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Boy presents with severe unilateral loss of vision over 3-month period
Examination revealed unilateral vision loss and bilateral field loss.
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A 7-year-old healthy boy first presented to the Floating Hospital for Children when his parents noticed an inconstant head turn as he watched TV. The parents had been unaware of any problems in their child’s vision. There had been normal growth and development.
On initial examination, the Snellen vision was 20/40 in the right eye and 20/50 in the left eye. There was no strabismus. The anterior segments as well as the fundus examinations were unremarkable. Cycloplegic refraction disclosed +2.25 sphere in the right eye and +2.25 +2.50 × 110 in the left eye. The boy was placed in a spectacle correction (+1.25 sphere right eye; +1.25 +2.50 × 110 left eye), with follow-up every 3 months. Six months later, his vision had improved to 20/20+1 in the right eye and 20/25-2 in the left eye.
The child continued with no visual or systemic complaints until 1 year 10 months later when he returned for a regular 3-month follow-up visit. His parents had noticed no vision or behavioral changes. He was doing well in school.
Examination
Snellen acuity in the previously normally sighted right eye measured 10/300, while the amblyopic fellow eye was unchanged at 20/25-2.
The right eye exhibited a fine, very high frequency horizontal oscillation. Visual fields were markedly constricted to confrontation in all quadrants in both eyes. None of the Ishihara test plates were seen with the right eye; all were correctly identified with the left eye. The pupils were equal in size and briskly reactive; there was a small right relative afferent pupillary defect (RAPD). There was mild pallor of the right optic disc (Table 1).
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Loss of vision
The history of amblyopia was not relevant: Amblyopia will never cause a precipitous visual loss over a few months. Moreover, the visual loss occurred in the previously normally sighted eye, not the amblyopic eye.
The loss of vision in the right eye, accompanied by dyschromatopsia, RAPD and disc pallor, pointed clearly to a right optic neuropathy. Although all of the above support a unilateral process, the contracted confrontation visual fields — in both eyes — confirmed bilateral pathology.
Goldmann visual fields rather than automated fields were obtained. Goldmann perimetry permits the perimetrist to interact with the patient as the test is proceeding, a potential advantage when testing young, distractible patients (Figures 1 and 2). Both eyes demonstrated significant field constriction.
Source: James Constans, MD, and David Reese, MD
An MRI was ordered, with special attention to the sellar area (Figure 3). The MRI revealed a large mass measuring 70 mm in diameter, with compression of the optic chiasm and contiguous optic nerves. The signal characteristics and enhancement were most compatible with craniopharyngioma. There was a mass effect on the optic chiasm and intracranial portion of the optic nerves.
A craniotomy was performed, and the right optic nerve was found to be stretched extremely thin. The tumor was densely applied to the ventral portion of the optic chiasm. A rim of tumor adherent to the optic chiasm was not resected in an effort to preserve what little remained of this child’s vision. The pituitary gland was sacrificed. The histopathology showed characteristic features for craniopharyngioma (Figure 4).
Discussion
Craniopharyngioma is the most common non-glial brain tumor in children, with a peak incidence at 5 to 10 years of age. The term craniopharyngioma is somewhat misleading because the tumors arise from buccal mucosa or Rathke’s pouch, not from the pharynx. They usually arise from the anterior superior pituitary gland and grow into the sellar area to involve the pituitary gland, optic nerves and chiasm, infundibulum, hypothalamus and third ventricle.
Patients usually present with symptoms caused by mass effect and tumor invasion of the sellar and parasellar space. The most common presenting symptoms are vision changes, endocrine abnormalities and effects of increased intracranial pressure.
Despite the huge loss of visual field, the dramatic drop in the visual acuity of the right eye and the size of the tumor, this patient remained asymptomatic. The unaffected visual acuity in the left eye camouflaged the visual loss in the right eye.
The poor vision in the right eye was explained by the fact that the visual field loss involved central fixation; central fixation was spared in the left eye.
Clinical course continued
Seven months after surgery, the MRI revealed an increase in the residual tissue that had been unable to be completely excised. The patient underwent proton beam therapy, which allows precise targeting of the residual tumor tissue with minimal risk to nearby structures. He developed an expected panhypopituitarism postoperatively. This has been managed by the pediatric endocrinology service.
Sixteen months after craniotomy, the child is continuing his normal activities. His vision is 20/20-1 in the right eye and 20/20-3 in the left eye. His visual fields, while still constricted, are significantly improved (Figure 5).
Conclusion
It is incumbent upon clinicians to be vigilant when managing patients with amblyopia or other such chronic “benign” conditions. This patient’s brain tumor was detected because the child was being followed closely for the unrelated condition of amblyopia. Had this child not had amblyopia and a few more days or weeks elapsed before diagnosis of the tumor, the result could have turned out to be far worse. In view of the blitzkrieg effect of the tumor upon acuity and visual fields, this child might have lost all vision.
- References:
- Grkovi D, et al. Med Pregl. 2016;69(3-4):79-84.
- Karavitaki N, et al. Clin Endocrinol (Oxf). 2005;doi:10.1111/j.1365-2265.2005.02231.x.
- Mediero S, et al. Neuroophthalmology. 2015;doi:10.3109/01658107.2015.1039549.
- Stefko ST, et al. J Neurol Surg B Skull Base. 2016;doi:10.1055/s-0036-1571333.
- For more information:
- James Constans, MD, and David Reese, MD, can be reached at New England Eye Center, Tufts University School of Medicine. 800 Washington Street, Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Adam T. Chin, MD, and Omar Dajani, MD. They can be reached at the New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.