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Editor,—Anterior ischaemic optic neuropathy (AION) is a disease that occurs most frequently in middle aged and elderly people resulting from vascular occlusive disorders or transient decreased blood flow in the territory of the short posterior ciliary arteries. Although rare in the young, it has been described in association with a number of conditions such as migraine, juvenile diabetes, collagen vascular diseases, haematological disorders, prothrombotic state, pre-eclampsia, hypertension, episodic hypotension, embolism, and even in the absence of other ocular or systemic condition.1 We would like to report on a case of AION developing in a child with sickle cell trait and migraine. To our knowledge this association has not been reported so far as a cause of AION.
An 11 year old black boy was seen because of transient episodes of monocular loss of vision in both eyes. The patient had a long standing history of migraine usually triggered by fatigue, anxiety, hunger, and some foodstuffs. In most of the episodes he complained of severe throbbing hemicranial headache with no visual symptoms, but occasionally he noticed blurred vision in association with the pain. He used to take aspirin or paracetamol (acetaminophen) for pain relief. He also complained of recurring transient loss of vision in the left eye with no headache during intensive physical exercises such as playing soccer and doing gym at school. Four months earlier he had had an episode of headache in the morning followed by decreased sight in his left eye which persisted even after relief of the pain. He was seen at another hospital where a left optic disc oedema was observed and he was given prednisone 60 mg a day for 14 days with a partial recovery of vision.
Ophthalmic examination revealed his best corrected visual acuity to be 20/20 in the right and 20/60 in left eye. The right eye was unremarkable but the patient could read none of the Ishihara plates with the left eye, had a dense centrocaecal scotoma , and a pale optic disc in this eye, as well as a left relative afferent pupillary defect. There was no retinal abnormality.
Laboratory examination including complete blood cell count, blood chemistry, platelet count, prothrombin time, partial thromboplastin time, protein C, protein S, antithrombin III, and factor V activities were normal. Tests for anti-phospholipid antibodies and for collagen vascular diseases, echocardiogram, chest x rays, cranial magnetic resonance imaging, and cerebrospinal fluid analysis with immunoelectrophoresis were all negative. A visual evoked response study showed increased latency and reduced amplitude in the left eye. Haemoglobin electrophoresis revealed a double band of A and S mobility. The S haemoglobin was 38%, A haemoglobin 62%, and the red cells sickled under classic conditions. Careful systemic evaluation for possible complications of sickle cell trait was unrevealing.
Infarction in sickle cell disease is probably a very complex and multifactorial process. Its intricate mechanisms still remain to be elucidated but a number of disturbances such as intimal hyperplasia due to abnormal adhesive and procoagulant properties of sickled red blood cells, time to gelation, and platelet changes may play a role.2 3 Altered vascular reactivity and vasospasm may be also important.4 Although complications of sickle cell trait are rare they occur under extreme conditions such as vigorous exertion at high altitudes. Reported neurological complications of AS haemoglobinopathy include seizures4 and spinal cord and cerebrovascular thrombosis.5 6 Migraine with resulting vasospasm may be a factor in triggering vascular occlusion in some of these patients.7 8Complicated migraine may even be found in higher prevalence among people with sickle cell trait.7 Posterior ischaemic optic neuropathy has been reported in a patient with sickle cell anaemia and migraine,9 and in a case of SC haemoglobinopathy.10 Our patient presented loss of vision during a migraine attack. Extensive investigation did not suggest demyelinating disease or haematological disturbances other than sickle cell trait. The present case is the first to be described with AION in the set of AS haemoglobinopathy and migraine. It is possible that sickle cell trait may increase the risk of AION in patients with migraine.