Sir,

Optic nerve infiltration may occur in central nervous system (CNS) relapse of acute lymphoblastic leukaemia (ALL). We report a patient in whom prompt radiotherapy and intrathecal chemotherapy resulted in remarkable visual recovery and ALL remission.

Case report

A 14-year-old boy was referred with a 2-day history of painless reduced vision in his left eye. He had a previous diagnosis of ALL with multiple relapses over 10 years and had previously received 1800 cGy prophylactic cranial radiotherapy. He was currently in remission with monthly maintenance intrathecal chemotherapy. Visual acuity was 6/9 in his right eye and 6/36 in his left. Fundal examination revealed asymmetric bilateral optic nerve infiltration (see Figures 1a and b) also seen on magnetic resonance imaging (MRI) (see Figure 2). Immediate emergency radiation therapy was initiated, consisting of 1200 cGy fractionated over 6 days encompassing orbits and brain, with an additional 800 cGy boost to his posterior retina and optic nerves in five fractions. He also received weekly intrathecal methotrexate, cytarabine, and hydrocortisone. He subsequently returned into remission with a visual improvement to 6/6 in his right eye and 6/9 in his left eye at 6 months of follow-up, back on monthly maintenance chemotherapy. The disc swelling had fully resolved by that point.

Figure 1
figure 1

(a) Fundal photograph of the right eye showing mild disc swelling and peripapillary haemorrhages, representing optic nerve infiltration. (b) Fundal photograph of the left eye showing dramatic creamy-white optic nerve infiltration and peripapillary haemorrhages.

Full size image
Figure 2
figure 2

T2-weighted FLAIR sequence MRI scan of the CNS and orbits showing diffuse bilateral optic nerve infiltration worse on the left (arrows).

Full size image

Comment

Ocular involvement in a child known to have leukaemia has been associated with significantly poorer visual and mortality outcomes.1 The CNS and the eye are sanctuary sites at the time of initial chemotherapy for ALL and thus common sites of recurrence. Optic nerve infiltration represents a CNS relapse and leads to blindness, and as such should be treated as an ophthalmic emergency. It is also important to distinguish it using MRI from papilloedema secondary to brain relapse.

Previous case reports have shown that vision can be salvaged in optic nerve infiltration by prompt appropriate treatment in the form of radiotherapy to the orbits and CNS,2, 3 accompanied with aggressive intrathecal and systemic chemotherapy.4 Chemotherapy alone has been reported as being unsuccessful in improving either survival or visual outcomes.5 Radiotherapy to the CNS was given to our patient, as optic nerve infiltration represents a CNS relapse. Though his long-term prognosis remains uncertain, he does highlight the importance of prompt diagnosis, referral, and subsequent intervention in children with suspected CNS relapse of their leukaemia.