Main

Sir,

Linear or nonlinear skull fractures that enlarge with time are termed growing skull fractures1, 2, 3. These are commonly seen in children, possibly because of the greater malleability of the infant skull and the tighter adherence of the dura to the bone.1 This growth of the fracture may cause atrophy of the underlying cerebral tissue along with the formation of a porencephalic cyst, which may extend through the skull defect into the subgaleal space, all of which may result in progressive neurological deficits.1, 2, 3

We report an unusual case of a young boy harbouring a large porencephalic cyst, who was found to have vertical gaze palsy on ocular examination in the absence of other neurological signs and symptoms.

Case report

A practitioner referred a 10-year-old boy with no systemic abnormalities to our strabismus clinic with the diagnosis of alternate convergent squint, present for the past 9 years. Ocular examination revealed a visual acuity of 6/6 (Snellen's alphabetical chart) bilaterally, with no significant refractive errors. Right suppression was present. Ocular motility examination revealed mild restriction of right abduction associated with nominal contracture of the right medial rectus muscle on passive ductions. Gross restriction of upgaze and downgaze was present in both eyes but the forced ductions were normal (Figure 1). The Bell's phenomena were intact (Figure 1). Fundus examination revealed mild pallor of both the optic discs. The rest of the anterior and posterior segment evaluation was unremarkable bilaterally. A diagnosis of vertical gaze palsy was made, and the patient was referred for neurological evaluation, which was reported to be normal.

Figure 1
figure 1

Clinical photograph of the patient showing esodeviation in primary gaze. Restriction of ocular movements in upgaze and downgaze and mild underaction of the right lateral rectus muscle was present. The Bell's phenomenon was intact.

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The father subsequently revealed a history of head trauma to the child at 8 months of age due to fall from a height. CT scan evaluation performed at that time revealed a left parieto-temporal fracture with subcutaneous haematoma and oedema of the underlying cerebral tissue (Figure 2, left). There was no history of progressive neurological deficit or seizure disorders. The right esotropia appeared at about 9 months of age.

Figure 2
figure 2

(left): CT scan of the patient taken at the time of head trauma in 1993 revealed a left parieto-temporal bone fracture with oedema of the underlying tissue. A subcutaneous haematoma overlying the fracture was present. (right): MRI scan of the brain demonstrating a large porencephalic cyst starting from the left lateral ventricle to the fracture site. There is no evidence of an actual bulge of the cystic mass outside the fracture site or a midline shift of the ventricle intracranially demonstrating normal ICP at present.

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We ordered a MRI scan of the brain, which revealed a large porencephalic cyst extending from the left lateral ventricle to the site of the fracture (Figure 2, right) with an extremely thin layer of overlying cerebral tissue. No bulge or gross defect was felt on clinical examination. As the patient had been asymptomatic for 9 years, no surgical intervention was performed. The child was kept on a close follow-up.

Comment

A porencephalic cyst is a cavity within the cerebral hemisphere, filled with cerebrospinal fluid that communicates directly with the ventricular system.1, 4 These are usually associated with various ophthalmic and neurological signs, mainly compressive in origin.4, 5 It is generally recommended that in the presence of increased intracranial pressure (ICP) or progressive neurological deficits, surgical modes be adopted to treat these cysts by shunt surgery with or without closure of the defect by a duro-cranioplasty.1, 2, 3, 5

The vertical gaze palsy alerted us to the possibility of an intracranial lesion in the present case. Subtle morphological changes in the brain have been observed in patients with infantile esotropia.6 However, in this case the esotropia was probably due to the increased ICP at the time of trauma resulting in lateral rectus palsy that developed secondary concomitance later.7 This probably accounts for the mild restriction of abduction seen in the right eye at present. The pathogenesis of the vertical gaze palsy remains unclear, but could be due to the extensive cyst compressing the vertical gaze centres.

It remains controversial whether a duro-cranioplasty should be performed prophylactically in a patient such as this to prevent any future deficit,1, 2, 3, 5 or whether he should be kept under close monitoring and be operated only if necessary.8, 9 The role of strabismus surgery also remains controversial.