediately on re-establishing the functional patency of the shunt. Her lateral rectus palsy and papilloedema had resolved at 3 months’ review.
Bilateral papilloedema is the hallmark clinical sign of increased intracranial pressure. Unilateral papilloedema is rare, being found in 2% of patients with papilloedema1 and occasionally occurs in idiopathic intracranial hypertension.2 Thus, unilateral papilloedema can pose a diagnostic challenge for the unwary clinician.
The exact cause of this atypical presentation remains elusive. Two proposed mechanisms are, first, anatomical nerve sheath anomalies preventing the transmission of the raised CSF pressure to the immediate retrobulbar region of the optic nerve, and, second, unilateral axoplasmic blockage of the lamina cribrosa.2 The absence of hydrocephalus in our patient with a blocked ventriculoperitoneal shunt may reflect an early stage of increased intracranial pressure or less pliable brain parenchyma in a young patient with past effects of aqueduct stenosis.
Although unilateral optic disc oedema is more commonly caused by inflammation, ischaemia, compression or infiltration of the optic nerve, increased intracranial pressure should always be considered, especially if the visual acuity is preserved. Furthermore, our case emphasises the need to pursue this possibility even in the absence of ventriculomegaly and with a ventriculoperitoneal shunt in situ.
Contributors TC and ATA conceptualised, researched and wrote the manuscript.
Competing interests None declared.
Patient consent Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor of the journal. Neither the figure nor the text contains data that can identify the patient.
Provenance and peer review Not commissioned; externally peer reviewed. This paper was reviewed by Christian Lueck, Canberra, Australia.
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