Superficial siderosis: A rare occurrence in children
A twelve-year-old boy presented to the neurology outpatient clinic with a history of intermittent holocranial headaches since two years and recent-onset blanking spells. The headaches were moderately severe, with no diurnal variation, occurring once in two weeks with no particular aggravating factor and subsiding with analgesic medication. He had a normal birth and early development. However, at two years of age, he had developed sudden-onset vomiting, irritability, and imbalance which was progressive, not associated with fever, trauma, or varicella infection. Over the subsequent month, he developed a divergent squint. A computed tomography of the brain revealed a mass lesion in the cerebellar vermis with supratentorial hydrocephalus. He underwent near-total excision of the tumor, with a thin rim of the tumor left behind. The histopathology of the tumor revealed medulloblastoma. For the residual rim of tumor margin, he was subjected to external radiotherapy to the posterior fossa with 6 MV photons (total dose being 5040cGy/28Fr/54 days) and was declared free of the disease subsequently. He was asymptomatic till the age of 10 years when he developed the headaches. A magnetic resonance imaging (MRI) of the brain was done which was normal except for postoperative changes; hence, the headaches were treated with plain analgesics. Over the next two years, he developed intermittent brief episodes of blanking spells, when he was referred to our center. On examination, his mini-mental state examination score was 28/30. A thorough neurological assessment revealed nystagmus, ataxia, and dysarthria with a normal tone. Deep tendon reflexes were pendular with flexor plantars. An electroencephalogram done for the blanking spells showed mild epileptiform abnormality and he was put on oxcarbamazepine. He was lost to follow-up for the next two years. Then he had a flurry of seizures and was admitted to our hospital. This time on examination, his dysarthria and ataxia had clearly worsened. His mini-mental state examination score had dropped to 22/30. He had acquired mild hearing impairment. A repeat MRI revealed cystic space in the posterior fossa (as a result of the previous surgery) and hypointensities around the cerebellar folia []. This was confirmed to be hemosiderin on the susceptibility weighted images. Assessment of brainstem auditory evoked potentials confirmed bilateral mild sensorineural hearing loss. A repeat clinical assessment after six months showed significant deterioration in dysarthria and ataxia. A repeat MRI after six months showed progression in the deposition of hemosiderin in the cerebellar folia from the previous one []. The clinical picture of a progressive worsening ataxia with sensorineural hearing loss along with the neuroimaging findings of the deposition of hemosiderin in the cerebellum clinches a diagnosis of superficial siderosis in this child, secondary to the surgery of the posterior fossa done in early childhood.