27 August 2008
POST-VARICELLA IDIOPATHIC INTRACRANIAL HYPERTENSION IN A CHILD
Idiopathic intracranial hypertension (IIH) is a condition characterised by increased intracranial pressure (ICP) in the absence of any intracranial mass lesion or ventricular dilatation, with normal neurology and cerebral spinal fluid (CSF) composition. Diagnosis of IIH is more difficult in children, as the disease characteristics differ substantially from that in adult. We report a case of post-varicella IIH in a child that presented atypically.
A 5-year-old Chinese boy with good past health was referred for bilateral blurring of his vision 4 days after developing vesicular rashes of chickenpox. Contact history with chickenpox patients was positive. The blurring was initially on-and-off in nature and later became persistent. The child was alert and playful, with no headache, nausea or vomiting.
He had vesicular rashes over his face, trunk and four limbs, and was afebrile. Neurological exam was normal, with no neck stiffness nor any cranial nerve abnormalities. Ophthalmic examination revealed visual acuity (VA) of 20/60 and 20/100 in the right and left eye, respectively. Both pupils were equal in size and reactive to light. There was no relative afferent pupillary defect. Fundoscopy showed bilateral disc swellings, being more severe in the left eye (Fig. 1). The normal cup was obscured whilst the discs remained pink. No chronic sign of disc swelling was present and there was no macular star. Extra-ocular movements were full, and there was no pain on eye movement. The child refused to be examined on colour vision and visual field at the first assessment.
A non-contrast Computer Tomography (CT) of the brain was normal. Blood tests, including complete blood picture, liver and renal function tests, erythrocyte sedimentation rate, C-reactive protein, anti-nucleic acid antibody, double-stranded anti-nucleic acid antibody, rheumatoid factor and C3 C4 levels, were all normal.
Based on the history, physical findings, lack of symptoms of meningitis or increased ICP and a normal CT brain examination, a diagnosis of parainfectious optic neuritis was made. His VA improved to 20/25 in both eyes 2 days later. Colour vision and visual field were normal bilaterally. Observant management was agreed in view of the quick and spontaneous improvement of VA. The child was then followed up and he did not have any further visual complaints. However, 2.5 months after presentation, the optic discs swelling persisted, which was atypical of parainfectious optic neuritis. VA and visual evoked potentials were normal bilaterally. Repeated visual field showed mild generalised depression in sensitivity with bilateral enlarged blind spot, suggesting the possibility of chronic raised ICP. Magnetic resonance imaging of the brain and orbit showed non-dilated ventricles, normal optic nerves and no features suggestive of dural sinus thrombosis. Lumbar puncture revealed an opening pressure of 39 cm H2O. The CSF was clear with normal glucose and protein levels. Gram stain and culture for bacteria were negative and oligoclonal bands were absent. CSF and serum IgG levels were also normal. Urine toxicology and blood cortisol levels were normal. The final diagnosis was revised to IIH. The patient was started on oral acetazolamide 125 mg daily and there was gradual clinical improvement.
Although the pathogenesis of IIH is still not clear, this disease is well described in adults, in which there is a strong female preponderance and an association with obesity. However, the clinical characteristics of IIH differ in the paediatric age group, especially in pre-pubertal children. Childhood IIH has no gender predominance and obesity is uncommon. Some of the most common symptoms in children at presentation include headache, decreased vision, transient visual obscurations,1 but pre-pubertal children often present with stiff neck, diplopia and strabismus.2 Papilloedema and strabismus tend to resolve more rapidly in children with or without treatment.2,3 However, similar to adults, some children continue to lose vision (up to 20%) and visual field (up to 91%) despite treatment.1,4 Therefore, prompt diagnosis and management are important.
There are two case reports in the literature suggesting an association between IIH and varicella. In both cases the patients presented with symptoms of increased ICP with headache, vomiting and bilateral discs swelling.5,6 Our present case posed a diagnostic challenge because of its atypical presentation. Other than the initial short-lived reduction in VA and discs swelling, he had no typical symptoms of increased ICP that was present in the two previous reports. Together with normal sensorium and neuroimaging results, the initial diagnosis of parainfectious optic neuritis was explainable. Our case illustrates the importance of vigilant follow-up. IIH in children is rare, and post-varicella IIH is even rarer. The association of IIH with varicella infection is still not well understood. With the acute visual disturbance, normal initial visual field and the lack of chronic disc swelling changes, the possibility of pre-existing, asymptomatic IIH seems unlikely.
In our case, lumbar puncture was initially withheld, and was later performed when the optic disc swelling persisted. Although lumbar puncture is generally safe, it is still an invasive procedure with a theoretical risk of causing low back pain and intraspinal epidermoid tumours. In retrospect, we should have been more aggressive in pursuing the cause of the disc swelling. The initial normal visual field was not typical of parainfectious optic neuritis and the spontaneous visual recovery misled us that the condition was self-limiting. We therefore recommend that in case of doubt, lumbar puncture should be performed for cases of bilateral optic discs swelling once intracranial lesions have been excluded.
To the best of our knowledge, this is the third description of a child with IIH presenting within a week after developing varicella, and the first case suggesting an association between IIH and varicella in a Chinese child. Children with IIH present differently from adults. Both paediatricians and ophthalmologists must remain vigilant to the complications of IIH, and early diagnosis with lumbar puncture, followed by treatment are imperative to prevent visual loss.