Megaloblastic wobbliness: A reversible neurological condition

Vitamin B12 deficiency has been associated with a very wide spectrum of neurologic manifestations and the majority of cases occur in infants, pregnant women, and elderly people. In children, common neurological complications include neuropathy, neuropsychiatric features, infantile tremor syndrome, developmental delay, cognitive decline, spastic paraparesis due to subacute combined degeneration of cord, seizures, encephalopathy, extrapyramidal features, and neuropathy. Vitamin B12 is known to cause sensory ataxia, along with impaired position and vibration sense, as well as variable spasticity, as a part of subacute combined degeneration of the spinal cord. However, only a few cases of isolated cerebellar ataxia caused by vitamin B12 deficiency have been reported in published literature.

We are reporting a case of isolated cerebellar ataxia progressing over months in a 13-year-old boy. He also had associated knuckle hyperpigmentation, megaloblastic anemia and his magnetic resonance imaging of the brain was normal. Complete blood count showed hemoglobin of 8.6 gm/dl and peripheral smear showed macrovalocytes and few hypersegmented neutrophils. Serum vitamin B12 level was low (134 pg/mL). He was started on daily intramuscular vitamin B12 supplementation and he showed a favorable response after the first week.

Clinicians need to consider vitamin B12 deficiency as one of the rare etiological possibilities in children presenting with isolated subacute onset/chronic ataxia, as supplementation of this vitamin is likely to cause a complete reversal of ataxia in such children.